77gr .223 for AR platform?

[d'zaster]

Hey Guys,
I have a pile of 77gr sierra match king bullets and wondering if anyone has experience with such a heavy bullet with AR platform. I heard that it's too heavy and would beat up the gun. My AR has a 1:8" twist and is quite accurate with 60-62 grain bullets.

Comments/suggestions are appreciated.

Gary

 

[Llama Bob]

It's not too heavy at all and will not hurt your gun. You need a 1:8 twist or faster barrel, which you've got. Load data is available in many places, including from Hodgdon online for free. Many powders in the 4895 burn rate range work well.

The military loads that bullet as the M262 (mod 0 or mod 1) long range load. Mod 1 has an added cannelure on the bullet. It's used for the Mk12 special purpose rifle among other uses.

 

[BrocLuno]

Look at the tread about IMI 77 grain bullets. Good info there. No need to worry. 77 grainers are issue to the designated marksman in a squad.

https://www.thehighroad.org/index.p...core-77gr-smk-5-56-ammo.817996/#post-10488488

 

[Varminterror]

77 SMK's are hot business for 1:7 and 1:8" AR's. They're made to fit in AR mags too, which is a bonus for such heavy bullets in their class.

With such a small case, they won't win any drag races, but for long range punching, the 77SMK's are tops.

 

[Pete D.]

I have been using 77 grain Sierras for years. Propellant of choice is RL-15. Winchester factory primed brass. Colt Match Target AR with a 1-8 twist barrel.
Shoots just fine.

 

[Robert]

My 1:7 parts bin AR loves the 77 great SMK. I am running them over 4064 with very accurate results. 5 shot groups the size my thumbnail at 100 using my rage badge for a rest and a 4x ACOG.

 

[wally]

I asked on the NFA forum, but so far no response. Does anyone shoot these suppressed? It won't take much initial yaw with such a long bullet to potentially cause a baffle strike, which is why I'm asking.

 

[Llama Bob]

I asked on the NFA forum, but so far no response. Does anyone shoot these suppressed? It won't take much initial yaw with such a long bullet to potentially cause a baffle strike, which is why I'm asking.

Yes, I shoot them suppressed. TBAC Ultra-9 .30 cal can, so lots of space in there. No problems other than a hot, dirty gun.

 

[wally]

Yes, I shoot them suppressed. TBAC Ultra-9 .30 cal can, so lots of space in there. No problems other than a hot, dirty gun.

I'll be using a 5.56 suppressor, so your experience doesn't necessarily apply, But thanks for the response.

 

[Varminterror]

I run them in a 22 cal Ultra 7 and an OSS Helix. Nary an issue thus far. Have ran a lot of 75grn A-Max's too, which are far, far longer than the 77smk.

 

[md7]

1:7 and 1:8 aught to handle 77 grain SMK's well.

Load em up and get after it!

 

[wally]

I run them in a 22 cal Ultra 7 and an OSS Helix. Nary an issue thus far. Have ran a lot of 75grn A-Max's too, which are far, far longer than the 77smk.

Thanks, I won't be afraid to give them a try now.

 

[Varminterror]

If you have crown issues or your threads aren't true, baffle strikes happen. Just because they've worked for someone else doesn't mean you shouldn't do some checking for concentricity before blowing a $1,200 can off of your barrel.

 

[d'zaster]

Hi All,
Thanks for the great inputs!! OK time to dial-in a new pet lead

Gary

 

[d'zaster]

Look at the tread about IMI 77 grain bullets. Good info there. No need to worry. 77 grainers are issue to the designated marksman in a squad.

https://www.thehighroad.org/index.p...core-77gr-smk-5-56-ammo.817996/#post-10488488

Thank you, BrocLuno.
I saw that right after I posted. Much appreciated.
-Gary

 

[wally]

If you have crown issues or your threads aren't true, baffle strikes happen. Just because they've worked for someone else doesn't mean you shouldn't do some checking for concentricity before blowing a $1,200 can off of your barrel.

Been shooting 55/62 grain bullets with this can and rifle for a long time. Just wasn't sure about using the 77gr bullets.

 

[MrSpiffy]

Just tested my first reloads, which included 77gr SMKs. They worked well in my 1:7 twist 18" barrel. If you dont want 'em, send 'em my way.

Distance was 100yds, powder is Vihtovuori 140. Dots are approx. 1" in diameter. Got my load data here.