I've always neck sized for my bolt guns. What about AR's? I currently full length size as I always heard that neck sizing only would affect feeding. What's everyone else doing?
I've always neck sized for my bolt guns. What about AR's? I currently full length size as I always heard that neck sizing only would affect feeding. What's everyone else doing?
The general consensus is that you must full length size for AR's to assure feeding reliability.
Most competition shooters are switching to full length resizing as well, at least in F Class and Palma. I'm not sure about the BenchResters!
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Von Gruff
Tikka,
Take a piece of you fired brass from your AR and drop it in the chamber. Now ease the bolt and carrier down by holding back on the charging handle. Push on the fwd assist to snap the extractor over the rim and see if the bolt will even close without significant force on the fwd assist. On most gas guns the shoulder moves forward enough that the bolt will not close without significant force on fired brass that has not had the shoulder bumped back. Push the shoulder back 0.002 to 0.003" to save your bolt and to prevent making a bunch of ammo that will not chamber. The link that mseric gave is a good one.
Best,
PA
Last Febuary I had a slam fire or AD as we call it. The only thing we could figure out was I was running a suppressor and it was cold that day. I full length resize so the round went in to battery. But the suppressor dose cause more dirt and fouling I think between the dirt and maybe the bolt lube was cold enough the weapon fired when it made it to battery.(The dirt and cold lube kept the firing pin in it's forward firing position and the use of commercial primers) Yikes that will scare the poop out of you. Tore the weapon down and cleaned it could not find anything wrong. I now only run #41 primers in my Tactical Range guns. We practice safe handling and no one was hurt but that's why we have a weapons ready spot before entering the course. My piont is these are combat weapons full length resize it's not worth the posssibility of an AD for you or your weapon. Happy shootin !!
Last edited by Grimmy; 06-06-2012 at 01:17 PM.
Grimmy--- Be careful, you may have a different reason for why this occured. Pull out your bolt and bolt carrier assembly and you can check this as I describe it.Originally Posted by Grimmy
When your bolt carrier travels rearward during the firing cycle your bolt rotates and moves forward. Your firing pin cannot travel fully forward with it. That is an intentional provision to prevent exactly what you described. The bolt carrier will not allow a firing pin to move any further forward than it takes to make proper contact with your bolt until after it has rotated back onto the locked position in battery.
If your firing pin were to freeze up (stuck forward) on firing it would not allow your bolt to travel far enough forward (and rotate) to unlock and cycle.
In the AR systems early years there was an inertia caused slam firing problem that was created by firing pins that had fatter and heavier heads. We called them "fat head" firing pins, and they were removed from the inventory. I would vary rarely find a missed one doing armory inspections, but the odds of encountering one these days are pretty slim.
I thought a had a similar problem to what you encountered with my 10.5" Grendel while very heavily fouled from using a can. Logic told me the pin couldn't actually be the problem, but I couldn't figure it out. I have a nice divot in my asphalt where it popped a round on chambering. I thoroughly cleaned everything and did a function check. Came up OK.... Now fast forward about 6 months and this time upon chambering a round I got a new double divot in my asphalt to go with the first one. OK, deadlined the gun until later.
After close inspection I finally located the culprit--- I had a Knight M16 match trigger set in it (legal registered DIAS) and the damn thing had come just far enough out of adjustment that it could trip once in a while. I had function checked it before and it passed, but now it wouldn't.... WOOPS!!!
Anywhoo, not saying that's exactly what happened in your rig, but you better take another look. Do you have an adjustable trigger in your rifle?
No onthe adjustable trigger I've had this thing apart ten times since can't find anything wrond or different and have put about 1200 rounds through it since the incodent. Thanks for the info though that's what makes this site great. Trigger is a Rock River two stage.
GR33:
Most likely a primer that wasn't seated deeply enough. Or a worn firing pin. I go with the primer, particularly if it was loaded on a progressive.
LR1955
The upper is only a year old I leaning toward the primer also and I only run #41 in that rifle now. It's an 11.5 YHM upper and it only likes to shoot handloads. Standard surplus ball isn't that accurite out of it. I like to run it on the tatical course because of it's compactness and it dose well out to 250 yards.
I got away with neck sizing for My AR... for a while. Severl close calls, and then one severly stuck round will made me find another way for my AR. that's too bad, because I'm very happy neck-sizing for my bolt guns. Rats. wish I could say otherwise, but if you only neck size, sooner or later it will cost you!
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