Barrel Twist Rates

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rod45acp

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Greetings,
I am hoping someone may be able to help.
I have been looking unsuccesfully on S&W site for handgun barrel twist rates.
Also the number of grooves, the type of rifling and the rifling method used, ie Ballard cut or something else and are the barrels hammer forged, buttoned etc.
I'm looking for this info for the 5" barrel M&P9 and M&P9L.

Thank you for any assistance :cool:
 
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1/10 is standard for the 9mm. You will not find many different unless its a special order of some kind or special build. This is because the 9mm bullet is short and pretty easy to stabilize. So there isnt much need of anything more. Barrel twists rates are more commonly found in rifles, due to more available ammo with both heavier and lighter grain.

For the .38 special and the 3.57 s&w uses a 1/18.75 because they have longer/heavier bullets and extremely wide velocity of range.
 
Smitty357 said:
1/10 is standard for the 9mm.
Click to expand...

Just because it’s on the internet doesn’t make it true.:D

S&W standard 9mm barrel twist rate was 1-18.75 or 1-16, (depending on who you talk to.) Five grove, cut rifling is still the standard I believe for all S&W barrels.

I understand on the post 2011 M&P barrels they’ve switched to a 1-24 to try and get better accuracy with 115-124 gr. bullets.
(longer bullets require faster twist’s and will tumble in slow twist barrels. Shorter bullets don’t seem to mind faster twists, so manufactures normally use a twist to stabilize the heaviest bullet their customer may use.)

Most firearm manufactures use the old Greenhill formula to determine twist rate. It’s a mathematical formula taking into account the bore diameter, bullet length and velocity to come up with an “ideal” twist rate. You can use this formula for almost any caliber from 17 caliber to artillery and you’ll find that whatever twist rate comes up, that’s pretty close to what all the manufactures have been making for years.

Except 9mm Parabellum. Using this formula, the “ideal” twist rate for a 9mm with a 147 gr. bullet would be 1-22” yet manufactures can’t agree on what’s an ideal twist rate. Most American companies use a 1-16” but european companies use much faster twist rates. Glock, Sig and H&K use 1-9 to 1-10 and I’m told the original P-08 Lugers used a 1-7 twist.

Looking at aftermarket match barrels, we see there are basically two choices. 1-16” to stabilize even 160 grain lead bullets and 1-24” for folks building open class race guns that will only see 100-125 gr. bullets.

Jeff
 
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fltbed said:
Most firearm manufactures use the old Greenhill formula to determine twist rate. It’s a mathematical formula taking into account the bore diameter, bullet length and velocity to come up with an “ideal” twist rate. You can use this formula for almost any caliber from 17 caliber to artillery and you’ll find that whatever twist rate comes up, that’s pretty close to what all the manufactures have been making for years.

Jeff
Click to expand...

Very true except the Greenhill formula was developed during a time when state of the art projectiles were lead and round nosed. It doesn't work very well with boat-tailed match bullets and falls apart with with VLD projectiles. It fails completely with mono-metal bullets like the Barnes.

However, since we're talking about pistol bullets, it works well enough.
 
MichiganScott said:
Very true except the Greenhill formula was developed during a time when state of the art projectiles were lead and round nosed. It doesn't work very well with boat-tailed match bullets and falls apart with with VLD projectiles. It fails completely with mono-metal bullets like the Barnes.

However, since we're talking about pistol bullets, it works well enough.
Click to expand...

That’s not entirely true.
In 1879 when he first published his formula the state of the art projectiles were lead but defiantly not round.
While his original formula didn’t take into account what the bullet was made from, before the end of the 19th century he modified it for artillery projectiles, giving different Specific Gravity (SG) values for lead, brass, copper, steel, etc. It’s that later variation that everybody still uses today. And yes, it works just fine with boat tail, VLD, and solid copper alloy bullets as well.

Jeff
 
fltbed said:
Just because it’s on the internet doesn’t make it true.:D

S&W standard 9mm barrel twist rate was 1-18.75 or 1-16, (depending on who you talk to.) Five grove, cut rifling is still the standard I believe for all S&W barrels.

I understand on the post 2011 M&P barrels they’ve switched to a 1-24 to try and get better accuracy with 115-124 gr. bullets.
(longer bullets require faster twist’s and will tumble in slow twist barrels. Shorter bullets don’t seem to mind faster twists, so manufactures normally use a twist to stabilize the heaviest bullet their customer may use.)

Most firearm manufactures use the old Greenhill formula to determine twist rate. It’s a mathematical formula taking into account the bore diameter, bullet length and velocity to come up with an “ideal” twist rate. You can use this formula for almost any caliber from 17 caliber to artillery and you’ll find that whatever twist rate comes up, that’s pretty close to what all the manufactures have been making for years.

Except 9mm Parabellum. Using this formula, the “ideal” twist rate for a 9mm with a 147 gr. bullet would be 1-22” yet manufactures can’t agree on what’s an ideal twist rate. Most American companies use a 1-16” but european companies use much faster twist rates. Glock, Sig and H&K use 1-9 to 1-10 and I’m told the original P-08 Lugers used a 1-7 twist.

Looking at aftermarket match barrels, we see there are basically two choices. 1-16” to stabilize even 160 grain lead bullets and 1-24” for folks building open class race guns that will only see 100-125 gr. bullets.

Jeff
Click to expand...
Jeff, Thank you for a great reply. Very much appreciated. I do understand the twist rate for handguns is not so apparently important as rifles when stabalizing projectiles. However there is obviouslly a benefit to having the correct twist rate for a given projectile whether handgun or rifle. Mine was more of an academic interest. Also I found it annoying I could not readily find the info. Even the S&W handbook that comes with the M&P does not specify, the twist rate. Once again thank you for such great input.:cool:
 
Smitty357 said:
1/10 is standard for the 9mm. You will not find many different unless its a special order of some kind or special build. This is because the 9mm bullet is short and pretty easy to stabilize. So there isnt much need of anything more. Barrel twists rates are more commonly found in rifles, due to more available ammo with both heavier and lighter grain.

For the .38 special and the 3.57 s&w uses a 1/18.75 because they have longer/heavier bullets and extremely wide velocity of range.
Click to expand...
Smitty 357, Thank you for your response to my post. Very much appreciated. :cool:
 
I understand S&W is now producing the M&P 9MM with 1 - 10 twist barrels. This would the same twist rate Glock, CZ, FN, Tanfanglio and HK use in their 9MM guns. The 1 - 18.5 twist rate is really to slow to stabilize the 147 gr 9MM bullet.

From my experience my CZ's will shoot inside an inch at 15 yars using the Lyman 147 gr 9MM bullet. The same bullet of my MP using the same load won't hold 4".

I hope to be able to get a 1 - 10 barrel from S&W once they become available.

Take Care

Bob
 
That’s interesting to hear but I honestly don’t think the barrel twist rate has much to do with the accuracy issues the M&P 9mm has. Since I only use my M&P 9L for USPSA production division. I think I’ll just follow what the Team S&W pro shooters did and replace the barrel with a fitted match grade barrel.

Jeff
 
I have a 40c that I bought in 2009. I just bought my wife one a couple weeks ago. As I was giving her instruction on breakdown and cleaning I noticed that the rifling in my barrel was a slower twist than in hers. I believe that's the way the it was. I would have to look at them again to be sure which way it was but I do know for sure they were different.
 
My Shield 9mm barrel

Very unscientific, but reasonable accurate. Using a cleaning rod marked so I can see the twist and measure length of movement. Pushing firmly packed cleaning patches through the barrel, I measure a little more than .2 turn for 2 inches of movement, which would equal 1 full turn in 10 inches or a little less. My barrel would be 1/10 or 1/9 twist, not that either rate is going to make any difference in accuracy.

Checked twist rate for Storm Lake Barrels on Midway's site, and for all calibers they show a 1/16 twist rate. Went to the Storm Lake's website and can't find anything showing their twist rates.

Bob
 
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Hello all

just saw this thread while looking at something else. I contacted S&W and got my reply back from them yesterday. According to my Serial # DXZXXXX, my M&P9 was mfg'd in 07/2012 and according to Smith it has a 1-9 twist.

As for accuracy I can't complain but I am planning on swapping out the stock sight for something a Lil cleaner, The trigger has smoothed out just fine for me so I dont think i'll mess with a Apex, as for reset...I think to much is made of it myself, just learn to shoot your gun.

8)

UPDATED 5/2/2013

OK after further talking with the rep at Smith it has come to light that the information I had been given was incorrect. The barrel does in fact have a 1:18.75 or as stated by Paul G 1:18 and 3/4 and all new models come with a 1:10. So my question is are the aftermarket ie Storm Lake barrels a good enough upgrade over factory to justify getting one?
 
justcruisen67 said:
OK after further talking with the rep at Smith it has come to light that the information I had been given was incorrect. The barrel does in fact have a 1:18.75 or as stated by Paul G 1:18 and 3/4 and all new models come with a 1:10. So my question is are the aftermarket ie Storm Lake barrels a good enough upgrade over factory to justify getting one?
Click to expand...

It depends on what kind of “upgrade” your looking for.

When I first got my M&P9L, (early 2010) it barely averaged a 4” group @ 25 yards with 147 gr. ammo. The S&W CS rep I spoke to said that was the standard and their was nothing they would do. At the 2012 area 8 match (maybe 15K rounds later) it would only keep a 5-6” 25 yard group but the velocity fell off over 100 f.p.s. I ended up going sub minor (Power Factor) on chrono stage and shot the match for no score.

When I got home from the match, I sent it back with a test target and letter and they replaced the barrel with one that had a noticeably different breach block and even slower rifling twist. (1-24” I was told) That barrel chronoed slightly faster and accuracy at 25 yards was 4-5” but at 50 yards it would keyhole a shotgun pattern. Called S&W to send it back again but the CS rep I spoke to said it was “within spec” and try lighter weight bullets.

I got tired of waiting for the Bar-Sto and KKM gunsmith fit barrels and when Storm lake drop in barrels showed up at Midway last winter, I grabbed one. Glad I did! Now the gun shoots 2.5-3” at 25 yards and 5-6” @ 50 yards.
Velocity is also back up to normal as well.
147 gr. FMJ ammo used at the 2012 Area 8 match:
Original barrel- 820 f.p.s. (just before I sent it back)
New S&W barrel- 860 f.p.s.
Storm lake barrel- 950 f.p.s.

So, like I said, it all depends on what kind of upgrade your looking for. For me, who only uses the M&P for USPSA matches, it was a huge upgrade. For you…only you can answer that.

Jeff
 
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