20 GT AI (First Shots Fired)

[ZenArchery]

This little fire crackers is accurate tested 3 or 4 different powders. All held under 1.25MOA.
Un-fire formed case holds 43.2gr H20
Fire formed case holds 45.5gr H20
GRT predicting around 4200-4300 FPS with fully fire formed cases using 40gr bullet. So basically 22-250 velocities with same 40gr bullet weight.

 

[urbanrifleman]

Keith Olson was getting pretty close to that with the 40 Vamx in the 20 Sploder (20 223a) in my barrel.

 

[urbanrifleman]

@Gabe22BR what were you getting with the 20bra with the 40? Or did you shoot that bullet?

 

[chuckshooter]

I don't always use a dime to show my group size, but when I do, it's this dime.

 

[Gabe22BR]

@Gabe22BR what were you getting with the 20bra with the 40? Or did you shoot that bullet?

All depends on if you want accuracy or velocity…
Can’t have both!!!!

I don’t shoot Hornady bullets… use to fireform only..

 

[Tommie]

All depends on if you want accuracy or velocity…
Can’t have both!!!!

Really?

 

[Gabe22BR]

Lose primers or make single holes @ 100yds-
Take your pick….

 

[Gabe22BR]

I like the 20GT AI ideal !!!

 

[urbanrifleman]

All depends on if you want accuracy or velocity…
Can’t have both!!!!

I don’t shoot Hornady bullets… use to fireform only..
View attachment 1585051

Does that say 4490fps?

 

[RegionRat]

BTW, just for fun I wondered about the rev rate the OP's bullets were seeing.
For example, the ones at the 1:43 mark in the video were showing 4113 fps, so...
(4113x720)/8= 370170 RPM

Pretty wild rev rate! Even the ones at 3900 were doing 351000 RPM!

Just wondering out loud since the AR and these powders are in a little uncharted water till you get some fire forming shots... would it be wise to maybe shut off the gas system just till you fire form and then use GRT to estimate the port pressure?

ARs are really hard on brass, but especially if the port pressure gets higher than normal. And since fire formed brass gets sort of precious, I am wondering if the brass might survive the experimental stage a little better in places were the port pressure wants to rip them out of the chamber too soon?

I'm kinda liking the sound of the GT case for a 20 cal wildcat. The case volume seems about right for a Berger 55 with H4350?

 

[806guns]

I'm planning a Howa mini 20 grendel with 55 bergers. Current reamer is shooting them at 3960 fps

 

[Bodhisafa]

Thinking about a 20 GT, what powders will give the best case fill