Crosman 1377 Flat Top Valve and Piston - Install + Chrony

Was on the fence regarding this modification then I saw.
Getting the kit plus the top end and 2 stage trigger. Goal is a match worthy pistol.
Thanks for the walkthru.

Don't know why the don't use a hydraulic seal I stead of an o ring witch is round and only pushes a certain amount of pressure on the contrary the hydraulic seal is a unidirectional sea with a sharp conical shape that in extreme pressure it expands and seals even tighter I'm planing on machining mi own but with upgrades. nice video cheers for Florida USA

What was the cost of the kit? Thanks

Thank you and good video.

The guy on ebay that sells these parts, Alchemy Gunwerks, is a hack. He's also a raging liberal.

Well I hope you are happy. Now I have to spend months of time and a small fortune buying half the stuff that GMAC makes.

I haven't done a valve to mine but went with a longer barrel and all the other mods. I easily take dove and pidgin at close range - 25 - 30 foot elevation by 20 foot length +/-, .22 cal. It doesn't reach 45 + feet in elevation, I see the pellet hit an elevation and just arches down drastically from that point. It runs out of velocity before it runs out of lethality for the birds. I wouldn't try rabbit with it. I have a p-rod or discovery that would work for that. I like my pumper. I'm thinking of doing the valve and like your video. I went with a threaded two piece retaining pin instead of the roll pin at the pivot.

Nice video! I encourage you to get an inexpensive set of roll pin punches to avoid flaring the side of the pin while driving it out. It looked like you were using a tapered punch. Thanks for the post. It was very informative.

Did they neuter yalls air pistols. Our crosman 1377s in america average 5 -6 ft lbs of energy. Yours got that after modifying it. Makes me wonder what they did to neuter it down. Unless your chrony is wrong.

Thank you for the video I have to fix my 1322 so I'll try to modify it . I DONT KNOW IF MY VALVE IS SHOT OR THE PISTON RING IS GONE WE'LL SEE.

my CDN. 🇨🇦 spec.
piston , transfer port has a bleed hole that vents above the plunger hole .
I’ve found #2 x 56 NC
ideal size thread tap for a screw to plug said bleed .
Thanks for your excellent guidance !

Now you should see how many pumps until until you retain air after the shot back off the number of pumps until it doesn't and check your velocity's

would be nice if you moved the camera further back because the most important steps only showed the floor. sorry but your video was a waste of time.

Bán không bạn

My maxed medalists has an 18in barrel with an enlarged air reservoir. With 30 pumps it will knock down a crow at 45mtrs. My latest build a co2 crosman pistol conversion. With an enlarged air reservoir adjustable hair trigger and trigger spring tension. I started with a 24in barrel and drilled it out for 2.5 in at 7.5mm. then cross drilled the 2.5in for a shroud silencer. This is super quiet and powerful. My next build, a crosman lower and Chinese parts for a PCP rifle with the same 24in shroud barrel. I love playing with crosman's. None better for the price.

👍😉

Nice

I have a 1322 and I have recently purchased a new valve, bushing and an 18" barrel. I was looking for instructions for the valve installation. This video is exactly what I needed. Thank you.

Hi, how much does Crosman cost?

Bought a 1377c today, inspected how Trudeau had it neutered. Don’t think I can overcome that😢, ordered a modded piston, thank you good ole US of A😂

Good upgrade work 🐻
It's a powerful piece of kit now and it was good at first but now it is better ⚖️🦉

Brute force was required for re-inserting Pin because a lot of energy was absorbed by the cardboard pillow it was laying on.

If you dont want to spend much on your low power Canadian 1377/1322 then you can block the bleed hole on your valve. Its just a matter of tapping the 2mm hole with a 2.5mm thread and plugging it with a tiny 2mmx2.5mm screw and some loctite.

Just done mine this week, im getting 5 foot pounds on ten pumps, and 5.7 foot pounds on 14 pumps. I could probably get a little bit more with a bigger transfer port. I would like to make 5.7 ft lbs at 10 pumps ideally.

Have you experimented with different barrel lengths for more velocity?

Cool 👍

Can’t believe how much control they have over yall

Use air gun oil or 3 in 1 oil multi purpose, regular gun oil will eat the air seals.

The black seal goes into the tube with the short side of the transfer port down do so with a trace of oil and the long side goes into the barrel which is located in the breech.

i take it you do know that you can take these up to 15 ft pounds and now with the stock fitted its a rifle by law and can go up to 12ft lbs.. . many people have the 1322 and 1377 to over 11 ft lbs... it depends on the amount of pumps.... your spread is mainly because the chamber is not fully empty between shots because you need a more powerfull spring for the hammer due to the flat top valve holds more air.. now being as you have the new flat top valve chamber it holds more air and needs to have more pumps to get the psi in the chanmber to be the same as original.... a gune in good condition that needs 10 pumps on a new flat top valve might need 12 pumps for same psi.. velocity is down to how fast the air can be released intothe barrel ( high airflow port). or you can open the flat to ppiston and put a weaker spring in there, ( not advisable ).

Damn, I should have gone to this setup. I when with alliance hobby in NA and my performance has actually dropped vs stock. 9 pumps = 260fps. So frustrating since I spent the $$ on it.

❤❤❤

That spread will get better the more you use it. I love my flat top upgrade. I put a 12" barrel on it to get over 600fps.

whay did you not try 15 pumps???

Can those still be brought

Does anyone review their own videos?

Thought it was a brawd

Hi, I bought my 1377 25+ years ago. Didn't know nothing about 1377c being Canadian . lol So I looked at the box it came in ( yes still have the box)and it said 1377c, so didn't there was a difference . now I'm looking at doing some upgrades lol . I'm in the U.S.

I have a 1322 and was wondering whether the piston diameter was the same in the 1377 as in mine. If the bore were larger, could the barrels be swapped for a probable increase in velocity without the shorter (I have been dubiously informed), life expectancy of the piston swap?

Hi Jamie, graphs and tables are not at all boring! Very useful video, thank you. I've been looking at the 1377 as an SHTF bag addition but was put off when I learned that the UK version was underpowered. Seeing 5.9 on your chart reignited my interest and the upgrade will be an interesting project. GMAC seem to have gone into liquidation. Where would you get your parts from now please. More thanks, James.

I have a crosman 1322 pistol..all original excpet for 14.5 inch barrel .Is it possible to get this pistol to shoot around 600 FPS { with 12.9 Gr lead pellets} with only 12 pumps or less , by only doing a transfer port mod and a air valve mod ? I assume that taking material out of the air valve, will not meet my goal, because that would result in having to pump the pistol more then 12 times ?

Thanks for the video

You will never starve with this weapon. Pellets and bb’s are cheap.😎🔫

Truly awful filming , out of focus or off the screen .

Awesome video! Thanks. Question though, where did you get the replacement screw for the metal breech?

What rail did you used ?

Bugger Gmac parts now out of business 😢

Thank you! Very helpful!