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  #1  
Old 07-23-2010, 08:52 PM
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Question Rate of twist for M&P 9 ??

I have been all over their website and all the specs I could find, but still don't know the rate of twist in the factory 4.25" 9mm barrel..?
I would also like to know which is better for the lighter/heavier grains...quicker twist or slower twist??
Thanks in advance
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Old 07-23-2010, 09:09 PM
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18.75" same as they have been using for .38 Special for about 111 years.

Heavier (longer) bullets call for a faster twist.
But the 18.75" has been good for 158 and even 200 grain Specials for a long time now so there is nothing to worry about in 9mm

Most European 9mms have a 10" twist (probably 9.84", four turns per metre) and they don't "overstabilize" a 115 grain bullet, either.
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Old 07-23-2010, 09:43 PM
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thanks for that info. I was curious because the Storm lake barrel for the 9mm has a 1 in 16" twist and the KKM barrel has a 1 in 20" twist....The stock barrel falls right in between.
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Old 07-24-2010, 02:21 PM
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WOW... thanks for the facts WATSON!!!!
Interesting to know..........
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Old 08-24-2012, 11:56 AM
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Quote:
Originally Posted by Jim Watson View Post
18.75" same as they have been using for .38 Special for about 111 years.

Heavier (longer) bullets call for a faster twist.
But the 18.75" has been good for 158 and even 200 grain Specials for a long time now so there is nothing to worry about in 9mm

Most European 9mms have a 10" twist (probably 9.84", four turns per metre) and they don't "overstabilize" a 115 grain bullet, either.
Why so stark in difference between the Europeans' design choice vs S&W's choice for twist rates?
Is this what is causing the accuracy issue reported in the last couple years?
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Old 08-24-2012, 01:46 PM
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That would be if the accuracy issue really exists. It seems to be popular these days to assign blame for any inaccuracy on the gun itself. If a shooter cannot master his weapon and someone else claims to have problems with theirs it is far to easy to say "Ahha, that's why I'm such a poor shot". I am sure there are some guns out there that do have issues. I cannot imagine a manufactured product that comes out perfect all the time. I would think however that if it were the rate of twist then any problems would be across the board and everyone would be having it. Mine shoots very well as do thousands of others.
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Old 08-24-2012, 02:12 PM
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You are right and I agree that there's one extreme where one small group of inexperienced people who are just making noise about some issues that do not exist.

On the other hand, there's also the other extreme where the group of people are experienced competition shooters and S&W refuse to look into the issue. Same thing with certain forum websites that brush the issue asides as a small anomaly occurring only in a small number of pistols.

As to whether the accuracy issue is real or not; perhaps, one should drop by some websites where competition shooters frequent (like Brian Enos and Pistol-Forum) and you'd understand what I meant. The people who brought up the issue are, certainly, not green-horns making noise.

You are lucky, you got one of the good ones. Many others and I are not as lucky as you.
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Old 08-24-2012, 02:26 PM
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Velocity also plays a part in optimum barrel twist.

Excessive twist will raise pressure, and can destabilize a bullet. I have a friend that would load his 6mm rifle so hot the bullets would spin apart as they left the barrel.

So heavy slow bullets need a faster twist than light fast bullets. But then you throw in length of the bullet and you get all screwed up!

Why S&W has such a slow twist is beyond me, but it works. Or maybe it doesn't and we never notice because we don't shoot very far.

See this article which has a twist rate formula and some good information by Chuck Hawks. RIFLE BARREL TWIST RATES
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Old 08-24-2012, 02:37 PM
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Using that twist rate calculator, I can see where the optimum twist rate for rounds between 800 and 1200 fps in 9mm size could vary between 1:17 and 1:21.

Not that 'optimum' twist rate will be any better than standard, but there could be some leeway, especially if you are getting some really hot loads or are shooting very slow loads.
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Old 08-24-2012, 02:42 PM
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Quote:
Originally Posted by 1sailor View Post
That would be if the accuracy issue really exists. It seems to be popular these days to assign blame for any inaccuracy on the gun itself. If a shooter cannot master his weapon and someone else claims to have problems with theirs it is far to easy to say "Ahha, that's why I'm such a poor shot". I am sure there are some guns out there that do have issues. I cannot imagine a manufactured product that comes out perfect all the time. I would think however that if it were the rate of twist then any problems would be across the board and everyone would be having it. Mine shoots very well as do thousands of others.
The problem is real, but you are also correct in that people do not shoot all that well either.

The other problem is that the poor twist rate coupled with the loose fitting barrel hood ONLY shows itself after 15yds. Since most people shoot INSIDE of 15yds, they never find any issues.

Are there some M&P's that shoot 5" or better at 25yds? Yes. So it does happen.

Just so you know, I believe that EVERYONE on the S&W pistol shooting team is running a fitted Storm Lake barrel. I would say that this is a clue!


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Old 08-24-2012, 03:27 PM
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I just think that any new M&P owner should work on his skill first before blaming the gun itself. If you are not accustomed to a striker fired pistol at all then there may be some bad habits to overcome first. I grew up with revolvers. The few semi's I've owned were single action only. When I got my M&P I was appalled to see how poorly I shot it. My groups all seemed to be low and even as close as 25ft 4+" was about the best I could do and I would sometimes have random fliers that missed the target completely. By chance I ran into an accomplished shooter who was experienced with his own M&P. Using my pistol at 25ft he fired a 10 shot group center target, not over about 2". At that point I realized that I had to overcome some bad habits that weren't so noticable when firing a revolver single action. I'm still somewhat handicapped by my vision (not a kid anymore) but find that offhand at 50ft I can easily keep a 3+" group and well below 3" in a sitting position. Fliers are now 2 to 3 inches off the main group and not off the paper. For me anyway, poor trigger control was the culprit.
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Old 08-24-2012, 03:36 PM
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Quote:
Originally Posted by 1sailor View Post
I just think that any new M&P owner should work on his skill first before blaming the gun itself. If you are not accustomed to a striker fired pistol at all then there may be some bad habits to overcome first. I grew up with revolvers. The few semi's I've owned were single action only. When I got my M&P I was appalled to see how poorly I shot it. My groups all seemed to be low and even as close as 25ft 4+" was about the best I could do and I would sometimes have random fliers that missed the target completely. By chance I ran into an accomplished shooter who was experienced with his own M&P. Using my pistol at 25ft he fired a 10 shot group center target, not over about 2". At that point I realized that I had to overcome some bad habits that weren't so noticable when firing a revolver single action. I'm still somewhat handicapped by my vision (not a kid anymore) but find that offhand at 50ft I can easily keep a 3+" group and well below 3" in a sitting position. Fliers are now 2 to 3 inches off the main group and not off the paper. For me anyway, poor trigger control was the culprit.
Sure. Or just put the gun on a sand bag and see what you got (no need to free hand it). No sense in trying to learn to shoot on a gun that shoots 6-8" groups IMHO.


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Old 08-24-2012, 04:03 PM
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Quote:
Originally Posted by 1sailor View Post
I just think that any new M&P owner should work on his skill first before blaming the gun itself.
That is all well and good, and never a bad reminder for newbs, but such advice could be viewed as sorely misplaced in a discussion with shooters who have owned many stiker-fired guns and/or multiple M&Ps. Not trying to pick on you here, but I did want to point out that the majority of problems being reported here (about the FS9) are not coming from novice shooters or those new to striker-fired pistols.

We had a lengthy discussion last week on this very subject (see: I ordered a M&P9 and now I read about all the accuracy issues. Wonderful! ), and one the more telling posts came from Grant, who stated:

"For the record, my personal M&P FS 9mm shoots 7-8" groups (from a Ransom Rest) @ 25yds."

If more people here had a Ranson Rest (or access to one), I believe we would have a laundry list of similar reports being posted.
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Old 08-24-2012, 04:32 PM
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I brought that up because I have seen on more than one occasion where a new shooter comments on poor marksmanship and it is immediately pointed out that M&P's have an accuracy problem. Obviously some do but, from my own experience I also know that it's not always the gun. I'd be curious to see how my pistol performed in a Ransom Rest but here in BFE that ain't gonna happen.
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Old 08-24-2012, 10:39 PM
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here's another thread that we were having a deeper discussion ...

My M&P9 - Brian Enos's Forums... Maku mozo! - Page 2
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Old 07-05-2013, 01:18 PM
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An old thread but it came up on a Google search. Since this thread started S&W has gone to a 1:10 twist or 1.9XX twist if you prefer. Does anyone know either the date or the serial number of when the new barrels first appeared?

Is it possible to buy the new barrels from S&W?

Take Care

Bob
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