Some test results 1377 mods

Started by JWL79, June 10, 2018, 07:33:39 AM

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JWL79

I have been tinkering with my 1377 for some time now and I finally got a chrono. I did a lot of testing with 9 different pellets and got some decent results. I tested each pellet with 3, 5, 8, 10, 15, 20 & 25 pumps. I can post all results if you are interested. I have so far added a stock, FT valve & piston, steel breech, 16" barrel, adjustable trigger, polished the sear and trigger, polished hammer, and made a few valve mods (change port angle & valve stem mod). I am considering cutting a few threads on the Male portion of the valve to gain some space but I don't know if it is worth the trouble.

After messing with the  valve mods I got the following at 25 pumps:
Crosman Destroyer 7.4gr 775.6 fps or 9.89 fpe
Crosman Penetrator 5.4gr 867.1 fps or 9.02 fpe
Crosman ultra mag 10.5gr 677.5 fps or 10.7 fpe

arkmaker †

Those look like great numbers JW! Looks like you have done your homework. Is the accuracy as good? I think that the tree rats will be moving out of your area once they know that you have that :-)
I Am A Natural Mad Air Gunner  -  Full Of Hot Air & Ready To Expel It Quickly!

114 Rifle, 2240XL Pistol, 1861 Shiloh Pistol, 357 Pistols, Titan GP Rifle, PM66 Rifle, 2400KT .177 LW Carbine, CZ T200 Rifle, Benjamin Discovery .177 Rifle, Hammerli 850 Air Magnum in .22

JWL79

I haven't taken it out past 20 yards but it is a tack driver, nickel size groups usually, dime size if I am trying hard. 10 yards once I  put 5 pellets thru the same hole.

BillK

Those are great numbers!  And it sounds like you have an accurate barrel to go along with them.   
IIRC increasing the valve  volume on a .177 is not recommended.  There are some mild gains to be made in .22 but not in .177.  Something about the capacity of the barrel to make use of the additional volume of air from an increased volume valve. 
However pinning the valve is definitely recommended.  With the number of pumps you are using, that valve should be pinned.  It, pinning, will be more helpful than increasing valve volume and will prolong the life of your gun.
It's a "must do" IMHO.  Lots of info here.  Check out Wyoman posts.
Have fun & straight shooting....... :) 
West Michigan
Crosman Nitro Venom .22
Crosman 760 - 782 - 1077
Sheridan S S - H - E9
Benjamin NP pistol - Disco - Prod
MIC B1 .177
2300S - 2300T - 2400kt
1740 - 2240 - 2250 - 1760 - 2260 - 1701P
1322 - 1377
MK I & II

onebaddj

Dang, those look good to me. Your 1377 is a beast of a gun. Nice work.
i wasnt born with enough middle fingers. Marolyn manson.

The Zen Master

Quote from: BillK on June 12, 2018, 12:34:25 AM
Those are great numbers!  And it sounds like you have an accurate barrel to go along with them.   
IIRC increasing the valve  volume on a .177 is not recommended.  There are some mild gains to be made in .22 but not in .177.  Something about the capacity of the barrel to make use of the additional volume of air from an increased volume valve. 
However pinning the valve is definitely recommended.  With the number of pumps you are using, that valve should be pinned.  It, pinning, will be more helpful than increasing valve volume and will prolong the life of your gun.
It's a "must do" IMHO.  Lots of info here.  Check out Wyoman posts.
Have fun & straight shooting....... :)

Do you have any direct links to Wyoman's post about pinning? Just searching Wyoman could leave someone reading for months till they find the info they're after as happened with me when looking for shortening a barrel - I gave up after reading about 4-pages. ;)