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Need advice for twist rate.

JustsomedudeJustsomedude Posts: 418 Member
I'm trying to order a bbl blank for a customer that wants me to pimp out a MN 91-30. He already has a stock, timney trigger and the bolts already been turned down. He's also going to be shooting bulk ammo. I'm aware of the 310-311 diameter bullets but I'm not sure what twist to go with. I was thinking 1:8, but I also have the options of 9.5, 10, 11.25, 12. What says the wisdom of the forum? 

Replies

  • BigslugBigslug Senior Member Posts: 8,145 Senior Member
    A 10" twist was pretty much The Thing for all of the .30-ish caliber rifles of that era.  Presumably the M.N.'s were 9.5 - likely due to some metric or arshin-based measurement system.  Shouldn't matter - either will let you shoot the full range of 150 (late) to 210 grain (early) projectiles.
    WWJMBD?

    "Nothing is safe from stupid." - Zee
  • knitepoetknitepoet Senior Member Posts: 20,846 Senior Member
    edited May 27 #3
    What he said ^ ^ The 10" for the 30-06 originated in the 30-03 with its 220gr RN.
    So again, as Bigslup said, a 10" SHOULD handle anything he wants to do.

    I'd be wary of the 8" in a rifle destined to shoot surplus ammo. I remember hearing somewhere, that a faster twist could raise pressure some, due to there being more resistance in getting the bullet started down the bore. Have no clue if it's factual or not, but would go with a slightly slower twist, that will handle anything I need it to, as opposed to unnecessarily spinning the bullet faster at the risk of increasing pressure

    Most 7 and 8 twist 30 cal barrels I'm aware of, were intended for shooting subsonics in the 300whisper/BO where you need the faster twist rate to get those long, slow moving, bullets spinning fast enough to achieve gyroscopic stability
    Seven Habits of Highly Effective Pirates, Rule #37: There is no “overkill”. There is only “open fire” and “I need to reload”.


  • ZeeZee Senior Member Posts: 23,517 Senior Member
    edited May 27 #4
    I run an 8T in my 16.5” barreled .308 Winchester that is pretty much my Go-To pig gun. 
    If I build anything else .30cal, it will have an 8T or 10T at the slowest. 
    "To Hell with efficiency, it's performance we want!" - Elmer Keith
  • Ernie BishopErnie Bishop Senior Member Posts: 7,425 Senior Member
    Zee said:
    I run an 8T in my 16.5” barreled .307 Winchester that is pretty much my Go-To pig gun. 
    If I build anything else .30cal, it will have an 8T or 10T at the slowest. 

    This
    Ernie

    "The Un-Tactical"
  • BigslugBigslug Senior Member Posts: 8,145 Senior Member
    Depending on what this guy is trying to do, there MIGHT be some sense in a 1-9"  My thinking there is that he might get a wild hair to shoot 190 grain Match Kings - ordinarily .300 Win Mag or custom .30-06 food.  The 7.62x54R does have good accuracy potential, but it doesn't sound like that's what he's after.  At any rate, he can get it with a 1-10" using the 175 version.  This of course assumes a .308" barrel, which if he's crunching Russian surplus - - you'd better mic some rounds before you order.

    The 1-10" originated for round nose bullets of the late 1880's-early 1900's in the 200-220 grain weight class.  It stuck around at the time because of pre-existing barrels, pre-existing tooling, and to a lesser degree, pre-existing stockpiles of ammo or specialty rounds, even though dropping to an 11-12" twist would work fine for the flat-based 150-ish grain spitzers that became norm.  It sticks around today simply for versatility - very few people shoot 200+ grain bullets in their .30-06's, but we all love the rifles because they CAN.

    Knitepoet's right about the faster twists for supressors and slow, heavy slugs.  I knew a guy back in the '90's who was experimenting with 7 and 8 inch twists for boosting the range of .308's - his theory being that the extra spin would defeat the instability known to creep in when they made the transition down to subsonic.  Don't know how successful that ultimately was, but it's probably wasted on a guy who's going to be shooting bulk-lot Wolf.
    WWJMBD?

    "Nothing is safe from stupid." - Zee
  • Big Al1Big Al1 Senior Member Posts: 7,754 Senior Member
    I'd find out what the twist rate is on one of the Finnish captures that were refurbed by Sako, they seem to have got it right! Found it, they changed to 1-10 from 1-9.5

    http://www.mosinnagant.net/finland/finnish_mosin_nagantm39.asp



  • Ernie BishopErnie Bishop Senior Member Posts: 7,425 Senior Member
    I have two rifles that are 10T.
    One has 22" barrel and the other has 30"
    I shoot 168's in the 22" and 180-230 (Primarily 200 grain) grain bullets with the 30"
    I would have no problem with a faster twist.
    Ernie

    "The Un-Tactical"
  • snake284snake284 Senior Member Posts: 22,387 Senior Member
    Doing some searches about various rifle twists I learned some things. This is a bit off topic for this thread but rifle twist can make or break a cartridge-rifle.

    For example, the popular story about why the .244 Remington was a flop is a bit flawed. I was always told that when the .243 Winchester and the .244 Remington came out the reason the Remington flopped in the market place and the .243 was a success was that Remington envisioned a varmint rifle and Winchester's idea was a dual purpose rifle for both varmints and medium game. Actually Remington also envisioned the .244 as primarily a medium game rifle that could also double as a varmint rifle. Remington came out with the 90 grain Soft Point Spitzer which they felt was more than enough bullet for medium game such as deer and Antelope. They also offered a 75 grain bullet for varmints. They decided on a slower twist as to not have problems with over spin which could lead to higher pressures and loss of accuracy. Winchester, on the other hand designed the .243 around the 100 grain Spitzer which had a but faster twist but would stabilize the heavier and longer 100 grain bullet.

    The problem which lead to loss of sales for the Remington was that many gun writers thought the 90 grain was a varmint bullet and too light for medium game. Remington designed the 90 grain soft point Spitzer to be tough enough to stay together at 3200 FPS, and tough enough to penetrate into the vitals of deer sized game.

    In 1957 Remington changed the twist rate to 1:9 for the Remington 722 in .244 Remington. But later discontinued production of the .244 for a couple years until it was re-introduced as the 6mm Remington with the 1:9 twist.

    But I never knew that they made some .244s with a 1:9 twist. But by then the .243 sales were out the top and the .244 nor the 6mm ever really caught up even though the cartridge would out perform the .243.
    Daddy, what's an enabler?
    Son that's somebody with nothing to do with his time but keep me in trouble with mom.
  • Ernie BishopErnie Bishop Senior Member Posts: 7,425 Senior Member
    Today I would hope that most manufactures are smart enough to be using the faster twists, for cartridges.  
    Ernie

    "The Un-Tactical"
  • ZeeZee Senior Member Posts: 23,517 Senior Member
    Today I would hope that most manufactures are smart enough to be using the faster twists, for cartridges.  
    Nope. Remington is still in the dark ages with most of their twist rates. 
    "To Hell with efficiency, it's performance we want!" - Elmer Keith
  • Ernie BishopErnie Bishop Senior Member Posts: 7,425 Senior Member
    That is sad and stupid.
    Ernie

    "The Un-Tactical"
  • snake284snake284 Senior Member Posts: 22,387 Senior Member
    edited May 28 #13
    Today I would hope that most manufactures are smart enough to be using the faster twists, for cartridges.  

    Yeah at least a moderately faster twist. In this day of heavier bullets to hinder a Swift or .22-250 with a 1:14 twist is neanderthal. Also, if pressure was a concern, these days with modern powders such as RL-17 or RL-26 and such, depending on which cartridge you're dealing with, with the right slower powder it should be no problem. As it is or was I'm guessing it was a minor concern. I can't see twist making that much difference. Now I can see it limiting velocity but not by a whole lot. and that's Muzzle velocity. Down range it would more than make up for it. It's time for the manufacturers to get with the times and take the hindrance off these fine old cartridges. Think about it, a .22-250 or a .220 Swift with an 80 grain VLD bullet. That puts it in another class.
    Daddy, what's an enabler?
    Son that's somebody with nothing to do with his time but keep me in trouble with mom.
  • JustsomedudeJustsomedude Posts: 418 Member
    Went ahead and got the 9. Thanks for the advice everyone. It just didn't seem as cut and dry being that the guy is going to be using bulk ammo which is usually 310-11. 
  • snake284snake284 Senior Member Posts: 22,387 Senior Member
    Went ahead and got the 9. Thanks for the advice everyone. It just didn't seem as cut and dry being that the guy is going to be using bulk ammo which is usually 310-11. 
    1:9 or 1:10 is probably way good enough. I don't see anybody shooting one of those long range and a 1:9 will stabilize most any regular hunting bullet which will be plenty good for shooting out to 300-400 yards which is plenty for for 99% of what you'd use a MN for.
    Daddy, what's an enabler?
    Son that's somebody with nothing to do with his time but keep me in trouble with mom.
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