thinking about converting a 1377 to .22

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super7

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I think I just need a new barrel and breech bolt and I'm good to go. How much velocity would I loose if the 1377 starts pushing a .22 pellet? Will it be significant? Any thoughts on how I would keep the velocity right at 495 while pushing a .22 pellet? Can I get a 1322 valve/piston from crossman and will it fit the 1377? Any other ideas?
 
You can get the barrel and bolt from scopesandammo.com ,you can also get an after market flat top valve and piston there too.This will keep you where you want to be with your pumper.
 
If it is a Canadian 1377, then it has been detuned in 2 ways to get it under 500fps. It has a restricted transfer port between the valve and the barrel. It also has a bleed hole in the back of the valve. A stock 1322 shoots below 500fps and does not need either of these detuning measures.
 
Yes its canadian. My guess is that with the stock valve/piston, it was shooting about 375fps....seemed very close to a gamo compact I have. Well so far I have the flat top piston and valve installed as well as a lighter valve spring. Power is night and day from stock. Don't have a chrony so can't say what the fps currently is.
So if I swap this barrell to .22, I'll loose some velocity but gain in energy/hitting power?
 
Cheaper to buy a 2289.Plug the bleed hole for more HP as well as flat top piston......A chrony will keep you informed to FPS.To keep things legal................Harold A 2289 is not considered a pistol so at least you can use it
 
Ok, I've converted my 1377c from .177 to .22. First I installed the flat top valve and piston from scopesandammo. I also put in a lighter valve spring as it was not releasing all the air even at 8 pumps. Anyway, the difference in power was night and day from stock. Although I didn't have the chronograph until after I installed the flat top valve and piston, based on how deep the pellet would go into a piece of pine, I figure it was pretty close at 10 pumps to my gamo compact which chrony's at 350 fps....so I'm guestimating about 350-375 @ 10 pumps when stock.
After I installed the flat top valve and piston I got the following numbers(using crossman .177 copperhead 7.9grn pellets):
4 pumps - 400 fps
5 pumps - 434
8 pumps - 506
10 pumps - 531
11 pumps - 548
12 pumps - 559 with air left in valve

(so at 10 pumps stock = 375 and with FTV&P = 531)

After I converted it to a .22. I got the following numbers (using crosman premier .22 hollowpoint 14.3grn pellets)
5 pumps - 348 fps
8 pumps - 409 fps
10 pumps - 437 fps
11 pumps - 449 fps

and with gamo magnum 15.43grn:
10 pumps - 421 fps

So basically at 10 pumps I'm loosing about 100 fps from .177 to .22 but hopefully gaining lots of energy. :)
 
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there's no bleed hole in the flat top valve....there is a washer/gasket between the valve and breech that a little fitting fits in and transfers air from the vale to the breech. Wouldn't you need that to get a good seal?
 
Tried making a new transfer tube piece out of aquarium tubing but I actually lost about 20 fps. I found it very hard to get a perfect cut and I think it was just a hair too small in diameter.
Anyway I took the metal one out and bored it out some with a drill bit and gained a few fps. Before boring it out I was getting:
10 pumps - 437.......after 481

Would like to replace it entirely but will have to find the right material.

That was great, thanks for the info!
 
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super7 said:
Tried making a new transfer tube piece out of aquarium tubing but I actually lost about 20 fps. I found it very hard to get a perfect cut and I think it was just a hair too small in diameter.
Anyway I took the metal one out and bored it out some with a drill bit and gained a few fps. Before boring it out I was getting:
10 pumps - 437.......after 489

Would like to replace it entirely but will have to find the right material.

That was great, thanks for the info!
Click to expand...

Aquarium tubing is too soft.You need to use the harder plastic tubing like they use on ice machines.It's the harder white tubing.You also have to make sure that you make the cuts perfectly straight so you don't have any blow by.It may take a few tries,but you'll know when you get it right.When i first tried with my 2240,i almost threw the friggin' pistol against the wall!three ties was the charm.
 
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