Specialty Pistols
6-223 or 6mm TCU twist rate?

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June 22, 2020, 07:13 PM
Steelkiller
6-223 or 6mm TCU twist rate?
I bought a 6-223 xp custom built used. No info on the twist rate of the barrel. When I finally got a cleaning rod to turn by pulling the patch through, I measured 12" . Was this caliber designed to shoot very light bullets? I can't get anything over 75 grains to shoot very accurately.
June 22, 2020, 07:38 PM
Bobby Tomek
Stability relates more to length than weight. A 1:12 will likely do OK with an 80 grain flat-based bullet.

I've had several 6mm-.223s over the years and preferred a 1:8, which handles everything from the little 55 grainers through much longer/heavier target projectiles with terrific accuracy. Back then, I primarily used the 80 grain Sierra SSP.
June 22, 2020, 07:54 PM
KYODE
Myself, I wouldn’t do a small six with less than 10” twist. I have at least 3 barrels with that rate. That said, my ott 15” 6tcu has 12” twist that has shot an 80gr nosler bt great.


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June 22, 2020, 07:59 PM
KYODE
I think it would do its best with 80gr and lighter. What are you doing with it?


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June 22, 2020, 08:10 PM
Steelkiller
I am trying to shoot 1/2 scale IHMSA silhouettes. 80 and 85 grain Sierras with 22-24 grains of H322, Fed SR Match primer, and Starline brass. Best groups are barely under 3 inches at 100 yards so far. It's "enough gun" with those bullets, but I need to get to 1" ctc with anything to at least give myself a chance. What's a standard twist for a 243 Winchester? They shoot 75 grainers well in a rifle I once shot.
June 22, 2020, 08:20 PM
KYODE
1:10” with most 243s id bet.

Will a 70gr knock over 1/2 size? Id think so??? but im not a steel shooter by trade. Razz


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June 22, 2020, 09:43 PM
aggshooter
quote:
Originally posted by Steelkiller:
I am trying to shoot 1/2 scale IHMSA silhouettes. 80 and 85 grain Sierras with 22-24 grains of H322, Fed SR Match primer, and Starline brass. Best groups are barely under 3 inches at 100 yards so far. It's "enough gun" with those bullets, but I need to get to 1" ctc with anything to at least give myself a chance. What's a standard twist for a 243 Winchester? They shoot 75 grainers well in a rifle I once shot.


I suspect if you go back to 70 or 75 grain bullets and it will do everything you want it to. I have a 6x47 rifle (6mm on 222 mag case) with 1:12 twist and it shoots in the 3's with 70-75 grain bullets. It will not stabilize 80 grain or more. In the case of 1/2 scale, a friend here shot it with a 22 Hornet and toppled rams. I have never lost a 1/2 scale target with a .222, so yes, the light bullet weight is plenty.

If you shoot paper with the heavy bullets, you will probably see the bullet going sideways thru the paper (enlarged holes) at 100m because it isn't stabilized. Shooting lighter bullets is much cheaper than rebarreling and shooting heavy bullets. You're shooting 200m at a top heavy, 12 pound target balanced on 2 legs. You're not trying to drop a 300 lb mule deer on the spot.
June 22, 2020, 10:30 PM
braud357
I have been trying to work up a 6 TCU for the past 1.5 years. granted, I have had few opportunities to shoot it. Mine has a 1-8" twist, and was supposedly very accurate with Nosler 107 grain bullets. I am also trying to shoot it prone, with a rifle scope, so I was trying moderate loads. The accuracy results were like yours - not very good. I decided to try a lighter bullet, and tried some Hornady 87gr. V-Max, with AA 2015 powder. I was finally able to match-test it this past Saturday. I fired it in full-size UAS, and easily fired a 40x40 with it. The accuracy achieved was easily accurate enough for half-scale. My conclusion is that I was probably not pushing the heavier bullets hard enough, but it certainly seems to like the 87 grainers !
June 22, 2020, 10:32 PM
jsh
If that’s all ya want, H335 and 70 grain TNT. I used LC brass.
The TNT will fly flat and I never had a ringer on 1/2 size hand set targets. Full size, go to a good full throttle load with an 80 and ya should be good, shoot rams low in the ham and they should pivot off with hand set.


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June 23, 2020, 08:51 AM
shot1
Back in the 1970's Bob Milek writher for Gun's and Ammo was the pistol guy. He had a bolt handgun made in 6mm-223 and I believe it had a 12" twist and he could not shoot bullets over 80 gr. If memory serves me correctly he built the pistol with varmints in mind then tried to switch up and use it for deer. I think he was shooting a 75 gr bullet but found that he could only trust a neck shot. I got a Contender barrel in a estate sale that is 14" in 6mm-225 Winchester which has a 12" twist and it will not shoot anything over 80 grs that I tried. It shoots the now discontinued Sierra 80 gr SSP bullet GREAT. Doc EV-Hitman suggested that I give the Nosler 85 gr Partition a try because is worked for him in 12" twist. I got some but never tried them because I got a 30-30AI barrel to deer hunt with. I did not like the results of the 80 gr SSP on deer. It expanded too quickly for me and would not exit on the 50 to 125 yard shots I was getting. Last few deer I killed with it I settled for neck shots.
June 23, 2020, 09:27 AM
shot1
Sometimes it pays to be a pack rat. I found an old G&A Handgun Annual 1984. It has Bob Milek's further experimenting results with his 6mm-223. He states that for mule deer you need more bullet but for pronghorn he found that these two loads worked just fine.
Speer 80 gr Spirzer H322 25.0 grs Rem. 71/2 primer, Federal case 2693 fps.
Sierra 85 gr HPBT, H322 24.5 grs Rem 7 1/2, Remington case, 2712 fps.
June 23, 2020, 03:34 PM
Steelkiller
Smile Ok! thanks for all the great comments!
June 24, 2020, 06:04 PM
Bobcat
My 6mm Mongoose has an 8 twist and shoots everything from 55 grains up to at least 100 well, I have not tried anything over 100 yet. I have an Encore barrel in 6mm-.284 12 twist that I haven't had any luck with anything over 85 grains yet.


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June 25, 2020, 10:06 AM
WV Hitman
I had a SSK 6mm/.223. Don't know the twist, probably 1:10, but it shot great with 70 gr. BTs, 70 gr. SXa. Killed 10 or so deer with the BT. All ran 30-70 yds. Always used H322 in it. I doubt if 10 gr. will make a difference in performance for shorter shots, but may on longer shots.
June 26, 2020, 08:59 AM
Jay HHI6818
I shot 1/2 size a few times with 221 FB with 60 grain bullets and it took the rams which were free standing targets.
70’s or 75’s will work for you
June 26, 2020, 11:47 AM
old leghumper
I've said before and I will say it again - USE a ballistic stability program
http://www.jbmballistics.com/b...rs/calculators.shtml


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