9mm bore diameter size regarding S&W M&P guns and Sig Sauer guns

[WOLFIE]

I shot a new Sig MK-25 yesterday and experienced terrible accuracy issues. Before anyone says the accuracy problem was my shooting skill level, I am a good enough shooter to determine it was this firearm and not me. I also shot a new Sig P227 yesterday and was pleased with the group size. I even went back and forth between the firearms and shot +p 45 rounds. The 45 Sig was awesome and the 226 was sporadic. There was no group with the 226. At ten yards, the shots were 3 - 5 inches away from point of aim. Both firearms have the same standard trigger (not SRT), both are new guns and they are even the same color. Distance was ten yards. One person suggested the slide roll pin could be broken. The slide for the MK-25 is a one piece slide; it is not a two piece as some older Sigs are. This does not mean it is not the roll pin. I don't know. Another suggestion is the bore diameter is larger than needed for 9mm bullets so that 357 sig or 38 special bullets can be used. Is it possible the bore is larger than needed and is it possible the 9mm M&P guns have an over sized bore that contributed to accuracy problems as discussed in a prior thread?

[Chuck Haggard]

Did you try more than one ammo type?

The only way to check the bore is to slug the barrel, at least as far as I know. That's what we did in the olden days.

[LSP552]

I'd do what Chuck suggests and see if a different, duty type loading did any better. If not, I'd call SIG, ask for a shipping label, and send it in for them to check.

[WOLFIE]

I'd do what Chuck suggests and see if a different, duty type loading did any better. If not, I'd call SIG, ask for a shipping label, and send it in for them to check.

That sounds like a good plan.

[GardoneVT]

Wolfie,I do not wish to present myself as a jerk, but very few people shoot two pistols of two different designs exactly the same way. I've yet to witness it in either myself or another, and subtle differences in grip design can make a major difference in how pistols handle in a person's hand.

Perfect case: a Beretta 92 and a Beretta M9 do not share the same backstrap design. The former pistol has a radiused back strap which alters the handling much more then its minute nature suggests.A Sig P227 is not a Sig P226, similar though they may be.

In the position of the OP, I would hand off the weapon to a different and better shooter then myself. If the weapon still shoots off, then further action is called for.

[ReverendMeat]

I would think that if you can shoot the 227 well then there's no reason why you can't shoot a 226 well and I doubt any subtle differences in grip shape matter for slow fire. Try a different brand of ammo first and if the problem persists send it back to SIG, it's an issue with that particular pistol's barrel or slide. What ammo were you using?

[JV_]

but very few people shoot two pistols of two different designs exactly the same way. Probably not, but 'close-enough' does come in to play. I may not shoot a 19 as fast as my 17, but I'm unlikely to group great with one and terribly with the other - especially if time is removed from the equation.

Chuck's question is worth repeating, how many different types of 9mm ammo did you try?

[JHC]

10 yards? Pistols I've had that grouped like soccer ball diameter at 25 could still produced a deceivingly attractive group at 10 yards.

If you can eliminate YOU from the equation; and you shot a Sig 227 side by side to a high standard so I'm assuming you can; I'd suspect that gun is seriously jacked up.

[HCM]

Just to be sure and to save time re: the first questions SIG CS will ask I would do the following:

1) try 1 or 2 different types of ammunition
2) have another known competent shooter fire the gun

Nothing against your shooting skills Wolfie, just a reminder that Gun company CS reps deal with a lot of Derp and the steps listed above will help get them focused on fixing your gun instead of questioning your shooting ability.

I recently picked up a SIG p226 Texas edition 9mm which was giving me fits due to getting 2-3 flyers opening up otherwise decent 25 yard groups. First I learned the didn't like 147 grain ammunition but even with 115 & 124 grain the flyers remained. I brought out my known good P226 .40 cal and swapped slides. The 9mm upper grouped just fine / no flyers when fired kff my 40 frame and conversely my known good. 40 upper produced the same flyers on the new 9mm frame. When i reversed the "transplants" the 9mm again had clyers and the. .40 was good to go. Near as I can tell the issue is trigger over travel causing me to mess up the follow through. I'm debating between sending it to SIG Or just trying the Grayguns trigger for the built in over travel stop.

[WOLFIE]

I finally made it back to the range and shot Magtech 9mm 115 grain which grouped just fine. I shot the ammo which did not group and it still did not group. This was not a gun problem; it was an ammo problem.

[Wayne Dobbs]

Wolfie,

You say it groups "fine" (a dangerous word in my experience) but haven't defined what "fine" is. Tell us what it does for 10 shots off the bench or other solid support at 25 yards. That gives us a usable metric. As JHC stated, 10 yards doesn't tell us anything from a full sized standard caliber service pistol. Not trying to step on your puppy, but if you will go and read some of Molon's posts on this forum, you'll get an idea of what careful testing looks like and it's not done at 10 yards.

[WOLFIE]

Wolfie,

You say it groups "fine" (a dangerous word in my experience) but haven't defined what "fine" is. Tell us what it does for 10 shots off the bench or other solid support at 25 yards. That gives us a usable metric. As JHC stated, 10 yards doesn't tell us anything from a full sized standard caliber service pistol. Not trying to step on your puppy, but if you will go and read some of Molon's posts on this forum, you'll get an idea of what careful testing looks like and it's not done at 10 yards.

10 yards will work for sighting in a pistol. It may not show the complete inherent accuracy potential of the gun. You set a target 10 yards away and the rounds go into one ragged hole (not so ragged if shooting a flat nose bullet such as the 40 S&W) one inch to the left. You may now adjust the sights and bring the group one inch to the right. If the rounds and we can use a 10 shot group go into one hole again in the center ring, you have adjusted the sights. If the sights are off, you will be able to determine that is so at 10 yards.

I was trying to determine if the ammunition caused the problem or if it was the gun. The good ammunition - one inch group. Bad ammunition - 3.5 inch group. This test was measurable. For what I was trying to accomplish, the 10 yard test worked. In theory:
If a target was placed perfectly behind the 10 yard target but at 25 yards, bad ammo - greater than 3.5 inch group. Good ammo - greater than 1.0 inch group.

[Bruce Gray]

For my part, I'm impressed with the results you obtained with MagTech!

FWIW, we test and zero a couple thousand pistols a year here, most of them SIG Sauers. In recent memory, the only SIG I recall that did not group at least acceptably (and most are flat stellar) at 13 yards was an SP2022 with a badly mis-machined slide. Out of one 64-unit batch, a few got out with this unseen flaw. They were replaced.

-Bruce

[Alpha Sierra]

Another suggestion is the bore diameter is larger than needed for 9mm bullets so that 357 sig or 38 special bullets can be used.
Just for your FYI

1) 357 Sig uses the same exact bore diameter and bullets as 9 mm Luger. Both CIP and SAAMI say so.
2) Nobody reputable deliberately oversizes their 9 mm barrels to work with Ø0.357" bullets

[WOLFIE]

Just for your FYI

1) 357 Sig uses the same exact bore diameter and bullets as 9 mm Luger. Both CIP and SAAMI say so.
2) Nobody reputable deliberately oversizes their 9 mm barrels to work with Ø0.357" bullets

I have wondered this. I did hear that Smith and Wesson makes oversize 9mm barrels to accommodate the 357 Sig bullets to make manufacturing simpler or cheaper. You mentioned SAAMI though.

[JV_]

Another suggestion is the bore diameter is larger than needed for 9mm bullets so that 357 sig or 38 special bullets can be used.

Are you confusing 357SIG and MAG? .357 Magnum and .38 Special have the same bore diameters. 357SIG uses a 9mm bullet.

9mm / 357SIG = .355"
.38 Special /.357 Mag = .357"

[Tamara]

I did hear that Smith and Wesson makes oversize 9mm barrels to accommodate the 357 Sig bullets to make manufacturing simpler or cheaper.

Whoever told you that was wrong.

[WOLFIE]

Are you confusing 357SIG and MAG? .357 Magnum and .38 Special have the same bore diameters. 357SIG uses a 9mm bullet.

9mm / 357SIG = .355"
.38 Special /.357 Mag = .357"

I am not confusing 357 Sig with 357 magnum or 38 special. I could be wrong but isn't 357 Sig .356 in diameter ?

[WOLFIE]

Whoever told you that was wrong.

It is nice to hear that is wrong.

[Maple Syrup Actual]

I am not confusing 357 Sig with 357 magnum or 38 special. I could be wrong but isn't 357 Sig .356 in diameter ?

That depends...what's 9 millimetres in thousandths of an inch?

[JV_]

I could be wrong but isn't 357 Sig .356 in diameter ?Most often, jacketed 9mm is .355" and it's +.001" to .356" for lead 9mm.

357SIG would be jacketed, so .355".

[JV_]

That depends...what's 9 millimetres in thousandths of an inch?

exactly

[Tamara]

I am not confusing 357 Sig with 357 magnum or 38 special. I could be wrong but isn't 357 Sig .356 in diameter ?

.357SIG uses the same projectiles as 9x19mm. The same bullets. They are the same size.

[Jared]

Perhaps he's confusing 357 SIG and 38 Super? Wasn't the original spec for the Super to use .356" bullets? (Jacketed bullets I'm meaning here).

[Fire-Medic]

.357SIG uses the same projectiles as 9x19mm. The same bullets. They are the same size.

While this is true to a point you need to take care on bullet selection. A 9MM projectile with too much ogive will cause headaches with bullet setback.

[Tamara]

While this is true to a point you need to probably not be reloading .357SIG because that way lies heartache and, eventually, madness.

FIFY. ;)

[tomr]

That depends...what's 9 millimetres in thousandths of an inch?

not to be a smartass....
9/25.4=x/1
.35433071

[tomr]

While this is true to a point you need to take care on bullet selection. A 9MM projectile with too much ogive will cause headaches with bullet setback.

Huh? Setback occurs from a poor crimp. Thats taper crimp of case mouth to bearing surface.

[tomr]

Bullet diameters vary within .001" independent of lead or jacketed. Hornady for instance, catalogs both .355-.356 bullets for the 9mm.

http://www.hornady.com/store/searchammo.php?mode=search&main_cat=250&categoryid%5B%5D=260&categoryid%5B%5D=421&categoryid%5B%5D=414&x=40&y=6

One can order lead with even greater variance for a given caliber, particularly if chasing accuracy in a revolver where matching chamber throats usually is preferable to bore diameter......

[Tamara]

Huh? Setback occurs from a poor crimp. Thats taper crimp of case mouth to bearing surface.

Check a box of commercial .357SIG FMJ and notice that it has flat point bullets. This is because a the short bearing surface of a long, gradually-tapered 115- or 124gr .355" projectile is a poor match to the short neck of the .357 SIG case.

Google ".357 SIG setback flat point coal" sans quotes, and you'll find it discussed in many a thread like this (http://www.thehighroad.org/archive/index.php/t-598916.html) one.

[tomr]

Check a box of commercial .357SIG FMJ and notice that it has flat point bullets. This is because a the short bearing surface of a long, gradually-tapered 115- or 124gr .355" projectile is a poor match to the short neck of the .357 SIG case.

Google ".357 SIG setback flat point coal" sans quotes, and you'll find it discussed in many a thread like this (http://www.thehighroad.org/archive/index.php/t-598916.html) one.

Ah! Thanks

[Fire-Medic]

TY Tamara I had not seen this until now but you covered it perfectly.