Calibers for UAS/HS

[Chuck40]

I am just getting back to IHMSA after a long layoff, and want to put together a UAS/Half Scale gun. I am looking at a 300 Whisper/Blackout, since I know that works and works well. 125 grain bullets for Half Scale, and 150 to 165 for big bore, no worries.
Having said that, flat and fast is always a good thing. I have been told that nowadays, you can actually get away with 223/222 Mag with 80 - 90 grain bullets for BB. This sounds a little bit marginal to me. I always thought 105 6mm was the bare minimum.
Does this actually work?

[aggshooter]

Welcome back Chuck! It has indeed been a long time.

There are a couple guys in Oklahoma that that are running a 7 twist 223 improved or 222 mag improved. I have seen some less than perfect scores from them, so only they can tell you if it is 100% or if there is an occasional stuck ram. If I were going to rebarrel with a 223 boltface ( the typical 12-14 factory twist isn't fast enough) I would look more to an old school 6x47 based on the 222 mag with a 7 or 8 twist. Just open the neck and run any bullet you want.

You may want to check with Greg on his targets. A lot of us have pre AR-550 steel targets and 2200-2300 fps is about the limit. My Rampro 222 with 80 grain bullets will chrono 2400, I have only shot BB one time with it. Normally it's a half scale gun. With a scope, it's pretty easy to shoot BB rams in the head or above center body.

I also run a fast twist 6br loaded with a sissy amount of discontinued SR4759. 85 grain thru BB turkeys and all of half scale. 100-105 grain on BB rams and some 500 meter stuff. I can't recall ever losing a 200y ram, but I rarely shoot full size with it.

Rich

[JACKIE40X40]

I am just getting back to IHMSA after a long layoff, and want to put together a UAS/Half Scale gun. I am looking at a 300 Whisper/Blackout, since I know that works and works well. 125 grain bullets for Half Scale, and 150 to 165 for big bore, no worries.
Having said that, flat and fast is always a good thing. I have been told that nowadays, you can actually get away with 223/222 Mag with 80 - 90 grain bullets for BB. This sounds a little bit marginal to me. I always thought 105 6mm was the bare minimum.
Does this actually work?

Three of us,at OKCGC used the 223 Improved.Me personally, I used a 1x8 twist Shilen Rachet barrel,with the 75 Amax.
No problem for 3 seasons.Rich is 100% right go with a 6mm & what ever bolt face you have.

[Chuck40]

Thanks, gentlemen! You are the folks I wanted to hear from!

[jmoore]

FWIW, I managed a 60x60 UAS last match using a 1-7 twist .223 Wylde Green Mountain barrel slapped onto the front of a manually operated AR kluge pistol. 88gr Hornady ELDs worked fine on both free standing and hinged Rams. That included some pretty low body hits, as my usual zero wasn't spot on!
I think the long dwell time helps.

We found out last year that 60gr bullets don't always take BB Rams even with higher hits. 75 and 77gr bullets launched from the .223s have worked except with very low hits over the past three years or so. (Unlimited and UAS)

[nutcase]

Me personally, the 300 whisper would be the more versatile caliber. You can push up to match the 7TCU or download down to subsonic and have very low recoiling load.

The .223 can be marginal Especially with a Factory contender barrel as the twist rate is too slow for any bullet over 60grs.

[braud357]

I would have to vote for the 300 B/O (Whisper). You could shoot anything from 100 - 220 grain bullets with a fast-twist barrel, and recoil is light

[THE300BLK]

I run an AR pistol in 300 BLK with a 7.5” barrel and a Vortex red dot. It’s my truck gun, but I’ve been able to use it as UAS/UASHS and have never had a problem knocking them over. I run 17 gr of IMR 4227 behind a Speer 125 gr TNT HP and can stack rounds at 200m from a bench. Velocity out of the short barrel is 1675 all day long and has knocked over everything I’ve hit. The red dot is a little large for half scale, but I still managed a 29/40. Barrel twist is 1/7. Recoil is nominal.