Monday, January 26, 2009

The Unintentional Straight Pull Bolt Action Rifle

So it seems like Ambulance Driver is having a little trouble with his AR. It'll run for 30-100 rounds, then it becomes a straight pull bolt action.

Well, we've all been there at one time or another. Hell, I had it happen to me at a rifle event once (bad ammo).

Thank god it never happened when I actually NEEDED the rifle for serious social purposes (which is why I always have known good ammo and magazines, and clean and lubricate properly).

Since the rifle in question is a decent quality piece (a Bushmaster), the problem gets progressively worse the more he shoots, and he doesn't mention having problems with his magazines (the usual culprit when ANY semi-auto isn't cycling properly); I'm guessing it's one of two problems:
  1. Cheap nasty steel cased ammo

  2. Overlubrication
Seriously folks, I don't care how cheap you are, or how expensive ammo is, AR's are not designed to function with anything other than brass cased ammo.

Brass and steel cases expand to seal the chamber (called obturation) differently, and retract from that seal differently. This alters the timing of the weapon and causes unreliable extraction. This is especially true of M4's with their shorter, higher pressure gas system; which is much more sensitive to proper timing.

Also, steel rims, combined with that different timing, work the extractor of an AR MUCH harder than designed; and can detension an extractor spring in as little as 500 rounds instead of the 5000 or so (or 20,000 if you have the machine gun spring buffer, and an o or d ring in) you'll get with brass.

Also, the powders they tend to use in steel cased ammo are nastydirty; and will gum up the gas system and bolt, and blowback more residue into the receiver, coating everything with FAR more carbon than in higher quality ammmo.

Additionally, that difference in obturation causes firing residue to blow back into the chamber, progressively coating it with more hot sticky stuff; until extraction and even feeding become difficult. If the extraction get's sticky enough, it can actually chip the extractor, or tear the head off a cartridge leaving you with a not every effective club.

Again, these issues are exacerbated in shorter length carbines.

It doesn't matter whether it's polymer or Lacquer coated; steel is just generally not great for ARs. It will have problems with extraction over time, I guarantee it to you.

Seriously, that's just more to clean, and less reliability; don't use it.

I suspect the biggest problem he's having though, is that he's overlubing the weapon.

Almost everyone does.

Even better, most folks don't recognize overlubricating for what it is, think they're UNDER lubricating the weapon, and make the problem worse by squirting even more goop in there.

Then when that fails, they make it yet worse by switching to another product incompatible with the first that has suspended nano super slip lube in it or somesuch crap; and they might as well squirt superglue into their action.

Overlubing will gum up your rifle in a magazine or three pretty easily; even if you're using clean ammo, and you're not in a dusty environment. Add in dirty ammo or dust, and again, you might as well be using superglue for lube.

So, what is the proper lubrication for an AR (this applies to an M16 as well; you just need an additional drop or two for the auto sear mechanism)

Alright first things first, you need to undo the damage.... actually you should do this when you first get your AR, and every 1500 to 5000 rounds (depending on conditions and ammunition) or every six months anyway.

For this you will need your normal cleaning supplies, CLP (or something similar), original Militec (or something similar), and a non-chlorinated degreaser/cleaner that doesn't attack ABS plastic (I use M-Pro 7, Slip, or Hoppes elite; all essentially the same thing); and you may need a carbon solvent (I use Hoppes elite).
  1. Detail strip and clean the rifle, paying special attention to your bolt and carrier, trigger mechanism, and your chamber and chamber extension. Clean them to bare metal, with a degreaser, and if necessary a carbon solvent (especially the internal passages of the bolt and carrier). Use a chamber brush and barrel extension brush to make sure they are really properly clean.

  2. Spray your trigger mechanism, the internal surfaces of your receiver, your barrel extension, and your receiver pin bosses, LIGHTLY with CLP. Then cycle the trigger a few times to distribute, and let sit to dry.

  3. After a few minutes, wipe every surface you can reach clean and dry. If you happen to have some compressed air, you can let it sit a few minutes then blow it off; but lightly means lightly, so that shouldn't be necessary.

  4. If you reassembled them after cleaning, disassemble your bolt and carrier mechanism; then coat your bolt and carrier mechanism and all components thereof (including the internal passages, using a q-tip if necessary) liberally with CLP.

  5. Let sit for a few minutes, and wipe all the parts down til completely dry. Remember to pass a Q tip through the firing pin passage in the bolt and carrier to wipe them dry.

  6. Then let it sit for a few more minutes, and wipe them all down again.

  7. Put a single drop of militec or something similar on each trigger pin.

  8. Put single drop of militec into the trigger and sear, and smear a bit into the hammer hooks and disconnector, then cycle the trigger a few times to distribute. If this is an M16/M4, also put a single drop on the auto hooks, and a single drop on the auto sear pin.

  9. Put a single drop of militec on the safety or selector, and smear it around with a q-tip; then cycle the safety a few times to distribute.

  10. Wipe everything you can reach with your fingers or a qtip, to distribute the lube. Nothing should look "wet" or greasy.
That may seem like it's a bit fussy, or a lot of work; but remember this isn't your general clean and lube procedure. You only need to do this every few thousand rounds.

Also, it sounds a lot more fussy than it really is. It took me longer to write it up than it does to actually do it.

What you're doing there is cleaning off all the pre-existing or built up residue and lubricant; then establishing a coat of protectant and baseline lubrication level on all surfaces.

Now, when you reassemble from your detail strip, and again every time you clean the rifle:
  1. Put a single drop of militec on both of the bolt rails, then spread up and down the rails.

  2. Put a single drop smeared evenly around the body of the bolt and a little into the cam slot and onto the cam. DO NOT put any lubricant into the gas rings, the firing pin passage, or under the extractor; enough will be there from the CLP earlier, or will migrate there during use.

  3. Fit the bolt and cam back into the bolt carrier, then work them back and forth a bit to distribute the lube, and disassemble again.

  4. Put single drop on a q tip wiped around the entirety of the bolt ears; then wipe it off with your finger tip to spread it out a bit, and a dry q-tip to make sure no lube builds up in the corners. DO NOT LUBRICATE THE BOLT FACE, EJECTOR, OR EXTRACTOR; they will get enough lubrication from the initial CLP coat, and through surface migration.

  5. Wipe all the bolt and carrier parts down with your fingers to spread the lube evenly; and so none of the parts or surfaces are actually "wet".

  6. You generally don't want to re-lube the trigger mechanism with every cleaning; because you don't detail clean the trigger every cleaning, and it can cause lubricant and residue to build up. If however you're feeling any drag or grit in the trigger or selector mechanism and don't have time for a detail cleaning, re-lube the trigger and selector as above.

  7. Reassemble taking care to ensure the gas ring gaps are not aligned; then cycle the weapon and dry fire a few times to distribute the lubricant.

  8. Finally, wipe down every visible surface you can get to with a clean dry cloth.
When you're done, no surface on the rifle should look "wet", and if you wipe any part with a clean white cloth you should come back with a slight oily residue, but no heavy smear of oil and no carbon.

Again, this sounds a lot more fussy than it really is. It takes less than five minutes, and no tools; and even the q-tips are optional (you can spread lube into small spaces with the firing pin and your fingers; it's just not as easy or convenient as a q-tip).

That's it. Everything else is overlubing and will attract residue, dirt, and grit like a magnet.

UPDATE: Reposting with some edits on a Monday, because there's a lot of AR owners who really need to read this; and nobody ever reads anything posted on a Saturday.

Also, I have heard several supposedly knowledgeable "authorities" stat that it is "impossible to overlubricate an AR". Those people are on crack.

Actually, I'd guess they are overgeneralizing from their own personal experience; which is limited to environments where overlubrication isn't a problem. They are most likely people who never shoot anywhere but on a clean range with clean commercial ammo; or they are garrison or fleet marines who never served in a desert environment.

Seriously, I think sailors and fleet marines believe lubricant is best applied with a firehose. Also someone should teach them yes, it is actually possible to clean your weapon too much. When you're wearing off the hard anodizing, that's a sign you've gone too far.

Most airmen on the other hand (outside of those who have served in combat support of course), if they even remember what an M16 looks like, think lubricant is something purchased with their other Class VI "critical supplies".