bbl.Twists ?

[Old Corps 8541]

from what I've read when the USMC's ** MTU started building the M-40's they used Bbl's with a 1 - 11.25 twist. I've often wondered why that twist ^^, and why only a very few barrel makers offer that twist today .
** Don't know about the Army's MTU
^^ running both the JBM and Sierra stability programs they both say a 1-12 will handle a 175 SMK ?

 

[Lowlight]

The 1-11.25 is super common 308 twist rate

308s are usually offered

1-10 (My favorite)
1-11.25
1-12

The 1-12 is the least desirable today, they all shoot a 175 fine

 

[Supersubes]

from what I've read when the USMC's ** MTU started building the M-40's they used Bbl's with a 1 - 11.25 twist. I've often wondered why that twist ^^, and why only a very few barrel makers offer that twist today .
** Don't know about the Army's MTU
^^ running both the JBM and Sierra stability programs they both say a 1-12 will handle a 175 SMK ?

It was the army M24 that had the 11.25 twist. First barrels were by obermeyer/rock(i think), then later Remington factory made them.

USMC M40 used 12 twist Schneider barrel.

 

[Random Guy]

Here's my understanding:

USMC:
1966 to 1977: M40's used 1/10 twist, 24" long barrels made by Remington. It was designed/assumed for use with the M118 ammo (174 grain bullet)
1977-2016: M40A1/A3/A5 used 1/12 twist, 24" SS barrels made by various makers, with Schnieder being the most common since early 200Xs. It was designed for the M118 and then in the mid-to-late 1990s the improved M118 LR round, which used the more consistent 175 grain SMK bullet.
2016-present day(?): M40A6 used a 1/10 twist, 20" SS barrel made by Schnieder. (Barrel shortened to 20" for shorter overall length w/ suppressor, and twist rate was increased to 1/10 to presumably provide enough rotational spin for the 175 grain SMK bullet in the shorter 20" barrel.)

US Army:
1988-2011: M24s adopted the 1/11.25 twist, 24" long barrels. Why? It's a good compromise. US Army snipers were trained to use M118 with 174 grain LC ammo (and later the M118 LR w/ 175 SMK), but in an urgent/combat situation in some foreign land, snipers needed to be able to shoot M80 machine gun ammo (147 grain bullet) out of an M24, and retain relatively good stability/accuracy. Obviously accuracy would suffer with generic M80 compared to M118 match ammo, but the 11.25 twist rate back in the 1980s was reportedly tested and adopted as the ideal compromise between the two ammo types that a US Army sniper would have access to in the field... Big Army being Big Army, presumably wanted maximum flexibility re M24 ammo usage. My 2cts.

As an anecdotal observation on the 10th Special Forces Group M14 sniper rifles made at Ft Devens MA (aka the M25 rifles). The original XM25 sniper rifles made in the late 1980s used a 1/10 twist 22" medium weight match barrel, but pics/documentation on the later M25s made circa 1993-94, showed that 1/11 twist heavy profile 22" barrels were used. The ammo used was the same in that era, M118 Special Ball. I thought that slight switch in twist rates was curious, but I guess by the early-to-mid 1990s, the 1/11 twist rate became popular, in part due to the M24's use of the unique 1/11.25 twist rate.

 

[Frank Green]

Random Guy I think is very close on what he all wrote.

Original M40 barrels where 10 twist and 6 groove for rifling. Just back in 2012 I got to look at and confirm that with an original M40 rifle barrel that was built back in 1966 that was here in the shop so we could check the exact contour dimensions etc...

As far as current M40 type barrels..I literally just quoted (like 5 minutes ago) some more 30cal for the PWS shop and again they asked for 10 twist barrels. I do believe these are team/match barrels. M40 contour and 5R rifling.

I have the whole M40A3 drawing packet and I can look to see what the barrel spec was called out if need be.

As Lowlight mentioned and I'll add a little more... a 12 twist will handle up to conventional 190gr match bullets at 308w velocities. Your pushing that though. I'd run a 10 myself. I've shot 8 twist, 10 twist, 11, 11.25 and 12 twist. I don't see a difference accuracy wise. 10 and 11 twist are my favorites.

Later, Frank
Bartlein Barrels

 

[Baron23]

Ah, thanks guys....I have a Rem 700 5R SS Gen 2 (got to love dem' loooong names, right?) with a 20" 1/11.25 barrel and I often wondered with the 11.25 came from....particularly the .25 part! haha

Its just a bog standard eastern whitetail deer gun but it shoots 168/175 FGGM and 178 ELD-X just fine. I've not had any stability issues shooting it out to 300 yards which is as far as I'll ever need to shoot at a deer in my neck of the woods.

Cheers

 

[Frank Green]

Ah, thanks guys....I have a Rem 700 5R SS Gen 2 (got to love dem' loooong names, right?) with a 20" 1/11.5 barrel and I often wondered with the 11.25 came from....particularly the .25 part! haha

Cheers

If I recall correctly but I cannot remember exactly who.... but either the military or a place like KAC or someone else wanted Obermeyer to make 11 twist rifled barrels but Boots didn't have the gear set up for 11 twist. So he picked the gear combination closes to 11. I think he ended up making 11.27 twist barrels but everyone called them 11.25 twist.

I might be partly wrong about that....but it's pretty close that's how the 11.25 came to be.

So places like Obermeyer, Krieger that do cut rifling and use Pratt hydraulic rifling machines....those machines originally where set up for one twist and in 30cal it would've been 10 twist. So Krieger etc...modified the machines with a gear plate/changing system. By changing a combination of gears they could do different twist rates.

We do single point cut rifling but we built new machines and do it all with cnc controls. So we can offer pretty much any twist you want. Tooling still plays a part to some extent.

Later, Frank
Bartlein Barrels

 

[Lowlight]

Wasn't the 11.25 Mike Rock ?

I thought it was Rock who coined the 11.25

 

[kthomas]

My understanding was also that the 1:11.25 was a gearing thing.

I researched this a couple of years ago when someone on a Canadian firearm forum claimed that 1:11.25 twist was the most accurate twist rate for .308 because that's what the military uses, and through their extensive testing on twist rates this is what they determined (of course with no sources). This guy was trying to tell me that 1:11.25 twist is superior to 1:10 on .308's because of this

So to prove he was full of shit I did my own research, and found out that it's like @Frank Green states - it was essentially a coincidental twist rate through gears on the manufacturing equipment. I don't remember the specific details however.

 

[GIXXER2000]

I have shoot well over 5000 rounds in 1-12 in a Steyr SSG04 and it shot 175SMK and 175 Berger great. till the barrel was worn out. I have about 2000 or so rounds on a Schneider 1-10 P5 26in barrel for my AI-AE and it shoots 178 ELD-M great. I shot a local 1000 yard match and scored 93 1x with 1 flyer in the 8 ring and beat guys shooting 6cm,.243,6.5cm, 6.5PRC, 7mm. The winner that day shot 96 3x.

 

[Frank Green]

Wasn't the 11.25 Mike Rock ?

I thought it was Rock who coined the 11.25

It might have been but I cannot say for sure.

Then I will say that goes back to Mike did work for Boots so I think it started back at Obermeyers shop. Best I can tell ya. You might be right that Mike coined it and pushed it to some extent at some point in time.

 

[Random Guy]

Wasn't the 11.25 Mike Rock ?

I thought it was Rock who coined the 11.25

Then I will say that goes back to Mike did work for Boots so I think it started back at Obermeyers shop. Best I can tell ya. You might be right that Mike coined it and pushed it to some extent at some point in time.

Attached is the history of the development of the M24's barrel circa April 1986 when the US Army's 'Market Research' statement was released, to the the July 1988 era, when Remington formally won the award. The twist rate was determined by formal testing back in 1986 of different barrels and twist rates, and Remington couldn't meet the Army's accuracy spec at first - but they settled on 1/11.25 w/ 5R rifling - which finally met the Army's accuracy requirements as outlined in the Market Research/RFI statement. It is also true that Boots developed the 5R rifling, and Mike Rock made the barrels for the 6 Initial Test Rifles and the 19 "First Article Test Rifles" circa 1987. I think Remington made all of the 'production' M24 barrels after the contract was awarded in July 1988. The Army received the first production 100 M24s on October 25, 1988.

Anyhow, hopefully the attached documents will explain some of that early history and the first 25 US Army trial M24s. Source of attached pics & info: Collecting the American Sniper Rifle 1945 to 2000, (2014), by Joe Poyer. (There are various errors in this book, but the section on the M24 history is from the Remington archives and interviews, and do not appear to have any errors that I can detect). Random last pic is likely from the 1988-89 era.