Minimum Barrel Length for Long Range Suppressed

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12 years 10 months ago - 12 years 10 months ago #9867 by txlongshotb4
Minimum Barrel Length for Long Range Suppressed was created by txlongshotb4
I need some help from the Gurus here.

My AR10 is currently sporting a 24 inch heavy barrel. It is also sporting a Gem Tech HVT Suppressor which is about 9.5 inches long. Thus, I have 33.5 inches of weapon system on the mean end of my receiver group to contend with, and that's not a lot of fun to tote around, particularly in the woods.

My intent when I built my rifle was to build a gun that would A-hit at 1,000 meters and B-be a superior weapon the the Knight's M-110 that I've used in the Army, mainly because I am sick that they cost so much and are so terribly...well...terrible. In my opinion I have achieved both tasks.

Recently, I attended a training event that has changed a lot about my way of thinking concerning long range marksmanship. During the training event, we spent several days on a known distance range shooting stock grade military issue M-4 rifles equipped with Trijicon ACOG optics at ranges from 200 to 800 meters. Before this training, had I been told that the M4/ACOG combo was an 800 meter capable system, I would have staunchly disagreed.Now, having both seen it done and done it myself, I cannot help but to agree. It set the wheels upstairs to turning. If I can hit my target at 800 meters with a .223 from a 16 inch barrel platform, then do I really need 24 inches of barrel on a .308 to do the same?

Back story told, what I am requesting here is a little help from the gang. I am thinking about either re barreling my gun, or having the existing barrel cut down and turned.I'd like to know if any of you guys out there are shooting 16 inch barrels, and what they are doing in terms of muzzle velocity, say with a 175 grain or 168 grain match bullet like Federal Gold Medal or Black Hills Match-or even better, military grade M-118LR.

My second question, and this goes out to the suppressor guys, is a question of minimum barrel length for a .308 in regards to NOT burning out my baffles with over-pressure and excess heat build up due to having my barrel too short. Does anyone out there know the guidelines for such a thing, or where to look for them? I know that Gem Tech isn't going to quote me any information to avoid liability here.
Last edit: 12 years 10 months ago by txlongshotb4.

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12 years 10 months ago #9872 by LebbenB
Replied by LebbenB on topic Re: Minimum Barrel Length for Long Range Suppressed
I chrony'd unsupressed M118LR out of my AR10A4 carbine at ~2600 FPS. That means the bullet is just starting to go trans-sonic out at 800m or so. The big advantage to a 16-18" barrel is the shorter barrel is less prone to droop/muzzle whip as the barrel heats up. This is particularly important when you hang 8-10 inches of supressor on the end of it.

As far as burning out your baffles goes, minimum .308 barrel length for complete powder burn off is (IIRC) 15.5 inches. So I would think that a 16 inch barrel would be the shortest you would want to go and not have undue wear and tear on the can.

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12 years 9 months ago #10174 by weshowe
Replied by weshowe on topic Re: Minimum Barrel Length for Long Range Suppressed
txlongshot,

I'm shooting a G.A. Precision AR-10 with a 20" barrel and flash hider, but have just ordered a GemTech HVT. When it clears I'll try to get some solid ballistic data for you.

Right now I'm chronographing M118 Special ball at 2,624 FPS from my 20" Schnieder barrel. That's the old load with 173 gr boatail FMJ.

A handload with 190 gr SMK's is giving me an honest 2,500 FPS from the same tube.

How do you like your HVT? Any issues?

Wes

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12 years 9 months ago #10194 by txlongshotb4
Replied by txlongshotb4 on topic Re: Minimum Barrel Length for Long Range Suppressed
Wes

Good choice on the GAP rifle...I own two of George's bolt guns and I have yet to find a rifle out there that can out shoot either of them.

Also, good choice on the HVT. I got the QD model, and I am very pleased with it. The accuracy is great, and the point of impact shift is only about .5 MOA.

I have only two small issues with the HVT.; First,the weight. This is a pretty heavy can, and I have a 24 inch barrel, so it's way out there. Gemtech makes a titanium version of the same can called the sandstorm, but it's quite a bit more money. Second, I have to put about 3 to 5 rounds downrange before the can gets hot enough to maintain a solid zero. I suppose this has to do with the gun/suppressor heating up to it's "sweet spot". My cold bore shot starts out about 2 inches out to the 9 o'clock position, and over the course of the next 3 to 5 shots (depending on how fast I send them downrange)they gradually pull into the x ring.

When I bought the suppressor, I looked around a lot.The weight of this can compared to the other non-titanium models out there is pretty much the same. As far as the point of impact shift is concerned, I couldn't ask for more. And as for the stringing of the first few rounds, well, I figure it will be the same no matte what make and model is used-and at least it's repeatable.

All in all, I think the HVT is the go-to for accurate suppressed fire.

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12 years 9 months ago #10195 by txlongshotb4
Replied by txlongshotb4 on topic Re: Minimum Barrel Length for Long Range Suppressed
That was some good intel,Ranger.

2600fps is good news to me. I get 2630 out of my bolt guns, and they are both 1K rifles. I think 2600 will do just fine. Thank you Sir!

Su Sponte.

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12 years 9 months ago #10216 by JeffSavannah
Replied by JeffSavannah on topic Re: Minimum Barrel Length for Long Range Suppressed
Tx, barrel length: A 21.75 inch barrel with 1:10 twist is a "sweet spot" that has a very consistant harmonic from what I've read. Consistant oscillation tendancies. Might be the perfect length for your purposes sounds like.

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12 years 9 months ago #10221 by foxhunter
Replied by foxhunter on topic Re: Minimum Barrel Length for Long Range Suppressed
I have an AR10T with the 20 inch and one with the 16 inch and for target shooting on the back 40, at 200 yards, I can't tell any difference in drop or accuracy. If I had to chose one rifle, I would take the 16in barreled gun just because it is useful for hunting as well as target shooting. The 20 inch gun is heavier and more unwieldy in the woods. I think if my hunting were for predators like coyote and bobcat on open western land and I didn't have to walk far from the truck to set up, I would stick with the longer barreled gun. So your answer is... you need one of each. simple.

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