Canadian Airgun Forum

I guess it depends on how "clean" your upper sear edge is. On my particular build, the rough hardened upper sear edge pushed a burr over on the end of the sear slot. Combined with the heavy pressure the rva caused at all-in, it was enough to create a bind point on the tube. Went by trial and error on this myself, until I got the sear slot long enough that the sear would not rest against the tube...

I'll dig and find the 2100 sear. I think it is cut slightly differently than the 13 series, iirc...

-D.S.

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"Ain't no half-way"
-S.R.V.

Ok thanks, good to know. Probably safest just to cut some out then polish it good. I'll take another look to see. Thanks for the tips!
I made a new end cap out of that old valve tonight. Never got to try it tho after I tapped it for the top and bottom screws. Hopefully it'll help! It was still burping out air through the port on the first pump, even with it cocked, though the second pump burp was gone. I took the valve apart and put a different valve stem in. If that doesn't help I'll have to polish the area where the stem seals and try seat it with the drill attached to the stem and spin it. Anyway hopefully it'll seal now without that, and I can try out my extended back end!
I'll take a picture once I get it together.

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Well, got the valve stopped leaking at the valve stem. I couldn't seem to get it to seal with a lighter spring though, not sure why. It was bigger in diameter than the stock one so maybe that's the problem. I found an extra sear spring after I got it together so maybe I'll tear it apart again and try that.
I made an ens plug out of an old flat topped valve, but somethings not working right now, I think I need to put some wire around the screw under the breech to keep pressure off the back of the tube. It'll cock with the top screw out but doesn't want to with it tightened down. Always something, and no time to work on it lol. Once my wife's mom comes from Finland and I finish classes towards the end of June, then hopefully I'll get these guns working and get a few good gopher hunts in! Looking forward to it, just need to find a farmer that wants to get rid of some gophers! Shouldn't be too hard to find.

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Well I was feeling pretty discouraged that my 2200/1322 was taking so many more pumps than Bob Sterne's uber carbine. Then I looked at his thread again and realized something that I'd forgotten, that Bob shortened his front end on his valve and cut a new oring slot. (thanks for the nicely detailed posts, Bob, on this great project you did!)
That gave him more air than I'm pushing, and into a smaller valve space, which would give more pressure both ways. No wonder his is so much more efficient in pumping! I'm disgusted now that I've ruined my tube for such a setup cause I drilled my front grip frame hole, so I can't shorten my valve, not that I could have done what Bob did on the front since I don't have a lathe or mill. I would have had to get a 2200 valve back end, and notched the bottom like I did the back of the 1322 valve, if that is possible on the 2200. Doc Sharptail recommended the 2200 valve back end and I never got around to ordering one. Should've listened!

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Oops, I guess Bob's valve wouldn't have any less volume cause he just cut back the solid front part of the valve, so it would only be that extra air space that helped him. I'm thinking I probably need to drill out my ports more on the valve and barrel and port sleeve though the sleeve is probably almost maxed out. I'm sure that extra quarter inch still would have made quite a big difference for the amount of pressure built up in the valve on the uber carbine. Will have to keep experimenting! My goal really is to have the gun shooting in the low 600s and between 5 and 10 shots with the 16g cartridge attached. Guess we'll see! Right now Im not even reaching 600 so it needs some port/spring work.

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My valve was moved back as well, which combined with the shorter nose allows for significantly increased pump stroke.... hence fewer pumps to reach the same pressure.... When I saw that you drilled your tube for the front trigger screw I figured there was no point mentioning those changes, it was too late for you to copy me....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal; Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!

Right! I did notch my valve and move it back like you had and drilled the 2nd transfer port but forgot you had shortened the nose. Too late now!

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Finally got this gun working, lol. Was having valve trouble and power trouble. Finally got the valve to seal and with a light valve spring in was getting two shots at 12 pumps between 480 and 500fps. By chance I decided to switch out the trigger grip assembly for an older style one Doc Sharptail had given me and I was surprised that suddenly I was now getting close to 600fps before it started retaining air (14.3gr). Now it takes 20 pumps to get two equal shots in between 520 and 550 fps. Not as efficient now for pumping but more power. Not sure which I'll go with but I can always cut a couple coils off I suppose or go back to the other trigger! At least I found out the reason why I could never get any speed out of the gun previously. There must be something different with the sear that's catching on the hammer on the newer style trigger.
Here is a picture from earlier in the thread. It has the 14.5" barrel.

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Been trying to figure out what is causing the gun to sometimes shoot over 540fps at 6 pumps and usually only 450fps. I discovered that the hammer pin is pretty loose and sometimes partly falls out, plus the slot on the 2100 is wider than the 1322 for the hammer pin. I discovered also that the hammer binds if the pin leans a little to the left so I took the hammer out and polished it up, and glued the pin in then stuck a piece of tiny tightly coiled spring on it to prevent it from moving side to side so much. Unfortunately it didn't make the gun consistently. Ore powerful so I still have work to do, lol. I also ground the sear hole longer because that was causing my one trigger sear to not catch properly on the hammer. Looks like I need some more internal polishing or something to let it slide better. Will have to buy some finer grit sand paper. Right now it will get two shots around 500fps at 14 pumps, I think it's 14 pumps anyway, lol, bad memory. [emoji57][emoji846]
The fastest I've gotten it to shoot is right around 600fps. It's definitely capable of a lot more if working properly!


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It could be that you're pumping too quickly or carelessly. The compression tube needs to fill completely when you swing the arm open. Look at the inlet, see how that looks, it might be a little restricted.
I built one of these guns about 10 years back. Ended up getting 700fps out of 11 pumps.... Maybe, don't quote me on it. but it was quite the shooter.
Nice little projects they are.

Thanks for the input! I'm pretty sure it's not the pumping though because when I pump it open there is about an inch gap between the piston and the end of the slot so lots of room for air to get in. Almost positive it's something to do with the hammer binding, but I haven't gotten it apart again to try Doc Sharptail suggestion of the bushing on the back breech screw. Hopefully this will do the trick. I've ordered a 2100 hammer and spring too, for interest sake. First I'd like to get it shooting hard and consistently though before I try to tune for more than one shot.

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