10mm vrs. .40 S & W accuracy?? - Pistolsmith

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Old 10-25-2005, 05:04 AM   #1
Join Date: Aug 2003
Location: Winfield, IL
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10mm vrs. .40 S & W accuracy??

I've been reloading for over 25 years and like others, found some cartridges more "inherently accurate" than others. Examples include .45 ACP and .357.

After shooting USPSA and the folllowing with .40 S& W, I found that cartridge very difficult and quite limited to its "sweet spot" for accuracy; however, with the same power factors, I've found the 10mm, like the .45 ACP, to have many superbly accurate loads.

I'm surprised how many shooters don't know the case differences between the .40 S & W and the 10mm. One is weak and scalloped inside with a small primer and the other is strong, rifle like, with a large primer. My thinking is that even though these two use the same .40 bullet, factors like case capacity, internal design, primer differences, power curve differences, and even lock time play a major role in accuracy. Plus, shooting flat has a major advantage, even at moderate distances.

My 10mm 1911 upper will outshoot my 1911 .40 S & W upper every time with ease; however, critics say the difference in my barrels is the root cause.

So does anyone have a 1911 with the same barrel maker in .40 and 10mm to support my claims that with the same power factor, the 10mm is more accurate?
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Old 10-27-2005, 04:32 PM   #2
Join Date: Jan 2002
Posts: 291
Can't disagree with your comments on the .40S&W's apparent lack of inherent accuracy, as that's been my experience too. All the factors mentioned in the third paragraph of your post are critical to the 10mm's superior level of accuracy.

I've handled and shot a lot of 10mm pistols and their .40 counterparts. For example, I own and shoot S&W 10mms. Their accuracy with any number of factory 10mm loads runs from merely great to phenomenal. I've shot several S&W .40s, like the 4006, and wasn't impressed at all. Groups fired with typical .40 ammo are nowhere near as tight as those produced by the S&W 10mms using average-grade 10mm fodder.

Likewise, the Glock 10mms are tight shooters, better than some supposedly "custom" target 1911s I've fired. However, some early 2nd Gen Glock 40s I shot (G22 & G23) left only "pie-plate" groups at spitting distance and were minute-of-barn-door further away.

I've only shot one .40 1911 (a Springfield). This one had been throated and polished, and had it's trigger lightened. Groups weren't too bad with the owner's pet handloads (loaded specifically for that gun), but when we ran factory 180gn .40 FMJ loads through it the groups ballooned bigtime. No surprise, of course, but this gun wasn't even in the same universe, accuracy-wise, as my Tibbets-customized Delta Elite firing average factory 10mm loads (e.g., CCI/Blazer 10mm 200gn; UMC 10mm 180gn).

The only .40 pistol whose accuracy impressed me enough to hold my interest (if I ever wanted to buy a .40) was the Sig 229. I've shot a number of those in the last few years. I don't know specifically what Sig did to the gun to enhance the accuracy level of the .40 rounds coming out of it (where other makers failed), but they definitely got it right with the 229. I haven't shot the larger 226 in .40, but a couple of people who own this full-size Sig have told me the accuracy is just as good.

Old 10-27-2005, 05:05 PM   #3
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M. Hall's Avatar
Join Date: May 2001
Location: Tucson, AZ
Posts: 2,141
It's kind of funny, but by far the most accurate pistol I've ever owned was a Glock 20, and the
absolute worst was a Glock 23....
Old 10-29-2005, 03:50 AM   #4
Join Date: Nov 2001
Posts: 111
Originally Posted by M. Hall
It's kind of funny, but by far the most accurate pistol I've ever owned was a Glock 20, and the
absolute worst was a Glock 23....
And one of the most accurate .40's that I've ever owned or shot was a Glock 24C. It would group right up there with most any $2000 custom pistol including my EGW built Delta 10mm.
Old 10-29-2005, 05:10 AM   #5
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Location: Virginia
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I don't think the 40 is an inherently innaccurate cartridge any more than the 9mm. In both cases, production guns and ammo are aimed at the military/government/law enforcement/self-defense markets. These markets do not require match grade accuracy, but do require consistant functioning. The ammo and guns are built to function reliably, but not always accurately. The same can be said for 45 ACP except for the fact that the 45 has evolved into match grade guns being commercially made and commercial match grade ammo.
Old 10-29-2005, 10:42 AM   #6
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Location: Tucson, AZ
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standds, I'll give you the reliability factor, that gun never did miss a beat, but it shot like a
shotgun.....consistant 15-20 inch groups at 20 yards..... :-?
Old 04-21-2007, 07:36 AM   #7
Join Date: May 2003
Posts: 90
on my svi pistol i have 5 shot groups that is about an inch to an inch and a half at 25 meters using . vv n230 4.5gr. and 180 coated heads with an oal of 1.180
Old 06-22-2007, 09:54 AM   #8
Join Date: Mar 2007
Posts: 305
I may be sensing a little bit of bias here towards the 10mm. Mind you I do own some, and will admit that my Delta Gold Cup Ten is extremely accurate, but it's had some work done on it. I'm an avid USPSA shooter and compete mainly in limited division where the .40 S&W is the dominant caliber. None of the .40's I use display any of the accuracy issues some of you allude to, namely the 15 to 20 inch groups. I'm also not just defending the .40 in my custom USPSA guns, but in all the examples I own such as: H&K USP Tac, SIG 229, Vektor SP1, S&W 610, STI 1911 (o.k., that ones custom), STI Hawk. Any of these will easily hold a 2" group at 20 yards off a bag. The dedicated USPSA guns, P16 Limited, CZ Standard IPSC, Benny Hill 6" Fat Free STI, will all do tighter groups than previously mentioned or else they would be sent back to the smith for some tune up!
Old 06-23-2007, 05:17 PM   #9
Join Date: Nov 2003
Posts: 571
Ken, I agree with you. I am not a forty fan, although I own a few. I have not seen their tendency to be inaccurate. I have shot many different guns (most not my own) in my Ransom Rest. I have tested loads in forty from the factory and many hand-loads. Most everything will shoot into four or five inches and many will shoot under two inches.

My Glock 24 with the factory barrel will shoot about two and a half average and with the Long Wolf Match barrel it will do better. My Glock 22 is a 3 inch gun with the Wilson barrel installed and I am not sure what it will do with the stock barrel.

I do not have inserts (Ransom Rest) to fit my new STI .40 so I cannot tell you for sure how it groups. I think it will shoot with anything I have including some very accurate .45 acp's.

If you are shooting off of a sand bag, gun bag, V rest, or golf cart, or whatever, you don't really know how well your gun will shoot. You only know how well you shoot. On any given day you may shoot a 2" to 6" group and the next day you may (and probably will) shoot a different size group with the same gun. Nail your gun down in a machine rest and see what it will do before you condemn it.

The 10 mm may be more accurate than the forty, but at most USPSA distances, shooting off hand, you will never know.
Old 07-29-2007, 05:20 PM   #10
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Location: Georgia
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For quite some time I simply shot 40s in my 10mm Delta Elite barrel. The 40s always shot as well as the 10mm loads. I didn't shoot any downloaded 10mm.

Later, I had a Bar Sto 40 barrel fitted to the gun and now the forty is alot more accurate.

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