Help with a AR-15in 300 blk

[43PU]

I just bought a completely upper from live free armory in Florida. It is a 16 inch barrel with pistol length gas and a 1/7 twist.

The problem is when the bolt goes home the bolt sticks to the point to get it open I have to grab both sides of the charging handle and put the stock on my chest and pull as hard as I can I mean I'm 6'4 and it is hard for me to rack open. I have shot about 100 rounds of FMJ through it and it just doesn't like cast :( any ideas to help with the lock up?

[Gtek]

Check the neck OD size of a fired case against a new boolit loaded neck.

[Boolit_Head]

Check your OAL as well it may be sticking in the throat.

Also mortaring the action could help, pull back on the charging handle and bump the stock on the ground to free the bolt.

[43PU]

No the bolt is sticking on an EMPTY rifle

[Boolit_Head]

Yikes that indicates something is really wrong. Was the bolt supplied with the upper? If so I'd be on the phone with the supplier you got it from.

[Tnfalconer]

That is interference with the bolt head and barrel adapter. Before you do anything else, strip the upper and check the barrel adapter for obstructions. Then remove the bolt head from the BCG and check it's fit to the barrel adapter. That will tell the tail.

If those are all ok, check and or lube your bolt. It may not be rotating in the assembly to lock and unlock as it is retracted.

[BUCKEYE BANDIT]

"If those are all ok, check and or lube your bolt. It may not be rotating in the assembly to lock and unlock as it is retracted. "

Had to run mine REALLY wet for the first few hundred cast loads.

[lefty o]

id send it back, you shouldnt have to fix something new.

[No Blue]

Look at the bolt lugs with a magnifying optic, especially the lug surface that faces the rear. You're looking for a high spot that is polished, that's probably where it's hanging up. Also eyeball the rest of the lugs surface, never know what you'll see.

You can also put Magic-Marker on the bolt and see where it gets wiped off, something like Dykem, machinist marking fluid would be best.

[43PU]

Yeah I do run my rifles really dry i will try adding a big more lube

[mcdaniel.mac]

Yeah I do run my rifles really dry i will try adding a big more lube
ARs need to be wet. Motor oil works just fine.

That said, bargain AR uppers tend to be roughly finished, so inspecting for burs with a bright light is a good idea.

[Moonie]

My sons new 223 Abe upper is hanging up on the barrel extension. I told him to manually cycle it with no ammo about 500+ times to smooth things out a little.ive seen that advice given for new tight ar's before.

[tunnug]

Another for the wet run, most of the problems I've encountered with AR's were because of not enough lube.

[curator]

. I have shot about 100 rounds of FMJ through it and it just doesn't like cast :( any ideas to help with the lock up?

If your problems are ONLY with cast boolits, you need to do a little research on various neck thicknesses of the parent cases used to make the .300blk brass. Your FMJ slugs will measure .308 but a proper cast boolit will be in the .310-.311 diameter. The slightly larger cast boolit can result in a cartridge neck being a bit too large to chamber/extract easily. I had this problem initially when first reloading cast in the .300blk. Using the correct brass eliminated it. While you are researching brass to make .300blk out of, research the "pogo-stick" method of clearing AR rifles.

[Boolit_Head]

I forgot about that. I chose Lake City brass to convert so the neck thicknesses are ok for cast. Various other head stamps have varying thickness brass at what ends up being the neck on a blackout. Some are way to thick to even chamber with jacketed.

[Smoke4320]

If on an empty gun, you have a bolt to extension fit issue as said above it may be as simple as a high spot on the back of a lug
check carefully with a magnifying glass . if found lightly polish and gun gun very wet for 100 rds or so and it will wear in
if no hi spot found and your not gun smith handy return for replacement
YMMV

[308Jeff]

If it were me, I'd send it back.

[Texas by God]

Squirt a fair amount of 3in1 in those two holes in the valley of the bolt carrier and shoot a bunch of cheap ammo. I've seen TiN wonder bolt carriers balk when dry.

[No Blue]

If it were me, I'd send it back.

But you don't learn how and why when you send it back; what does he do in a couple of years, has the same kind of problem? Or with a used gun, without a warranty?

If you're a complete zero with anything mechanical, then send it back; you'd probably cause more damage messing around with it.

[43PU]

I bought the brass here made from.LC13 and it does very good I have checked the throat of the rifle and checked the empty brass I always make sure to size my bookies to .310 which is .005 bigger than an empty neck on a fired case. I'm not completely stupid with guns I have built 13 AKs and a couple of rifle, I even shoot in the Allegany(spelling?) sniper match once a year. I just don't know squat about ARs but I wanted a 300blk and thought I would get the upper. I have a 7.62x38 ultra which is a 7.62x39 straight walled with a AI shoulder on it where I can get 308 velocity. 2 5.56 uppers, a 458 socom upper and a 204 Ruger upper. All of which total have had less than 100 rounds put through them...I'm just not an AR guy which is why I came here with my problems. Thanks for the help

[Boolit_Head]

.310 is fairly large for what should be a .308 bore. Adding the thickness of the case neck may put that tight in the chamber. Try sizing a handful to .309 and see how they work chamber. Stuff like this is why I like the Sinclair slotted gauge. THey are tighter than most chambers but show you where it is interfering.

[Boolit_Head]

Been thinking about this more. If you are sizing to .310 add .020 for cases that measure .010 neck wall thickness. That puts you at .330 when the SAMMI max is .334 ish, any thing that is slightly thicker will get tight quick. If your case neck is thick at .014 that puts you over at .338 and/or you could have a tight chamber to boot. Check the neck wall thickness and try the .309 bullets.

[Smoke4320]

Guys you are missing his second post.... "No the bolt is sticking on an EMPTY rifle "
its not cases or bullets that's the problem

[lefty o]

Guys you are missing his second post.... "No the bolt is sticking on an EMPTY rifle "
its not cases or bullets that's the problem

i didnt miss a thing. that unit would already be on its way back if it was mine.

[Geezer in NH]

Send it back!!!!!!