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Title: 1377 and estimated FPS
Post by: mcc1961 on February 24, 2012, 02:43:32 AM

I am building a 1377 carbine with a 24" barrel,FT piston and valve,discovery spring and power adjuster.How much can you guesstimate my max FPS will be at 10 pumps?Here is a pic of the truck bed coating on my stock and pump arm.Waiting for parts so I can get it back together.

Title: Re: 1377 and estimated FPS
Post by: breakfastchef on February 24, 2012, 03:23:11 AM

Here are some of my numbers. Two of my 1377's are setup similar to yours without the Disco hammer spring or a power adjuster.

14" barrel - 630 to 650 ave. fps at 10 pumps
18" barrel - 630 to 670 ave. fps at 10 pumps

Velocity averages change between chrony sessions.

Title: Re: 1377 and estimated FPS
Post by: JMJinNC on February 24, 2012, 03:55:02 AM

I'm getting 695fps with 8.44 grain JSB Exacts and 640ish with 10.3grain JSB heavies. Over 700 fps with sub 8 grain pellets.

24" barrel, ft piston & ported valve setup, extended probe bolt, stock springs.

Details in this thread:

http://www.crosman-air-pistol-owners-forum.com/board/index.php?topic=6135.msg62960#msg62960 (http://www.crosman-air-pistol-owners-forum.com/board/index.php?topic=6135.msg62960#msg62960)

JMJ

Title: Re: 1377 and estimated FPS
Post by: pirouge on February 24, 2012, 06:45:35 AM

WoW, I shoot a 1377c carbine with a 16" barrel, I need to look more into that flat piston, I would be happy with a honest 600fps using 7.9 crhp's, I need to look into a crony also.

Title: Re: 1377 and estimated FPS
Post by: 0351_Vet on February 24, 2012, 09:44:29 PM

Custom 1377-10 pumps 670fps with Meisterkugeln 7.0 Grain Wadcutters, very accurate.
MAC1 prepped 12" barrel. AC Custom flat top piston and valve.

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Crosman air pistol - General => Crosman air pistol - General discussion => Topic started by: mcc1961 on February 24, 2012, 02:43:32 AM