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Education / Training Can nitrogen be used in PCPs?

Can nitrogen be used in PCPs?

by B.B. Pelletier

This report was requested by Pestbgone, but, from my years working at AirForce, I know that a lot of shooters also wonder about it.

Here’s the argument: Air is composed of approximately 78 percent nitrogen, 21 percent oxygen and the remainder a smattering of other gasses. With nitrogen as the principal component, they want to know why a precharged airgun can’t be operated on it exclusively. I will answer that today.

What I used to tell people who called in with this question is that we only recommended our guns for use with breathing air and no other gasses. The seals in our guns were selected for use with air (true) and we couldn’t be responsible for their use with any other gas (also true).

Do you have any idea of how much money an airgun manufacturer pays EVERY YEAR for liability insurance? I won’t tell you, but it’s a heck of a lot more than many of you make in a year. I’m not talking about the level of liability, now, just the cost for the coverage (the bill)! The cost is based in part on how many guns you expect to sell, so as you prosper, your rates increase because the insurance company’s exposure increases.

Just to get covered, a company has to have solid literature, solid technical data on its products and a solid base of customer information that directs the customer in the safe use of the product. Remember, and this is no laughing matter, that there once was a man who sued a lawnmower manufacturer for damages he received when he picked up the mower deck while the lawnmower was running in an attempt to trim his hedges! He won a settlement for that! That’s why all mowers sold in the United States today have a kill switch that must be depressed at all times for the mower to run. It’s that bar you have to squeeze when operating the mower.

So, is nitrogen dangerous?
Will nitrogen hurt your PCP? No, it won’t. Nitrogen is an inert gas that doesn’t react with most things. Oxygen, on the other hand, supports combustion, and the oxygen that both medical personnel and welders have access to has been known to blow up airguns!

Oxygen can kill you!
Now, here is the bad news. Do you think that nobody would be stupid enough to use straight oxygen in a PCP? Think again. It has happened many times, once probably resulting in death. That one happened in England in the 1990s, but look at Pyramyd Air’s experience with it.

This Fire 201 9mm rifle was filled with oxygen instead of air. The caliber doesn’t make any difference. It’s the oxygen that does the damage.

This is what happens when a VERY HOT flame is held against aluminum for a long time! It looks like a cutting torch has been used on this gun from the inside out. This was a Fire 201 9mm rifle.

Note the discoloration of the anodizing. Forensic scientists use clues like this and the bending of the steel barrel to determine how much heat caused the damage and how long the fire lasted.

This is the SECOND time Pyramyd AIR has had to deal with this same problem. The first time, a medical technician called in to ask them why his Career 707 was shooting a blue flame out the muzzle on every shot!

So what? We’re talking about nitrogen
What this has to do with nitrogen is this. Simply this, people don’t pay attention! Nitrogen can come in tanks compressed to 6,000 psi instead of 3,000 psi. I once met a guy who thought the way to fill a PCP was to connect the hose to the gun and open the valve as fast as he could. The gun filled right up in a couple of seconds, though it did get hot. If you don’t understand why, please re-take your high school science class where they explained about the heat generated by compression.

Now, you take a paintball player who has access to nitrogen in 6,000 psi tanks and the same attitude as the guy I just described, and you’ll have large pieces left to bury. But, take a medical technician with the same attitude and access to pure oxygen and the pieces will be both smaller and probably toasted.

What about other gasses?
What about helium? Yeah – what about it? Will it make a pellet go faster? Maybe. Do I care? No. I have firearms for whenever I need to go faster or hit harder.

Show some respect
Guys, these are AIR guns, and they need to be operated with some respect. Yes, the shark blowing up in Jaws was Hollywood theatrics, but we are dealing with some serious technology here, and we need to respect it. It’s funny watching someone else on YouTube shoot a propane tank with a .22 rimfire and getting consumed in the resulting explosion, but it’s not as funny when you’re the one at ground zero.

So, what am I saying? I’m saying that our current precharged airguns are built to operate on breathing air and that’s how they should be used. Let’s leave the serious accidents to the skateboarders, stunt cyclists and America’s Funniest Home Videos.

author avatar
Tom Gaylord (B.B. Pelletier)
Tom Gaylord, also known as B.B. Pelletier, provides expert insights to airgunners all over the world on behalf of Pyramyd AIR. He has earned the title The Godfather of Airguns™ for his contributions to the industry, spending many years with AirForce Airguns and starting magazines dedicated to the sport such as Airgun Illustrated.

72 thoughts on “Can nitrogen be used in PCPs?”

  1. B.B.,

    Your last words were very funny. You really have to know what your doing when trying things that are not of the norm. It seems like these people would at least research on the subject.

    I would hate to have that lawnmower guy cut down a tree for me. Some people are more accident prone than others. I guess its in there nature and not a want to hurt themselves and sue others, who knows.

    • All good and fine, and yes safety is always a prime consideration and more than that it should be addressed to the same degree as you never point the muzzle of any gun where you do not want it to shoot.

      A high pressure nitrogen tank, (with proper regulator) stress proper regulator so someone not aware cannot blow up the PCP tank is about the only option in town for many of us.

      Scuba bottles are limited at best, and dive shops only fill to 3350 or so, so there is no getting a 4500 psi bottle filled, at least not around here and most dive shops I have ever been to their delivery station will not allow them to deliver 4500 psi, I am sure they could, they just do not do such.

      Buying a compressor is very costly, even the little Freedom 8 is expensive, then you need a small aux compressor, a dryer, some hoses and if you plan to fill a 4500 psi tank, you have to baby sit the thing and stop and grease it every couple hours etc. Using it around the house is fine as it takes not long to just fill the PCP tank only. But it is costly.

      A nitrogen bottle rental and fill around here is 175 bucks a year. Buy a regulator for around 380 bucks, a hose with a bleed down and you are set. Unless you shoot a really lot two fills a year is all you will ever need as there is a lot of volume in that big high pressure tank.

      Nitrogen is not O2. To compare this with nitrogen is not fair at all. That is like saying do not put high pressure gasoline in your gun and light the match.

      Or you can use a hand pump, comical as it is at 3300 psi, I generally sit on the handle. Lol!! Even one time tied it to my butt with a rope around the handle and around my legs, just stand up and sit down. Chuckle.

      Nitrogen works for me, but yes I do observe safety and even a nick on a hose requires replacement. But nitrogen is not O2. That is not fair.

      • If you can’t comply or do it right maybe don’t do it at all. No law says that you have to use an airgun.

        If you break the rules keep it to self don’t involve others in the stupidity.

  2. Helium is one of the worst gasses for expansion as it heats up. Possible it could burst a rifle on a hot day. They used it in the Apollo spacecraft as a compression agent for certain fuel tanks, but the tank was equipped with a “burst disk” to blow out when it finally expanded too much. Nitrogen, we used on our F-18’s in the tires and in our hydraulic accumulators and shock absorbers. Low expansion, inert, etc. They’re even using it on automobile tires (they say it’s better for the rubber, but I think it’s a bit impracticle myself). Could be ok for a Pre-charged, but with the extra regulator to fill and the lack of common sense in some would-be shooters, it’s safer not to equip for Nitrogen. JP

  3. The nitrogen tanks used in paintball have a regulated out put of 450psi. They wont blow up a PCP rifle, they’ll just cause the pellet to fall out the muzzle.

    The large fill station tanks are extremely high in pressure, but many modern one use a compressor that slowly fills the tank on your gun, so that you can shut it off at the proper pressure and prevent over fills.

    My HPA tank that I use in paintball has a regulated output of 800psi. It will fit on an AirForce gun with CO2 adapter because they both use the standard paintball ASA threads. I have no clue as to how a pellet gun will preform, but HPA vastly improves performance in unmodified CO2 paintball guns.


  4. Scott298–Good morning B.B.–Most readers are not aware that the oxygen that welders use are pure oxygen—far different than what we breath. I’m no expert but I believe the air we breath is less than 50% pure oxygen. This number could be way off but it should get the point across–pure oxygen is a highly explosive gas. Weldders will constantly check their valves because the slightest piece of foreign matter will form a catalyst for combustion. It has been known that even something as small as a spider web inside the valve is all it takes. When the pure oxygen hits the web—-BOOM!!! You have an explosion. On tv you’ll see welders lighting a cigarette from their torch–some had tried this and snding off part of their jaw. Pure oxygen is highly flamable and should never be used in an air rifle

    • Can you please clarify this oxygen hitting a spider web and exploding phenomenon you were mentioning? First I have ever heard of any this.
      So I am fairly new to the PCP world but have been welding for a few decades now as a hobby. Started with and still have a standard industrial oxygen and acetylene cutting and welding outfit. Then I expanded in the world of MIG, plasma cutting and AC and DC TIG.
      So i think the main thing people should takeaway from all this is that these airguns are designed and tested to be used with exactly that, compressed air. (What we find in the atmosphere on earth)
      I think where the dangers come is the lack of knowledge on the effect of rapid compression and expansion of specific gasses.
      Thats is a huge risk factor and shouldnt be messed around with. Let me clarify for every one that pure oxygen is not something dangerous as far as it being super flammable. In fact, it is standard practice when gas welding and you get something too hot and a fire starts. You turn off the acetylene, you turn the oxygen to full blast, then blow out the flame with high pressure pure oxygen. Almost always, this will blow out the flame. Now, in the event that the flame does not get blown out by the pure oxygen Blasting, then that means no amount of you trying to blow out the flame by hand and mouth is going to work and the flames are very big. Turn off your torch assembly and go get a fire extinguisher.
      So again, the danger comes under rapid compression and decompression. Like someone else mentioned the properties of Helium and its potential risk for explosion when rapidly compressed on a hot day.
      Essentially, it’s like a diesel engine. There is nothing that ignites anything (no spark plug and no spark for ignition), the combustion occurs due to the very high levels of compression.
      Same thing force-induced engines want to avoid. Turn the boost up too high on your turbocharger or supercharger and you get pre-detination or knock or pinging.. Basically the intake charge was over compressed and too hot so when it enters into the combustion chamber, it explodes when it is not suppose to and without spark ignition. Thats how you blow holes through your pistions.
      So for what its worth, try and stick to the manufactured recomendations but if you do deviate from it, make sure you do your reseach and due diligence to know wtf you are doing and wtf is going on through every step of the process.
      Otherwise… Well, Darwinism?

      • revmachine,

        Okay, you are asking a question of scott298 who posted his comment 13-1/2 years ago. As far as I know he isn’t reading this blog anymore.

        Next, in the years since this report was written, AirForce Airguns has changed their policy and they now allow their guns to be filled with nitrogen. As I reported, nitrogen doesn’t support combustion, so as long as the pressure isn’t exceeded, it is okay for use.

        The rest of your comment seems spot-on.

        Welcome to the blog.


        • Oh, sorry. I did not look at the date of when it was posted. My bad. Also, thanks for the update on nitrogen being approved now. It must be a pain in the butt for them to go about certifying something like that because after you allow one, there will be others asking about the gas in the compressed cylinder they have in the garage
          There are some fairly exotic tri gas mixes for welding weird stuff and back in ye ole times of transformer welders, helium was one of the sheilding gasses too. They called it heliarc but that’s just about extinct nowadays.
          When you mentioned liability and lawn mowers i had a slight chuckle. Even with the many failsafe measures they have, i know at least 8 people with parts of their hand missing due to trying to bypass the failsafe and injuring themselves. An old coworker’s brother was a semi high ranking soldier in Vietnam, fought against the viet kong for over a decade in the front lines much of the time and was totally fine. Then he moved to america and lost 3.5 fingers mowing his lawn…. Go figure‍♂️

  5. Mech,

    Although I wasn’t referring to a paintball tank – just someone who used a nitrogen tank normally used to fill paintball tanks to fill an airgun – you do know that regs fail and can blow the entire force through them?


  6. Hello,

    Sorry, couldn’t leave a post yesterday. The Benjamin Discovery sounds pretty promising for entry-level PCPs. For the time being, though, I’ll stick to my spring-pistons.

    On other matters –

    I talked to the guy who used to reload my ammo for me last Friday night and found out he has one of the Taurus PT-1911 pistols. He wanted one of the Stainless models, but could only get the blue at the time. He’s had it for about a year now. He said he hasn’t really had any problems with it. Uses his own handloads, any bullet shape hasn’t posed much of a problem for him. I didn’t shoot it, but it felt pretty good in my hand. One fallacy of the 1911 design for me was the lack of ambidextrous safety standard equipment on even the base models (I’m a lefty).

    Also, in addition to Tom Gaylord’s Remembering When Blog – http://remembering-when.blogspot.com/ I found another dealing with airguns – http://kodiakden.blogspot.com/ It has some pretty fun stories too.

  7. B.B.,
    Thanks for today’s post. Seems like part of the theme here relates to the old saying, “Common sense is not that common.”
    Because I like to tinker, I occasionally do things that are a tad risky, but I find the idea of trying to blame someone else for my mistakes (stupidity?), abhorrent.

    Message understood, though, I’ll stick with the manufacturer’s recommendations, at least to the best of my ability, and if I must deviate, I’ll do the proper research first.

  8. Yah, unfortunately lawyers can perpetuate stupidity by enabling people to be stupid and be rewarded!

    I have often wondered if making PCP guns would raise the insurance cost for a manufacturer and perhaps that is one reason they were expensive. I’m glad to see Crosman make a reasonably priced one!

  9. BB,
    I have never had, nor know anyone who has had a reg on an HPA tank fail, but I have seen the regs on fill stations fail several times, mostly with CO2.

    One time, at a tournament, I was filling my HPA tank and the station’s reg failed. It blew out my fill valve. Luckily my tank and its reg were undamaged. I was able to replace the valve and continue to play.

    Curiously enough, the fill nipple on PCP rifles is the same one that’s used on HPA paintball tanks. I just don’t think I’m up to filling a 92ci tank to 4500psi with a hand pump.


  10. My mental jurry is not yet in on the new crosman PCP. I have been chewing the idea of the super streak in 22. I like the idea that I can just grab some pellets and hit the field (I am looking at them as hunting rifles) with the super streak, but the PCP has of course peaked my interest.

    I think I’ll wait for all the hard work to be done and reported on for both guns in .22 before I make up my mind.

    If crosman release EITHER gun in .20 that would make up my mind for me though. .20 is completely under appreciated, I wish there were more of a selection, especially from crosman in this calibur.

    I also think that if crosman produced a PCP pistol (using the 22XX platform) that it would sell in the Amarican market quite well.

    I will be buying either the discovery or super streak in .22 sometime before next hunting season, so will be following these two rifles closely as real-world testing and reviews are done.

  11. B.B.

    This blog was very entertaining I have to admit, and if I needed any encouragement NOT to tinker, this would be it.

    Thanks to don in Indiana for diagnosing my problem with the 747. So how was I supposed to know that when the manual says to open the pump lever prior to adjustment that it was only partway? (This is correct right?) Anyway, when I did open the lever partway and closed it, there was absolutely no resistance at all. I probably adjusted the pressure the lowest it has ever been on this gun! So odd that it was still shooting like a house afire even in this state. I then turned the castle adjustment wheel down numbers of turns and got to a point where I felt slight resistance to closing the lever arm at the correct point. The castle adjustment wheel was also turning easily at this point, so there’s no more gouging of the metal with the screwdriver.

    I’m not quite out of the woods yet, though. After shooting, I did another check of the adjustment and wasn’t sure if I could feel resistance. I fiddled around and got something but it’s very slight, and I don’t know if I’m imagining things or whether the resistance is from the pump linkage screws instead of air. If anyone could give me more details of the signs of correct adjustment that would be great.

    B.B. thanks for mentioning the basics of match pistol shooting in a blog some time ago. That is, inhaling as you raise the pistol, then holding the breath as you drop the sights onto the target, and squeezing off your shot in a few seconds. This is very close to traditional Korean archery that I’m more familiar with. Anyway, it is as important as the artillery hold for springers as far as I can tell and I wouldn’t have hit anything without it.


  12. To all who expressed interest in my Crosman 1077 disaster in December, I just got a replacement from Crosman. To review, the rifle was shooting great when one day it shot pellets all over the place then quit working all together. It took about a month to get a return package, and it looks like Crosman just replaced the rifle. The new one is deadly accurate just like the old one and even has a slightly smoother trigger. We’ll see how it holds up, but you can’t complain about the Crosman customer service.


  13. B.B.,

    Hate to hijack your post with a question on a different topic, but here goes. I have a RWS 48, and I’d like to scope it. I’m aware of the mounting issue, and I’d like to hear your recommendation on what mount/scope to get. I use the rifle for hunting out to about 40 yards.



  14. Hi BB,

    Innovation is not my strong suit, so I never would have considered using anything other than air in a PCP. It’s very interesting to see what some people come up with.

    I had no idea what issues can arise from a manufacturers standpoint. That’s one of the things enjoy so much about your posts, I learn something new every time.

    That said…

    Waiting on your posts for the new Crosman PCP reminds me of when I was a kid, sitting in the back seat of the car, impatiently waiting to arrive at some exciting, new, fun filled destination.

    So, in time honored tradition I have to ask:



  15. Felipe,

    The 48 has good power and range, so I recommend a Leapers 4-16X50 scope:


    I would mount it in a one-piece B-Square Adjustable mount.



  16. I have never posted before, but I would like to comment about the use of nitrogen instead of compressed air, especially as it relates to the new Benjamin Discovery. Crosman is selling a HPA tank to fill your gun with as well. They also say you can get it filled at your local paintball or scuba shop. Many paintball fields use high pressure nitrogen tanks to fill the HPA tanks they use. They do not have compressors, and the nitrogen can be used without problems. THey have to ensure that they do not overfill, and fill the tank slowly, but other than that, it is perfectly safe and harmless to your gun. If this is an issue, then the manufacturers need to advise against using air from paintball shops, as most of them here use nitrogen, infact they call the tanks “nitro” tanks, not HPA. Sure 6000 psi can adversely affect your gun, but not pure nitrogen. 6000 psi breathing air would do the same thing. Before advising against nitrogen, the manufacturers reccomendations should be checked, and the availability of air should be checked in your area. In my particular instance, if nitrogen wasn’t available to me at the paintball shop, I could not get air tanks filled. There is not a scuba shop close enough that will do it. Other gases can be and are dangerous, but nitrogen is harmless when used properly, just like “breathing air”. Used wrong, they can all be hazardous. If I was to get hurt and couldn’t pump, and Crosman said I could not use nitrogen, they would lose a customer, because I would be unable to get air for my gun. My guess is, they will say nitrogen is a perfectly acceptable gas for use in their guns, just not anything else. Just my .02, Billy

  17. B.B.,

    For fixed power, what do you think about /product/bsa-4×32-ao-rifle-scope-crosshair-reticle-1-4-moa-1-tube?a=272

    Would this be good for 30 yards or so? It comes with free mounts, but I’d have to ditch those. Thanks for your variable power recommendation. I’ll have to work on not being intimidated by all the features if I go that route.



  18. BB., Since we are on scopes, I have a ?. I have an RWS. Night Pro 3-9×44 /30 mm. tube w/ accurest mount on my RWS. 54. (no scope mount movement in thousand shots!) When I first set it up I had AO. set at around 30 yrds. , this gave me good focus from 15-50 yrds. (aceptible focus) Ive had great result hunting at various ranges since. Paper punching as well, I hold over past 35 yrds. & hold over 15 yrds. & closer, all good! (sighted dead on at 20, like you say) Son & I playing 50 yrd. comp. & REALLY turning AO. ALOT Sun. really had me off today! I always thought AO. was for focus, but after 2 hrs today it sure seems to change POI. You say there are no dumb ? but boy do I feel DUMB!! DOES AO. AFFECT POI.??? ( unless this Discovery thing has put me over the edge shure looks so!) Sorry so long of post. Thanks BB.! Tim.

  19. BB., I DONT KNOW! But at 20 yrds. When I changed AO. from 20 to 30 yrds. POI. changed!! Tried several times,not only elv. but windage as well! At 50 yrds. POI. changed 1″ elv.&1/2″ wind.! (aprox.) At 20 yrds. here is what I shot: (3/4″ bull) AO. set at 20 yrds.–5 shots @ 8 o,clock. AO. set at 25 yrds.–5 shots, one hole almost dead center. AO. set at 30 yrds.–5 shots one hole at about 1 o,clock! (for me POI. is changing!)( ctc. spread,5/8″) Notice my groups string from low left to high right, only 5/8, but AO. needs to be left alone,(for me). Im perplexed BB.! I thought AO. did not affect P.O.IMPACT but today, it did for me! I know about your “spot weld” teck.,after several K shots from my 54& especially Im consistant for a single shooting session! Untill I learn more, Im setting at 30 yrds.& keep my damned hands off THE AO.!!(maybee my old eyes CANT HANDLE AO.!!) One more thing, as if Ive not said enough, when I changed AO. from 30 to 50 yrds., my 50 yrd. groups moved up about 1″ !!????? If any one has had this in any respect happen to them PLEASE set my mind at ease! Thanks,Epoxied AO. at 30 yrds.,Tim!

  20. Billy, I agree that if you stick to 2000 PSI, it doesn’t seem like air or Nitrogen would matter. However, the Discovery probably doesn’t have a burst disk. Paintball tanks do. If something goes wrong with the Nitrogen fill and it goes to 5000 or 6000 PSI, it might not be pretty!

    The Crosman FAQ at https://www.crosman.com/pcp definitely states that using Nitrogen will void the warranty.

  21. B.B.,

    Well, after much thought, I went with a Beeman aperture sight. At what range can I reasonably expect to still get head shots on small game such as rabbits?



  22. SUMO: Too windy yesterday! Breezy today, but shot a few 50 yrd. groups today. Was very happy to get groups around 1″! 5 shot groups managed to get 3 in one raged hole!! However,POI. changed! The more I messed w/ AO. , the more POI. moved! Groups are great,But, I would like them to hang out around the 10 ring!! (wont touch “clickers” untillI get some more feedback or figure it out for myself!!)Really think I can shoot sub 1″ groups reguarly! When wind calms down& I get AO. figured out Ill post results!Later my friend! Tim.

  23. Tim,
    I think you spot weld is affecting the opi. If you have no paralax at 30 and you move to 50 your head positioning coud change the location of the crosshairs on the target. If this is the case your consistant groups could be a result of a perfect spot weld. This is just a theory. You might want to read over some old paralax postings and see if you can dig up an answer.

    Nate in Mass

  24. Hey B.B.,

    Why do air gun manufacturers get insurance since you said that the manufacturer is NOT liable for any misuse of the airgun by the user (the manufacturer is “not responsible” for misuse)? Or is it just the really big air gun manufacturers (Crosman, Gamo, etc.) that have to get the insurance since they sell hundreds of guns every week? I was wondering about the ones who sell their own air guns, individually and not on a corporate basis, would they have to get insurance too? It makes me sick too, when consumers sue for stupid common sense things, often just to see what money they can get! Thanks!

  25. NATE: Thanks for your advice! My “spot weld” is pretty consistant on my 54, Ive shot at least 3000 rounds thru it. I never have had accuracy issues w/it at all untill yesterday when I “messed” w/ AO. adjustment!I now have it set at 30 yrds. witch seems to be a good compromise for me,(focus wise). 15- 35 yrds. and farther. I need to learn more about PARALAX ! Thanks Nate for your advice.Tim.

  26. Dragonslayer,

    AO is supposed to eliminate parallax, and thus, cheek weld from consideration, as well as allowing accurate use at closer ranges than conventional centerfire and rimfire models (traditionally 100 and 50 yards respectively). Any scope free from other problems even w/o AO could theoretically be consistent at multiple ranges with a perfectly centered eye position, i.e., cheek weld/spot weld. On the other hand, an AO scope with incorrectly adjusted (set to wrong distance) objective will have parallax, just like a non-AO scope, and thus be prone to variations with spot weld.

    This blurb is handy summary.

    One thing I can think of is that the AO scale is probably not terribly accurate (e.g., you shot better at 20y with AO at 25y setting). Was the scope in better focus at 25y setting for the 20y target? If so, I would simply go by the focus and forget the absolute range reading, except for adjusting elevation, if that makes sense. I.e., I’m not sure if all scopes have accurate enough range numbers on the AO to measure distance absolutely or to set by distance beforehand.

    Hope that helps more than hurts.

  27. TO ALL:Pyramid Air now lists Benjamin Discovery!! P.A. Rifles/Ben. Sher. scroll down, there She is! BEHOLD!!! A 3000 psi. pump! WOW, thats about $250! Oh yhea, for an extra $130 they will throw in a really nice pcp./co2 rifle W/ Walnut stock, William sights, ect.!! (did I mention steel breach?)I paid $40 for steel breach $60 for William sights. Walnut stock??? I guess Crosman will have to pay me $20 to try this gun!!! I guess they will make it up in volume!! George.

  28. Felipe!

    BKL 260 D7 mount, and don’t look back. No tiny adjustment screws to stip/loosen/wander, and 30 moa of droop in built in to acommodate Diana barrel angles. The massive 6-screw base of this one piece mount WILL NOT SHIFT on the rail of your 48.


    As a long-time insurance professional I’d like to comment on the statement that “The cost is based in part on how many guns you expect to sell, so as you prosper, your RATES increase because the insurance company’s exposure increases.” Actually, the RATE (cost per unit of exposure) will either remain the same or (more likely) go down, due to economies of scale offsetting certain fixed costs as you sell more guns. The PREMIUM will go up, as it should, as there are more units of exposure distributed among more Ralphies eager to find new and creative ways to Poke Their Eyes Out.

  29. BG-Farmer:THANKS!!I never thought Ao. yardge was accurate. I set it for focus & forgot it! Like moa. clicks, it is subjective.I never thought as AO. to be a hold over tool. Im set at indicated 30 yrds. AND HOLDING!! Ill test MORE!! Thanks my friend, maybe I have not lost it afterall!!Tim.

  30. Scott289,

    I read your statements about oxygen and have to dissagree with you, I don’t believe that oxygen by itself, even pure, can explode. Nor is oxygen itself flamable. Oxygen is A necessary ingrediant for combustion, so if no oxygen, there’s no explosion or fire.

    When the three astronauts were killed in their capsule at Kennedy Space Center during A test, The small fire that started flashed through the capsule because of the pure oxygen that was being used at that time. There was no explosion. That is why NASA now uses almost Almost pure nitrogen mixture now.


  31. Dragonslayer,

    I’m not sure I helped or not, but I owe you big-time for the 760 enjoyment, so I hope so:). Since your groups seem to be consistently-sized (as Nate pointed out), your cheek weld seems consistent as well, but maybe not perfectly centered with respect to the reticle, so that varying parallax (turning AO adj.) moves your POI. I would play around with it by setting up at known ranges and seeing where the AO setting works best by purposefully changing my cheek weld — i.e., when AO is set properly (regardless of range reading), the groups should get smaller even if your eye position is varied.

  32. I understand there are 2 grades of nitrogen available – and the “dirty” nitrogen WILL destroy seals in air rifles in short order.

    The clean nitrogen will not do this – and is used by some paint ball people. BB has made very good recommendations given the amount of Ralphies reading this blog eager to find new and creative ways to Poke Their Eyes Out…

  33. Sorry, BB, but your Gaylord alter ego is showing. I have 2 PCP’s, a Talon SS and a BAM B50, both run on nitrogen. And the N2 comes in a 4500 psi industrial cylinder. As you said, N2 is INERT, that means it’s non-flammable, non-reactive, non-corrosive, pretty much non-everything. How can that be LESS safe than breathing air which is about 20% O2? And any seal rated for use with compressed air is not going to have any problems with nitrogen. And your issue about high pressure is spurious, too, or maybe you haven’t heard of carbon fiber SCBA tanks? You know, the ones that are filled to 4500 psi. And a regulator failing is also a non-issue, how many regulated scuba or SCBA tanks have you seen? If you’re going to use your blog to spout the Air Force liability party line, at least have the honesty to tell people what you’re doing. Personally, I don’t think you made a single valid point. And the idiots blowing themselves up by filling with pure oxygen, well, that’s just cleaning up the gene pool. Later.

    Dave Dunn
    Twisp, WA

  34. Dave, I agree and disagree. I agree that those who use nitrogen properly are probably fine. However, as nitr0_fish stated, there are two grades of N2. There are also high pressure N2 tanks and with no burst disk on the gun, an overpressure accident COULD occur. SCUBA regulators may not fail often or catastrophically, but that doesn’t mean other regulators won’t. BB has to give advice to the lowest common denominator here so don’t get stuck thinking BB is giving Air Force party line stuff. Put yourself in his place where you personally would be liable if someone says, “BB said I could do it,” and then blows themselves up!

    By the way, using N2 in the Discovery voids the Crosman warranty, so it isn’t just Air Force.

    .22 multi-shot

  35. BG-Farmer: Thanks for your advice& yes it has been helpfull your last advice helped me fig. this out.(not eye on cent ret. & changing AO.MAKES sense to me!) I have never taken the time to “center” mt retice like BB.does. Ive gotten by with alum. shim under rear of scope CAREFUFF mount set up & sight in! For now Im set at 30 yrd.(AO.setting) & all is good again!! (IF IT AINT BROKE DONT FIX IT LOL.) Oh yea, our 760 fiasco was great fun! I have not laughed soooo hard in alooon time!! (I think BB. probly at least giggled!) Thanks Farmer & to all that helped me with this!Tim.

  36. BB,

    Thanks for the clarification — I was oversimplifying a bit. The point I was trying to make was that AO “reduces parallax to a minimum” for only the range its set at, i.e., parallax still exists at other ranges. There may also be sources of parallax aside from the objective that may remain uncorrected.

    A consistent spot weld with eye centered is still critical to optimal results. Dragonslayer has an amazingly consistent spot weld, which is great, but it seems to me that his eye may be off-axis. Experimenting a little to get a feel for how AO works on his scope and then employing both techniques (AO at appropriate setting for range and modifying his spot weld to center the eye) should give him the most consistent results.

    Is this correct? I apologize for any confusion I caused or am causing.

  37. BG_Farmer,

    You taught me something here. I hadn’t considered the off-axis possibility, but if you are off-axis, any slight movement will be magnified tremendously.

    Because I test so many different airguns all the time, and because very few fit me right, I guess I am finding ways to center my eye that most shooters never consider. I never thought about it until now.

    I think you made a good call.



  38. BB., bg-farmer,& others. When I first asked about my AO. problem,I was a little embarased,& felt kinda dumb. After all the responce,& even the “big boys” involvement on this subject, I feel so much better! Farmers last post about my eye off axis makes PERFECT sense to me. A while back I took BB.s advice & put small pc. of tape on my stock to help w/ repetitive spotweld, great advice! It works! After a while,that pc. of tape just did not apeal to me cosmetic wise! Today I was installing some custom cabinets, & had a brainstorm for a more permanent astheticly aceptable solution, yha, you guessed it, a stick on, clear rubber bumper used on cabinet doors & drawers!! Never underestimate an uneducated,(col.) “non spellin” REDNECK!!LOL.!! Farmer,yesterday I was happy to go back to my “set it and forget it” mind set. Now, thanks to you,BB. & others, Im going to REALLY pursue this AO. thing!! If I didnt I would be selling myself short! Again, Thanks to ALL,Tim.

  39. bobc–Scott 298–I took a welding class at Lincoln-Home of one of the better welders on the market. Pure oxygen is a gas and will explode with a catalyst added. B.B.–you can jump in at ant time if I,m not reporting things correctly–When you fire a rifle cartridge, what you have is a fire, as more powder burns the heat and gasses from the fire expand and push out at the weakest point-if things go according to plan the weekest point will be where the bullet is crimped into the brass cassing-thus sending the bullett on it,s way. In the case of the astronauts-god rest their soul-the raw oxygen created a flash fire, and the only thing that probably stopped the capsul from exploding was that there was enough volume present to allow the flash fire to spread and thus eliminating the pressure so no explosion existed. Even dynamite is a fire that leads to explosion. Place a stick od dynamite in the middle of an open room you will get an explosion and ruin a good section of the house. Place the same stick of dynamite in a tool bok, place the tool box in a closet in the same room and the results will be multiplied, causing a heck of a lot more damage.

  40. BB Pelletier:

    You are a great source of wisdom on guns and technically related matters.

    However, you should not delve into the legal realm without seeking expert advice. The lawn mower story is nothing but urban legend. It does not belong in your blog.

    Kindest regards

  41. Urban legend,

    I wondered whether it might be a legend. But then, since I did a similar thing as a teenager, I figured it was true.

    While cutting the grass one day I became frustrated at the grass catcher chute clogging up every 30 feet, so I started cleaning it out while the mower was running. After a few trys of reaching in to clean it out, I finally contracted the blade and had to go to the hospital.

    So you see, I knew that even if the story of the hedges was legend, the stupidity wasn’t.

    Been there. Done that.


  42. BB I was hoping you coul tell me where I could get an upgrade mainspring/tune kit for my rws 48. Im hoping for more power I want to shoot the heviest pellets i can.177 also what kind of energy can you get out of these rifles with the right tune? thanx for your time. keith

  43. G’day BB

    As usual I have seemed to have found the answer going through your blogs but I am a little confused.

    After reading articles on PCP guns I thought an FX or Theoban could be up my ally. However the ancillary equipment I thought could be overcome by using G size bottles of either compressed air or nitrogen to which I have access.

    I just checked my gauges on a G size bottle of high purity nitrogen and it goes upto around 30,000 KPA. I checked another gauge with both KPA and PSI on the dial and ball park figures suggest 4000 PSI is about 28,000 KPA. Now a kevlar scuba tanks have a 4,500 PSI max. So… is it OK to use a G size bottle of compressed air or nitrogen to fill a PCP?

    I just spoke to a solicitor mate I had not seen for a few years who cut of his thumb about 6 months ago. Plastic surgery stuck his thumb back on…it looks like a thumb but doesnt work real good.

    Whilst he was in the plastic surgery ward a fellow came in with his fingers cut off by a lawn mower when he lifted it up to trim his hedge. This is no joke or urban myth…another fellow came in about 2 hours later with his fingers cut off doing the same thing. The second fellow admitted was driving past the first fellows house and he thought it a great idea!

    Two Stellar Awards in 2 hours!


  44. Bob,

    Only one pellet gun manufacturer in the world permits filling their rifle with nitrogen, and that’s AirForce. The rest specify air, only. However, the chemistry of nitrogen and air being what it is, many people understand that it really isn’t a danger.

    As for using a high-pressure air tank, it makes absolutely no difference. Think about your car. You fill your petrol tank from a HUGE reservoir that contains tens of thousands of liters of petrol, yet there’s no problem. That’s because you stop when your car’s tank is full. Same with high-pressure gas tanks.

    It makes no difference how much pressure is behinds the gas filling your tank. You stop when the inline gauge indicates your tank is full.

    I use a 4500 psi carbon fiber tank to fill my USFT rifle that only fills to 1600 psi. No problem.


  45. Hello BB, an old post I know, however I have been filling my Sumatra .22 for years now with food grade N, either direct to the gun or by topping my scuba tank. We use a lot of G sized cylinders of N at work and at 205Bar/3000PSI they are the precise pressure for the gun. I love the stuff! No Oxygen=no corrosion and no explosion so I can be generous with internal lubrication. I made up all the fittings needed with Scuba gear all rated to 205 Bar. If you have acess, go for it.
    Roger de Grauw.

  46. I'm not clear on why manufactures don't allow (or discourage) nitrogen as a propellant…it's composition and performance is much more predictable and as gases go, is pretty much inert. Where as air that's is collected via a pump can vary wildly in it's composition depending on humility, and other contaminates, etc. Just curious?

  47. Rabbit,

    I can answer that! In one word–liability. Manufacturers fear that if they open the operation of their guns to other industrial gasses, what will prevent someone from using Argon or medical Oxygen? In fact there have been a number of tragic accidents when Oxygen was used in a PCP.

    AirForce Airguns now permits the use of Nitrogen in their PCPs, so perhaps the industry will come around on this issue.


  48. Greetings all,

    couldn't bear to read all the posts as there was some pseudo science experts making rational, but inaccurate comments.

    I like the original "they're meant to be pressurized with breathing air" comment the best. Keep it simple, excellent post.

    Several other commentators were quickly a drag as it seems they lined up and jumped off the same bridge without even looking.

    Real quick:

    We breathe air that is roughly 19.1% Oxygen concentration normally at sea level.
    Oxygen is a catalyst [look up the word]; it does not burn, it simply enhances the burn. Therefore it does not explode itself. I know this will create numerous "what?!?" comments for those who failed chemistry, but can't let that one go…
    If I go on it will only make it worse. Please do a little research before you post 🙂


  49. We know that oxygen doesn't burn, but what we also know is that it vigorously supports combustion of all kinds, including the kind generated by a small spark. Look at the Apollo 1 tragedy for more on that.

    We have seen numerous airguns either blow up of catch on fire and melt when they were filled with pure oxygen, so the caution will continue to stand.

    As for nitrogen, of course it is the primary component of air. But it is also sold in tanks that are compressed to 5,000 psi. Some people do not look at the gauges when they fill their guns, and this sets up a dangerous situation. So the warnings to use breathing air will continue.

    You have posted to a three-year-old old blog. Since it was written, AirForce and Crosman have both endorsed the use of nitrogen at the correct pressure. So in effect, you are railing at an historical document.

    Please join us on the current page and comment on what is being said today:



  50. Burning, or combustion, is the process of reacting with oxygen, and the elements if fuel (typically a hydrocarbon) actually combine with oxygen to form new compounds (CO2, CO, H2O). A catalyst to a reaction does not get used up by that reaction. Oxygen does get used up, therefore it is not a catalyst.

  51. This article is more focused on warning than on informing. The answer to “Can nitrogen be used in PCPs?” is simple:

    Yes, if the compressed nitrogen supply is regulated down to the airgun’s rated pressure.

    For example, an informed airgunner can fill an industrial gas cylinder with nitrogen to its rated pressure (say 4000psi), then, in turn, use it to fill a PCP airgun through a pressure regulator set at the airgun’s rated pressure (say 2000psi). The airgun is now charged to its rated pressure with nitrogen. It can be operated safely and effectively, similar to using compressed air.

    Industrial nitrogen supply is typically dry & filtered and, therefore, superior to compressed air. Ambient air is potentially full of moisture, which can condense as liquid water inside the airgun’s own cylinder, causing corrosion.

    The warning about over-pressure applies to ALL gases, including air.

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