2012 M&P FS 9mm Twist Rate

This is a discussion on 2012 M&P FS 9mm Twist Rate within the MP Full Size Pistols forums, part of the Smith & Wesson MP Forum category; Don't worry about it gupter! A few of us like to treat things with humor. It's all in good fun, but sometimes things get taken ...


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Old April 12th, 2013, 07:23 PM   #16
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Don't worry about it gupter! A few of us like to treat things with humor. It's all in good fun, but sometimes things get taken seriously!

Last edited by Bill in Tx; April 13th, 2013 at 08:55 PM.
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Old April 12th, 2013, 09:49 PM   #17
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It might be nuts, but everyone better go out and give a new M&P's trigger a couple of test tickles.
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Old April 12th, 2013, 10:30 PM   #18
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It might be nuts, but everyone better go out and give a new M&P's trigger a couple of test tickles.
Now THAT'S what I'm talking about, let's perforate some paper. Jason, could you remind me to take my meds? Never mind, ruthless savage has my back.
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Old April 12th, 2013, 11:09 PM   #19
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Now THAT'S what I'm talking about, let's perforate some paper. Jason, could you remind me to take my meds? Never mind, ruthless savage has my back.
Maybe next time I'm driving through I'll leave a note on your door reminding you, just don't shoot.
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Old April 14th, 2013, 06:02 AM   #20
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No worries, I don't get offended easily! And, you will find I misspell words all the time so you will just have to look over that.

Maybe i'll try to make a youtube video of the trigger and you experts can tell me if anything has changed.
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Old April 14th, 2013, 02:22 PM   #21
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I made a video of the triggers and put it in a new thread:

Thread:
M&P Trigger update w/ Video

Just the video:
M&P Shield vs. M&P Full Size 9mm Trigger Comparison - YouTube
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Old April 14th, 2013, 09:11 PM   #22
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This brings the twist rate more like the Europeans have been using for years. Should help with the accuracy issue and help to stabilize the 145+gr bullets I have been casting. Now I just got to get my hands on a new barrel for my Pro 9.

Take Care

Bob
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Old April 15th, 2013, 09:22 AM   #23
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There's a calculation for gyroscopic stability called the Miller Twist Rule. Please, spend a little time with it before you make any assumptions about twist rate a stability.

At least consider the possibility that going from a 16" twist to a 10" twist is not the answer to an unstable 147 gr. bullet, no matter what the Europeans are telling you.

I realize there are folks here that would rather not learn the mechanics of firearms and ballistics, going with someone's claims or personal experience instead, but give the math a once over before you throw money at it. Try this experiment: Enter the bullet and barrel twist of your favorite 5.56 load, then see where the bullet destabilizes as you go with a longer twist.
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Old July 1st, 2013, 07:22 AM   #24
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The faster twist rate likely will solve some of the reported accuracy issues with the 9MM guns. I know my two, older M&P 9MM's, a 5"PRO & a FS, won't stabilize Lyman's 147 gr lead boolit. At 10 yards they are going into the target sideways. I size them .357. A friend in Washington experienced the same issues with his older PRO's he uses for competition. His guns won;t stabilize the 147 gr boolits either.

124 gr boolits sized .357 function just fine. The 1 - 9 twist rate is more in keeping with mu CZ's and STI Trojan, all of which have 1 - 10 twists. These guns run the 147 gr boolits just fine.

I may try to order new barrels for my two 9MM guns once the supply issues settle down in the US.

Take Care

Bob
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Old July 5th, 2013, 10:29 AM   #25
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Originally Posted by KRWeiss View Post
+1

My M&P40 easily shoots sub 3" groups at 25 yards on a bad day, approaching 1 1/2" on a good one, and that's with a well worn 2008 factory barrel. Our 1 in 16 twist rate SLB 9mm conversion barrel prints 2 1/2" groups pretty much all day long. I truly doubt that changing to a 1 in 10 twist rate will do much to improve 8" groups. Also, unless they've improved the wear characteristics of their barrel steel, faster twist rates wear the barrel faster.
How much do you think the above has to do with the issues with the 9MM guns? I have two M&P's a PRO and a FS and neither will stabilize a 147 gr bullet with the 1 - 18 twist. Now if you don't mind bullets going sideways inot targets it is a non issue but...

S&W has made the change for one reason and that was to accommodate the 147 gr bullet and deal with the accuracy issues associated with the heavier bullet. I know of no European gun manufacturer who doesn't use the metric equivalent of a 1 - 10 twist rate so to dismiss the new twist rate is just silly. Maybe the Miller Twist Rule needs tweaking.

Take Care

Bob
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Old July 6th, 2013, 01:51 AM   #26
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Hello.

I have different results with the 1/18

I have good group with 147gr (FP) but very inaccurate withe 115, 124 RN in all my M&P !

Group at 25 meter with bench.



I have the same result than 10-8 performance


Quote:
Original Production Barrels with 1:18.75” twist: These barrels tend to shoot about 3” or better with 147gr ammunition. They do not shoot very well with 115gr and 124gr ammunition, and groups larger than 8” at 25 yards were common.

Now I have one 1/10 Barrel and the results are better with all the combination of bullets weights/profiles


1/18



1/10



Marc
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Old July 9th, 2013, 06:20 PM   #27
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Hey Marc where did you get the 1/10 barrel from? I have a 1:18 in mine and it shoots like crap at 10 yards using 115gr ammo but admittedly it was my only range trip with the gun and standing, plus I hadn't shot in a long, long time. I just put in an Apex Sear, Apex USB and Apex Ram (but no springs were changed) in her and finally got some 147gr ammo to try out (15 rounds of Winchester 147gr White Box and 100 rounds Federal 147gr 9MS, which should match POA and POI with my HST carry ammo). I am worried it will do bad too with the 147gr ammo and want another barrel to try while I still have some ammo to use, 9mm is impossible to find here, even reloads, haven't seen a box in person for over 8 months, paying shipping and ammo cost online sucks.
My Ruger SR9 is my carry gun for now, though I hate the safety flag (I plan to replace that part) it shoots far better than my M&P using any ammo. Shame as I really want to carry the M&P and have already gone and got a lot of expensive but worth it gear for her for that specific reason.

Last edited by StuartBoyer; July 9th, 2013 at 06:25 PM.
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Old July 13th, 2013, 01:49 PM   #28
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Emailed Midway who I found had barrels in stock but they said they didn't know the twist rate and to email S&W. So I did and still haven't got a reply from them yet.
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Old July 30th, 2013, 05:00 PM   #29
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Got a reply a bit back. They said that all new barrels are 1:10 and that is what Midway is provided with. Well I ordered a new one and sure enough its a single dimple 1:10 twist. I can also tell a difference in the crown of the old and new barrel.

New and Old side by side


Old


New


I can tell a huge difference in the lockup on the slide. Its much better with the new barrel.

Last edited by StuartBoyer; August 1st, 2013 at 12:31 PM.
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