Low clearance, high clearance, and tolerance

[wacki]

In this thread:

http://www.thehighroad.org/showthread.php?t=230072

People said that an AK will be just and accurate as an M16 if the tolerances are the same. People said clearance has nothing to do with accuracy. If that's true is there any reason to have a low clearance weapon? Is there any advantage to high clearance? It seems like a high clearance weapon would be a common sense move yet our military uses low clearance weaponry.

 

[Oleg Volk]

Parts with large clearances can batter against each other when moving, leading to greater clearances still over time. That would affect longesvity.

 

[wacki]

Parts with large clearances can batter against each other when moving, leading to greater clearances still over time. That would affect longesvity.

yes but is there an advantage to having low clearance?

 

[jlmurphy]

A tighter chamber might improve accuracy, but the main reason the AK series is less accurate is the entire gas system is hanging on a relatively thin barrel. The AR series uses a small, light tube to divert gas to the bolt carrier, behind the chamber. It is possible to almost free float a heavier barrel, similar to a bolt gun. It is impossible to to this with an AK.

 

[jstpush]

Quit worrying about tolerances

Match your weapon to your circumstances.

If you are going to be shooting out past 500 meters, I definitely wouldn't be using the AK. But I also would take one of my FN-A4s or Rem PSSs with 10x scopes to clear a house.

The selection of tools is based on what you know you will be encountering 80-90% of the time, and being able to do that the best. The conditions for the remaining 10-20% of the time need to be handled, not excellently nor mediocre.

The AK fits the bill 110% for the type of environment, soldier training level and budget, for the areas where it is used. Our M4's may not handle the environment well, but are more accurate than anything that is being fielded against them.

It is funny though, how we select a weapon that requires higher training levels and more maintenance than anything else available. Give me an impulse driven weapon for use in the sandbox.

If I know that I'm going to be playing battlefield pickup, I'm not going to use the most engineered, tightest toleranced weapon out there. I'm going to adopt what I can readily take off my enemy after they are dead. My mates don't take to kindly when I try to steal mags/ammo off of them, even when they are dead. But that's another thread.

I don't personally own an AK at this time, but I've got plenty of 7.62 ammo/mags, to fill the ones that will be dropped! Why buy now what I will get for free later?

 

[wacki]

Quit worrying about tolerances

I think you missed the point of my post. This is more about engineering than any single firearm.

 

[vanfunk]

Maybe I'm missing the boat here, but remember that "clearances" and "tolerances" are not the same thing. Tolerance refers to how much a part, or the space between parts, is allowed to vary from the specification. A Pakistani forge turning out hand-wrought AK-47's is likely to have large tolerances, for example. Clearance relates very specifically to how much "room" there is between moving parts or assemblies. Most modern AK's have large clearances but small tolerances, i.e. the "looseness" between certain parts is part of the design. Good AR's have both small tolerances and tight clearances. For repeatable accuracy, it is best for all the moving parts in a system to come back to exactly the same place each time the rifle is fired. This is very hard to accomplish with the AK's large number of moving parts, high reciprocating mass and large clearances. The AR has very few moving parts, and the direct impingement gas system eliminates much of the reciprocating mass. The tight lockup of the locking lugs and chamber makes for a highly "repeatable" arrangement between shots.

HTH,
vanfunk

 

[wacki]

For repeatable accuracy, it is best for all the moving parts in a system to come back to exactly the same place each time the rifle is fired. This is very hard to accomplish with the AK's large number of moving parts, high reciprocating mass and large clearances.

See I haven't heard this. And according to many of the moderators in the thread I linked to, you are wrong. I personally don't know. But they seemed say that clearances have no impact on accuracy.

 

[jlmurphy]

Clearances and tolerances aside, there are some auto loading designs that are better than others when it comes to accuracy. I said accuracy, not reliability. Most military designs are rugged, reliable, inexpensive, and accurate, in that order.

 

[vanfunk]

I'm not sure the others are saying I'm wrong. I think most knowlegable firearms afficionados know that, all else being equal, it is harder to manufacture a tackdriving rifle based on the AK platform than it is to do it with an AR-based action, or a bolt action. The bolt action is advantageous because that bank vault action (on a well made action, anyway) is locking up with a very high degree of consistency from shot to shot. The AK is definitely capable of more accuracy than many shooters give it credit for, due IMO to the poor sights and ergonomics as was previously stated. And you will occasionally find an AK that'll outshoot an AR, but that is rare indeed. The way the AR action is designed, with narrow clearances and very low reciprocating mass, gives it a big leg up in the accuracy department compared to other semi-auto designs. An M-14 pattern rifle can shoot impressive groups, but chances are you're going to have to spend alot of money to make it so.

vanfunk