Well I want to use an AR for both target practice and varmint hunting,mostly the latter. I have a bunch of older varmint bullets laying around and have shot some of them out of a 1-7 twist barrel and no things did not go well. This rifle is a fine shooter using 75 gr. Hornady BTHP match bullets but unless the bullet has a plastic tip or a hollow point as in a match bullet it will tumble bullets in the air hitting my backstop almost sideways at 50 yards. The bullets are often in good condition other than the jacket has peeled out from the lead tip and I guess that catches enough wind to destabilize the bullet, some actually come apart. Interesting how much energy a tumbling bullet loses as the bullets end up just a bit better than 1/2 buried in the plywood. So I won't shoot any bullets longer than the 75 gr BTHP mentioned above, this bullet shoots just fine out of my Remington Model Seven 1-9 twist barrel so it should out of an 16 inch barreled AR. If not I could easily get by using 68-69 grain bullets if I just had to. Commonly available twists are 1-8,1-9, is there any reason to pick the 1-8 if most of the bullets I shoot will be between 50 and 62 grains? And I am thinking about getting a 223 Wilde chamber, good or bad idea?

My duty rifle is a 1:8 twist and it handles 55-75 grain bullets just fine. My 1:9 twist doesn’t like anything over 62 grains and even at that it’s not very happy.

I think all 223 wyldes are 8 twist. Wylde is pretty ideal for any bullet typically shot out of an AR.

My Model Seven will shoot Hornady 75 gr. HPBT into tiny groups. It is a Predator model with a 22 inch barrel and a 1-9 twist. It actually shoots nothing better but several other bullets just as well.

Maybe the older thin jacketed lead tipped varmint bullets are not the typical AR bullet though. I have a big stash of 45 grain Hornady spire points I would like to burn up also. I probably would be well served with a 1-10 or 1-12 twist.

I own three .223’s:

24” 12 twist bolt gun- it loves the light stuff up to 60 grains. Favorite of the three for varmints with light bullets.

22” 9 twist bolt gun- it shoots 50 grainers up to 77 grain SMK’s very well. It does not however shoot the long profile heavies worth a dang.

16” 7 twist AR with a .223 wylde chamber- it shoots 55’s on up through the long and heavy projectiles equally well even though velocities do not approach what I get in the longer barrels. Fun target gun and works best of the three for long heavy projectiles I like for targets. The twist is too fast for the light Bullets I prefer for varmints.

My thoughts:
If I was setting up an AR for varmints, I would go with a 20” 9 twist.

I don’t have experience with an 8 twist but If I wanted to throw targets in the mix I would try a 20” 8 twist. Hopefully the guys that shoot 8 twist barrels will comment on what they do well.

If I also wanted to add home defense to the mix, I would sacrifice velocity for the handling of a 16” barrel.

I have shot 55 grain varmint bullets out of an original colt HBAR 1:7 with no problems. All the way up to 75 grains worked fine. Same with a 1:8 Rock River. I saw a guy shooting 100 yards and doing well but could not stay on paper at 200 scoped. Found similar sideways bullets on his target. Turned out his barrel had copper fouled. Ended up taking 50-60 patches and and hour to get the copper out. After that it shot great. He swore the barrel was clean. Turned out he had fired a couple TSX bullets and somehow they either fouled the barrel or it was fouled and they made it 10X worse.

1/8:wylde

You are actually thinking 180° from what is really going on.

Jackets coming off is from over spinning them. Not from lack of twist rate. 1:7 is a very aggressive .224" twist and will like long, heavy bullets.

Search "rifle barrel twist rate chart" there are several available for every bore size there is.

1:8 in my 556 Rock River and it eats up everything from 55 to 75 with no complaints. Haven't tried anything lighter than 55.

I think that is exactly what I was saying, that the fast twist is over spinning the old style lighter varmint bullets. Especially 50 grain bullets.

The first barrel I had on the AR was a 7 twist. It worked fine on bullets from 40 gr to 65 gr. It just wasn’t accurate enough to suit me. The barrel in place now is an 8 twist, which handles the same bullets quite well. The OP’s problem is probably not the twist rate, but a bullet issue, which I think has already been suggested.

I probably have some old match bullets in the bullet pile. Either 52 or 53 gr Hornadys, I think. Maybe I’ll give them a try in the next loading session, and see what happens.

Was the OP using old Sierra Blitz bullets? I think Sierra went to Blitz King bullets because the old Blitz bullets were prone (under some circumstances) to fly apart.

A variety of bullets, Hornady, Speer and Sierra, not the SX or Blitz versions. Mostly 50 and 55 grain old style soft points. I have lots of them. Some like you said just don't shoot well enough but make it to the target. All of these bullets work in the Model Seven Predator. I have had no problems with match HP's. My first barrel I had on an AR was a 1-12 twist. Way back then it was a popular twist rate. Wish I still had that old SP1.

Does barrel length matter with 1:8 twist?

What’s the difference between Winchester 55 gr. and 62 gr. Green tip, besides bullet weight? Is the 55 gr. a lead tip, and green tip a plastic ballistic tip? Is a stripper clip for ease of loading into magazines?

Ttt

I’m not sure I understand the question. Barrel length and twist impact stability. Is there a specific barrel length and bullet you are asking about?

Green tip has a small metal core and is considered to be, “light armor piercing”. Most any range out there will not allow you to use green tip ammo.

The above conversations are about barrel twist and bullet weights. There’s not much mention about barrel length, and I see AR barrel lengths 16”-20”.

16” 8 twist would work with anything 77 grains and under.

Thank you!