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John Farnam's Quips - 18May10.html - Tight Chambers!
Tight Chambers!
18 May 10
Comment on pistol chamber dimensions, from a colleague:
"My SIG P250 has no problem digesting 9mm hardball, but, when I run high-performance ammunition through it, like Cor-Bon DPX, I occasionally experienced 'soft-extraction.' That is, when the slide moved back upon firing, the extractor let go of the fired case too soon, leaving it laying there, instead of ejecting it. Of course, that instantly generated a stoppage!
Replacing the extractor didn't solve the problem.
The SIG folks suggested confining myself to ammunition with nickel-plated cases. However, I believe my 9mm pistol should cycle normally with any ammunition labeled '9X19,' as I'm not sure what I'll be able to get my hands on when I find myself far from home.
I had my local gunsmith run a chamber-reamer into the barrel. An infinitesimal amount of metal was removed. I could barely see shavings, so I suspect we removed less than a half-thousandth from the chamber surface. In fact, all metal removed was toward the front of the chamber.
In any event, it made all the difference! My pistol now runs DPX, and all other high-performance ammunition, nickel-placed or not, normally.
If there has been a decrease in accuracy, I can't detect it!"
Comment: It is common knowledge among manufacturers that tight chambers and a high-degree of accuracy go hand-in-hand. Who brag about the accuracy of their pistols usually achieve it through tight chambers.
However, tight chambers also go hand-in-hand with unreliable operation, only a peripheral concern to non-serious owners, but a critical concern to those of us who regularly carry guns for important purposes.
'Accuracy' is a relative term. Extreme accuracy from a pistol is largely irrelevant for most practical purposes. It provides scant advantage to the Operator.
I carry many different pistols, including the 250. All are reliable, or I wouldn't carry them! Accuracy from any of them is no better than mediocre, and I'm comfortable with that.
I try not to have unrealistic expectations! Given the choice between a pistol that is (1) too accurate, or (2) too reliable, for one, I'll error in the direction of the latter... every time!
/John
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created on Tuesday May 18, 2010 23:59:1 MDT
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