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lampy · Veteran Member

I was a little bored this evening so I put together something I have been thinking about for a while. I have had a 1377 for a few years now, never really shot it much. Shortly after getting it I put a steel breech kit on it and put together a wood stock for it, but still never really liked shooting it.
I had a Crosman .22 cal barrel from another project and a spare .22 bolt from putting a steel breech kit on my 2260. I used a barrel band from an old 760 to hold the barrel. Long story short after digging through my parts stash I now have a 1322 rifle that will put 10 pellets into a dime sized group at 10 yards. Velocity is about where I was expecting 450 fps at 10 pumps. A little tweaking could bring that up a bit but I'm happy stacking pellets at 10 yards in my basement.

AirGunEric · Site Admin

How long did it take to construct the stock?

lampy · Veteran Member

lampy · Veteran Member

I didn't think about there being any interest in the stock, I wish I had spent more time on it now.
I used 3/4" poplar plywood to build it. I cut the rough shape that I wanted. I traced the outline of the grip frame onto the wood. I used a router to rough out a recess 1/2 the thickness of the grip frame into both halves. There was a bit of slop in the fit so I mixed up some 2 part epoxy, covered the grip frame with plastic wrap and screwed the two halves together around the grip frame. When the epoxy had cured I fine tuned the shape with a rasp and sander until I was happy with the shape. I added a couple dowels to keep the two halves aligned but I don't think they are really needed, the screws keep things lined up well enough.

lampy · Veteran Member

I decided to try this setup as a .177. A barrel and bolt change and I have a fun little pumper. It won't keep up with my 853 but it's not too bad. 17 out of 20 shots touching the 1/4" bullseye. The barrel had never been shot before this so I'm hoping the accuracy improves after some more lead slinging.

lampy · Veteran Member

Inspired by Rsterns post about adjustable pistons http://airgunhome.com/agforum/viewtopic.php?t=10091
I decided to mod my 1377 rifle with an adjustable pump piston to see what the improvement was in fps.
I went with the stock Crosman pump seal and valve and was shooting 7 gr. RWS Meisterkugeln.

Pre-mod and post mod fps
3 pumps- 425 - 450
5 pumps- 520 - 556
10 pumps- 620 - 675
15 pumps- 660 - 730
20 pumps- 680 - 760

The adjustable piston really shows its benefits after 10 pumps. Keep in mind I have a 1760 barrel on this 1377 and the extra barrel length is going to add some velocity over the shorter 1377 barrel.

AirGunEric · Site Admin

I think 6 pumps might be perfect!

lampy · Veteran Member

I have to agree that 6 pumps is the sweet spot for this set up, it gives the best performance for the least amount of work.
While I was testing I noticed the Extreme Spread tightened up once I got to 520 fps. ES was at 10 fps at 425 fps and dropped to 5 fps at 520 fps and stayed in the single digits for everything above that.
15 and 20 pumps were way to much work but it did give a very satisfying THWACK when the trigger was pulled.
I'm thinking about switching back to the .22 barrel to see what kind of numbers I get with the larger bore. The .22 barrel was more accurate than the .177 barrel. If I can get 500 fps at 6 pumps with the .22 setup it will stay a .22.
UPDATE:
The .22 didn't work out, it took 10 pumps to get to 500 fps. Thats more work than I want to do plinking. It is back to a .177 now and I dug out an old project to work on as a .22.

lampy · Veteran Member

I'm done with this project for now. It is back to .177 and I ended up buying a 1399 stock to replace the one I made.