AR bolt sticking inside carrier?

[Vlad G 345]

Hmm .. I don't think it is just finish. The wear is only on the rear of the pads and it looks "bumpy" is if the pads are making unequal contact. 

 

Plus keep in mind the finish might be crap, but that is steel under there and the upper is not. If there is wear on the carrier, whatever it is wearing against is also taking a beating.

 

Do a careful inspection of the inside of the upper and see if you see any wear.

[Vlad G 345]

As long as your upper is also a carbine length you are fine!

 

What? the upper is the upper, it has no special lengths.

[ynososiduts 0]

Hmm .. I don't think it is just finish. The wear is only on the rear of the pads and it looks "bumpy" is if the pads are making unequal contact. 

 

Plus keep in mind the finish might be crap, but that is steel under there and the upper is not. If there is wear on the carrier, whatever it is wearing against is also taking a beating.

 

Do a careful inspection of the inside of the upper and see if you see any wear.

There's some marks on the inside top of the upper that have similar jittery marks to the wear on the bolt. They look darker than the metal surrounding it, like the finish from the bcg is rubbing off on the upper.

[Vlad G 345]

Well if you are not seeing shinny aluminum when you clean the inside of the upper then don't worry to much but keep an eye on it.

 

Also lube the CRAP out of that thing, even a think coat light grease on the contact pads wouldn't be a bad idea.

[ynososiduts 0]

Well if you are not seeing shinny aluminum when you clean the inside of the upper then don't worry to much but keep an eye on it.

 

Also lube the CRAP out of that thing, even a think coat light grease on the contact pads wouldn't be a bad idea.

Yup, have a tube of superlube coming in with my boresnake. I just gave it a small drop of CLP on each side and spread it with my finger before I went to the range.

[JohnnyB 4,323]

What? the upper is the upper, it has no special lengths.

Vlad, they do make A2 and A4  buffers and springs. Some say they are the same and some say reliability can be affected. Since I have only carbines (m4s) I am not sure if there is any difference.

I will trust your more knowledgeable opinion that it won't make a difference and retract my previous advice about M4 buffer and M4 upper. I live and learn!

[Vlad G 345]

Yup, have a tube of superlube coming in with my boresnake. I just gave it a small drop of CLP on each side and spread it with my finger before I went to the range.

 

Nah, drench it. AR's always run better when wet. They'll be ok dry most of the time buy they are happy wet. Like messy wet.

[Vlad G 345]

Vlad, they do make A2 and A4  buffers and springs. Some say they are the same and some say reliability can be affected. Since I have only carbines (m4s) I am not sure if there is any difference.

I will trust your more knowledgeable opinion that it won't make a difference and retract my previous advice about M4 buffer and M4 upper. I live and learn!

 

It's all cool, I just though I misunderstood you. All AR uppers are exactly the same size (assuming you don't wonder into 308 ones). If in spec, you should be able to slap any upper to any lower, and they should work, regardless of recoil system.

 

Think of it this way, it's not as if they make different lowers for carbines and rifles, and the pins are in the same place regardless

[High Exposure 5,662]

Vlad, I think JohnnyB is referring to paring a gas system with its corresponding receiver extension (otherwise known as a buffer tube) eg: A carbine length gas system with a carbine type receiver extension, carbine length action spring and a carbine (or H, H1, H2, H3) buffer. Or a rifle length gas system with an A1 receiver extension, rifle length action spring, and rifle buffer.

 

You can run into reliability issues mixing gas systems lengths and receiver extensions setups (action springs and buffers) but generally they will run.

 

Putting the wrong guts (buffer and/or action spring) into a particular receiver extension can also cause issues especially on guns that already have gas issues.

[Vlad G 345]

Hmm, maybe, but it hasn't been my experience. I've ran carbine length gas systems on rifle recoil systems, and rifle gas systems on carbine systems with no issues.

 

If you mean that what is inside the receiver extension needs to match the receiver extension (ie don't put a carbine buffer in a rifle extension or the the other way around, same with springs) then absolutely, that matters.

[El_Mal90 0]

Vlad, I think JohnnyB is referring to paring a gas system with its corresponding receiver extension (otherwise known as a buffer tube) eg: A carbine length gas system with a carbine type receiver extension, carbine length action spring and a carbine (or H, H1, H2, H3) buffer. Or a rifle length gas system with an A1 receiver extension, rifle length action spring, and rifle buffer.

 

You can run into reliability issues mixing gas systems lengths and receiver extensions setups (action springs and buffers) but generally they will run.

 

Putting the wrong guts (buffer and/or action spring) into a particular receiver extension can also cause issues especially on guns that already have gas issues.

Yeah, the springs are either looser or stiffer depending on the the location of the gas port and the resulting pressures. So a carbine spring would be stiffer than a rifle because the carbine gas port is closer to the action which causes a higher pressure.

 

As High Exposure mentioned there could be reliability issues, but the setup will almost always run.

[Vlad G 345]

Yeah, the springs are either looser or stiffer depending on the the location of the gas port and the resulting pressures. So a carbine spring would be stiffer than a rifle because the carbine gas port is closer to the action which causes a higher pressure.

 

Err not really. The springs are stiffer and shorter in a the shorter recoil system so they will fit, it has nothing to do with the gas port pressure.

 

The AR system needs X amount of gas delivered over Y amount of time to function,  but there are many variables at play. The gas port is not equally sized on a 14.5 barrel and on a 20" barrel. For example the Colt specs call for 0.093 gas port for 10.5" barrel, 0.063 for a 16" barrel, a 20" barrel will be 0.086" etc.  This are calculations based not only on the length of the gas system but also on the remaining dwell time of the bullet past the gas port and expected pressure at the gas port. 

 

A properly built barrel with a proper size gas port for its length will actually let the correct amount of gas into the system to operate the gun. In theory, the spring rate and buffer weight should provide the correct amount of resistance to slow down the carrier and return into battery, regardless of the type of recoil system. 

 

Of course these are all in various ranges. The gas port sizes I gave are the small side of the spec, and there is a high end of the spec and there are barrels made out of spec. A lot of barrels tend to be on the sloppy side of gas port sizes because as a rule of thumb it is probably "safer" as in the gun will run with crappy underpowered ammo more reliably. If you were building a gun for 5.56 only you could get away with much smaller gas ports. Thus people end up adding heavier buffers to their carbine systems to slow the thing down a bit when the guns are over gassed, and end up with H3 buffers which weigh as much as the rifle buffer does.

 

This is from someone who runs a rifle buffer system, with all the weights removed from the buffer, and every one of my uppers will run on it, from the 18" competition setup with lightened carrier and undersized gas port running both 2500fps 55gr ammo and 69gr ammo 2850fps, to the 14.5" setup with full mass carrier running 5.56 full power ammo. All the uppers also run on my standard H1 buffered carbine lower.

 

It isn't about the lower, it is all about the upper being properly setup to put out the correct amount of gas. A lot of the advise about buffer weights and stuff like that is because of over gassed uppers, in my experience.