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Education / Training Crosman 13XX rifle, a modified 1377 pistol: Part 2

Crosman 13XX rifle, a modified 1377 pistol: Part 2

by Tom Gaylord
Writing as B.B. Pelletier

modified Crosman 1377 pistol
A 1377 pistol, converted to a .22 caliber rifle.

Part 1

Today’s report is Part 2 of the conversion report on a Crosman 13XX pistol into rifle by reader Benji-Don.

If you’d like to write a guest post for this blog, please email me.

And now, over to you, Benji-Don.

Crosman 13XX rifle, a modified 1377 pistol: Part 2

This report covers:

  • Pumps vs Velocity
  • Barrel weights
  • Accuracy
  • Costs
  • Conclusions

Pumps vs Velocity

In this report all of my velocity numbers are with Crosman Domed 14.3 gr pellets. I have three sets of pumps vs velocity data to show the progression in the efficiency of the gun from the stock valve. In all three sets the stock 0.142-inch transfer bushing has been drilled out.

Set 1 – The rifle has the stock plastic barrel band, stock piston, stock valve, stock valve spring, and stock hammer spring. The transfer bushing had been drilled out to 0.156-inches (5/32) ID. For this set I dry-fired the gun until there was no air left between shots. I also did not record shots with obvious valve lock that effected the velocity. Sometimes that would be throwing out quite a few shots.

Set 2 – The rifle has the stock plastic barrel band, MV valve and piston, the ultralight valve spring, 3/8 inch preload on the stock hammer spring and 0.172-inches (11/64) transfer bushing.

Set 3 – Is similar to Set 2 except it has the custom metal barrel band, and the light valve spring.

Note: The 0.172 inch ID leaves a very thin wall going to the valve gasket side of the transfer bushing that has an OD of 0.177-inches. I would stick with the 0.156 inch bushing and barrel opening there is not a significant increase in velocity going to 0.172 inches.

Here is a graph showing the results:

modified Crosman 1377 pumps vs velocityS
Pumps vs velocity. The lines are smoothed. The data points are raw data.

Barrel weights

To see if there were barrel harmonics (vibration and/or wiggle) affecting accuracy I tried different weights on the end of the barrel. I pressed a Silencer Adapter 1.0 oz from the Maximus Hunter on the muzzle. It has the U.S. standard 1/2 inch fine bolt threads (20 threads per inch).

I have three different end weights that screw onto the barrel silencer adapter.

Weight 1 – A plastic dust cover 0.1 oz, a total 1.1 oz (Crosman part).

Weight 2 – A copper pipe flare fitting 0.6 oz, a total 1.6 oz (copper flare pipe fitting and adapter).

Weight 3 – A brass coupling 1.5 oz, a total 2.5 oz (copper coupling iron pipe size 1/4 inch tapered threads and adapter).

modified Crosman 1377 barrel weightsS
Silencer adapter and three barrel weights.

Prior to the metal barrel band/pivot pin bracket, the floated barrel was a little more accurate with the flare fitting. Once the metal barrel band was installed I didn’t find any difference between the different weights and accuracy so I went with the plastic dust cover. The flare fitting did kind of go with the gun’s looks though.

To really tune the barrel the copper coupling could be used — cutting it to different lengths to find the best weight and then adjust its location by how far it is screwed on the barrel adapter. I really don’t have the patience for that. I also have not had any issues with harmonics with the Maximus barrels.


My original 1322 gave me few issues and was accurate right off with Air Arms Falcon 13.43-grain pellets. I worked on my 13XX gun for over 7 months off and on and it took most of that time just to get it close to the accuracy of my earlier 1322 rifle. For much of that time the wind would be perfectly calm until I get set up and then the wind gusts would start. Trying to wait for the wind to calm for each shot can be very tiring and frustrating.

My 13XX groups are about 0.38 inches for 10 shots with JSB Exact Jumbo Heavy 18.13-grain pellets at 25 yards on 11 pumps.

modified Crosman 1377 13XX 25 yards
A 0.38 inch 10 shot group at 25 yards.

My 13XX groups 10 shots in about 0.58 inches with 15.89-grain JSB Exact Jumbo pellets at 42 yards on 13 pumps.

modified Crosman 1377 13XX 42 yards
A 0.58 inch 10 shot group at 42 yards.

Based on the 42 yard shots I think the JSB 15.89 gr pellets would do better at 25 yards than the heavier pellets. I also shot a 0.46 inch 10 shot group with JSB 15.89-grain pellets at 35 yards on 11 pumps so it seems to be holding its group size as the distance increases well.

My original Crosman 1322 groups were about 0.35 inches on 10 shots with Falcon pellets at 25 yards with 11 pumps. It opened up to about 1.16 inches on 10 shots with Falcons at 42 yards on 12 pumps.


I knew when I started this project that it was going to cost more than the other Crosman 1377 and 1322 guns I have modified. I had $200 in my previous rifle without the scope. I wanted this one to be the best I could do. I even considered putting a high dollar target barrel on it but felt that would require someone else to do the machine work and I wanted to do this with the tools I have, or at least the tools I can make.

Here are the parts and costs of my new 13XX rifle:

1377 pistol…………………..……………$60 PA (PY-198-561).
Maximus Barrel………………..….……..$29 PA 6-GBMP22-001
Steel Breech…………………..……….…$38 PA (PY-A-4387)
Trigger Parts…………………………….$57 Crosman
Maximus Hunter Silencer Adapter..…  $14 Crosman 6-2250XL-001
Silencer Dust Cover……………………..$2 Crosman GBMP-033
Metal Barrel Band Pump Pivot………..$34 GMAC 002-3050
Flat Top Piston, MV valve ……………$130 *
Brass Safety…………………………….$11 GMAC 001- 0360
Misc Bolts, Screws Springs……………$10
Approximate Shipping…………………$30 much of the shipping was free


* Peter Nollan – Crosman 1322,1377, 2289 Aluminum Flat Topped Piston, Part # (223375277773) MV Valve Combo. From eBay

If you are on a budget, adding the Crosman stock, steel breech and Maximus barrel will get you very close to the same results for about $80 plus the cost of the pistol.


Was all this money and work worth it? For me, yes, as this is my hobby and I like tinkering with airguns as much as shooting them. This gun gave me some challenges but with persistence I was able to develop it into a nice bench rest gun and I have a gun that is all metal and wood. I would guess that the Maximus would do about the same for less than $200 but requires an air source.

I would like to test it at further distances but only have 42 yards available in my back yard.

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.

59 thoughts on “Crosman 13XX rifle, a modified 1377 pistol: Part 2”

  1. Folks,

    The last time I went up to my cabin I tested the 13XX at 53 yards. I estimated the yardage to be 50 yards using the scope parallax adjustment, but when I measured it turned out to be 53 yards.

    There was so much drop I had to build a special target. I took a large piece of cardboard and put a large stick-on bullseye on it. I then shot a couple of rounds to see where they hit. Then I taped a 8.5 by 11 inch sheet of paper over where the holes were in the cardboard. I also marked a dark vertical line on the target so I had a reference to reduce scope cant. I had a tail wind, from about 210 degrees, of a somewhat steady 4 mph (my guess) not ideal but that is typical up there until it hits 20 mph in the afternoon.

    I used JSB Exact Jumbo Monster pellets 25.39 gr. and 15 pumps for the test. The heavy pellets do better with the wind. I shot a 10 shot group and got 1.27 inches center to center. Seven of the pellets did make a much smaller group. I think some of the spread in the group was from the wind. The pellet drop was 14.6 inches.

    When I got home I tried to run Chairgun to estimate the drop and realized I did not have velocity numbers for that pellet with 15 pumps. I set up the chronograph and measured the velocity at about 510 fps. I also had changed the settings on my scope when I tried to sight the gun in at 53 yards, the scope did not adjust that far so I dialed it back towards the middle of the elevation adjustment. After that I did not know where my zero site distance was so I checked that also and determined it to be 30 about yards. Hard Air Magazine gives the Monster pellets a bc of 0.039. When I entered that data in Chairgun I was getting less than 9 inches of drop using any numbers close to my measured muzzle velocity and zero sight distance. It took me a while to remember that at 6000 feet I had 20 percent less air than at home near sea level. What the heck I reduced the muzzle velocity by 20 percent to 408 fps. as a guess. Then I was getting around 14 inches of drop. I knew the zero sight distance would also not be correct for the high elevation. There was too much guessing to make much out of this other than there is a significant loss of power in a multi-pump and high elevations. I will try to remember to take my Chrony next time and get a comparison of velocity vs pumps from 140 feet above sea level at home to 6000 feet at the cabin. I may try to test the difference in zero sight distance also. I later remembered that with my Dragonfly multi-pump I had to add a couple of pumps to match my zero sight distance between home and the cabin.

    So with a multi-pump you need to redo your hold overs and unders at higher elevations. That is true with all guns due to less air friction, but air friction is minor compared to lower pressures with multi-pumps because your valve pressure is also going down for the same number of pumps with increasing elevation.

    Below is a picture of the target I used for the test. I also did not have the windage adjusted correctly. I have no idea where the blue came from it is a white sheet of printer paper on the cardboard target.

    • Benji-Don,

      Another great report. Thank you.

      I use your 53 yard most of the time when I test gun/pellet combos. I always adjust the sights, if I’m using the sights, ( you may be aware that I test some guns while they are clamped in a vise and I wouldn’t require the sights) so that the point of impact is above or below the aimpoint. This allows me to preserve the aimpoint sticker and I just slide the paper that is recording the impact over to a clean spot when I fire my next group. I’ve found that my sandbags get a nice set to them if I shoot to the same aimpoint rather than shooting at multiple targets, especially at short distances, and I end up with a more consistent body position for each group as I shoot, since I’m not shifting the rear of the gun around to take a new aim. I need all the help I can get. I even use the reference line for the same reason that you mentioned.

      When you are testing more than 50 pellets you can get quite a bit of exercise getting up and down and going out to a distant target holder to move the paper over for the next shot. ( next SERIES of shots, if you were smart enough to mount a mildot scope, which I seldom do.) 🙂


      • Half,

        With a multi-pump it is not easy to use a vice. I have not had any luck pumping the gun in a vice I have tried. What I used to do to check the sight in when I was a kid was to pump up the gun and then put it in a vice, shoot it at my desired distance and then adjust the crosshairs to match the poi. That worked well for my Benjamin 312.

        Well there is nothing like a trip to the backyard range to get your exorcise. Testing 50 pellets is going to require many trips to the target no mater how you set up. If you use a multi-pump and test 50 pellets you will also get quite the arm workout. I seem to remember you are using a hand pump, that would also be quite a work out.

        The 13XX is very easy to pump but say 50 pellets with 10 shot groups and 15 pumps is 7,500 pumps. I would go with 5 shot groups and 5 pumps at a closer distance but that would still be 1,250 pumps. I think the most I have done is about 20 sets of 10 shots with 10 pumps so 2,000 pumps, I was feeling it by the end.


        • Don and Halfstep
          That’s one of the things I don’t like about multi-pump guns. Pumping them while your testing.

          But once you get your pump’s and holds figured out they are great tools.

        • Don,

          I don’t usually vise any guns except CO2 and PCP. As you point out, I can’t really hold pumps still in the vise setup that I use. I HAVE vised Daisy 717s and 777s, since they are very light cocking side lever Single Pump Pneumatics. On the other hand, I have been testing one of my two P17s and it is too hard to pump to put in the vise. That is unfortunate because the pistol scope that I have mounted on it is not corrected for parallax at my 12.6 yard range. That is a tricky setup to use since there is no “cheek weld” to help compensate for the parallax.

          I’ve been shooting 5 shot groups, since the P17 is hard to pump and I have so many pellets to test. By the way, I’m getting some good groups with pellets in the 10 grain and under weights. I initially avoided the pellets that weren’t very close to 8 grain, just because I thought they wouldn’t do well traveling so slow, but I decided that as long as I was set up already, I should test all that I could and have been pleasantly surprised.

          I started the P17 testing because of BB’s reports. I wanted to compare my results from when I first got the guns in 2017, only to find that I had no data on either gun,… I thought!. After I got into the recent P17 testing I found the misplaced data in another gun’s folder on my computer. That was for just one of my two and it happened to be the one that I am currently testing. It was based on 10 shot groups and produced much bigger groups than my current 5 shot groups. It was also limited to the, much fewer, pellets that I owned in 2017.

          I noticed that some of the old groups would have 7 or 8 in a tight group and the total 10 would be MUCH larger. I usually note this in my file when I see it, so I was able to compare many of the pellets and found that the ones with those tight clusters THEN, are also the ones that gave me the best 5 shot groups NOW. I plan to refire the pellets that gave good 5 shot groups to see how they do at 10 shots. I believe that I may not have been as aware of the parallax issue back then and that could account for the blown groups in 2017.

          A couple weeks ago a local store had Daisy 880s clearance priced at $21, so I bought one and can’t believe how easy it is to pump, compared to my Benji 392. I still could’t use the vise, but it’s yet another cheap gun that has also shown promise, so far, with 5 shot groups. ( It’s easy to pump but still too time-consuming to do 10 shot groups for every pellet !!) After my initial testing, I wanted to go back and pick up a few more at that price, as gifts for my cheap-*ss friends, but my wife’s knee replacement surgery got in the way and now they’re gone. 🙁

          You are right about the hand pump. I did use one until I bought an AV compressor and a 45 minute composite SCBA tank. Now I only use the hand pump on small capacity PCPs like my ONIX pistol that is impossible to fill slowly with a 4500 psi tank.

          Keep your reports coming. I’ve enjoyed them all.


        • Benji-Don,

          “Well there is nothing like a trip to the backyard range to get your exorcise.”

          Not that I want to keep you from getting your exercise but here is an idea:

          Quite a few choices. One thing to be thought about is which choice of line. I have used 1,000 lb test clear fishing leader bought in bulk. I chose it because it is light weight, STRONG, weather proof and stays flexible when it is COLD. whatever you use think of the conditions it will be out in if you make a permanent installation. It is easy to set up a temporary installation with a few additional parts. In more permanent setups a target docking system will control things if those winds are a problem. Otherwise a Balsawood frame works well and can be made to be self leveling.

          I also use an inexpensive LASER level to orient everything so I don’t need to drag out my big one every time:
          You will pay more if you want longer daylight range (do it at night with a less costly LASER!) and precision also usually costs more.


          • Shootski,

            Good ideas. I have a couple of cheap laser levels. I use them at dusk or dawn for longer distances, they are better than a hand level. Well I go with dusk most of the time. It takes me a long time to wake up in the morning.

            One day my friend Jim came up to shoot and it was snowing pretty good so we hung our targets on the clothes line and sat at the kitchen table to shoot, right next to the stove. Our clothes line goes out about 25 yards from the back door to a big pine tree so it worked out. we did not even need to leave the porch. If I set one up on my new 100 yard range I would put a motor on it. I would need to take it down in the winter though. That would be a long span and I need the exorcise. I set up a spot for three targets and if I use the pistole targets I get 12 bulls per target. So not too bad. I hope to build my backstop next time I go up to the cabin. The last backstop I made was with earth, well mostly rocks. I don’t like the rocks too afraid of a ricochet or starting a fire. My next one will be a pile of logs.


        • Benji-Don,

          Rotate the rifle 180° in the vice then pump and shoot it upside-down. It may work to make it a little easier for you; at least some of your tasks.

          Hope you have a pair of snowshoes makes that trek to the Target Pit fun ;^)


    • Yogi,

      I thought about drilling some holes in the coupling for changing the weight but did not think about making it an air stripper that would be interesting. I have been interested in intermediate/transitional ballistics for a while. I may give it a go.


  2. Don,

    Fine write up. I admire your innovation. Short on time now. Here is what I have on the Maximus,…


    It worked better than anything I tried and is on there today.

    Good Day to you and to all,……… Chris

    • Chris U,

      I remember you discussing the baffle before I have added one to my wish list to have on hand.

      I second Hanks question. I don’t remember what you said previously.


      • Don,

        I use it as is. No sleeve. I bought a proper air stripper as well and I think it did the worst no matter how I adjusted the cone. The only other thing I did was the stock muzzle cap. All 3 variations showed POI differences,… quite substantial as I recall.


      • Don,

        That said,… I think that the POI differences speak to barrel oscillation influences from the various muzzle adders. As I recall,… I moved the barrel band back about 3″ from the factory position. That was best,… going 1/2″ increments. Oh,… pellet type/weight was the same when testing muzzle adders which again points to oscillation influences. Gun was topped off between type test to keep things the same. I am pretty sure I had the Maximus regulated at that time,…. without checking notes.


        • Chris U,

          Ok that makes sense. One of the best barrel weights I have used is the aluminum weight like the one on the Crosman 2300S. I have a few extra of them but for some reason did not try one on the 13XX. In the back of my mind I think the aluminum acts against the harmonics of the steel barrel. I bet the plastic does the same. The material and the weight contribute to harmonic dampening.


          • Don,

            Also,…. if you are getting into adjust hammer tension and striker position adjustments,…. DO NOT assume that the adjustments are holding position. I found the striker adj. on my .25 M-rod to move at least a 1/2 turn,… if not a full turn after a good number of shots.

            I ended up checking it by backing it out/full in and then counting the turns out. I did that several times. Stock,… there is a plastic thread locker “strip”. After some repeated adjustments,… that looses it’s ability to hold. Repeated checking and then thread locking with some blue Loctite,… and then (not) adjusting is the way to go. Gunfun1 said he has had no issues ever but I can for sure say that it was an issue with me.

            Take it for what you will,…. but be aware that loosing adjustment can exist,.. which can skew your testing data.


            • Chris U,

              You made a great point.


              My memory is bad and I have not written down the adjustment each time but it seems to be loosening after a long shooting session. I even thought about building a spring lock or putting a set screw in the tube cab that will lock the adjustment in place. Now I am leaning towards a set screw. I had forgot about that. I was going to use Loctite but think a set screw will be a better way to go on my Fortitude. I used a plug on the 13XX so no chance of that changing.


              • Don,

                As I recall,…. I would adjust something and then shoot. There was differences at the start (wanted) and then eventually the data showed results that were the same/similar from the (previous setting). I know that is a general statement,… but that is what prompted me to zero out and then adjust to verify the setting. It raised suspicion.

                The set screw idea that you and Shootski came up with is a nice idea if it can work for the application. I might be concerned with the locker screw moving the main screw during the locking up procedure,…. but it sounds very solid once completed.


            • Chris USA,

              An idea (not original) that works very well:

              You can lock down the treads of the adjuster with a set screw(s). You may/will need to drill and tap a hole(s) in the breech to intersect with the threads of the adjuster. A small round of Nylon inserted before the set screw (if you can’t find a set screw already having a soft point) will keep the threads from being damaged.


              • Shootski,

                Sounds good. It would work. I prefer to avoid thread contact. A main screw with another set screw (behind) it would lock things up pretty nice,…. assuming the main screw would not move while tightening the locking screw.

                I have found blue Loctite to be pretty resilient to multiple adjustments,… while still holding a new adjustment. It keeps a “sticky drag” while the plastic locking strips loosen up noticeably after only 2-3 adjustments.


    • RR

      Thanks, I wish it could have been more systematic so each step could have been evaluated. I went two steps back too many times to follow the process linearly and I did not plan on a report until I got at least half way through the work.

      The good news is I had a lot of fun getting the gun to shoot decently with all the mods and tuning.


      • Don,

        LOL! I do understand. I probably could have written a couple of interesting blogs myself if I had thought of it at the time and slowed down to write it up as I went.

  3. Interesting write-up Don – thanks for sharing your experience!

    Never considered altitude for my shooting, locally we are about 400 feet above sea level and you would have to travel quite a distance to add/remove 100 feet to that.

    Question: Do you know if the Maximus barrels are choked at all? I am in the middle of fitting a Maximus barrel to my Crosman 101 and I can’t feel any restriction when pushing a pellet through.


  4. A bit off topic…

    We sometimes have to deal with distractions while shooting – mosquitoes are a common one, here I have to contend with the deer as well. We have 4 adult does, 3 sets of fawns and a yearling buck that like the security and protection of being close to the house.

    A little while ago I mentioned that it was hard to concentrate with a deer snuffling in your ear while aiming and a friend messaged me that that was kinda hard to believe. Just to show that I was not exaggerating, attached is a picture of one of our does greeting my daughter…


    • Hank
      Yep I have to say ole Gunfun1 would have a problem shooting if I had a deer whispering in my ear. 🙂

      I heard of distracting the opponent. All I can say is those deer are getting smart. 😉

      But on the serious side. Yep that’s cool. And the deer come up by the house all the time here. We pet them and the daughters have played with the fawns (they play like a puppy) but haven’t had no kisses in the ear yet. It seems something always distracts them. They always alert me when something is coming near.

  5. Don425,

    I was going to respond to your message, but could not find it in the comments.

    The transfer port size may be the only way to control the velocity with the gas sproing as these are not adjustable like they used to be. That would be a difficult undertaking though, requiring machining.

    Another possible way would be a stack of neoprene washers between the piston head and the end of the compression tube with the idea of reducing the volume of compressed air and length of stroke. An interesting possibility. Has anyone out there in La La Land tried this?

    • RR,
      I deleted the comment during the editing period, but you still received the email.
      The comment was on your comment in the Stoeger S4000E blog about adjusting gas springer power.
      I like your idea of reducing the volume of compressed air. Washers would block the transfer port if it is not in the center. Is there a reasonable way to modify the cocking mechanism to reduce the length of piston travel?

      • Don425,

        Doh! I did not think of that. You just made my simple idea more complicated. Pooh.

        As far as modifying the cocking mechanism itself, that would be dependent on the design of the particular air rifle, but I seriously doubt it. However, one of the ways sproingers are reduced in power is by lengthening the upper portion of the piston, thereby shortening the stroke. Once again it would be dependent on the design of the particular piston and gas sproing and would also require a machine shop, but in many instances that can be done.

        I myself would prefer an adjustable gas sproing, but everybody over here keeps overfilling them and destroying the piston seals and they are more expensive to manufacture, so nobody bothers with them anymore. Pooh two.

  6. Nice shootn’ Don. The 13xx is a great platform that can be fun to work on too.I like how you fit the stock on the grip frame.
    I think we are seeing the value of the new production Maximus barrel?
    I was thinking of using a Maximus airtube on the Marauder pistol, making it a long tube Prod,
    or a Maximus with a pistol grip, not sure. Putting a fill valve and airtube on a 13xx, include a
    2K psi pump in the blister pak, one could see a PCP at around $100.?
    Anyway, great accuracy and enough power to put a bunny in the pot too!

    • Rob,

      I picked up a Maximus air tube a while back. I planned to use it to build a multi-pump. I don’t know how that would work out. I have not got a round tuit.

      It is too bad that the Dragonfly multi-pump used the air tube from the pcp gun. It was not the correct diameter and length for a multi-pump rifle. They compromised with a short stroke and small pump diameter so they had to use a small valve volume to keep the number of strokes down. Other than the efficiency of the power plant the Dragonfly has all the features I would like in a multi-pump.

      Gunfun1 has posted some pictures of a pistol grip on I think both the Discovery and Maximus guns. Then you can use the Marauder pistol trigger.

      I just ordered a Sheridan 2260, I plan on putting a Maximus barrel on it. I have had good luck with the Maximus barrels.


      • GF1,

        I don’t think the Fortitude breech will either. Maybe with some modifications to the tube, tube plug and the valve to accept the bolts.

        My Fortitude has now calmed down and shooting very good. I don’t have much bad to say other than the adjustment on the hammer spring is a little glitchy. I used a longer spring and less preload (0-3) turns on the adjuster and it now works good. It is easily minute of squirrel at 30 yards, even the first shot after sitting a week or more. I am shooting at a little over 700 fps and getting 60 plus shots if I remember correctly.


        • Don
          I have no exsperiance with the Fortitude. Don’t know what bolt pattern the breech uses. But from what I have seen with the block type breechs that Crosman/Benjamin uses a different pattern. Here’s some examples of the guns I’m talking about.

          The 1720T, Marauder pistol, Marauder rifle and of course the Fortitude. There’s others I think too. Just can’t remember right now off the top of my head. Or not.

          And 60 shots. That’s nice. Also first shot accuracy after sitting for some time. That’s a very important thing to me with any gun.

          And Don I need to ask this question. Again not trying to steal your report but need to know.

          This is a question about cold bluing.

          Will it do nicks and scratches in small areas? And here is why. And can’t wait to here what is said about this.

          I did some trading on a Walnut stock (and here it goes) Left Hand Tx 200. Yep left hand. I shoot right handed and I’m shooting it that way. I’m having no problem at all. The gun is very comfortable to shoot. Go figure.

          But I would like to take care of the small nicks it has in the front of the scope dovetail. Can the cold bluing work for that?

          Anybody try something like that.

          • GF1,

            I have used the Birchwood Casy Super Cold Blue for touch up. Obviously it will not hide a nick but will blue the bare steel. The area to be blued must be completely clean of anything like grease or oils or anything else. Use a small item like a tooth pick or Q-tip to apply the bluing only to the area that is not blued. Keep adding more coats until the area matches the rest of the bluing. It won’t be perfect but will not be very noticeable. Its been a while for me so read the directions to be sure how to apply the coats.

            If you sand and polish the nicks you will have a larger area to blue and it will typically not match the original bluing perfectly. So keep the area as small as you can.

            I am sure others have more experience/expertise than me. Hope they chime in.


  7. Don,
    That’s a great report! I especially liked the 53 yard group with the JSB Monster Jumbo pellets; an inch and a quarter group at that distance is excellent (in my opinion). If I am reading you correctly, in your comment you mentioned that at 15 pumps those Jumbo 25.39 grain pellets are clocking at 510 fps; that’s 14.65 fpe…wow! That’s twice the energy of my 1322; so well done on the mods and keep up the good work on the reports. =>
    take care,

    • Dave,

      Yep the 510 fps was at near sea level. I am sure the larger valve volume in the gun helps quite a bit with the heavier pellets. It is able to maintain more pressure against the pellet all the way down the barrel.

      If I had dead calm wind I think the lighter 15.89 or 18.13 JSB pellets would do well at 50 yards with a much flatter trajectory and I could use the mil dots for holdover and be around the bullseye.


      • Don
        Wonder what a .177 would be like with the modds you mentioned. It would have to shoot flatter.

        That could help at the longer distances too because velocity would be up

        • Shootski,

          Thanks, that is a handy calculator.

          My spreadsheet I set up for valve pressure in a multi-pump is set at sea level. It would be fun to come up with a chart for sea level and then 6000 feet for comparison. I will see what I can do.


        • Shootski,

          Here is the results of my pumps vs pressure spreadsheet using some measurements from Hank “Vana2” from his Crosman 101. It would be nice to have the numbers to run my 13XX with the smaller scale pump and valve and less head space. Maybe someday I will try to finish my spreadsheet to include pump handle force for each pump. It is interesting but obvious after seeing the results that with continued pumping the difference will only be the difference in the air pressure between the two elevations. I used 14.7 psi for sea level and 11.78 psi for 6000 feet.

          At the typical 5 to 15 pumps the difference is significant. With 15 pumps at sea level it takes 20 pumps to achieve the same pressure at 6000 feet although the difference in pressure is not as significant as with less pumps.

          Also I would like to point out that all typical multi-pumps top out after around 20 pumps and you can pump as long as you want without any gain in valve pressure. That is all based on the head space in the pump. The less head space the higher the final pressure that can be achieved.


          • Benji-Don,

            Your last is spot on as far as minimum headspace providing/allowing the higher pressure.
            I will throw this out for your consideration: Much is made of attaining highest pressure and to a point I agree with that but now to my point. This is pneumatics with a closed system (at least until the pellet leaves the barrel) high pressure is certainly important to get initial acceleration. With such a long barrel you need volume (at high pressure) to fill the barrel behind the pellet until it exits. If the pellet gets a good initial kick but then the pressure begins to drop precipitously the pellet will not achieve maximum velocity and may actually slow. The example that comes to mind is the old PCPs that used long barrels at very low pressures to achieve amazing results they achieve it on volume. You have a difficult task with Multipumps in balancing volume, pressure, and flow. You can optimize up to a point with pellet selection and number of pumps but eventually you just run out of air volume at a high enough pressure to get the maximum velocity.

            What do you think?


            • Shootski,

              Well you ask the question. With a spring gun the potential energy is in the spring. When the trigger releases the spring it coverts to compression (air pressure) and kinetic energy, the velocity and mass of the piston. Both of those energies are transferred to the pellet very rapidly by converting both the pressure and the piston momentum to pressure behind the pellet. Thus the short barrel for the Springer (sorry I forgot RR spelling) before the barrel friction takes over.

              With multi-pumps it is basically the same as a pcp, as far as the energy after the trigger is pulled Just pump till you get the optimum pressure. The difference in multi-pumps is the onboard pump. The gun (valve, air transfer and barrel length) and pellet will determine the optimum pressure but the onboard pump determines the efficiency and usability of the gun. The balance of the piston bore and stoke combined with the valve volume is what makes all the difference. Look at the two extremes the 13XX with a small bore, stroke and valve volume and the Apache Fire-Ball with the large bore stroke, and valve volume. Both work great for what they do. Then take the Dragonfly it has a short stroke, moderate sized bore and small valve. It is not as pleasant to shoot because it is harder to pump, at least in my opinion.

              The problem with multi-pumps, in my opinion, is they need to be optimized for each caliber and barrel. That makes them more costly. Also turning them into a pcp repeater defeats the concept of a compact lightweight and symmetrical pellet gun.

              So I like a smaller pump bore, longer stroke, long pump lever, large valve volume and long barrel. I will take more easy strokes over less hard strokes. That is just me, everyone is different. So one size does not fit all in the multi-pump world. The .177 caliber is more sensitive to long barrel lengths and air friction in the barrel and elsewhere is significant. With larger calibers not so much, so more volume with lower pressures and longer barrels will work.

              My optimum multi-pump has the pump dimensions and valve volume of the Apache Fire-Ball in .22 or .25 caliber with a floating barrel and a picatinny rail. All wood and steel and adjustments to the hammer spring and piston head space, and a quality adjustable two stage trigger. I don’t think this will happen in today’s market. B.B. wrote a blog on the subject a while back. I was off grid and missed my chance to comment I really regret missing that chance. Here is the link.



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