300BLK Cycling?

[sgreen3]

Well I finally got to get my 300BLK out for the first time and the first time Ive ever shot 300BLK. Did however encounter one problem, after shooting a round it would not charge another round. leaving it to me to charge the weapon manually after each shot. I am loading the rounds for this gun so Im assuming its an ammo issue. I did notice that after I shot the last round out of a mag the bolt did not hold open like normal. So Im assuming the bolt is not being sent back far enough to pick up another round to chamber it. I loaded the rounds I was using today with 110gr Hornady Vmax over 18gr of IMR 4227 (yea Id like to have some H110 but it cannot be had anywhere around me) so this power was the only one I could find in stock with data to shoot the bullets I wanted to shoot. My question is do I need to step up the charge weight to get it to cycle? According to my data 17.6gr is the starting loaded for this bullet and powder. An Im using a pistol length gas system with standard carbine buffer. Thanks for any help fellas!

 

[mammynun]

I can't help you with handloads (I'm still researching reloading), but I'd suggest trying some factory ammo as a way to eliminate a problem with the rifle.

 

[ljk]

more info about your upper please. is it SBR/Pistol?

just remember most of the 17gr-19gr load data is based on 16-18" barrels, you will need a can to hold back enough gas to cycle the short barrel.

you said this is the first time took it out, how's your load development? I normally do 2.5gr increments, ie. load 10 round each from the minimum load at 17.0gr, then 17.3gr, 17.5 gr, 17.8gr, 18.0gr, etc. just to figure out which one works the best.

 

[fireball168]

Can the bolt be manually retracted far enough to be held by the bolt stop?

Might want to pop your rail off, slide the gas block forward and see what the carbon ring looks like around the barrel gas port.

If you have the means to measure your gas port, it isn't a bad idea - I've fixed other manufacturer's barrels that wouldn't cycle because they didn't drill the gas port all the way through to full diameter.


I run a .077" pistol port on my personal 16" 7 twist barrel, I can go load up some with your load of 4227 if it would help.

 

[sgreen3]

Can the bolt be manually retracted far enough to be held by the bolt stop?
Yes it can be held back when done manually, what do you mean by checking the carbon ring? What should I be looking for?
Might want to pop your rail off, slide the gas block forward and see what the carbon ring looks like around the barrel gas port.

If you have the means to measure your gas port, it isn't a bad idea - I've fixed other manufacturer's barrels that wouldn't cycle because they didn't drill the gas port all the way through to full diameter.


I run a .077" pistol port on my personal 16" 7 twist barrel, I can go load up some with your load of 4227 if it would help.

Yes it can be held back when done manually, what do you mean by checking the carbon ring? What should I be looking for? Should I check the gas port with a certain size drill bit?

 

[sgreen3]

more info about your upper please. is it SBR/Pistol?

just remember most of the 17gr-19gr load data is based on 16-18" barrels, you will need a can to hold back enough gas to cycle the short barrel.

you said this is the first time took it out, how's your load development? I normally do 2.5gr increments, ie. load 10 round each from the minimum load at 17.0gr, then 17.3gr, 17.5 gr, 17.8gr, 18.0gr, etc. just to figure out which one works the best.

Its a 14.5" barrel with pinned flashider. Pistol length gas system. I just started using the 18.gr so that's all I loaded. But I went ahead and loaded a few more different charge weights with some 150gr fmj bullets I had left to just see if it would make difference. I loaded 17gr an 17.5gr to see if that would make any difference. Just sucks cause like an idiot I loaded 200rds of the one that don't cycle . So it would be awesome to get those to work even though I doubt that will happen cause I really don't want to pull all of them apart lol

 

[fireball168]

Yes it can be held back when done manually, what do you mean by checking the carbon ring? What should I be looking for? Should I check the gas port with a certain size drill bit?

If you have fired more than a handful of loads, when you slide forward the gas block you will see a black ring (hopefully) completely surrounding the gas port in the barrel.

You may find the gas port was restricted by gas block misalignment, poor manufacturing, etc.

Drill bit is the easiest unless you have pin gauges.

 

[sgreen3]

If you have fired more than a handful of loads, when you slide forward the gas block you will see a black ring (hopefully) completely surrounding the gas port in the barrel.

You may find the gas port was restricted by gas block misalignment, poor manufacturing, etc.

Drill bit is the easiest unless you have pin gauges.

Ah ok I see what your saying Ill have to look an see if this other ammo doesn't work. Or will look to see if it needs opend up so I can possibly shoot the ammo I have all loaded up. What size drill bit should fit you think?

 

[fireball168]

.0625" is often stated as being the minimum for supersonic, I've found it to be closer to .067" with my loads.

General use with subs and super at pistol length, I run .072"-.080" depending on the barrel and intended loads.

 

[sgreen3]

Ok I guess ill have to get some of the different drill bits to see what diameter I have. Maybe that will yield some answers if the other ammo I loaded does not cycle either.

 

[fireball168]

Look down the barrel when you insert them to make sure they will go all the way through.

 

[sgreen3]

Ok will do. thanks again for the help. Ill post my findings after I get it checked out.

 

[TBaker]

When I first got my AAC 300 Blackout I shot factory subsonic ammo without a can. It would fire a couple rounds and then do exactly what you're saying. I called AAC and they said it should cycle even without a can. It fired supersonic ammo fine. Ahem I got the can I had no problem with the cycling of subsonic.

 

[sgreen3]

Welp got the rifle out today again for just a few test fire shots and good news is that it cycled perfect running 150gr FMJBT over 17.0gr and 17.5gr of IMR 4227 (17.8gr being the max charge for this bullet weight). One thing is that bolt did not hold open on the last round, but I don't really care about that honestly since its just a range toy. im just glad it cycles now. So I guess Im going to just load the rest of my 150 projectiles to 17.5gr and use that as my plinking rounds since the bullets are cheap enough. Now the bad part being I have about 260rds of ammo loaded with 110gr Vmax over 18gr of 4227 that the rifle wont cycle and I don't feel like pulling it apart.