Spring piston seals

by B.B. Pelletier

Yesterday, TC told me he wasn’t familiar with what a piston seal looks like. I linked him to the 13-part “Spring gun tuning” report, but nothing in that report really explains a piston seal, so today I thought I’d do that.

History
The first piston seals were simple, flat, leather pads screwed to the end of a steel piston. They worked but weren’t too efficient. Around the turn of the 20th century, the cupped leather seal was born. The cupped end faces forward and fills with air as the piston rushes forward. The air inflates the leather cup, driving its sides against the compression chamber wall. That gives a better seal than a flat leather pad.

Piston rings
In the middle of the century, there was a brief use of metal piston rings as seals. They work exactly as they do in a car, sealing the compression chamber by expanding into the wall. They had several drawbacks. First, they are precision metal parts and cost a lot to make. Second, because of their location, the volume ahead of the piston is not as small as it would be if the seal were located on top of the piston instead of around the side. For this reason, piston rings are reserved for low-velocity airguns.


Piston from pre-1940 Webley Senior pistol has a beryllium-copper piston seal that looks like a automotive piston ring. When the piston is inside the gun, the ends of the seal are pressed closed. Pardon the grease, but I’m not about to relubricate my pistol for anyone. It will still work fine 25 years from now.
Teflon
Teflon is a synthetic with a low coefficient of friction. Also, it squashes and holds its shape, so companies like Weihrauch and Webley have experimented with it as a piston seal. It works well in the HW 45/Beeman P1. You fit this seal by dry-firing the gun several times. It simply squashes to fit the cylinder. No lip is possible because of the squashing nature of the material.


The Beeman P1 has a Teflon piston seal. This is the top or front – the side that faces the air transfer port. No lips are required because Teflon squashes to fit the compression chamber.
Parachute seals
The synthetic parachute seal is best seal of all. It can be fitted to the compression chamber so it drags very little; but, when it goes forward, the lip of the seal inflates and expands against the compression chamber wall just like the old leather cup.

There are many variations on the shape of the parachute seal, but they all do the same thing – expand against the compression chamber wall to seal the air in front of the piston. When you oil the piston, you help the seal do its job, because the oil fills in all the microscopic scratches on the piston wall. But, the oil also burns, so over-oiling causes detonations that can ruin the piston seal and mainspring.


This is a Beeman Laser piston seal that was part of the laser tune they sold for the R1. It’s a classic parachute seal because of the lip that blows out into the compression chamber wall. This one’s been fitted to my rifle. Because of the synthetic material in the seal, a special grease called Laser Lube was used with this tune. The round impression in the seal is from the air transfer port, made by the piston slamming into it several thousand times.

Vortek experimented with several R1 piston seals in the 1990s. I tested this one along with several others. It doesn’t have a typical parachute lip, but the flange around the top serves the same purpose. Note the V section on top was perfectly centered on the air transfer port.

The famed RWS Diana blue synthetic seal is one of the longest-wearing and most self-lubricating piston seals on the market. They often need fitting to the gun by thinning the sides of the parachute lip. They also require very little lubrication.

These two Chinese piston seals from the 1990s are examples of “Monkey see, monkey do.” The Chinese copied the parachute design without understanding it. The result was these colorful seals made from synthetic ticky-tacky that were totally inappropriate for the job intended. They don’t do well in airguns, but they look good enough to eat! The Chinese have since learned their lesson in seal-making.

The legendary FWB 124 was one of the first airguns to use synthetic parachute piston seals. Unfortunately, they used the wrong formulation material, which disintegrates over time. These are totally useless, having turned to the consistency of hard wax over the years. Modern replacement seals for 124s are made of much better stuff.

83 thoughts on “Spring piston seals

  1. I was wondering just how much friction should there be on a piston with a parachute seal?
    How much does it actually parachute during the firing cycle?
    I Have a rifle that I found during disassembly you can forcibly slide the piston back and forth. Not easily but not too hard to slide either.
    I thought this too little compression as I’ve never been able to do this on any other rifle I’ve disassembled.
    This one has a parachute seal.
    Will it open enough to create good compression without blow by when fired? Or should I look for a larger seal?


  2. BB, I was successful in cut/paste with the link you sent me about barrel cleanning. Unfortunately the google engine couldn’t locate it. Yesterday I sand bagged my Sierra and shot some more RWS rounds through it, and they went all over the target. I had the front of the scope set at the usual 20 yard position, and had the magnification set all the way up to 9 (it goes from 3 to 9). I started adjusting the turrets again and still all over. I set it down out of frustration, and pulled out ‘ole 397′ for a few rounds. I noticed that when I picked the Seirra up and set the magnification dial down to 6, my shots where coming closer to target. Most of my life, I’ve used open sites so scopes are fairly new to me. Any ideas/suggestions? Thomas


  3. Friction,

    I’ve seen pistons that would barely move in the cylinder, and others that slid easily. The lip of the seal only has to move a couple hundredths to seal the chamber, so the flexibility of the material comes into play.

    Don’t try to judge piston seals by how easily they slide. Use a chronograph.

    B.B.


  4. Thomas,

    The article is there, I just went to it. Are you on AOL and perhaps limited to what you can see on the internet?

    You MUST NOT lay a spring gun directly on sandbags! They go all over the place. Put your OPEN palm on the sandbag and lay the gun on your palm. Do not grasp the stock with your fingers. Then relax and hold the gun as lightly as you can. Allow it to recoil as much as possible. This will cancel all negative vibrations and your gun will shoot.

    The scope problem may be caused by parallax. Read this post (all three parts) The links to the earlier parts are at the top of the page, and they open new windows so you won’t get lost.

    http://www.pyramydair.com/blog/2008/02/why-does-my-rifle-shift-its-aim-point_28.html

    B.B.


  5. B.B.,
    The tech articles are always appreciated! I’ve heard about fitting a new replacement seal to the cylinder by chucking the piston and seal in a lathe or drill press and using sand paper or a file to get an easy slip fit. Could you expand on that a little?

    Also, seems like all the current replacement seals are molded. You mentioned Teflon, but are there any other materials you’re aware of that have or can be successfully machined into custom seals?
    Thanks,
    Pestbgone


  6. Pestbgone,

    Sandpaper and an electric drill is the classic way to fit a seal. That’s how I fit the Beeman Laser seal to my R1. When I got close on the size, I completed the work by hand – just holding the piston with seal in one hand and the sandpaper in the other hand.

    You are right that the replacement seals are molded. That limits who can make them, because the injection molding dies cost thousands of dollars.

    I suppose there are materials that can be lathe-turned, but I don’t know what they are. Because they have to be flexible, they challenge lathe-turners. One method I have heard of is freezing the blank before turning.

    B.B.


  7. BB,

    This post is really helpful in understanding how springers work. It’s now obvious that pellet weight and their corresponding dwell times would have an affect on a parachute seal.

    As usual, very good content.

    TC


  8. B.B.,
    Thanks for the additional info. The final hand work on the fitting is what I was missing. And like you said in the blog, the chrony is the final gauge.
    Thanks,
    Pestbgone


  9. Thanks for the links BB. I had to paste them to my yahoo search bar. I’ll try the ten feet site in like you described with the cardboard and two dots. Never realized the point of impact would be in lower in conjuction with the scope distance above the barrel. Plus a lot of other things I was doing correctly AND incorrectly. I did remove the scope nast night, and installed the BSA from my 397. I’ll site it in this afternoon. The reason I changed it, is the 52mm lens keeps getting a blurr from the front site. Maybe I’ll have better luck this time. The fancy scope that came with the Sierra might just work better on my Benji. Will the AA B-square mount you suggested adjust without removing the scope? Thomas


  10. Thomas,

    The B-Square mount can be adjusted from side to side without disturbing the scope, but if you need to go up or down, the scope must come out..

    What I do is rotate the front ring up one full turn from the bottom and the rear ring two full turns. That’s my starting point, but the rear ring may have to come up higher.

    B.B.


  11. Great!! Can you give me the model # of the mount you were referring to. I looked over a few models that would fit the 3/8″ dovetail of my rifle, but want to make sure we are on the same page. Plus if I put the fancy scope back on my Sierra, it would have to be high enough to accomidate the 52mm objective lense. Thanks, Thomas


  12. B.B.

    For a variable scope, does the power adjust continuously or in increments?

    I noticed that the Army Marksmanship Unit USAMU also recommends Hoppe’s #9 for bore cleaning, so I feel even better. Thanks.

    Matt61



  13. BB, one more question about the adjustable problems I’m having. What about using adjustable rings and doing away with the rail system. Or do you think they would be too easily moved by the recoil or spring pistons. I just don’t like how this factory rail I got is adjusted so high that the rear end of the rail is past the lips of the dove-tail. Thanks, Thomas


  14. Thomas,

    B-Square 10101.

    I’m not sure I understand your rail comment, but if the gun has a rail I would use it unless you can’t for some reason. You say a factory rail is ADJUSTED too high? What factory rail adjusts? Do you mean that it is positioned too high?

    I don’t think I understand your problem.

    B.B.


  15. B.B.,
    You say:
    “The lip of the seal only has to move a couple hundredths to seal the chamber, so the flexibility of the material comes into play.”

    I think you meant “thousandths”, as hundredths of an inch are large, relatively speaking. Unless you mean hundredths of a millimeter (.0004″).

    I made a parachute seal for my new/old Predom, but sized it to fit the bore where it entered – unfortunately the dimension had opened up where the seal actually fits from repeated use, so the end result was no compression…something to beware of on well worn guns – the piston bore may not be consistent along the whole length…

    Ordering some teflon rod stock today…





  16. henry

    Got a couple of knife-sharpening questions for you. Do you need an edge guide to get those super-sharp edges? The Razor-Edge System that I use said that an edge guide was an absolute necessity, but the one I bought from them does not work as well as doing it freehand. I don’t see how an edge guide could work with anything but a straight razor. On the other hand, I’ve definitely hit a ceiling and I’m wondering if it’s due to the uncertainty of freehand sharpening.

    Secondly, I wanted to ask about technique as opposed to hardware. My knowledge of technique is derived almost totally from the Cold Steel FAQs page. The basic method, they say, is that you sharpen one side of a blade until you get a burr which is where the edge gets so thin that it starts to bend. Then you turn the knife over and get a burr on the other side. That’s all with a coarse stone. Then with the fine stone you stroke just enough to remove the burr and no more. What do you think? This works so far although I’m not quite able to get their results.

    Matt61


  17. Hey BB, Sorry for not getting back to you sooner. What I meant, was that when I adjusted the factory rail (scope mount) with the scope mount stop screw, The edge of the rear side of the dove tail clamps were above the factory cut dove tails. In other words, the dove-tail milled into the top of the action was exposed under the rear end of the sc. mount. Hope you can picture that. Got good news!!! I played around with the fancy Sierra scope on my Ole 397, and it’s laying pellets in even tighter groups from 20 yards than before. Even better, the cheapo BSA ‘classic’ I purchased from wal-mart works better on the Sierra. Still have that annoying little green blur dancing around the bottum side of my field of view. Perhaps I should experiment by alignning it with the verticle reticle. I’ll let you know how that goes later. I do wish it could bring in the target a little closer, but I reckon it’s a give an take kinda thing. Is there any such thing as having an improper scope on a rifle? Some how I think that was the case with my particular rifle. Might not need that B-square mount after all. But I will write it down for future reference. Again, Thanks for all the advice. Thomas


  18. felica,

    Its not just well used guns, both my HW50 and HW80 had tighter rear tubes. I believe its because the factory only hones and polishes the forward part of the tube. Which is why its so important to deburr the rear portion of the tube before you put the new seal in or you may cut it.

    Sam


  19. Thomas,

    Thanks for the feedback. I know your message may confuse others who haven’t seen all the back and forth we did on the bottom of the Benjamin 392/397 posting, but now you know where we are, so I hope to see more of you in the future.

    B.B.



  20. BB,
    How big a difference is there in terms of consistency between a good leather seal and a good synthetic one? I can’t see leather’s supposed inferiority for average applications, i.e., it seems to last longer, is more adaptable to imperfections in cylinders, and provides a little fuel for combustion to boot. I can even imagine that a synthetic seal might result in lower — although more consistent — performance. Just curious.


  21. Don,

    The RWS Diana barrels droop more than any I know of. And I would still recommend those rifles. Droop is old news and we have been taking care of it for many decades with proper scope mounting techniques. Get a rifle that will last and has good accuracy. If $200 is what you have to spend, get an RWS Diana 34 Panther.

    B.B.


  22. BG_Farmer,

    Leather is fine and can be fairly consistent. I don’t see it outlasting a good synthetic seal, though. Only the seals that were the wrong material wore out. Good seals will outlast the owner of the gun.

    A good leather seal is more forgiving of a bad cylinder than a synthetic seal.

    You get combustion with both leather and synthetics. Leather probably burns more oil, but both burn with every shot. Cardew proved that.

    The thing about leather is you cannot get the hyper velocities that everyone wants today. I have just written a feature article for Shotguns news about the first four “magnum” airguns and do you know what their barrier velocity was? 800 f.p.s. When rifles passed 900, leather was left in the lurch forever. It doesn’t mean you still can’t love them though.

    B.B.



  23. Matt61,

    1) The knife doesn’t know if it’s being sharpened free hand or with a guide, so to speak. This means that its the same result if you can hold an angle.

    2) The burr is a result of over sharpening one side and the lack of a burr means that you have probably under sharpened. SO WHAT AM I SUPPOSE TO DO! Trapped huh, NOT A CHANCE. You go ahead and make your burr and take an equal amount of strokes on the other side. I switch off every five strokes, so nothing accumulates.

    Remember not to overestimate how far into the process you are, especially with a cold steel, as the blades are very resilient. The composition has cobalt and or vanadium.

    Can i tell you a secret?… I would say that what grit you go up to is of little importance compared to the geometry and quality of the steel being sharpened. For example, you could sharpen a piece of metal with a 90 degree bevel and you would just have a wall mirror. Do the same with a 15 degree convex edge and it cuts like a laser.

    The people that know how to get a knife sharp are normally the one’s that shave with it. To be honest, there is no advantage to a 200,000 grit lapping film (the stuff they use to polish fiber optic connections)
    over a 4000 grit warterstone for skinning a deer. And for Straight Razors, you don’t even want to go past the green compound stropping (30,000), it ACTUALLY GET TOOOOO SHARP! Who knew there was such a thing.

    It really sounds like you need a strop and some green compound. It’s the best. I may sharpen a knife to 1200 grit on a DMT duo sharp and then you to the strop. Im not planning on polishing the edge after the 1200, just making the burr a bit less obvious.

    You don’t use a trailing stroke do you? You should always push the edge into the stone.

    -Henry


  24. Don, as for .22 springers you might want to consider the MP513 IF power is a big concern. With the right pellet, it could break 20ft-lbs with very nice accuracy. The gun is also light and fairly easy to shoot well (at least mine is).

    But keep in mind that the cocking and trigger are quite stiff and the firing cycle isn’t the smoothest. It’ll tucker you out if you try to shoot it all day. In addition, it’s a bit of a pain to service.

    The Panther is a much better made gun, and my .22 is doing a little over 17 ft-lbs once I got the undeshimmed breach seal sorted out. But it won’t outshoot my ’513, and it is certainly at a deficit when it comes to power.


  25. Hi Vince..thanks,not sure what a unshimmed breach seal is..is that the o ring around the loading port?
    What happen with that. The only thing thats concerns be is the problem with scope mounting a Diana..I dont want to break the bank with a mount and scope.
    Don


  26. BB,
    Thanks for the response re:leather seals. If leather seals were indadequate for hyper-velocities, then I suppose that means they don’t actually seal quite as well under optimal conditions, which makes sense.

    800fps “magnums” — those would go over big nowadays, wouldn’t they! I’m guessing those ratings were at least with lead pellets and not plastic wire nuts with distillate boosters.


  27. BB,A question for you…
    I have two slavias a 622 and a 618,they both have flat leather seals,i would like to replace them but it seems like it would be difficult as the end doesn’t have a screw and it looks peened or expanded to hold the washer on,i cut the seals off of one piston and there seems like there was 2 leather seals.
    the seals would be easy enough for me too make but putting them on i would need a tip on that,maybe a website you could point me too or do you have knowlege on fixing these.
    Thanks
    Taz


  28. Don, the breach seal on the ’34 (and the ’350, for that matter) is a simple O ring that fits into a groove around the loading port. Appartently they machine that groove too deep for the O ring, then shim it out with a stack of thin washers until the O ring sits a little higher than the breach face (otherwise it won’t seal).

    My .22 Panther was doing less than 600fps with Crosman pellets when I noticed that the O ring seemed to be just about even with the breach face. I shimmed it out by an additional .020″, and the velocity is now well over 700fps with the same pellets!

    When I had this sorted out I took a look at my .177 Panther, and noticed the same thing. When I shimmed the seal on that gun the velocity went up by about 60fps, from about 870 to about 930.

    I had no such problems with my ’513, but then again the Panthers were not brand new guns (they wer factory refurbs). However, I remember that the new wood-stocked ’34 I had last year (in .177) also shot at around 870, so I wonder if that had the same problem.








  29. Ive never seen a swivel for the barrel to attach a sling..any idea where I can find one as I wont be able to use the wood of the forearm
    Don


  30. Taz,

    The piston heads of your Czech rifles look like the base of the FWB 124 seals? That’s common. Diana pistons are like that. You “button” the piston seals on that kind of piston. Soak them in oil for a few hours first if they are leather. With synthetics you just lube them with silicone chamber oil then button them on.

    The bottom washer is probably fiber instead of leather.

    Check with this man for replacements:

    John Groenewold, PO Box 830, Mundelein, IL 60060-0830, (847) 566-2365
    http://www.jgairguns.biz

    B.B.



  31. Matt61,

    here is a quote from someone who knows what they are talking about (not me – but i do know what im talking about when i comes to knives), “Remember that you are not sharpening the edge. You are removing metal until the edge is exposed.”

    There is no contest in terms of who has the sharpest knives, the optometrist wins by a light-year. Heres what they use…

    http://diamondsurgicalproducts.com/html/planar.html

    You see that! Flawless at 400x, now that is some knife. The scratches from any lapping film are present at 400x 4 sure!


  32. Don, I actually made a shim out of a thin washer. This is what I did: a) bored the center of the washer out to the right size, 2) put it on a bolt and locked it with a nut, 3) chucked it up in a drill and spun it so that I could shave the outside diameter down. I then hand-dressed all surfaces with a file to make everything smooth. As I remember, the dimensions came out to .35ID, .54OD, .038 thick.

    Since then, I believe I found a fiber washer in the McMaster catalog that wold work. I think they were about $6 for a bag of 100.


  33. BB, if you think this would be good for a guest blog, I can write something up and pass it along to you. I believe I can take some very decent photographs of the breach and shims showing the problem and what I did about it.



  34. henry

    Thanks a lot. I was hoping to get by without the edge guide. Yes, the strop and green compound sound good. I don’t use a trailing stroke except for steeling the knife to straight the edge, otherwise, I’m pushing the edge into the stone. I hadn’t even thought about optometrists as sharpeners. I thought barbers were the specialists. Thanks again.

    Matt61


  35. Vince,

    You’re a genius. As soon as I read
    of what you did to your 34, I went on to replace a thicker shim to the existing thinner one and guest what?. My .22 Panther was shooting
    Crosman wad at 650 fps, now it shoots the same at 756 fps and hobby was doing 704 fps, now is shooting at 800 fps. All I can say is WOW! it’s unbelievable such simple matter can add 100 fps to the 34. Vince, can you tell me something about the 48/52, is there anything to be done with it?what I mean is, is there any defects to be corrected?.

    Hank


  36. Vince,

    I was hoping you would do it as a guest blogger. A guest blogger has to compose his post in Blogger, using html as required. He also sizes and uploads the photos to the blog.

    I read it and edit it and them switch it over to the live blog.

    One thing I tell all guest bloggers is I don’t want to spend a lot of time correcting spelling errors, punctuation or grammar. Using there when you mean their and then when the right word is than, for example. Or breach when the word is breech. Every correction I have to make causes me to spend time, and at some point it becomes more trouble than it’s worth.

    If that sounds okay to you, please submit your email and we’ll get started.

    B.B.


  37. Hank waht did you do to make a washer..I dont have the machinery to do that. Also what holds the washer back in..does it just streach to fit?
    Thanks,Tom



  38. Hank, even though my gun isn’t shooting quite as hard as yours, I picked up even more velocity!

    My suspicions were aroused when I compiled a list of the mechanical specs of all my springers, including mechanical powerplant energy vs. measured muzzle energy. Turns out that my .177 Panther had the lowest efficiency of any rifle I tested at 27.8%. When I saw how my .22 was shooting, it was even worse. Since most guns were between 30% and 40% efficient, it became obvious that something was up. Hardly classifies as “genius”…

    As for the RWS48 series, I had bought a factory refurbished example that was a very nice shooter but slow, on the order of 20 ft-lbs. I ordered and installed a new factory spring for it, and it changed the character of the rifle. Harder cocking, harsher shooting – and close to 25ft-lbs with the right pellet!

    I don’t think that the ’48 would be similarly inclined to breach seal problems, since the pump cylinder will just slide forward until it contacts the breach. If the seal is a little too thin or thick, all it does is change the stop position of that cylinder.


  39. Hey BB, Let me start out by wishing you and everyone else a Happy Easter. This morning, I layed out another pellet trap at 30yards in the back yard. With the Sierra, I was hitting right of the target, but I’ll blame that on human error. Having to adjust to the recoil of springers, I’m still getting into the feel of it. I did however pull out ole reliable ( with the fancy scope we’ve discussed) and cracked off a few shots. Hit one dead center, and decided to retire my 397 for the day. Best to quit on a good shot!!! LOL’s!! Getting ready to see how the 392 does at this distance. The Sierra ‘is’ starting to come around, and I think with time and a proper “stance”, I be able to tweek it in to my satisfaction. I did try aligning the green blur from the front site into the vertical reticle, but the results are still inconclusive. The southern sun is bright this morning, and I couldn’t really focus in as well as yesterday afternoon. Took the filament out, but will put it back in later today, and see how things go. If it’s a pretty out today as it was yesterday ( hit 80 here), we’ll have a great afternoon shooting!!! Thomas
    P.S. Until my next order, will 3 in 1, or “Marvel Oil” be ok to use on the break hinge and locking clip of the barrel? tjk



  40. hello bb. I was wondering what rifle was better for accuracy and overall value the rws model 34 or the gamo whisper. Are there any accuracy differences between the 34 and 34 panther?
    thank you, happy Easter!


  41. Hiya BB,

    I am in the process of disassembling a 0.22 cal. Indian make air rifle. It shoots at 350 fps with 12 grain pellets.

    Did you fall off your seat seeing the super magnum fps ???! Yea, something’s wrong with it. So I’m checking it out. It looks horrible inside.

    Since you made a post on piston seals, here’s a leather seal pic, albeit worn out. There are other pics as well.

    http://s286.photobucket.com/albums/ll102/MajorKonig81/GI%20MODEL65/

    BTW, can you do a similar report on Breech Seals ?

    Regards
    RT


  42. vince
    the edge is all torn up, and sometimes when i cock the gun i’ll see its falling out.
    im not an exxpert when it comes to gun parts, but im pretty sure its the seal. its the round rubber thing that goes around the pellet skirt when you put the barrel back up.


  43. Tom,

    Hank here. I got my .22 Panther new 2 months ago and was a little disapointed because it shoots in the 600s. I know for a fact that if it’s advertised as an 800 fps it should be shooting at 700s.
    The shim is very simple just follow
    what Vince said. Me, I found a synthetic washer in my plumbing tool box near the size of the metal washer Diana put under their
    “O” ring, of course I had to shape it to the same size as the Diana washer, it’s easy to do so because it is synthetic. I also did a metal one for spare. My Panther is now shooting with accuracy and
    power. You will be amaze!.

    Hank


  44. Tom again,

    You won’t be sorry with the .22 Panther, you’ve picked the right one, much more now that you will have good velocity+accuracy. Mine shoots dime size at 20 yards.
    What holds the washer?, none, just drop it in & push the “o” ring back. All I can say is the Panther is a lot-lot more rifle for your money after you add or replace (shim) the washer. Just wait till my friends with the 34s see what mine does because all of them shoot in the 600s.

    Hank


  45. RWS Diana 34,

    I seem to be answering this question a lot lately. In my opinion, the 34 is the better rifle, as long as you can handle the extra cocking effort.

    The Whisper is great, but the trigger is heavy and it isn’t as accurate as the 34.

    B.B.


  46. Hey BB, Let me tell ya, I was lighting those cans on fire today!! After retiring the 397, I pulled out the 392, and was on the mark. hit the B’s E twice from the 30 yard line with no trouble and/or adjustment on the scope. The Sierra performed excellent using a variety of pellets! I used up most of the RWS meisterschuter ( haha!!sp?) wad cutters and about half the RWS Hobbies. Since I’m more into hunting than precision ‘Olympic’ shooting I was tickled pink!!! Not much need for them,…saving the diabolos and HP’s for November!!!I also shot Crosman Destroyers, Gamo Master Pionted’s, along with the Beeman silver arrows and Crows. Saving the Silver Bears for next season too. As the afternoon got later, I started shooting some Crosman Field Pointed Hunting pellets. About 6 p.m., the temperature droppped with sunset, and My accuracy went all to heck. At first I blamed the Crosman pellets, and gave the barrel a quick wipe down with the mop, but after that I was still off point with the Crosmans, Crows, and Arrows. Can fluctuation in temperature have such a drastic effect with air rifles,…or scopes!?!?!?? It doesn’t seem fair to blame the pellets since they all performed excellent in the preceding hours of the afternoon. As for the factory sight problem, I never re-installed the green filament today. I found that with a simple adjustment with the scope, and bringing the whole thing closer in, the blur from the front sight never realy came into play. I do plan on taking the rear sight to a friend of mine, who works in a machine shop, and see if he can duplicate the ‘cheap’ plastic sight with a much more stable replica out of steel,….which is what Crosman SHOULD have done in the first place!!! Hope you and yours had a pleasent and safe Easter Holiday! Thanks, Thomas



  47. BB, do you have any experience with either the Xisico XS-B3 (AK look-like) or the XS-B7, which appears to be the same gun but with a sporter stock:

    http://www.xisico.us/index.cfm?catid=1023#608734

    I thought I read that the XS-B3 had a leather seal, so I assume the XS-B7 also has a leather seal.

    The XS-B7 seems to be in the same power level as the Beeman R7, and at $60 appears like it might be worth checking out…unless you already checked it out, and decided that it’s not. Looking forward to your opinion; hope you had a pleasant Easter. Thanks. =>


  48. BB,

    In your report on the USFT, you mentioned you can do a blog on the power increase by spring adjustments,or increased swept volume of air…etc.

    I am very interested to read you post on this. Would be nice to look at pictures for comparisons.

    At what volume and pressure makes for consistent accurate shots? The USFT is proof that this can be done without a regulator.

    Thanks.

    David


  49. Hi B.B.

    I have XS- BAM-21 ( similar to Diana RWS 52 model ).
    I’ve changed after 5000 shoots original piston seal and main spring with ones from RWS. Old main spring was broken and chronograph shows only 215 m/s instead of normal 235 m/s with Gamo ProHunter pellets. New fits perfect as maybe you know. But now chrono shows only 205 m/s with the same pellets … Should a new piston and spring to be worked out to start making better performance or there is something else?
    Thanks in advance!


  50. thedavemyster,

    The B7 appears to be an update of the QB 88. It was an okay rifle with so-so accuracy. Definitely NOT in the R7 class. If they improved it, it may be better now.

    B.B.



  51. Edvig,

    You are using velocity numbers without any proof of where they came from. Did YOU chronograph the rifle at the higher velocity with those Gamo pellets? When you did, were the shots consistent or were they due to dieseling?

    It sounds like the rifle doesn’t like the new piston seal.

    You don’t mention whether you used spring dampening compound.

    There are too many unknowns in your question fro me to frame an answer.

    B.B.


  52. Well B.B. , 235 m/s was the usual velocity when the rifle was in perfect condition. After few thousands (5000) shots the main spring was broken and chronograp shows then 215 m/s. That velocity numbers i’ve read without any diesel effect. And as i know the reality for XS-BAM 21 is the exact those 235 m/s with Gamo ProHunter pellets ( almost 1 gram weight ).
    Somewhere i’ve read this: “Every spring-piston airgun requires a “break-in period” before optimum accuracy and velocities are reached. Most airguns require between 500 to 1000 rounds to “stabilize” “.
    Actually i was curious if it so or not? I mean using of new piston seals and main springs. Your comment?


  53. Edvig,

    After the rifle has been broken-in, as your rifle has, then a tuneup will need fewer shots to break-in. Maybe 100 or so.

    I suspect that new seal, or the grease you used on the mainspring.

    B.B.,


  54. Hi BB,
    I was given a Walther 55 and needs to be repaired. Is it worth the trouble? What can I expect from this gun in terms of power and accuracy? Thank you for your time.
    Yorgos.


  55. Yorgos,

    A Walther LG 55 is most definitely worth investing in! If you live in the U.S., this man can fix it for you:

    John Groenewold, PO Box 830, Mundelein, IL 60060-0830, (847) 566-2365
    http://www.jgairguns.biz

    The 55 is a recoiling spring rifle that can almost keep up with the finest Olympic rifles today. It should be able to hit an aspirin every time at 10 meters, once it’s fixed.

    Power is low, thankfully. It will be in the 580-640 f.p.s. range, depending on the pellets you shoot.

    B.B.



  56. I.B.McGinty,

    It’s impossible to tell from the listing., You need to call Pyramyd Air and have a technician go look at the parts bin to determine which seal you need. I’m pretty sure they have it.

    B.B.


  57. Hey BB,

    I have a Beeman RS@ combo that I lkove to shoot but is incredibly hold sensitive. I really have to push the stock back into my shoulder to get accuracy. And I’m having trouble getting groups at 30 yards with the .22. Would a gas piston cure some of the hold sensitivity and it is possible to install one.

    CRM 114



  58. Hi, I am new to tuning. I have disasembled my Benjamin super streak cleaned and deburred all the parts. I have read all the tuning articles, but I am still not sure what to use to RELUBE?
    What do I use on the spring? What do I use on the outside piston walls? DO you add any grease to the front combustion chamber? Or just a couple of drops of RMCOIL to a clean DRY chamber? I read one article on here that showed a pic of a greased piston and seal that was coated in grease, seal and all??(i though you did’t grease the seal) How about the rear part of the chamber where the sides of the piston body ride? If you use petroleum based grease won’t some of it squeeze forward into the combustion chamber and deisel? won’t the grease ruin the synthetic seal? The gun had a very slipery low viscosity CLEAR oil in it when I opened it up. Any idea what this was/is?

    Any comments very much appriceiated.

    thanks


  59. Anonymous that has the disassembled super streak,

    Please go back to 13 part series on tuning that B.B. did. The link is in the first paragraph in the article above. You want to re-read parts 10 & 11 (how and where to lube). Not only will your questions be answered but there are great pictures that show the amounts of tar (grease) to use which is as important and where to use them.

    In my opinion, the best lubes for spring gun tuning are available from Jim Maccari (air rifle headquarters). Jim sells a sampler pack that includes the 3 lubes commonly used in spring gun tuning. I think around $20.00.

    kevin


  60. Hi,
    I have an old Diana 35, the ones produced before 1987. It isn't producing much power, I opened it up, the spring is ok, but the piston seal is worn out. These guns have old, leather seals. Can you please suggest if I can use a different seal, like rubber or some other material? The leather ones are hard to find. Any help or pointers? Many thanks,
    Nauman


  61. Nauman,

    Yes, it would be possible to make a synthetic piston seal for your rifle, but it would not improve the performance. The Diana 35 suffers from a too-short piston stroke. The leather seals are just as effective in this rifle as synthetic seals would be, and I am afraid that it will always be a lower-powered air rifle.

    B.B.


  62. hy tom Gaylord sir i had remade my .22 35 model spring piston (copy of diana 350)changed the spring made it some extra long old one was 38 rings and i had used 46 ring got it in there very difficult had to make some very critical alterations and amendments in trigger and sear,so when it was the turn for the piston seal i used a A.K.A. dual core parachute seal that is two seals placed periodically turn by turn behind on piston side is synthetic and forward is leather parachute one it need and as i do usually lubricate it after 150- 200 shots so what would u recommend when to lubricate.and how is the idea of two seals instead of 1.


  63. Zeeshan,

    You have made a big model translation error. The Diana 35 is not the same as the Diana 350. They are two entirely different air rifles from two different times. The 350 is about three times more powerful than the 35. Hence, the mainspring from one will not fit in the other.

    Leather seals should be lubricated with household oil — the stuff you get at a hardware store. The additional piston seal you have installed has shortened the stroke of your gun, which reduces the power. No mainspring can overcome that!

    If you reduce the piston seal to just one, the power will increase. I think you are looking for a faster gun, so I recommend lubricating the seal with silicone chamber oil.

    B.B.


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