AR-15 barrel twist rate

[kawtech87]

Thanks you guys for all your help. You've answered my question and then some. I think im gonna take mc223's advice and on my next day off give mr. Holliger a call and see what he has to say and what the out the door price is on a custom upper with a 1/7 twist. That way i can run heavier loads if i want to. I knew i joined this forum for a reason, and you guys are that reason. people who know what they are talking about and willing to share and listen. Thanks again

 

[Zerodefect]

I run 1/7 in carbines and 1/8 in SPR's. (.556 55-77gn)

 

[Waywatcher]

Good plan!

Enjoy!

 

[mc223]

Thanks kawtech87.


What do you think of that 600 Kaw in the Gator?

 

[Lakedaemonian]

like Einstien's theory on time being relative. accuracy is also relative. accuracy is realtive to twist rate -vs- bullet grain. for instance, some people will tell you that a 1/7 twist will handle a 62 grain round very efficiently. since your twist rate is 1/9 i would say a 55 grain bullet will be most efficient to your selected firearm.

 

[suzukisam]

holliger makes his 1:7 sdm barrel in a 16" instead of a 20" custom for darrel at D9firearms.com.. mine is insane, and I would very much recomend them.. darrel gets some great prices from john also, since he buys big lots.. here is mine.

[/IMG]

 

[benzy2]

Also realize that the longer the barrel, the slower the twist needed, if you move to a powder that is more efficient in longer barrels. If you can push a bullet faster you need less twist to get the bullet to stabilize. A short barrel, or really a barrel that produces less velocity, needs more spin.

 

[helotaxi]

if you move to a powder that is more efficient in longer barrels.

All powders are more efficient in a longer barrel. You can't simply go with a slower powder for a longer barrel and faster for short. I doesn't work that way. Every cartridge and bullet combination have an optimal powder burn rate that is completely independent of barrel length.

If you can push a bullet faster you need less twist to get the bullet to stabilize. A short barrel, or really a barrel that produces less velocity, needs more spin.

The only time that this works is when the bullet is on the ragged edge of stability. Velocity is one of the destabilizing forces trying to upset the bullet. Adding velocity adds RPM to the bullet, but also increases the required RPM (though to a slightly lesser extent). If the bullet is unstable in a given twist and velocity, adding velocity within the capability of the same cartridge isn't going to be enough to make a difference in stability. To really make up for a slow twist with velocity, you're going to have to up velocity on the order of the difference between a .22 Hornet and a .220 Swift.

Bottom line, if you want to reliably shoot heavy bullets, you need a faster twist barrel.

 

[benzy2]

All powders are more efficient in a longer barrel. You can't simply go with a slower powder for a longer barrel and faster for short. I doesn't work that way. Every cartridge and bullet combination have an optimal powder burn rate that is completely independent of barrel length.

Not a story I believe. Many powders will not fully ignite in certain barrel lengths. If you run quickload you can see how much of a given powder has burnt with any given cartridge in a given barrel length. There are powders are more suited to longer barrels that allow proper time to burn. Sure, you aren't going to toss Sporting Clays in an SBR and H50BMG in a 26" upper, but within the acceptable powders for a given round, some are more suited for long barrels and others more suited for short.

 

[helotaxi]

Whether or not the powder completely burns in a given barrel length is irrelevant to efficiency. Look at the difference in burn percentage in Quickload if you want, but a better indicator is to look what powder gives you the best velocity. You will find that regardless of burn percentage, the same powder gives the best velocity in both a long or short barrel.

You'll also find that powders that burn completely in a short barrel are often lacking in the velocity department because they are poorly suited to the cartridge.

Whether or not you believe it has no bearing on its veracity.

 

[kawtech87]

mc223, John Deere has used Kawasaki engine in all thier lawn and garden equipment for years. Mostly because they cant build a decent small engine to save thier life. Kawasakis are some of the best out there. Thats why everyone uses thier stuff or copies it...ie the "gator".

 

[kawtech87]

i was cheaking out mr. holliger's website earlier and found a barrel i think i would like him to use on my upper. His SDM (squad designated marksman) barrel. Anyone have one? Its 20 inches long and comes with a 1/7 or a 1/8 twist. Any thoughts or opinions?

 

[mshootnit]

1/9 is best for the platform.

 

[kawtech87]

i guess i should have checked out all the post before asking those questions. Sorry suzukisam, SWEET rifle!

 

[suzukisam]

kawtech- you can't get the sdm in a 16" from holliger..I don't think, at least you couldn't.. but if your interested d9Firearms.com has them.. darrel is a great guy.. you can call him and ask him any questions, he has several variations too..

 

[kawtech87]

Thanks for the info sam. Ill look into it. What kind of lower do you have?

 

[suzukisam]

that particular gun is a RRA.

it is equiped with:

RRA two stage trigger
RRA winter trigger guard
YHM FF tube
badger tac latch
WOA 16"sdm
ergo grip
levang linear comp
Leupold mk AR

but honestly I've used many different lowers.. I have used YHM, RRA, sharpes, dpms, cmmg... all with great results

 

[kawtech87]

Nice, ive been looking at an RRA elite comp upper my usual haunt has on the shelf (that is if it hasnt sold yet). Any experiance with them?

 

[suzukisam]

No I haven't.. I tell you what, I have gotten to where I don't even look at "factory" stuff. I built that rifle for about 1200.00 bucks, I don't think you can get the rifle I have off the shelf for anywhere near that.. I build them just exactly the way I like them, actually I've gotten lazy and I let Darrel make them for me... I usually have a tab running on some new project.. My .02 is build what you want, and don't look back...

Even the colt "perfection" doesn't do anything for me, I like what I've built better...