Last week I asked for reader input concerning a nickel-boron-coated bolt carrier group as a way to solve various AR15 problems. Thanks to everyone who responded: your feedback has been very useful in resolving the issues I raised.
I'm implementing with my disabled shooter 'clients' the following 'fixes' recommended by readers:
- Getting those involved to shoot their AR's with very 'wet' bolt carrier groups (BCG's) and upper receivers. The heavily lubricated AR's do appear to minimize many problems. I have serious reservations about using a lot of lube in dusty or sandy environments, based on my experiences in Africa; and it seems my hesitation is shared by some of my friends who've been in the sandbox in more recent years. I also question whether one can store a weapon in a sufficiently 'wet' condition that it'll be usable in an emergency - won't the excess lubrication dry on the internal parts and gum up the action, or leak out of the receiver if the weapon's stored in an upright position, or perhaps affect the ammunition? I'd appreciate further input from readers about those points. However, as a way to 'break in' the AR's to the point that they'll run more reliably without excessive lubrication, it seems like a good start. We'll see how it goes.
- I've checked several of the 'problem' upper receivers for issues as per reader suggestions. Two cheap uppers do, indeed, show signs of dents or compression when carefully examined from the inside. There's not much showing on the outside, but there are definite (albeit minor) constrictions internally. Both will be replaced (of which more in a moment).
- It was suggested that poor ammunition might be contributing to the problem, and that Lake City ball (i.e. the standard US armed forces round) would be a good 'control' to check this. I duly sent out some of my supply of LC M855 (NATO SS109) 62gr. ball for testing purposes, and feedback was immediately positive. It seemed to feed and function in most 'problem' weapons, with very few issues except in the two suspect upper receivers mentioned above. I've therefore asked those involved to check their existing ammo stocks, and consider spending a bit more for higher-quality stuff.
I've been looking into replacing the upper receivers of two carbines that showed problems (described in point 2 above). In order to make things more affordable for my students, I may end up giving one of them one of my 16"-barreled uppers , and replacing it with a 20" (i.e. rifle-length) upper. That would give me a civilian AR15 equivalent to the US Marines' current M16A4 issue rifle.
It's long been a pet bugbear of mine how many people go with a 16" or 14½" barrel on their AR15 uppers. I don't think they realize how much bullet performance they give up in exchange for the shorter, handier weapon. Remember, the M4 (the military short-barreled version of the M16) was designed for use in armored vehicles and confined spaces, where the 20" barrel and fixed stock of the standard M16 proved less handy. Most of us in the civilian world are not going to use our AR15's from inside motor vehicles or in confined-space house-clearing exercises - or, if we are, we'd better have a whole lot more training than the average civilian AR15 owner!
The M16 was originally designed around its cartridge, and the modifications both have undergone since then have not always been beneficial to performance. Let's recap briefly:
- The original M16 and M16A1 rifles had 20" barrels with a 1:12" rifling twist and fired a 55gr. projectile, known as the M193, at very high velocities. The bullet tumbled and fragmented upon impact, producing vicious wounding effects that made up for its small caliber.
- The M16A2 went to a 1:7" rifling twist in its 20" barrel to stabilize a heavier 62gr. projectile. Its new ammunition was known in the US armed forces as the M855 and in NATO as the SS109. It was designed to penetrate hard cover better than the earlier M193. It succeeded in this objective, but at the cost of much lower tumbling and fragmentation effects upon impact - instead it poked a neat (and very small) hole through the target, producing much less trauma. As a result it's been widely criticized for being less effective against human targets than the earlier M193 round, particularly when fired out of the 20% shorter barrel of an M4 carbine. (The latter has largely replaced rifle-length M16's in much of the US armed forces, except for the US Marines, who've stayed with the longer M16A4. The USMC has always held, preached and practiced the creed of "every Marine is a rifleman" - for which, God bless 'em!)
- Subsequent ammo developments have produced the M855A1 (which initially exhibited serious problems), Mk 262 Mod 1 (designed for longer-range shooting) and most recently the Mk 318 Mod 0 rounds, all of which were intended to address the M855's shortcomings. The Mk 318 appears (based on initial reports) to be performing very well out of shorter barrels, but the USMC is apparently still issuing M855 ball for use in its M16A4 rifles.
All types of ammunition since the M193 (with the recent exception of the Mk 318) were initially designed to function out of the 20" barrel of an M16 rifle with a 1:7" rifling twist. Their performance out of the 16" barrel of an M4 carbine was reduced, as they did not have sufficient barrel length to develop the full velocity for which they were designed. Furthermore, most civilian AR15's have a 1:9" twist, adequate but not optimum for best performance with the military rounds. When expanding (i.e. soft-point or hollow-point) ammunition is used this is much less of a problem, of course: but velocity is still down compared to a full-length barrel, which can make a difference at longer ranges.
Based on my own experience in military service, I've long been biased towards wringing the maximum possible performance out of the ammunition available to me. I've therefore been considering for some time upgrading my 'defensive' AR15 to something closer to the US Marines' M16A4 rifle, including its 20" barrel. It occurred to me that my investigation into carbine problems, and the need to help a couple of students replace sub-quality uppers, would be an excellent time to pursue this. I accordingly started shopping around, with my emphasis being the best military-specification upper receiver available to me with a 20" barrel and high-quality components.
Many very positive reviews, including some cited by readers in comments to my earlier request for help, led me to Bravo Company. They appear to be one of the top AR15 manufacturers in the country, with a stellar reputation for quality and standing behind their products. Best of all, they have a milspec 20" upper receiver currently on sale at what seems like a very reasonable price. It comes without handguards, but with their bolt carrier group; you can select handguards and a charging handle when you order it, if you don't have them already. User reviews are uniformly very positive.
Mine arrived today. First impressions are of excellent quality of components and assembly. I'm going to be putting handguards on it soon, with Oleg's help, then we'll install it onto several different lower receivers and test it. If it shoots as well as it looks, I think I'll have found my new defensive long gun of choice. My existing 16" upper will go to one of the two students who most need one, and I'll look around to see whether I can locate another good-quality upper (or a complete carbine, for that matter) at an affordable price for the other one. (If any readers are able to help with that, please contact me - my e-mail address is in my blog profile.)
Thanks again to everyone who offered advice. You guys rock!