non flat top power with 12 " barrel

non flat top power with 12 " barrel

Joined: March 1st, 2003, 5:19 pm

January 27th, 2012, 2:52 pm #1


<span class="fv"></span>

<span class="fv">This is a converted 1377 to 1322 using a crosman steel adjustable piston head and stock cup seal. The valve is cone shaped to match and has the usual mods.At 12 pumps using 14.5gr Superdomes it spits them out at 550fps for just under 10ft lbs of energy. It will easily dump all 15 pumps and break 600fps but I dont need it.</span>
Quote
Like
Share

Joined: April 28th, 2010, 12:23 am

January 27th, 2012, 3:20 pm #2

Quote
Like
Share

Joined: July 17th, 2005, 5:16 pm

January 28th, 2012, 1:30 pm #3

<span class="fv"></span>

<span class="fv">This is a converted 1377 to 1322 using a crosman steel adjustable piston head and stock cup seal. The valve is cone shaped to match and has the usual mods.At 12 pumps using 14.5gr Superdomes it spits them out at 550fps for just under 10ft lbs of energy. It will easily dump all 15 pumps and break 600fps but I dont need it.</span>
With the same pump and valve set-up and a 24" 1760 barrel I'm getting 736fps with 7.9 CPLS on 12 pumps. Wish I could recall what I did to the valve before I do the next one in .22.;o(

I think our experience proves that flat-top valve and pump aren't absolutely necessary but being able to adjust the piston properly is the key. That said I've already made an o-ringed Delrin adjustable pump for the .22. Have everything else on hand just waiting on warmer weather for shop time.

Sorry can't post pics but it looks like a generic carbine with 1399 stock and 24" barrel---gawky.
Quote
Like
Share

Joined: December 10th, 2007, 3:34 pm

January 28th, 2012, 5:38 pm #4


...if you don't mind! I haven't gotten a Chrony...yet!

I do a Lighter Spring( from Ace),And compress Trigger spring & 1/4" O'D.
Poly(ice maker tube) for TP. I Usually test Penetration & Expansion on
Modeling clay @ 40ft.

Just got 2 1377's & a 1322( Yes the New one!) I want't to do a 1325 & 1320!

Mario
Last edited by Pumpmeister on January 28th, 2012, 5:38 pm, edited 1 time in total.
Quote
Like
Share

Joined: July 17th, 2005, 5:16 pm

January 28th, 2012, 7:02 pm #5

What do you do to Mod your valve...

Dunno if you were addressing me or the OP, but speaking only for myself I normally open up the passage into the transfer port to the next drill size and break the sharp 90 degree edge between the valve & TP, Nothing too cute----just let it breathe a little easier.

***********************************************************************
Poly(ice maker tube) for TP.

I gotta speak out on this to set the record straight! I was the dummy that came up with that idea. In desperation when the factory transfer port went missing on one I needed to get finished. The icemaker poly was my answer and I wrote it up in case others might need a work-around too. AFAIR I never claimed it was better or preferable---just a functional alternative. I'm pretty certain that I warned that cutting one to the exact length to avoid leaks was a PIA. I use the Crosman part if at all possible. In fact since that episode I keep several spares on hand along with the little seals just to be sure that I don't hafta mess with the poly tubing!
So I don't know when or how the public decided that the poly was a magic hop-up unless someone discovered the improvement after he replaced a leaker with it. Anything that cuts down on losses between pump cup and pellet skirt will help! A new pump cup, (properly adjusted!) bolt o-ring and TP seal on a gun with a few miles on it will usually net more improvement than $100 of custom parts. Tom
Last edited by TheOldBuzzard on January 29th, 2012, 7:03 pm, edited 1 time in total.
Quote
Like
Share

Joined: June 30th, 2011, 11:13 pm

January 29th, 2012, 3:06 pm #6

I am a reletive newbie to the Crosman scene and have read extensively about the poly mod. Lots of folks seek the perfect tube, cut and fit. Your post puts everything back into perspective for me.
Quote
Like
Share

Joined: December 10th, 2007, 3:34 pm

February 1st, 2012, 12:36 am #7

What do you do to Mod your valve...

Dunno if you were addressing me or the OP, but speaking only for myself I normally open up the passage into the transfer port to the next drill size and break the sharp 90 degree edge between the valve & TP, Nothing too cute----just let it breathe a little easier.

***********************************************************************
Poly(ice maker tube) for TP.

I gotta speak out on this to set the record straight! I was the dummy that came up with that idea. In desperation when the factory transfer port went missing on one I needed to get finished. The icemaker poly was my answer and I wrote it up in case others might need a work-around too. AFAIR I never claimed it was better or preferable---just a functional alternative. I'm pretty certain that I warned that cutting one to the exact length to avoid leaks was a PIA. I use the Crosman part if at all possible. In fact since that episode I keep several spares on hand along with the little seals just to be sure that I don't hafta mess with the poly tubing!
So I don't know when or how the public decided that the poly was a magic hop-up unless someone discovered the improvement after he replaced a leaker with it. Anything that cuts down on losses between pump cup and pellet skirt will help! A new pump cup, (properly adjusted!) bolt o-ring and TP seal on a gun with a few miles on it will usually net more improvement than $100 of custom parts. Tom
I appreciate the Info, I did not want to exclude your feedback,which is Just as Valuable as OP's replies, here in the Forum Thank you!

Mario

Lock - N - Load!
Quote
Like
Share