I already had a pic of the old and new style firing pin retainers side by side on my computer and simulated what they look like when the end breaks off. When my new style broke off it broke off a little bit higher than where the old style breaks, the whole pin was bent, the end that was left bent even farther, and it was weaker than an old-style retaining pin with a broken end. The new kind are flimsier but cheap to make. They're easier to pull out too. You have to push the old style out to get them started, but I still like them better. If you carry a spare firing pin, no problem. My drill sergeants always had a firing pin stuck in their pistol belt when we went to the range. They're a lot better than a bullet tip to make sight adjustments, plus you can push out pins with them, etc.
We didn't have much actual parts breakage on the M16A1s I worked on that wasn't caused by abuse. One of the things that happened multiple times was some grunt left his rifle laying in the open ramp of an M113 APC, the driver hopped in and closed the ramp, and they ended up with a barrel that was shaped kind of like
~. Straight line, 120 degree bend, an inch or two farther, another 120 degree bend back the other way. If they were lucky, someone stopped the driver before he drove close to some trees. They weren't always lucky. Your parents may have told you not to stick your arm out of the car window or it will get torn off. Well, someone should have told those grunts not to stick your rifle out a 113 ramp. Then there was the time I heard the jingling of crap in a sack before a guy got to the shop door with a mysterious garbage bag. I already knew it wasn't the sound of sleigh-bells and jolly old Saint Nick with a bag full of goodies. Oh no. Crap in a sack was
always a lot of paperwork. An M16 was run over by a company, or squadron or whatever it was of tanks, one right after another. I don't know whether the rest of the tracked and wheeled vehicles in the unit also ran it over, but at that point it didn't matter. What they found left of it pounded into the dust was FUBAR.
Once in awhile I had to replace a bolt carrier key. I don't know if people were dropping the bolt carriers on the floor or what, but the end of the keys were getting bent and sometimes a little piece broke off or it was bent so bad it cracked. Handy tip: if the hole in the key is whomped out of shape but everything is still intact, just put a punch in the hole and give it a couple of taps with a hammer. Most drift punches are way too long to get up to the shoulder but a short enough one is the perfect tool. Taper punches usually don't taper enough, but most of the time a center punch will do the trick. The original bolt carriers always had the keys staked in 3 places around the circumference of the screw heads. When we replaced them we didn't do anything like that. We used a cold chisel which
wasn't the sharpest tool in the box, and staked it on an angle on the left and right sides of the screw heads. It looks like that's where everyone is staking them from the factory now. I've never had one come loose or heard of anyone else staking them that way having them come loose, and we made sure not to raise enough metal on top to rub in the upper. But if you don't want to use a dull chisel, "The MOACKS II is available only as a complete unit; $180 plus $10 shipping via Priority Mail."
http://www.m-guns.com/tool_new.php?product=moacks I can sell dull chisels all day long for a fraction of the cost if anyone is interested.
Okay, I just dug out my M16A2 TM to see what it said about staking the key. They came out of the
factory looking like the "field replacement staking", and when we
replaced them in the field, they ended up looking like the revised staking where the
factories are staking them.
The revised staking is just to the right of the "original staking" that I've never seen on an original. Lo and behold, on the facing page they're using a "key tool" to straighten out the opening on a key. It looks like a drift punch to me but it's one of the 7 tools in Appendix E that it tells you to make for yourself. I can post them all in another thread if anyone wants me to.
ETA: They never explain how to make your own tools when you aren't equipped with the tools to make them. I was never issued a lathe or mill or anything other than one tool box and what was in it. And some of that was just paper tags for each missing tool that was on order, but I was glad to have it. For the first 2 years I didn't even have a tool box. Between the 5 of us in my shop at Ft. Polk, 3 who actually worked, we had a bench grinder, about a 3' long screwdriver that would reach inside the length of the shock absorbers on 4.2" mortars that we constantly had to work on
, and the head of a sledgehammer that someone gave us. We never did get a handle for it. We had to borrow everything else off the tank turret repairmen, artillery repairman, wheeled vehicle repairmen...