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Discussion Starter · #1 ·
My old AR15 was a shorty with a 14.5" barrel and a FS to make up the difference. If I tried to shoot anything over 55gr they would fly all over which left me limited to ammo I wanted to shoot.

What would be the limits of a 16" barrel?

It will not be a carbine or any kind of an entry short gun thing. I am looking at a decent rifle that I can shoot medium to long range and more importantly that my SO can shoot.

Gracious!
 
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Discussion Starter · #3 ·
I don't think it was less the length of the barrel and more the twist rate.
Hmm? It was a Bushmaster with a twist rate of 1:9. I was told by several people that the short barrel caused heavier weights to become unstable. So all Bushmasters cannot shoot anything over 55? that cannot be correct.
 
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Discussion Starter · #4 ·
Check the twist on the barrel. I think you need like a 1/7 or 1/9 to stabilize the heavier ammo.

I saw some targets with the old 1/12+ with the heavier ammo and it looked like the bullets went through sideways >.>
 
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Discussion Starter · #5 ·
Barrel length has little affect on the accuracy when using different bullet weight loads. Length does affect velocity a bit.

Barrel twist is the real determining factor when it comes to which bullet weight will shoot the best. For example, a 1:9 twist rate will, most likely, shoot the best with lighter weight bullets (55gr-70gr). A 1:7 twist barrel will usually have better accuracy with heavier bullet weights (68gr-77gr).

There are no absolutes, however. Some barrels that are supposed to be 1:9 are more like 1:8.8 (guessing) so, they may actually shoot the 75gr loads pretty well. A barrel that falls the opposite way...say 1:9.2...may not like anything heavier than 62gr loads. It just depends.

Since your gun only shoots 55gr loads well, I'm wondering if your barrel has a twist rate that is slower than 1:9 (like 1:10,1:11???). Either that, or the FH is improperly installed and is causing a problem.
 
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Discussion Starter · #6 ·
I have both (16" & 14.5") barrels. They both have a 1/7 twist and have similar accuracy out to 300 yards. I normally shoot M855 (62gr) out of both and have not seen a difference in accuracy.
 
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Discussion Starter · #7 ·
Hmm? It was a Bushmaster with a twist rate of 1:9. I was told by several people that the short barrel caused heavier weights to become unstable. So all Bushmasters cannot shoot anything over 55? that cannot be correct.
DM-SC pretty much covered it.

The higher the twist rates are better for the lighter bullet weight. Like a .22 has like a 1/12 TR.
I think a 1/9 is a good overall TR on an AR but my current one is a 1/7 TR so I just ordered some 62gr for it to see how it does (although I have no problems in accuracy w/ 55gr).
 
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Discussion Starter · #8 ·
Barrel length has little affect on the accuracy when using different bullet weight loads. Length does affect velocity a bit.

Barrel twist is the real determining factor when it comes to which bullet weight will shoot the best. For example, a 1:9 twist rate will, most likely, shoot the best with lighter weight bullets (55gr-70gr). A 1:7 twist barrel will usually have better accuracy with heavier bullet weights (68gr-77gr).

There are no absolutes, however. Some barrels that are supposed to be 1:9 are more like 1:8.8 (guessing) so, they may actually shoot the 75gr loads pretty well. A barrel that falls the opposite way...say 1:9.2...may not like anything heavier than 62gr loads. It just depends.

Since your gun only shoots 55gr loads well, I'm wondering if your barrel has a twist rate that is slower than 1:9 (like 1:10,1:11???). Either that, or the FH is improperly installed and is causing a problem.
The Flash Suppressor was factory mounted and I never took it off.

Yes I have seen where 50-100fps can be lost per inch of barrel removal. I have no idea, other than the stated twist from Bushmaster (1:9), what the rifle really had.

My experience is all from bigger calibers and I am used to shooting 150gr and bigger. I had never witnessed a mag of rounds (55gr) that would hit dead on and then switch to a slightly larger round (62gr) and have them nearly fly off the paper.

I suppose that I will buy the standard ar15 as I am not interested in getting into other bits just to get a little increase in round weight.

Maybe I should look into a 6.8?

Thanks for the post.

UB
 
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Discussion Starter · #9 ·
6.8SPC is a good round for defense and, most likely, some types of hunting.

I want a 20" AR in .204 Ruger.

I hope you get it worked out!
 
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Discussion Starter · #10 ·
"Length does affect velocity a bit."

I have a hard time agreeing with that statement, barrel length definitely affects a bullet's muzzle velocity
 
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