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05-13-2014, 03:22 AM
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Bore Conditions
Hi Everyone,
I just got my M&P Pistol brand new, and the picture shows the bore conditions.
Does the bore look normal to you?
The lanes (I think that they are called grooves?) do not seem to be even or leveled.
Is that okay?
Thank you
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05-13-2014, 03:39 AM
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Brand new & never been fired, right? Have you cleaned it yet?
I bet it will look better after you do.
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-Roger
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05-13-2014, 06:56 PM
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If you expected the factory to ship out clean pistols, well...they don't. Clean it before your first trip to the range is the usual advice...
The lands are the "ridges" in the bore. The grooves are the "valleys" from which the caliber of the bore is derived. These lands and grooves are cut in a circular fashion, to give the fired bullet it's twist rate...that is, the bullet doesn't just fly out of the end of the barrel...it spins in flight. The common convention is the right hand twist, which means the bullet spins clockwise as viewed (if it was possible) by shooter from behind the gun. Some guns have a left hand twist, which is not as common. The twist rate is a ratio the distance it travels per revolution, in inches. A twist rate of 1:12, for example, means the bullet makes one complete revolution for every 12 inches it travels. If your barrel is 12 inches long, that means the bullet makes one complete revolution as it exits the muzzle.
When the firing pin strikes the primer, it causes a detonation of the primer, not an explosion. The flame from the primer ignites the powder, which again, makes the powder burn, not "explode". This burning causes hot expanding gases, which drive the bullet out of the case and into the bore. When the bullet enters the bore, it is squished and elongated by the lands to match the confines of the bore - this seals up the bore, so hot expanding gases don't pass the bullet, but instead push the bullet down the bore. If the gases pass the bullet in the bore, this is an undesirable condition called blow-by which affects velocity and accuracy. This is also why bullets are made of soft metals - so they can be squished and elongated by the lands in the bore.
The loud BOOM you here when you fire any gun is all those gases leaving the bore behind the bullet - the gases expand violently against atmospheric pressure, since they're no longer confined to the bore and chamber.
I know I went overboard with this but maybe it will help some "noobs" understand what goes on when they press the trigger...
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05-13-2014, 07:15 PM
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Does the bore look normal to you?
Yes, it looks perfectly normal.
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05-13-2014, 08:39 PM
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Join Date: Jan 2012
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How'd it look after you cleaned it?
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05-14-2014, 12:26 AM
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Thank you very much, everyone.
A special thank to DullH for the awesome explanation.
To MichiganScott, I have not cleaned it yet. I am betting on 307-Niner/Roger that it will look better after.
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05-14-2014, 02:41 AM
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It's very difficult to take pictures of the bore. That doesn't look normal to me, but it could be dirty. I'd like to see a picture after the cleaning.
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Freedom isn't free.
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05-14-2014, 11:31 AM
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Clean it really good, and then look. Those marks may well be some sort of chatter marks or material flaw. Usually, bit chatter marks are not so random as your marks are, so it may well be that it justs needs cleaning. But then again, I have seen all sorts of bizarre things in barrels. Out here in west Texas, in several cases, I have seen scratch marks from the rifling leade up into the rifling itself. Cause? An accumilation of fine "Blow" sand that is real common out here(You oughta see some of our Dust Storms. Troops stationed in the middle east that are from here say they feel right at home when a "Haboob" blows in!) in the leade area in front of the bullet. Upon firing the weapon, the sand acts like it's abrasive self and does it's thing when it gets pushed by the bullet. Just past the leade and first rifling area, gas blow by clears out the sand so it no longer is there and Voila!, scratches in the leade area. It causes no problems with the function or accuracy of the weapon, but boy, does it look bad.
Anyway, clean it and check again. If they are deep, Contact S&W for assistance.
Ofc.JL
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