16 inch barrel with 1:8 twist

A

adam1122

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Full Member
Minuteman
Aug 10, 2010
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Tx
#1
Does anyone else own an M4 style weapon that has this twist rate? If so, what ammo does the barrel like? I don't plan on shooting any further than 350-400 yards max as I am just using iron sights or a Aimpoint with non magnification.

Need two reccomendations
1. Target ammo that is brass and not Wolff for practice.
2. Best hunting round out there for killing swine and varmints and every once in a while maybe a whitetail with this kind of barrel.

I live is Texas so that's why I'd like to know what works well on swine. It's a smith and Wesson m&p rig.


Thanks gents.
 
#7
Re: 16 inch barrel with 1:8 twist

P415 w/16.5" 1/8 barrel.
Hornady 223 75 gr Practice - 2550 fps. Steel case, but burns clean. 0.44/rd
Hornady 5.56 75gr. BTHP T2 - 2700 fps. Excellent to 400 so far. Still running over 1800 fps at 400 yds. 1.45/rd unless you are LEO.
Black Hills 5.56 50 gr. TSX - 3175 fps. Full expansion to 200 yds. 1.38/rd.

With the Hornady T2 zeroed at 100 yds, the TSX is +2" at 100, and spot on at 200. The TSX is sub MOA no problem.

The Corbon 70 gr TSX did not stabilize well in this 1/8 barrel.

Will be trying the Corbon 223 62 gr TSX next.
 
#8
Re: 16 inch barrel with 1:8 twist

I use lots of PMC 223 ammo in my carbine it groups between 2 and 3 moa which is all you need. Hunting wise I think there are a few 64grain soft point bullets out there I would handload with those.

If you want accuracy ditch the aimpoint for a magnified optic and handload with a match bullet. My 1:8 group the best close in with 52bthp loaded light.
 
#10
Re: 16 inch barrel with 1:8 twist

So what is the best ammo to zero by gun? I am torn between zeroing with the can on first or after I shoot without it?

Ultimately this one wil be shot without a can, however, I will still need to knw POA/POI so I can adjust.
 
#11
Re: 16 inch barrel with 1:8 twist

I need to use my google skills to see what I can find on what it best for zeroing a 16in M4 with 1:8 twist.....with or without a ca.

Yall please send me what works best in your rig anyways. 75-77gr seems to be the consensus so far.

Thanks again.
 
#13
Re: 16 inch barrel with 1:8 twist

Whats the cheapest place you have found Hornady 75's for? I've looked around quite a bit and while I sight in with quality ammo I will plink with surplus or 55gr cheap stuff. Just no Wolff
 
#14
Re: 16 inch barrel with 1:8 twist

If you can shoot 5.56 and want more velocity than the 223 round, the Hornady LE T2 TAP 75gr 556 NATO round is sold by GandR Tactical for $29 a box, when they have it in stock.

Occasionally I find a private sale, but typically no less than $22 a box.

LEO/Military can get a case of 200 for $135 at LESales
 
#18
Re: 16 inch barrel with 1:8 twist

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: D.Draig</div><div class="ubbcode-body">The 70 TSX is great, but needs 1:7 barrel to stabilize. It's marginal in a 1:8. </div></div>

70 is almost perfect for a 1:8 barrel. 75+ is where you start seeing a benefit from 1:7
 
#20
Re: 16 inch barrel with 1:8 twist

It would depend on the individual bullet, as weight in grains is really just a way to approximate length for a given caliber. Right? I think the weight distribution probably matters more than overall weight, in terms of twist.
 
#21
Re: 16 inch barrel with 1:8 twist

I'm not a ballistics expert, but did come across an article discussing the ability of the 70 gr TSX to stabilize in various barrels. Since it is solid copper, it is longer than a 77 gr SMK and it's specific gravity is much lower.

Quote:
<span style="font-style: italic">Besides being a long bullet, the 70 grain TSX has a specific gravity much lower than a copper jacketed/lead core bullet due to its sold copper construction. For example, the Hornady 75 grain BTHP has a specific gravity of approximately 10.3, while the Barnes 70 grain TSX has a specific gravity of only 8.9.

The Barnes 70 grain TSX will be unstable from a 1:9” twist barrel with a gyroscopic stability factor of less than 1 at all velocities. The 70 grain TSX will only be marginally stable in a 1:8” twist barrel with a G.S.F. of 1.05 at 2500 fps. A 1:7” twist barrel will produce acceptable stability with the 70 grain TSX with a G.S.F. of 1.37 at 2500 fps.</span>

Even if I could get 2730 fps (SSA's quoted velocity) in my 16.5" barrel, velocity drops to 2443 at 100 yards, meaning it is not going to be reliably stable at this range. Believe you me, I really wanted this bullet to work for me, but when I tested it, accuracy at 100 yards had degraded to about 3 MOA. I didn't get key holing at 100, but this barrel typically shoots sub MOA. Depending on velocity, the 70 gr TSX may be stable in a 1:8 at 50 yards, but it wasn't at 100.

You can check out the article here: Barnes 70gr TSX

Of the solid copper Barnes bullets, it is my belief that the 62 gr is the heaviest that will stabilize in a 1:8 barrel.
 
#22
Re: 16 inch barrel with 1:8 twist

Usually when we say 80gr we're talking about the 80gr SMK for highpower and long range use. The 75Amax works but must be single fed. the Berger VLDs work too.
As for 70TSXs out of an 8...don't know never tried them
 
#23
Re: 16 inch barrel with 1:8 twist

Sounds like I get to go buy 5 different types of ammo and see what will work best out of a 1:8 barrel. What a pain in the ass. Maybe if I can get an armorer or somebody on the phone at S&W they will they me what they see best under their test fire conditions.
 
#24
Re: 16 inch barrel with 1:8 twist

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SteelShot11</div><div class="ubbcode-body">Sounds like I get to go buy 5 different types of ammo and see what will work best out of a 1:8 barrel. What a pain in the ass. Maybe if I can get an armorer or somebody on the phone at S&W they will they me what they see best under their test fire conditions. </div></div>
69gr SMKs loaded to 2.28 OAL 24gr Re15 CCI450 primers. That load will shoot less than 1/2" if the barrel is good.
 
#25
Re: 16 inch barrel with 1:8 twist

The rounds will be coming out of a smith & Wesson m&p 16in barrel that has their melonite coating on it. I expect it to shoot the same as pretty much most decent barrels. It's no Kreiger but it should do just fine for my purposes.

So now I just need to go buy a bunch of different ammo types......zero it with the best kind and then stick my suppressor on it and re-zero it with the can. I wonder if shooting it with the can on the gun will like a different grain ammo or it will like the same as without the can. Too many damn variables. I think I will just go out and shoot it until I can get it to groups around 1" is good enough for me.
 
#26
Re: 16 inch barrel with 1:8 twist

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SteelShot11</div><div class="ubbcode-body">The rounds will be coming out of a smith & Wesson m&p 16in barrel that has their melonite coating on it. I expect it to shoot the same as pretty much most decent barrels. It's no Kreiger but it should do just fine for my purposes.

So now I just need to go buy a bunch of different ammo types......zero it with the best kind and then stick my suppressor on it and re-zero it with the can. I wonder if shooting it with the can on the gun will like a different grain ammo or it will like the same as without the can. Too many damn variables. I think I will just go out and shoot it until I can get it to groups around 1" is good enough for me. </div></div>
I'll just about bet that the actual twist rate of that barrel is 8.5 if you slug it, I know who makes them. The 69 SMKs should shoot well, the 77s will probably be right on the line. don't waste your money on the 75Amax it will be too long.
 
#27
Re: 16 inch barrel with 1:8 twist

Practice ammo that is brass and not Wolf - Federal XM193. I just bought 500rds for $175.

For hunting...would make sense to use a heavier round...especially for hogs/deer. My test target from my 16" OBR 5.56, 1 in 8, came in at .585" at 100yds with a 77grain...so they can work well. Test out several different boxes and see what works with YOUR rifle.

IMG-20120212-00007.jpg


Good luck and have some fun with that MP15!!!
 
#30
Re: 16 inch barrel with 1:8 twist

Black Hills, FGMM can be purchased from a number of vendors. I usually try to wait until Midway has a sale and buy a bunch. You also might take a look at Southwest Ammunition. They have 77 grainers in both Match and Run-N-Gun loads. The Run-N-Gun is a little less expensive, but quality ammo.
 
#31
Re: 16 inch barrel with 1:8 twist

Here is my 16", 1:8 twist and shooting 600 yards.


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#32
Re: 16 inch barrel with 1:8 twist

I strictly use Southwest Ammunitions's match load (Lapua and Win Brass new) in my DMR .308 rig and it is fanf**kingtastic. Im sure their 223 is just as good just havent checked the prices out just yet. I would like to buy a couple small boxes of ammo to see how the weapon shoots with each and then go back and buy a case or so of it.

The sheer number of manufacturers and even surplus ammo for 223 on the market right now is a little daunting. Im used to having to search hard for good quality surplus .308 and then paying out the yin yang for match/hunting ammo that.
 
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