AR10 possible headspace problems

[ironman56]

I've got a areo precision self built 308 that I think I might have headspace or other problems with , the parts are areo upper ,lower ,wilson combat super sniper 20" barrel, toolcraft BCG aero buffer tube ,spring and buffer all rifle length A2 type. The gun cycles ok ejects 3-4 o'clock, but all ammo including factory 4 differt types show some signs of over pressure ,flattened primers primers with slight lips around the firing pin strike and what I consider excessive soot or carbon around the mouth and shoulders of the fired brass, and the recoil seems excessive for 308 although I don't have another 308 to compare it to .I was going to buy a field gage, but after reading the literature on the midway site I'm not sure that would do any good , I'll load som pics of fired brass but the soot or carbon has worn off from carrying around in my pocket , these brass are factory AAC 150 gr blk tip at 2700ish fps.anyone have some thoughts on this , the accuracy is less than stellar also barley moa .

 

[FieldGaugeFailure]

What do your gauges say? I'm not sure what the midway site says, but testing a barrel with all three gauges is always a good idea, especially if you're doing DiY stuff, and definitely if you're not using a barrel that has been matched to a bolt.

 

[Cascade Hemi]

Looks like too much gas. I don't see anything that suggests too much headspace, just unlocking early. Typically long headspace results in excessive growth of the brass. Your second picture looks like early unlocking ejector smear.

Recently there was a thread about WC and gas tube length. How long is your gas tube? Can you post a picture of the end of the tube in the receiver?

 

[BCP]

Nothing in those pics looks terribly unusual, did you check headspace when you put it together?

 

[LRRPF52]

Headspace: the distance from the breech face to the point in the chamber that is intended to prevent forward motion of a cartridge.

I’m not seeing any evidence of there being a headspace problem.

Your primer blanking is from excessive firing pin aperture size on the bolt.

Notice the nice round edges of the primers.

Your rifle is ejecting at 3-4 o’clock, shooting ~ MOA, and working.

What more can you ask for with an Aero .308 DIY build?

Consider yourself blessed.

 

[ironman56]

Looks like too much gas. I don't see anything that suggests too much headspace, just unlocking early. Typically long headspace results in excessive growth of the brass. Your second picture looks like early unlocking ejector smear.

Recently there was a thread about WC and gas tube length. How long is your gas tube? Can you post a picture of the end of the tube in the receiver?

I used the recommended gas tube , wC was out of stock , got one for Frankford Amory iirc that was the same length, used WC's gas block , didn't have headspace gages for 308 , might have to get them .but even if it cked out of spec, I have no way of adjusting, other than swapping in another BCG.

 

[Rocketvapor]

I don't have a large frame AR but there is a bolt spec for it.

For example, the spec for the AR-15 is 0.153" to 0.156", with most I have seen about 0.154", from back of lugs to the bolt face. That can be easily be measured at home. Whatever the spec is for a large frame bolt, buying another probably won't help if the one you have is in spec. Go gauge and tape for the win.

 

[Cascade Hemi]

I used the recommended gas tube , wC was out of stock , got one for Frankford Amory iirc that was the same length, used WC's gas block , didn't have headspace gages for 308 , might have to get them .but even if it cked out of spec, I have no way of adjusting, other than swapping in another BCG.

It looks over gassed, not a headspace issue. There is a long thread on here about that same barrel. Take a look at it.

 

[MikeMiller]

Try a different brand of ammo such as Federal Match. Could be the ammo is over pressure

 

[ironman56]

Try a different brand of ammo such as Federal Match. Could be the ammo is over pressure

Try a different brand of ammo such as Federal Match. Could be the ammo is over pressure

Tried fedral gold medal match in two weights , can't remember if the primers were looking the same but accuracy wasn't impressive.

 

[BCP]

Your primers are fine the soot on the necks/shoulders could be due to a lighter load, some lube or carbon in the chamber, it all looks par for the course.

 

[wvfarrier]

Something else to keep in mind is some barrels are really tight. I had an 18" WC Super Sniper 308 barrel that would get pressure signs at suggested beginning loads for a lot of powders but is almost always 100-125fps faster than advertised velocities. Most higher end factory ammo will show pressure signs with it while no other barrel does. I ended up returning it to Optics Planet and they replaced it. New barrel (identical) works perfectly

 

[ironman56]

Something else to keep in mind is some barrels are really tight. I had an 18" WC Super Sniper 308 barrel that would get pressure signs at suggested beginning loads for a lot of powders but is almost always 100-125fps faster than advertised velocities. Most higher end factory ammo will show pressure signs with it while no other barrel does. I ended up returning it to Optics Planet and they replaced it. New barrel (identical) works perfectly

That could very well be my problem cuase I was getting high pressure signs with hand loads that were well below max advertised limits. But the accuracy was actually the best with those loads , go figure.

 

[bfoosh006]

I will second the tight chamber from Wilson Combat barrels.
Seems like I have read about that numerous times.

As far as the primer cratering, you might try a few different replacement firing pins... I bought about ten just so I could measure the tip sizes, and they varied quite a bit in size.