This is a discussion on For those with FS9s having accuracy problems... within the MP Pistol Tech Help forums, part of the Smith & Wesson MP Forum category; Originally Posted by EvilBetty Anyone? There are a variety of ways different organizations shoot and measure groups. For example, for the M9 contract the DOD ...
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|April 20th, 2012, 08:32 PM||#76|
Join Date: Sep 2007
Location: Rockville, MD
There are a variety of ways different organizations shoot and measure groups. For example, for the M9 contract the DOD used mean radius instead of the more common extreme spread most of us are used to. MR takes into account every shot fired while ES really only measures two shots... the rest of the group is noise.
The most commonly accepted way to measure pistol groups is the 25yd 5-shot group. Usually, this is repeated multiple times (I use five groups, for instance) to generate an average. If you're using extreme spread, this makes more sense than high round count groups because, as mentioned above, everything but the two farthest shots are just "noise" in an ES group. You could convince yourself that a 50-shot group is great but it only takes a couple of fliers out of those 50 shots to overshadow the overall accuracy of the gun.
Shooting multiple 5-shot groups provides a good balance between checking for inconsistency and measuring the accuracy of all shots instead of just the two worst outliers.
Ironically, while it's extremely common, shooting groups at 25yd is somewhat misrepresentative. The effects of stabilization -- or rather, the lack thereof -- often don't show up in the short time it takes most handgun bullets to travel 25yd. Where you really start to see major differences is at 50yd. Two guns that are both shooting 2" at 25yd could be wildly apart when it comes to 50yd accuracy. But because 25yd has become something of an "end point" in handgun distance for many people and organizations, and because many firing ranges are limited to 25yd, we have 25yd groups.
Re: barrel twist, all standard Bar-Sto barrels are 1:16 regardless of caliber. This is a cost savings measure. For large companies producing hundreds of thousands of barrels a year for a limited number of models (e.g., Glock) it becomes more economically feasible to incorporate rates of twist that are more caliber-specific. Glock, for example, uses a different rate of twist for its 9mm guns as opposed to its .45's. Glock even uses a different rifling pattern (octagonal) for its .45's compared to its other calibers (which are hexagonal). In fact, almost all aftermarket pistol barrels by all manufacturers are 1:16" twist. The reason some companies' barrels are more accurate isn't due to the twist rate, it's due to tighter tolerances and better fit providing more consistent lockup from shot to shot.
|April 21st, 2012, 09:01 AM||#77|
Join Date: Dec 2011
I shot my groups with a couple birdshot bags filled with rice under my wrist at 25 yards.I don't put a bag in front of the triggerguard unless I'm shooting a contender.This works better for me since I want the POI to be the same for what I'm using the handgun for.I like to hunt deer with a handgun sometimes.Resting the but of a handgun changes POI.It does steady the hold though but I like to practice what is usefull in the field.I shoot 5 shot groups.Some have gone 2 or 3 inch but most are aound 4.The last time I shot 3 5 shot groups 3 shots out of 15 took the groups out to 4 inch but the rest went under 3.That was with 3.6 grains unique and 147FN cast.My best load using 5.7 grains power pistol and win 147HP's shoot a full 17 round mag around 4 inch at 25 yards with all but around 4 under 3 inch.My 1911 45acp shoots 1 inch at 25 sometimes and has done 3 inch at 50 yards sometimes.I wish the M&P could do that but it isn't as tight fitted.The M&P feels great and it's a keeper but untill they can get it a little more accurate I'm sticking to my 1911.
|April 21st, 2012, 03:34 PM||#78|
Join Date: Apr 2009
This a million times over.
If the fitting is the same, you will not be able to tell the difference between a 1:16 twist and 1:18.75 twist (standard M&P barrel).
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|February 14th, 2013, 09:21 AM||#80|
Join Date: Jun 2012
Location: Terrace, BC
I see S&W is now producing the M&P 9MM with a 1 - 10 twist which is more suitable for the 9MM. The Europeans have produciing pistols for the 9MM for a very long time and use a 1 - 10 twist. Why? Better bullet stability equates to better accuracy particularly when shooting the 124/147 gr bullets.
I am hoping Bar Sto will follow suit.
|January 27th, 2016, 04:35 PM||#81|
Join Date: Jul 2011
|January 27th, 2016, 08:17 PM||#82|
Join Date: Jan 2016
Location: Central Maine
My recently purchased model # 10098 had accuracy issues but not 8" groups as the OP had. I sent it back and the barrel was replaced which helped. I replaced the barrel with a Wilson. That helped more, but I want to try an Apex barrel that I'll hand fit.
|January 28th, 2016, 02:10 AM||#83|
Join Date: Aug 2010
Location: West Michigan
Not being good enough for me, I got an Apex gunsmith fit barrel and now my groups are running 1-2 inches at 25 yards, with the same ammo.
|June 18th, 2016, 06:01 PM||#84|
Join Date: Jan 2013
This is an interesting and useful thread. Not the usual I shot a 2" group and seven yards and that's good enough for me.
My Pro is holding under 2" @ 25 groups with 146 grain reloads, last group was right around 1.5. All stock but I do use a rmr which helps with the groups.
My compact shoots 1/4" better, it is all stock with a rmr as well.
Neither has ever hiccupped but only have about 1500 rounds through each.
When I bought the Prop, I was concerned about accuracy but thought I could fit an aftermarket barrel, but, I am happy with what I have.
If my pistol was shooting over 3" I would not be a happy camper.
Would love to hear what some of you are doing to improve accuracy. I'm guessing the answer is to tight fit an aftermarket barrel.
|June 18th, 2016, 08:02 PM||#85|
Join Date: Jan 2016
Location: Central Maine
Golfer, you'd be correct in my case. My very last move before giving up was to install an APEX barrel and my groups shrank from 4" @15 yards to <2"@25 yards.
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