M5 308

[BLL]

I have recently built my first M5 .308. I am having issues charging a round. The bolt won’t close completely. If I put a round in the barrel first the bolt closes and will fire just fine. It will sometimes load a 2nd round but not every time. When it doesn’t load into the chamber, the round is stuck and extremely hard to remove with the charging handle. Any information would be greatly appreciated, for I am very new to this. Parts used in build:
Aero precision lower M5
Aero upper
Aero BCG
Proof research 18” Carbon Fiber barrel .875 gas port
Troy gas block .875
Jp Mklll hand guard
Precision armament hypertap muzzle break
Burris XTR genll Milrad scope
I believe that covers it. Thanks for your time and assistance.

 

[gimpy]

Factory ammo, or reloads?

 

[Bigtrucknut]

You have it lubed up good? Shooting store bought ammo or handloads? Does it cycle ok by hand without ammo, any tightness in the action? My first guess is that it sounds like a headspace issue. Did you check headspace with a Go- No Go gage when you built it? If you handload you could make a dummy round with a bumped shoulder and see what that does for you loading.

 

[BLL]

I have all factory Winchester ammo. It is all lubed and cleaned several times. Cycles fine without ammo. I ordered the Go- No Go gages, haven’t arrived yet. Is it common with a higher end barrel to have issues with head space? I also ordered a jp bolt, I was told that is what proof research uses. ?

 

[sam4886]

When I break in a new upper/BC I literally dip the bcg in 10w40 oil and run the shit out of it for a couple mags. Works great. Doesn't need to be dripping wet when you put it back in the upper, but wet for sure.

Wear glasses.

 

[fxdwgkd]

I had the same issue the first time I shot my aero. Tried running it dripping wet, tried dry and neither way would it run. Several times I had to pry the bcg back because I could not budge it with the charging handle. When I got home i stripped the bcg and cleaned with brake cleaner, lubed and reassembled. Manipulated it several hundred times by hand and have not had a single issue since

 

[msgriff]

I would consider the possibility that your barrel's chamber was reamed using the Armalite AR-10 bolt spec. There is about a 0.004" - 0.005" difference (sometimes more) between the Armalite and DPMS pattern bolts regarding the dimension that effects headspace. I could expound on this if anyone's interested. It should definitely be headspaced anyway. Many gunsmiths will check headspace for free if you bring in a stripped bolt and the barrel/upper/ rifle.

 

[Evintos]

+1 for checking headspace

Separate the upper and lower. Remove BCG then take a round drop it into the chamber. Press on it with your thumb. Invert the upper to see if the round will fall out with gravity. If it doesn't fall out, see if you can shake it or tap on the receiver to get it to drop free. If not, see if you can pull it out with your fingers. If your fingers are too big, use a pen or something to see if you can "pry" it free with light pressure.

Take the bolt out of the carrier and place it into the barrel extension, then rotate it. It should be able to rotate freely without binding. Any binding could mean dimensionally out of spec lugs, out of spec barrel extension or burs left from machining. If it rotates freely, take bolt out of the bcg, remove extractor and ejector. Drop a round into the chamber then insert bolt and see if you can rotate freely by hand with the round in the chamber.

If you have an overall length gauge, you can measure the throat/freebore as well. If you had a comparator you could also measure the once fired brass and that'll give you an idea of what the chamber headspace sorta looks like.

Those are some things to try while you wait for your headspace gauges to come in.

When it comes to headspace the bolt or barrel could be the cause of bad headspace.

 

[corey4]

What recoil spring are you using?

 

[BLL]

When I break in a new upper/BC I literally dip the bcg in 10w40 oil and run the shit out of it for a couple mags. Works great. Doesn't need to be dripping wet when you put it back in the upper, but wet for sure.

Wear

I had the same issue the first time I shot my aero. Tried running it dripping wet, tried dry and neither way would it run. Several times I had to pry the bcg back because I could not budge it with the charging handle. When I got home i stripped the bcg and cleaned with brake cleaner, lubed and reassembled. Manipulated it several hundred times by hand and have not had a single

What recoil spring are you using?

Rifle length 39 coil spring 12.5“ long relaxed. Buffer 5.3” @ 5.6 oz. I received my JP high pressure bolt today, gun shoots flawlessly. All headspace issue. Thanks for the input fellas.