Range Report 5.56mm 75gr SMK vs 77gr SMK

[USACS]

Has anyone noticed a major difference in long-range accuracy between the 5.56mm 75gr and 77gr SMK? I am building an SPR/Mk12 and will be making shots between 600-900yds for the long-range portion of shooting. I'm wondering if there's a major difference between the two, or if the differences are minimal to non-existent.

The rifle barrel would be either the DPMS mini-SASS 18" 1:8 twist or Noveske SPR 18" 1:7 polygonal twist. (still can't decide).

TIA

 

[Chiller]

Re: 5.56mm 75gr SMK vs 77gr SMK

900 yards?

isn't that pressing what a .223/5.56 can do on a regular basis?

 

[agent-smith]

Re: 5.56mm 75gr SMK vs 77gr SMK

If you want a "legitimate" 900yd rifle, I don't think that a .223/5.56mm is the best choice.

Yeah, of course it can be done, but it isn't the best choice.

 

[USACS]

Re: 5.56mm 75gr SMK vs 77gr SMK

Realistically, I won't be shooting this thing to 900yds much at all, but a couple SPR courses I'm going to be taking have shooting out to 900yds and they all recommend 77gr. I'm trying to figure out if there's a major difference between the 77gr and the 75gr, since I can't use reloaded ammo and factory 75gr match ammo is significantly cheaper.

 

[jrob300]

Re: 5.56mm 75gr SMK vs 77gr SMK

I'm assuming by 75g, you're referring to the Hornady bullet?

All rifles are different, but I loaded Nosler 77's, Hornady 75's and Sierra 77's with identical loads in .3g increments from slow to scary velocity/pressure and at every load the Nosler groups were the smallest, followed closely by the SMK's and trailing well behind were the Hornady's. I never found a load that shot them well (best was 3 MOA+) in my rifle (MP15 w/1:9) Yes, I know that 1:8 is the min. recommended twist. I try stuff.

The Nosler's could be made to shoot sub-MOA.

FWIW

John

 

[USACS]

Re: 5.56mm 75gr SMK vs 77gr SMK

Yeah, 75gr would be Hornady Match bullets by either Hornady or Black Hills. 77gr SMK would be SSA or Black Hills.

 

[USACS]

Re: 5.56mm 75gr SMK vs 77gr SMK

Does anyone have an opinion on 1:7 twist versus 1:8?

 

[Shooter21]

Re: 5.56mm 75gr SMK vs 77gr SMK

1:7 will stabilize the 90 VLD and a 1:8 is maxed out at 80s. The 77SMK turns into a parachute at about 800. The 75 AMAX, 80 AMAX, 80 VLD, and 77 Nosler are a better choice. I got 9.557" at 1100 with 80 VLD once

 

[AUJohn]

Re: 5.56mm 75gr SMK vs 77gr SMK

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Chiller</div><div class="ubbcode-body">900 yards?

isn't that pressing what a .223/5.56 can do on a regular basis? </div></div>

god, I hope not. Would hate for all those Fclass shooters who use it every weekend to find out

There are some using 20inch Tikka's doing 1K, so anyone who can get the speed (safe loads) with a fast twist has no issues. Of course, you need to use the correct projectile. As you do with the .308.

.223 and .308 are quite similar out to 1k. .223 is a bit harder. I use it as it's cheap and harder. I need to read the wind better for the same results.


OP, there can be a HUGE difference in accuracy depending on the projectile. I run the Amax's. I prefer the 75's but the 80's are legal for comps and much cheaper here so that's what I use.