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Discussion Starter · #1 ·
Spent a bit of time searching for threads that discuss effect of different twist on accuracy and didn't find a bunch of info.

If one were in the market for a heavy wt barrell for a rifle build and had a choice of 1-10, 1-11 or 1-12 what criteria would impact which twist to choose?
 

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Some say nothing! I say its bullet weight. All the reading I have done on the subject says the same. If there was no difference why would they make different twist? General rule of thumb. The heavier the bullet the faster the twist ie 1/10 for 175 grain rounds. I know that many have used 155 and lower in a 1/10 barrel and it works well as the day is long.

I have a question as well if I may. I read that shooting lighter bullets in a fast twist barrel prematurly wears the barrel out because of the lighter mass of the bullet. It get pushed past the groves more so than a heavier bullet. Has anyone else seen or heard of this? Is it something to consider? Does it really matter? I wish Gus or Art (Catus Comet) could get in on this one.
Another thing to consider is what the manufaturer reccomemnds. I bought a few barrels with 1/10 twist over the years, it the only twist I use due to the ammo I shoot, and was told 168-175 grain would be the optimal round I could use. Got that from SAI and Krieger. Is there something to what they have to say? Never stop learning!
 

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Discussion Starter · #4 ·
Tx Much!
 

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Now that you've read all those posts, here's the short answer:

You need more than one M14- for the different barrels!
GI2
 

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OK, I'm going to throw a hand grenade here and let the frag land where it may.

Most people over-twist on barrels... GI8

depends entirely on what bullets you want to shoot.

The USGI 147gr FMJ, and the Sierra 168 and 175 bullets were designed to shoot from 1:12 twist, as in all USGI 7.62 NATO rifles up until a few years ago.

Little known fact, and I have this from two sources... Faster twist rate reduces the BC of any given bullet. Told to me by Mike at Krieger Barrels, and backed up by an article I saw somewhere on David Tubb working up some wacky 6.5mm wildcat for long range. He prepared two identical rifles, one with a fast twist rate and one with a slower twist rate. He prepared a load for each rifle that gave identical muzzle velocity. He then fired both rifles through chronograph screens at 1000 yds... (kids, don't try this at home. GI8) and found that the slower twist rate had higher retained velocity at long range, i.e. higher BC.

I discussed this story with Mike at Krieger and he confirmed it.

Another story, told to me by Mike at Krieger who heard it directly from Boots Obermeyer's lips, so I guess that makes it a third-hand account... When the US Army M24 rifle was first being developed, it was specified with a 1:12 twist. The Army went to Boots for the first batch of prototype barrels. Boots at the time did not have the gears on hand for his rifling machinery to cut a 1:12, so he gave them the closest he had which turned out to be 1:11.24 twist. The barrels shot so well that the Army changed the spec of the M24 to be 1:11.24 twist forever, and the rest is history.

Ted Brown has posted a number of times that 1:10 twist is the most popular with competitors shooting the M14 type rifle in across-the-course NM competition... well that may be because the reduction of BC doesn't really show up out to 600 yds. Also, NM competitors may want the option of fooling around with exotic VLD bullets.

Twist rate is not determined by bullet weight, it is determined by bullet LENGTH. Usually, a heavier bullet will be a longer bullet, and that's where the idea that twist is determined by weight comes from. The truth is that most bullets of conventional design that are suitable for use in an M14-type (i.e. up to 175 gr) are designed to be stable from a 1:12 twist. The exceptions are the VLD type bullets that are extremely long and skinny for their weight. For those bullets you might want a twist faster than 1:12.

In conversations with Mike when I was doing the Krieger barrel group buy a couple of years ago he told me that 1:12 is the ideal twist rate for an M14 barrel, unless you want to play with exotic bullets. I asked him why they make 1:10 twist barrels and he said, "Because customers ask for them." I asked him why they make 1:11 twist barrels, and he said, "1:11 twist barrels are for people who can't make up their minds."

dance2dance2dance2dance2dance2

FLAME AWAY, I have my Nomex suit on. DI5
 

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Twist Rates

2336USMC is telling the truth. All his points are valid. I too have had similar conversations with Krieger barrels regarding twist rates. They even went so far as to state that the ideal twist for .308 may be 1:14".

My statements about the 1:10" twist are based on experience in competition shooting. I have shot 1:10", 1:11" and 1:12". I have not shot the 1:11" twist at 1000 yards, but I can't see any reason to doubt that it would perform well.

The .308 Wichester cartridge is at it's limit at 1000 yards regardless of the barrel twist. Most of us know that fast twist barrels shoot heavier bullets best. The .308 168 grain Sierra bullet won't stay stabile at 1000 yards in any twist. ON the other hand, the 168 grain Hornady A-Max probably will (I haven't tried them at that range). Long range is more about BC.

My point is that almost any of the recommended twists will work in the M14 out to 1000 yards. I still prefer the 1:10". It works for me and has been a standard for a long time. But, I wouldn't worry if I had to shoot a slower twist.
 

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...Twist rate is not determined by bullet weight, it is determined by bullet LENGTH...

I thought this was a great article when I read it and it may help shed some light as well. This is a comparison of the venerable .308 and the new 6.5s that are coming out. But where this is helpful, and agrees with the above, is bullet length and the resulting twist. (ie a dramatic length of a 240gr in a 1:10...) Read the article and make your own decisions.
I don't know if it mentions the author's qualifications, but if I remember correctly he's a ballastician for a major bullet manufacturer like Berger or Sierra... not sure.

http://www.longrangehunting.com/articles/30-caliber-1.php

Ciao, compari!
 

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If shooting Sierra 168 grain HPBT bullets exclusively, then 1 in 10 twist, 6 grooves would be my choice. For most other bullet weights, 1 in 10 twist, 4 grooves would be my choice. Just MHO.
 
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