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Old 12-16-2011, 06:41 PM
BobRowe BobRowe is offline
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Join Date: Jan 2002
Location: Livonia, Michigan
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Well, guys, I think I've found the major cause of the problem with the snap-cap ammo. BTW, I am not using the "Snap Cap" brand, but rather the brand "Traditions" which is likely a bigger seller (at least in Michigan) than the original brand.

Anyway, I finally found my micrometer and calipers, and I took various measurements of the snap cap and loaded ammo -- in this case, PowerBall 9mm ammo. I only found two dimensions that were really different, but those two dimensions likely relate directly to my extraction problem. They were: (1) Rim thickness; and (2) Rim diameter.

The PowerBall ammo was exactly what SAAMI (Sporting Arms and Ammunition Manufacturer's Institute) specifications state they should be. Rim Thickness was 0.035" and Rim Diameter was 0.392".
The snap cap ammo had significantly different dimensions. Rim Thickness was smaller than SAAMI, at 0.025". Rim Diameter was also smaller than SAAMI, at 0.377". So the snap cap rims were 0.010" smaller in thickness, and 0.015" smaller in diameter, than SAAMI specs.

I don't have the capability to measure the difference between the S&W M&P pistols and the Glock pistols, in order to explain why the snap caps work in the Glocks, but not in the M&P's. However, I suspect that one or both of the following differences exist: (1) The tip of the Glock's extractor claw extends further into the extraction groove than does the claw of the M&P; and (2) The spring tension on the extractor claw is greater on the Glock than on the S&W.

So, I'm satisfied that there's nothing wrong with my 9mm M&P pistols, and I've put them back into service. Thanks to all forum members who obsessed with me on this issue.

Bob
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