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Posted: 11/21/2003 4:27:24 AM EDT
I didnt know what else to title this. I have a franken AR that I built on a RRA lower. The upper came conmplete assembled from J&T with the bolt group and charging handle. The rifle functions perfectly, never so much as a little hiccup. At one time I unloaded a magazine by cycling the action. Last night i noticed that all the primers had a tiny little dent in them. just a tiny one. was the firing pin following the round and making this dent due to its own weight? that is what i suspect. would a lighter (titanium) pin solve this. it has never gone off if the trigger wasnt pulled, but it got me to thinking. thanks for the thoughts.
Link Posted: 11/21/2003 4:35:50 AM EDT
it's normal. all AR rifles do it. is it dangerous? Minuetley . When you load the rifle keep it pointed in a safe direction. (but you do that anyway, RIGHT?) what is happening is the firing pin in the AR is not bound by a spring and when the bolt falls forward it contacts the primer.
Link Posted: 11/21/2003 7:29:10 PM EDT
Perfectly normal. Definitely keep the gun pointed in an safe direction when chambering a round...
Link Posted: 11/24/2003 9:55:09 AM EDT
[Last Edit: 11/24/2003 9:56:21 AM EDT by I-M-A-WMD]
Normal...But should be checked none-the-less. If the dent is in fact too deep or if you were to cycle a particular round too many times which would, in time, allow for either a detonation or as the forces in Iraq have found, a round which will not allow detonation when needed. (Since the primer has been dented in too far to allow necessary contact to the primer by the firing pin when the trigger is pulled to detonate the round...Which IMHO I would have to think rarely ever happens) I have a Bushmaster 16" and my Dad and I were shooting off his bench. His bench is shaped like a "T" since I am a southpaw and he is right handed he sits on the left side of the bench and I sit on the right which allows us to both shoot while supporting our strong arm on the bench. Towards the end of the session my rifle discharged and the bullet struck the ground down range and to my right. Whenever we are not actively engaging the targets on our range, and since my Dad was to my left it is a habit to ensure that when loading, checking, or clearing my weapon I point my weapon to my right and he points his to the left. It was spooky as my Dad stopped firing and said, "What the hell are you doing?" After the round fired I literally froze since I knew I didn't have my finger on the trigger. The Rifle was new and I had neglected to check the extent of the firing pin inertia dent up to that point. I told my Dad, "Look at where my finger is." He glanced and said, "Well than what happened?" as he noticed that my index finger was on the BOLT RELEASE not the trigger. Here is what happened, the firing pin was denting the primers as normal, but just a bit much in my final opinion. Since we were winding down the session I was running low on ammo and had a few stray rounds that weren't loaded into magazines. I had taken my magazine out and was single loading by placing the round in the chamber, and then letting the bolt fly by depressing the bolt release. With the primer dent being slightly "excessive" and with a magazine loaded with cartridges riding the bolt, an AD was nearly impossible. But without a magazine inserted to allow some drag on the bolt and the cartridge sitting in the chamber, as the bolt went home the round was allowed to detonate "without intentional cause". I believe the rounds we were firing were reloads as well and more likely than not the primers were much softer than military surplus. We then checked the primer dent caused with a magazine and rounds loaded in the mag, then a mag without rounds in it, and finally once again no magazine inserted and the cartridge seated in the chamber. The depth of the dent increased as more rounds were taken from the mag and was on the spooky side without having a mag inserted. Some judicial honing on the point of the firing pin has ensured this doesn't happen again with this particular rifle. I have added the firing pin safety check whenever I acquire a new AR15 which is now part of my normal function check. This is to ensure the extent of the inertia dent on the primers. If I had been at a large range with shooters all around, they most likely would not have enjoyed seeing a round strike the ground inside the 10 yard line. By 308wood:
When you load the rifle keep it pointed in a safe direction.
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Worth repeating. By billclo :
Definitely keep the gun pointed in an safe direction when chambering a round...
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Most definately. IMHO, Do not go with a Titanium firing pin. From what I've heard they aren't up to spec and are merely an advertising scheme...A solution looking for a problem. Sly
Link Posted: 11/24/2003 11:41:23 PM EDT
Originally Posted By I-M-A-WMD: From what I've heard they aren't up to spec and are merely an advertising scheme...A solution looking for a problem.
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To clarify, The utility of the Ti pin is that it theoretically reduces lock time. The problem is that the vast majority of lock time in an AR, and any other swinging hammer design, is in the FCG. The reduction in lock time achieved with the Ti pin is absolutely minute compared to that accomplished through using a heavier hammer spring and a lighter hammer. Ti burns, that means the first pierced primer you have (possible due to the lighter weight) and you'll have a very expensive pin punch. Do a search on the properties of Ti and you'll see that for a number of reasons it's not the best material for use in a firing pin.
Link Posted: 11/25/2003 9:31:23 AM EDT
By Tweak: To clarify, The utility of the Ti pin is that it theoretically reduces lock time.
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Whether to decrease lock time or to minimize inertia strikes on primers, it seems ill suited for either purpose. Those are two of 3 reasons I've heard or witnessed for Ti Pins. The 3rd reason is there are those people out there who insist that if something is expensive, it HAS to be good. Which keeps useless items on the market to confuse decent folks. TGF ARFcom [wave] Sly
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