German-market (F-Type) Crosman 1377

[RJVB]

Hello

I ordered my 1377 from Germany as I couldn't find it for sale through a professional reseller here in France. Turns out Germany limits airguns at 7.5 joules ("F-Type"). From what I've seen this is not that far from the power a stock 1377C makes, but since France allows 10 joules maximum I'd like to try and get the pistol as close to that value as possible. I'm planning to order the flat top piston kit from GMac Custom Parts, but are there other things I sh/could do? Any ideas how the pistol may have been bridled to 7.5 Joules?

For the rest I don't regret my choice. The pistol seems pretty accurate: I sighted it in from about 5m, in a standing position resting my hands on a support, and got several pellets through the same hole on more than 1 occasion. It doesn't feel as much alive as the Webley Premier I had before, but certainly more than the HW40 I shot a couple of times!

[danco1987]

10 joules is roughly 7ftlbs.
Flat top piston and valve is a good start and will increase power.
An aftermarket breech and extended bolt is a must for me. The crosman steel breech and gmac's hollow extended probe is a good combination. Replace the metal transfer port with some poly tube the same diameter prevents lost air. A smoother hammer spring makes shooting nicer as well.

I've been tinkering with my crosman pumper carbine the past couple of days and am getting 10.5ftlbs with 13pumps. But mine has a longer barrel and i've modded the valve insides. I reckon with the stock barrel and all the above mods you could get around the 10 joules mark with 8-10pumps.

[RJVB]

Hello Danny,

Thanks for the suggestions. I've already installed the GMac extended brass breech (I wanted to keep the stock sight without modding it...) with the extended probe. I understand they don't do a hollow probe for the .177 version - what's the point anyway? I've also added a transfer port top seal, I'm guessing that has more or less the same effect as replacing the metal port with a vinyl one. Also deburred the transfer port.
I have the impression that this already increased the power - I'm now shooting through board that resisted previously.
The flat top piston kit from gmac will be next.

In fact, I was a bit concerned that there might be some security valve somewhere that would continue to limit the max output - any ideas if that's likely or rather not?

[danco1987]

There will be a bleed hole on the end of the valve near where the valve stem exits if there is one at all. I know the Canadian versions have this, I had a 2289 backpacker from Canada which had one. It prevents the valve reaching high pressures. If youre getting a flat top piston and valve from gmac then I wouldn't worry about this.

Gmac does have the the hollow probes in 177 now. They definitely increase fps, exactly how I don't know, probably channel the air more efficiently behind the pellet. He has videos showing this. They also make loading easier and smoother I find.

[RJVB]

Yes, I also understood the Canadian versions have some kind of bleed valve (from the review on replicaairguns.com). And I was indeed hoping that by installing the flat top kit, I'd simply be getting rid of anything of the kind

I'm a bit peeved I didn't notice the hollow probe for .177 ... I can easily imagine how it makes loading easier (maybe even compensating for the increased difficulty with the gmac breeches?). From the image it would seem that it sits over the transfer port and thus maybe helps to concentrate a bigger amount of air directly into the pellet skirt? I haven't seen a lefthand version though, have you?

[danco1987]

If you get the left handed breech, I think the bolt is threaded through so you can screw the handle into the other side - is that what you mean?