I bought the complete uppers from Aero Precision so I didn't install the gas blocks.
Ar build, 2nd round won’t fire?
- Thread starter davidbschenck
- Start date
I bought the complete uppers from Aero Precision so I didn't install the gas blocks.
I'm thinking possible buffer, I ordered some heavier buffers to try. I'll let you know if that was it.
One difference with these lowers is that they came with a bolt catch pin already installed that screw in. My previous lowers I had to intall with a punch. These may be screwed to tight and the bolt catch pin isn't floating freely but sticks open or closed in position. Need a tiny allen wrench small enough to loosen it.
dellet
Gold $$ Contributor
If cases are ejecting, the carrier is traveling far enough to reset the hammer.
If the second round chambers, it has enough gas to operate.
If you pull the magazine and slowly pull back on the charging handle, you will feel to clicks, resets, the first is the trigger setting, the second is the hammer. Both of these will happen before there is enough room for a case to eject, maybe an inch or so.
You have about three possibilities. It’s not going fully into battery, the hammer/trigger is malfunctioning, headspace. All of those may have multiple reasons for cause.
How do you load the first round?
Releasing the catch or pulling back the charging handle and letting go?
Things you can try or look for.
When it does not fire, try the forward assist. If it was out of battery, you will feel it move the carrier and set the bolt.
You can set this up to try at home if you take some care. Use a dummy round is the safest way. Ride the charging handle all the way until it stops, this most likely be just out of battery. You should be able to fully chamber the round with light thumb pressure. You will be able to see the difference looking at the carrier through the ejection port.
It might be worth trying to chamber empty brass in the barrel and see if it is loose enough to just fall out. Not uncommon for new treated barrels to have crap in the chamber.
Again with a dummy and the upper off, it should be very easy to confirm that the bolt is closing and locking in place. If you have to mark the carrier where it meets the ejection port on an empty chamber, and compare that to a loaded chamber.
While the upper is off make sure you can set the hammer by hand and check spring inhalation.
You might have two different problems. The springs in the 556. And headspace on the Blackouts. Under sized brass has been a huge problem over the years.
Check base to shoulder lengths if you can.
Don’t assume it’s one problem on all three, better to assume it’s three different ones.
Since you have 556 and 300 BLK out and confusion going on, make absolutely certain you aren’t mixing up ammo.
The only way gas or buffer weight will be an issue is if something is dragging on the carrier slowing it down, the forward assist check will help narrow that down.
This plays into headspace again. If brass is sized too long, it may not chamber on a short stroke. Dropping the carrier from the full back position on the first round, will have enough force to set the shoulder back.
If you are comfortable pulling the bolt out of the carrier, check headspace. You should be able to chamber a round, in the upper and push the bolt in and twist it. It’s easier if you strip the bolt, but it can dive done.
Some where in all of that the problem will likely show up.
If the second round chambers, it has enough gas to operate.
If you pull the magazine and slowly pull back on the charging handle, you will feel to clicks, resets, the first is the trigger setting, the second is the hammer. Both of these will happen before there is enough room for a case to eject, maybe an inch or so.
You have about three possibilities. It’s not going fully into battery, the hammer/trigger is malfunctioning, headspace. All of those may have multiple reasons for cause.
How do you load the first round?
Releasing the catch or pulling back the charging handle and letting go?
Things you can try or look for.
When it does not fire, try the forward assist. If it was out of battery, you will feel it move the carrier and set the bolt.
You can set this up to try at home if you take some care. Use a dummy round is the safest way. Ride the charging handle all the way until it stops, this most likely be just out of battery. You should be able to fully chamber the round with light thumb pressure. You will be able to see the difference looking at the carrier through the ejection port.
It might be worth trying to chamber empty brass in the barrel and see if it is loose enough to just fall out. Not uncommon for new treated barrels to have crap in the chamber.
Again with a dummy and the upper off, it should be very easy to confirm that the bolt is closing and locking in place. If you have to mark the carrier where it meets the ejection port on an empty chamber, and compare that to a loaded chamber.
While the upper is off make sure you can set the hammer by hand and check spring inhalation.
You might have two different problems. The springs in the 556. And headspace on the Blackouts. Under sized brass has been a huge problem over the years.
Check base to shoulder lengths if you can.
Don’t assume it’s one problem on all three, better to assume it’s three different ones.
Since you have 556 and 300 BLK out and confusion going on, make absolutely certain you aren’t mixing up ammo.
The only way gas or buffer weight will be an issue is if something is dragging on the carrier slowing it down, the forward assist check will help narrow that down.
This plays into headspace again. If brass is sized too long, it may not chamber on a short stroke. Dropping the carrier from the full back position on the first round, will have enough force to set the shoulder back.
If you are comfortable pulling the bolt out of the carrier, check headspace. You should be able to chamber a round, in the upper and push the bolt in and twist it. It’s easier if you strip the bolt, but it can dive done.
Some where in all of that the problem will likely show up.
Cases can be ejected and the hammer still does not get reset due to carrier travel being a little short. Depends on the ramp cut into the carrier.
Especially true with these aftermarket triggers.
I borescope the gas port to gas block bore alignment, so I know its perfect every time.
In my experience, buffers have little impact on function when you have a properly operating gas system. The exception here would be the 9mm PCC.
Especially true with these aftermarket triggers.
I borescope the gas port to gas block bore alignment, so I know its perfect every time.
In my experience, buffers have little impact on function when you have a properly operating gas system. The exception here would be the 9mm PCC.
Did you check the depth of the trigger pocket? It is possible it was milled incorrectly, even if it was done by a manufacturer.
Do the builds pass functions tests without ammunition?
Do the builds pass functions tests without ammunition?
divingin
Gold $$ Contributor
Exactly.
The other test is to fire the first shot, making sure to hold the trigger back. It should give a tactile and audible click when you do release the trigger. If it doesn't, likely the disconnector spring is installed incorrectly.
Easy test on the buffer weight: Load one round and see if the bolt locks back when fired. If it does, the gas and recoil system are operating such that it should at least cycle the next round. If it doesn't, the bolt is short-stroking due to insufficient gas, weak ammo, too-heavy buffer system (buffer weight or spring), or drag throughout the system.
Sounds like your hammer is following through. Check they disconnector and spring, make sure it moves and returns properly. Makes sure you have the proper disconnect spring and its installed properly. Other thing on some adjustable triggers if you adjust them too "perfect" they will allow the hammer to follow through by the disconnect not catching the hammer.
Also while its not ordinary its not out of the question that you are undergassed/ improper buffer spring combo.
With the tolerances of these guns and the wild sizes of aftermarket parts you can have a gun that cycles but does not allow the hammer to catch on the disconnect.
Also while its not ordinary its not out of the question that you are undergassed/ improper buffer spring combo.
With the tolerances of these guns and the wild sizes of aftermarket parts you can have a gun that cycles but does not allow the hammer to catch on the disconnect.
Sounds like the bolt is not moving back far enough to cock. Buffer spring or buffer wrong length?
dc.fireman
Sling & Irons!
Me three.
Jeff Porter
Gold $$ Contributor
If you load only one round in the magazine does the bolt hold open? This test will tell you if it is undergassed or a magazine/bolt catch issue.
From White Oak Armament FAQ page:
If the bolt does not lock to the rear or engages on the front of the carrier, then you do have a short cycling issue.
From White Oak Armament FAQ page:
How to identify a short cycling issue
One of the questions we get a lot is “Why doesn’t my bolt lock open when I fire the last round in the magazine?” Here is a simple test to help you identify the cause.- -A live round must be fired for this test so you must be in an appropriate location to perform this test.
- -Manually lock the carrier to the rear by pulling the charging handle to the rear and depressing the small tab on the bolt catch.
- -Insert one round into a magazine and then insert the magazine into the rifle.
- -Close the bolt by depressing the large tab on the bolt catch or by pulling the charging handle to the rear and releasing it.
- -While applying pressure to the small lower tab on the bolt catch, fire the round in a safe direction.
If the bolt does not lock to the rear or engages on the front of the carrier, then you do have a short cycling issue.
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