Last year I built these AR's: AR-15 Picture Thread | Page 13 | Survival Forums So, I build the rifles, take 'em out and shoot a few mags through them and everything is hunky dory. I make a few notes about changes I would make if I did it over again (maybe one size lighter barrel profile so I could use a lighter butt stock for balance, skip the BAD levers (still undecided), maybe skip the anti-roll pins for easier field maintenance, blah, blah, blah. Overall, I'm satisfied and happy. I'm getting ready to work up a defensive load based on the Nosler Bonded Performance, and I've bought a fair amount of XM-197 and M855 for practice that also generates brass for the new loads, and I need some brass. Last weekend I decide to generate a bit of said brass and decide to test rapid fire with some mixed loads, so 2x30 round mags of XM-193, 2x30 round mags of M-855, and 2x30 round mags alternating each round. Only a dozen mags total, so not a huge test. I'm at a childhood hunting camp I recently located, and somebody left a can, a suspected terrorist can, about 50 yards away where there is a nice 200' backstop. The can is dancing all over the place as fast as I can pull the trigger, has denounced Allah, and has asked for a bacon sandwich. Rifle number 2 gets through the first two mags, then 7 rounds into the M-855 I get a FTF. I recharge, fire it, and another FTF. I pull the mag and when I check to make sure the chamber is clear I see that the bolt is forward of where I expect. It turns out that the buffer has escaped the retaining pin. I play with it and sure enough I can replicate the problem manually. I use the remaining mags in rifle number 1 to keep that can in its place (pretty much disintegrated). The buffer tube in this rifle had a slight manufacturing error which I thought I had corrected when I built the rifles. The front portion had been cut at a very slight offset, so that when I tried to join the upper to the lower, the top of the buffer tube interfered. I simply filed a small amount away and made sure that the buffer would stay captive. It did, until it got just enough wear that it failed. A new buffer tube has now replaced it after close examination and very soon it will be tested to make sure it won't let me down when I need it the most. My point is not so much about AR's, firearms, or even equipment. It's about being able to rely on anything you intend to depend upon whether it be equipment, processes or even people. Something I haven't paid as much attention to as I should.
Excellent points both, about reliability and spare parts issues. One thing I've found in the past is weak extractor springs. They'll pull a case about halfway out of the chamber and the extractor will let go, leaving the fired case there. The bolt will then continue rearward, pick up a fresh round from the magazine and try to shove it into the chamber - jam. Happened on two of mine. Now I keep a few spare springs around, among other parts.
Another stumbling monkey and I have played a little with the 300 blackout. Love the round and it does everything I want except one thing. If you have a 300 round in a 223 mag it will work and chamber. Unfortunately the projectile will not fit in the chamber and if the projectile sets back in the case, the bolt will lock and the rifle fire. At that point something goes boom and nothing comes out the barrel. Seeing I have several 223 rifles, I decided to give up on the 300 blackout. Might ruin someone's day if the dropped mag they picked up after TSHTF had 1 300 round in it well down in the stack. When the AR15 is operated in a blow back operation rather than gas piston operation and the breach is locked, something has to happen and I am not about to try to find out what on one of my home assembled rifles. Has anyone else here played with 300 blackout and what are their thoughts on the cartridge?
300 AAC is effectively 7.62x39 for power/performance and a worthwhile cartridge. If I used it I'd put them in mags of a different color than my 5.56 mags. Another option, and cheaper to shoot is a 7.62x39 AR upper. A buddy of mine bought one and it works as advertised. This is the one: RF Upper 16" 7.62x39 HBAR RF Round Rail: FGS rail
Nice looking and worth considering. looks like I would have to buy new mags at about $20 each. I know that the 223 standard mags wouldn't work and I don't think that the standard AK mags would either. Price and specs on the upper looked good, like the USA bit in the add too.
The 556 mags will work for about 5-6 rounds. Some AR15 lowers will also work with AK magazines (never knew that before). Here is a link to some AR15 7.62x39 info. Magazines are discussed at the bottom: 7.62x39 FAQ
