My 300 black is going full auto on me!!! Help!

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tech180
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My 300 black is going full auto on me!!! Help!

Post by tech180 »

SO I took my 300 out to the range for the first time today. So I first loaded one round in there and fired, worked perfect so I then loaded 6. I pulled the trigger and 5 bullets came out almost instantly. I am pretty sure its slam fire.

I am using the AAC 300 blackout upper and it comes with the "Full Auto" BCG in it. Is it posible that heavy bolt is causing the slam fires? I am also running cci small riffle primers.

I shot the same brass that was used for the 300 AAC bullets and primers in my bushmaster AR15 and there was not a single slam fire, shot perfect.

My lower is a YHM with a DPMS parts kit.

Also, anyone know if its legal to have the "Full Auto" BCG in Washintgon state? It came from the facory like that.
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chrismartin
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Re: My 300 black is going full auto on me!!! Help!

Post by chrismartin »

More than likely your disconnector is missing or out of spec or disconnector spring is missing or installed upside down.
Check your BCG firing pin and make sure it is not stuck forward or bent or something.

You need to do a basic trigger safety check.
Make sure the gun is empty

1.
Cycle the action
Pull the trigger and hold the trigger back (do not release)
Cycle the action.
There should be no hammer follow

2. Release trigger
The hammer should stay cocked

3. Press trigger, hold to the rear
Hammer should drop

4. Cycle action
Release trigger, hammer should stay cocked

5. Put safety on (safe position)
Pull trigger (hard)
Trigger should not move, hammer should not drop
Release trigger

6. Put safety off (fire position)
Hammer should not drop

7. Press trigger
Hammer should drop

Repeat the above a few times
If the hammer drops when it should not, inspect trigger and replace the trigger if needed as it has failed safety check.

You can do the above with the upper off, but you need to put your thumb or other object in the way to catch the hammer falling so that it does not impact the lower and/or bolt catch (It will damage them)

As mentioned, check the disconnector spring, the fat end goes into the trigger, the skinny end goes into the disconnector.
Make sure the disconnector is free moving and catches the hammer properly.

Yes, "full auto bolt carriers" are legal to own, many (most?) rifle ship with them. This is not your problem. A FA BGC will not "make" your gun full auto, nor will it cause a slam fire (if so, when you charge the gun, it would fire) UNLESS your firing pin was stuck completely forward, but that would affect all BCG's, not just FA BCG's. I'd bet your trigger is the problem.
Gun-fun
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Re: My 300 black is going full auto on me!!! Help!

Post by Gun-fun »

If the problem is only happening with one upper, TAKE IT BACK, The batfe does not care how your gun is auto only if and they have no sense of humor. You do not want to be in possion even if it is defective.
-k-
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Location: OR

Re: My 300 black is going full auto on me!!! Help!

Post by -k- »

Does your FCG pass a function check?

Uppers do not make a semi lower full auto. A standard or "auto" carrier does not make the rifle fire more than one shot per trigger pull, so it is legal.
Todd
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Re: My 300 black is going full auto on me!!! Help!

Post by Rifleman »

chrismartin wrote:More than likely your disconnector is missing or out of spec or disconnector spring is missing or installed upside down.
Check your BCG firing pin and make sure it is not stuck forward or bent or something.

You need to do a basic trigger safety check.

*snip*

As mentioned, check the disconnector spring, the fat end goes into the trigger, the skinny end goes into the disconnector.
Make sure the disconnector is free moving and catches the hammer properly.

Yes, "full auto bolt carriers" are legal to own, many (most?) rifle ship with them. This is not your problem. A FA BGC will not "make" your gun full auto, nor will it cause a slam fire (if so, when you charge the gun, it would fire) UNLESS your firing pin was stuck completely forward, but that would affect all BCG's, not just FA BCG's. I'd bet your trigger is the problem.
THIS. That disconnector spring has caused more than a few home-build issues.
tech180
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Posts: 9
Joined: Mon Feb 27, 2012 5:58 am

Re: My 300 black is going full auto on me!!! Help!

Post by tech180 »

chrismartin wrote:More than likely your disconnector is missing or out of spec or disconnector spring is missing or installed upside down.
Check your BCG firing pin and make sure it is not stuck forward or bent or something.

You need to do a basic trigger safety check.
Make sure the gun is empty

1.
Cycle the action
Pull the trigger and hold the trigger back (do not release)
Cycle the action.
There should be no hammer follow

2. Release trigger
The hammer should stay cocked

3. Press trigger, hold to the rear
Hammer should drop

4. Cycle action
Release trigger, hammer should stay cocked

5. Put safety on (safe position)
Pull trigger (hard)
Trigger should not move, hammer should not drop
Release trigger

6. Put safety off (fire position)
Hammer should not drop

7. Press trigger
Hammer should drop

Repeat the above a few times
If the hammer drops when it should not, inspect trigger and replace the trigger if needed as it has failed safety check.

You can do the above with the upper off, but you need to put your thumb or other object in the way to catch the hammer falling so that it does not impact the lower and/or bolt catch (It will damage them)

As mentioned, check the disconnector spring, the fat end goes into the trigger, the skinny end goes into the disconnector.
Make sure the disconnector is free moving and catches the hammer properly.

Yes, "full auto bolt carriers" are legal to own, many (most?) rifle ship with them. This is not your problem. A FA BGC will not "make" your gun full auto, nor will it cause a slam fire (if so, when you charge the gun, it would fire) UNLESS your firing pin was stuck completely forward, but that would affect all BCG's, not just FA BCG's. I'd bet your trigger is the problem.
Thanks for the info! I did these steeps several times and it passed without issue. When I release the bolt using the paddle it leave a pretty large dent in the primer but dose not discharge untill I pull the trigger. After the trigger is pulled it then lets off multiple rounds. I do have a stock with the recoil springs in it, I didnt think to try shooting without it on my sholder, maybe its bump firing?

The firing pin is floating fine, not stuck or gungked up. I can turn the bolt up and then down and the pin floats effortlessly back and forth.

I am thinking about taking the bolt out of my bushmaster 5.56 AR and trying it in the AAC.

I know the full auto bolt wont make it full auto i was just thinking that maybe the extra wait causes it the slam close harder tossing the firing pin forward faster.
tech180
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Re: My 300 black is going full auto on me!!! Help!

Post by tech180 »

Rifleman wrote:
chrismartin wrote:More than likely your disconnector is missing or out of spec or disconnector spring is missing or installed upside down.
Check your BCG firing pin and make sure it is not stuck forward or bent or something.

You need to do a basic trigger safety check.

*snip*

As mentioned, check the disconnector spring, the fat end goes into the trigger, the skinny end goes into the disconnector.
Make sure the disconnector is free moving and catches the hammer properly.

Yes, "full auto bolt carriers" are legal to own, many (most?) rifle ship with them. This is not your problem. A FA BGC will not "make" your gun full auto, nor will it cause a slam fire (if so, when you charge the gun, it would fire) UNLESS your firing pin was stuck completely forward, but that would affect all BCG's, not just FA BCG's. I'd bet your trigger is the problem.
THIS. That disconnector spring has caused more than a few home-build issues.
Ahhh so other people are having this issue with the AAC upper?
Rifleman
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Posts: 112
Joined: Thu Dec 22, 2011 5:40 pm

Re: My 300 black is going full auto on me!!! Help!

Post by Rifleman »

tech180 wrote:
Rifleman wrote:
chrismartin wrote:More than likely your disconnector is missing or out of spec or disconnector spring is missing or installed upside down.
Check your BCG firing pin and make sure it is not stuck forward or bent or something.

You need to do a basic trigger safety check.

*snip*

As mentioned, check the disconnector spring, the fat end goes into the trigger, the skinny end goes into the disconnector.
Make sure the disconnector is free moving and catches the hammer properly.

Yes, "full auto bolt carriers" are legal to own, many (most?) rifle ship with them. This is not your problem. A FA BGC will not "make" your gun full auto, nor will it cause a slam fire (if so, when you charge the gun, it would fire) UNLESS your firing pin was stuck completely forward, but that would affect all BCG's, not just FA BCG's. I'd bet your trigger is the problem.
THIS. That disconnector spring has caused more than a few home-build issues.
Ahhh so other people are having this issue with the AAC upper?
No, just the parts kits when they assemble the parts themselves. If I understood your post, you have a Bushmaster too. Try swapping out uppers and fire each to isolate the problem.
tech180
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Posts: 9
Joined: Mon Feb 27, 2012 5:58 am

Re: My 300 black is going full auto on me!!! Help!

Post by tech180 »

-k- wrote:Does your FCG pass a function check?

Uppers do not make a semi lower full auto. A standard or "auto" carrier does not make the rifle fire more than one shot per trigger pull, so it is legal.
THanks for the reply. Yeah it seems to have passed. Just leaves huge dents in the primers when I release the bolt with the paddle.
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chrismartin
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Re: My 300 black is going full auto on me!!! Help!

Post by chrismartin »

tech180 wrote:
-k- wrote:Does your FCG pass a function check?

Uppers do not make a semi lower full auto. A standard or "auto" carrier does not make the rifle fire more than one shot per trigger pull, so it is legal.
THanks for the reply. Yeah it seems to have passed. Just leaves huge dents in the primers when I release the bolt with the paddle.
Since you have two AR15's, just swap bolt carriers and/or uppers and see if the problem follows the carrier.
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