1377 mods

D

djmay71

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Hey folks.

I've settled on a new project, to tide me over while my other fund pool for the AR build gets bigger and bigger (Daddy needs a NEA DMR 18" upper!)

Anyways, so I'm picking up a Crosman 1377 later today.
Some parts I know I'll pick up from Scopes & Ammo for this will be an extended bolt handle, muzzle brake, steel breach, and 18" barrel.
The first part of the build, obviously, is to upgrade key components, and to make it more versatile and accurate.

The second part will be to add to the power. (Respectively- we wouldn't want it going over 500 fps...)
At this point- I'll be dropping in a flat top piston kit.

So here comes the final question: Any other mods to add for power, or is the FTP kit the limit?
 
Hi Dj,

I've never done it myself by heard of 3 ways


1. I have heard of people enlarging or changing the angle of the channel/hole from the piston to the chamber to increase the rate of air pushing the pellet.

I haven't done this myself, as l think it is somewhat risky.

2.
The flat top piston has no relief hole, but Canadian models has hole in the piston has a small hole in the back of the piston. Theorectically, by plugging the hole in the back of the piston, would allow more air to be pushed up from the piston to the chamber.

3.
I've read that different longer bbl lengths up to a limit will result in increased fps.


Please let me know if you find more flattop pistons. As I don't see them on Scopes and Ammo anymore.
 
I've noticed Scopes & Ammo will remove stuff from time to time & then it will show up again a couple of weeks later, presumably because they ran out of stock?? I noticed it with the adjustable hammers for the 2240 - they were there, then disappeared, then came back on.

So keep watching the site, the flat tops are popular mods they may just pop up on the site again.
 
marcjer said:
3.
I've read that different longer bbl lengths up to a limit will result in increased fps.
Click to expand...

This is true. A stock 1377 shoots very close to 500fps out of the gate, adding a longer barrel may likely take it beyond the magic number without any further modification.

I got my 1377 a little over 27 years ago. :)
 
1377 with flat top valve and piston will shoot over 500 fps. I've added a 22 barrel to mine and its still very very close to 500 fps with a .22 pellet.
 
Unless it becomes a carbine it will be restricted like a real pistol and you will only be able to carry it about to and from an approved range.As stated above either the longer barrel or FT piston will take it over 500fps.
 
marcjer said:
Hi Dj,

I've never done it myself by heard of 3 ways


1. I have heard of people enlarging or changing the angle of the channel/hole from the piston to the chamber to increase the rate of air pushing the pellet.

I haven't done this myself, as l think it is somewhat risky.

2.
The flat top piston has no relief hole, but Canadian models has hole in the piston has a small hole in the back of the piston. Theorectically, by plugging the hole in the back of the piston, would allow more air to be pushed up from the piston to the chamber.

3.
I've read that different longer bbl lengths up to a limit will result in increased fps.


Please let me know if you find more flattop pistons. As I don't see them on Scopes and Ammo anymore.
Click to expand...

You are half right. There is a hole, but it isn't in the piston, it is in the rear half of the valve.
You also want to enlarge the exit hole (exhaust), not the intake hole of the valve. It is a lot of into to take in, sounds like you are getting a few mods mixed up between guns.
 
Woody-to said:
You are half right. There is a hole, but it isn't in the piston, it is in the rear half of the valve.
You also want to enlarge the exit hole (exhaust), not the intake hole of the valve. It is a lot of into to take in, sounds like you are getting a few mods mixed up between guns.
Click to expand...

Thanks for the clarification.

I've taken my crosman apart several times, but still haven't got the terminology correct.

1. as mentioned, the valve can screw into 2 halves it is the back part of the valve which has the relief hole which limits the canadian version of the 1377's fps.

2. As mentioned it is the exhaust hole.. The channel that feeds from the valve to the chamber behind the skirt of the pellet.

Thanks for the clarification. English isn't my strong point :)
 
marcjer said:
Thanks for the clarification.

I've taken my crosman apart several times, but still haven't got the terminology correct.

1. as mentioned, the valve can screw into 2 halves it is the back part of the valve which has the relief hole which limits the canadian version of the 1377's fps.

2. As mentioned it is the exhaust hole.. The channel that feeds from the valve to the chamber behind the skirt of the pellet.

Thanks for the clarification. English isn't my strong point :)
Click to expand...

If you haven't already done so, check out Canadian Airgun Forum. There are lots of us just waiting to correct you ;) There is a lot of information there and lots of guys willing to help out.
 
As per MBogo3's point.. best to get the Backpacker's clip-on extended stock to make it a non restricted carbine vs a restricted pistol. Although, I hope no one can demand that we take apart our airguns to prove ourselves.
 
Even if you put the stock on a 1377 it is still considered a pistol and would become resticted if it shoots over 500 fps. One way around this is to replace the tube with one from a backpacker (2289) as it came as a carbine. An email to one of the suppliers would confirm if the tubes are interchangable, but pretty sure I read that they are.

Good luck with your project & take a few pics as you do the build. :cool:
 
The 2289 backpacker tubes are available from Gravel Agency in Quebec for a reasonable price. Their phone number is available on Crosman's web-site. They are interchangable with 1377's and 1322's, I have one.
 
i've put the steel breech, stock, and flat top piston in mine. pretty happy with it, very noticeable difference in power. 10-12 pumps i can go through both sides of a soup can.
 
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