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Old 07-11-2020, 01:14 PM
BurninBogey6 BurninBogey6 is offline
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Default M&P Sport firing pin

Brand new M&P sport here, I noticed after chambering a round and ejecting it unspent, there will be a small dimple in the primer from the firing pin. I can reproduce this every time I chamber a round. It appears that the forward motion of the bolt group throws the firing pin at the round when the bolt suddenly stops.

Is this something to be concerned about?
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Old 07-11-2020, 01:20 PM
cyphertext cyphertext is offline
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Perfectly normal. Nothing to be concerned about.
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Old 07-11-2020, 01:21 PM
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I wouldn't continue to load and eject live rounds though, especially not the same round over and over.
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Old 07-11-2020, 01:27 PM
BurninBogey6 BurninBogey6 is offline
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I've only recently noticed this during periodic maintenance. In our house here in AZ, we keep all of our weapons hot. I'll just have to remember to put a different round in every time, or just put the round in the chamber myself and then ride the bolt forward and manually assist it.

It would seem moot that cycling the same round in all the time should matter, how many SM's cycle the same round back in while in deployment? I know I did when we carried hot while deployed in Bosnia.
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Old 07-11-2020, 01:56 PM
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Common to all standard M16/M1, Garand, M14, SKS and AK47 pattern firearms, due to inertia firing pins. One of the reasons that mil-spec ammo requires specific primer construction. Slam fires can occur while loading, so it is IMPERATIVE that the firearm be pointed in a safe direction when loading a round into the chamber. Also, NEVER, drop a round into the chamber and then hit the bolt release, allowing the bolt to run forward onto the chambered round under full power, that increases the chances of a slam fire. By having the bolt strip the round out of the magazine, it slows the bolt's forward inertia and lessens the impact of the tip of the firing pin onto the primer.

Last edited by mckenney99; 07-11-2020 at 02:01 PM.
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Old 07-12-2020, 11:36 AM
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Quote:
Originally Posted by cyphertext View Post
Perfectly normal. Nothing to be concerned about.
Absolutely true; when the bolt closes on a fresh round and goes into battery, due to inertia, the floating firing pin gives the primer a little love tap.
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Old 07-12-2020, 12:44 PM
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Quote:
Originally Posted by BurninBogey6 View Post
I've only recently noticed this during periodic maintenance. In our house here in AZ, we keep all of our weapons hot. I'll just have to remember to put a different round in every time, or just put the round in the chamber myself and then ride the bolt forward and manually assist it.

It would seem moot that cycling the same round in all the time should matter, how many SM's cycle the same round back in while in deployment? I know I did when we carried hot while deployed in Bosnia.
I was looking at it from more of a safety issue. I keep my HD weapons hot as well, but I don't clear them and reload them very often. Pistols stay in the carry holster when arming or disarming, and long guns stay where they are without any handling.

However, when I do clear my pistol, I do not chamber the round I just ejected. It gets set aside as range ammo to insure that it is only chambered one more time to avoid bullet setback. This article says you should do the same with rifle ammo as well.

Why you should NEVER rechamber the same AR-15 round twice - Prepared Gun Owners
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Old 07-13-2020, 07:16 PM
Moe Mentum Moe Mentum is offline
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Yep, a lot of rifles do this, free floating firing pin. Make sure when you chamber a round, it's outdoors, and in a safe direction.
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Old 08-01-2020, 07:50 PM
BurninBogey6 BurninBogey6 is offline
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Quote:
Originally Posted by cyphertext View Post
I was looking at it from more of a safety issue. I keep my HD weapons hot as well, but I don't clear them and reload them very often. Pistols stay in the carry holster when arming or disarming, and long guns stay where they are without any handling.

However, when I do clear my pistol, I do not chamber the round I just ejected. It gets set aside as range ammo to insure that it is only chambered one more time to avoid bullet setback. This article says you should do the same with rifle ammo as well.

Why you should NEVER rechamber the same AR-15 round twice - Prepared Gun Owners
Seeing that MAM from the Army was dated 1 month AFTER I got out of the Army in 2004. Thus why I never heard of this. This is all good info.
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