BCL 102 fail to lock bolt open and feed 2nd round from magazine.

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AR-15 Gunman

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Hi. I am sure this question has been beaten to a pulp.

I have a BCL 102 2nd gen receiver set with a newly mated McGowen Precision barrel (AR rifle length gas tube) and an aftermarket BCG. I checked headspacing prior to test firing. Stock is an A2 with a dpms ar 308 rifle buffer and spring. Ammo used is Nosler Match Grade 168gr BTHP.

Today I went out to conduct the barrel break in procedure. Firearm fires one round but will not lock back on an empty magazine nor will it feed a second. Bolt was pristine clean and had a good amount of CLP for function. The ammo was ejecting at the 4 o clock position about 10 feet away.

Thoughts Gentleman?
 
If the bolt isn't opening far enough to lock open when the magazine is empty, or pick up the next round, there may not be enough gas. Could be a variety of causes.
 
How does your brass look? Is there extractor claw marks on the rim? Is there a swipe on the head from the ejector?

I would first remove the handguard and gas block to see where the carbon ring is on your gas port.
 
griffin86 said:
How does your brass look? Is there extractor claw marks on the rim? Is there a swipe on the head from the ejector?

I would first remove the handguard and gas block to see where the carbon ring is on your gas port.
Click to expand...

I noticed the head stamp letters chewed or "sliced" away from the ejector. No more than two widths of the ejector. As for extractor claw marks there is nothing out of the norm. I compared some brass from another semi and the extractor wear on the brass seems similar.

As for the gas block what carbon rings do you mean?
 
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AR-15 Gunman said:
I noticed on the the some of the head stamp letters chewed or "sliced" away from the ejector. No more than two widths of the ejector. As for extractor claw marks there is nothing out of the norm. I compared some brass from my Norinco AR and the extractor wear on the brass seems similar.

As for the gas block what carbon rings do you mean?
Click to expand...

The port on the gas block is bigger than the barrel's, so you will get carbon around where it's not sealed off. This picture of my gas block isn't perfect, but it's good enough.

I think your rifle is overgassed since you are getting case head swipe and brass is being ejected 10 feet.

CTG0ACN.jpg
 
griffin86 said:
The port on the gas block is bigger than the barrel's, so you will get carbon around where it's not sealed off. This picture of my gas block isn't perfect, but it's good enough.

I think your rifle is overgassed since you are getting case head swipe and brass is being ejected 10 feet.

CTG0ACN.jpg
Click to expand...

Okay thanks.

I checked the carbon around the gas port on the barrel. It had a two and half times the size of the gas port carbon circle around the port. So I need to research overgassed then. If it is overgassed would that not at least make it cycle properly?
 
Can you manually cycle the rounds using the charge handle?
Maybe try that and see if they feed and eject
If they do then you know the extractor is working at least
 
AR-15 Gunman said:
Okay thanks.

I checked the carbon around the gas port on the barrel. It had a two and half times the size of the gas port carbon circle around the port. So I need to research overgassed then. If it is overgassed would that not at least make it cycle properly?
Click to expand...

You are getting case head swipes because it’s trying to eject the case while the bolt is rotating while there is pressure in the chamber.

The bolt carrier is moving too fast for the magazine to push up a round. When you have two rounds in the mag, does the bolt stop on the middle of the next cartridge?
 
griffin86 said:
You are getting case head swipes because it’s trying to eject the case while the bolt is rotating while there is pressure in the chamber.

The bolt carrier is moving too fast for the magazine to push up a round. When you have two rounds in the mag, does the bolt stop on the middle of the next cartridge?
Click to expand...

The one time the bolt fed a second cartridge from the magazine it ended jammed in the action/feed path. Didn't make it all the way into the chamber.
 
Consider... Adjustable gas block
heavier buffer and maybe a heavier spring.

Factory ammo caters to bolt rifles and may use powder that is slower/higher gas volume then desired. Fed GM seems to be a good solution... handloading would be best. Often, semis prefer faster for combo powders and lowering pressures.

For feeding, the OAL of the ammo for the bullet may be too long.. Again, handloading allows for adjustment to suit.

The BCL extractor may need to be changed or the spring may need to be changed.

Finally, the mag may need to be changed.

Try and make up dummy rds with the same layout as the ammo you want to shoot. Cycle that ammo by hand to ensure it will feed and eject. Once you confirm that the ammo dimensions will work in your rifle by hand cycling THEN test under fire and adjust the moving parts accordingly.

Let me know if you have further questions.

Jerry
 
Mystic Precision said:
Consider... Adjustable gas block
heavier buffer and maybe a heavier spring.

Factory ammo caters to bolt rifles and may use powder that is slower/higher gas volume then desired. Fed GM seems to be a good solution... handloading would be best. Often, semis prefer faster for combo powders and lowering pressures.

For feeding, the OAL of the ammo for the bullet may be too long.. Again, handloading allows for adjustment to suit.

The BCL extractor may need to be changed or the spring may need to be changed.

Finally, the mag may need to be changed.

Try and make up dummy rds with the same layout as the ammo you want to shoot. Cycle that ammo by hand to ensure it will feed and eject. Once you confirm that the ammo dimensions will work in your rifle by hand cycling THEN test under fire and adjust the moving parts accordingly.

Let me know if you have further questions.

Jerry
Click to expand...

Today I went to the range.
Using the same ammo as the 1st range session. (Nosler Match Grade Custom Competition 168 Gr HPBT)
I found that using 8 rounds in a XCR-M 10 round magazine had enough pressure upwards that I got 1 5 shot string without feeding problems.
I think I had a "loose" grip on the firearm, combined with a two stage trigger and heavy recoil created a situation 5 separate times that caused me to bump fire two rounds. Felt like doubling truth be told. On one of the doubles a primer was pushed right out of the empty case from pressure.
I have ejector sheer marks on the case head, brass shavings in the bolt face and in the chamber/first portion of the rifling.
It recoils very strong. This is not my first .308 and I have a gauge for recoil impulse. She barks.

So adjustable gas block?

Also when the bolt feeds from the right side of the magazine it will start to strip the cartridge and then as it goes up the feed path the bolt skips over the case head and then jams at a hard angle. ��

The bolt I am using is a high pressure Toolcraft bolt.
 
You need to slow that bolt down ALOT. Harsh recoil is the BCG slamming into the rear of the buffer tube. It hurts you and upsets the rifle harmonics. It also destroys the brass and tears up the rims. Get an adjustable gas block.

A BCG moving faster then desired will cause irratic extraction and often, no ejection. That then translates to a BCG slamming forward faster then desired.

Simple test, move the gas block FORWARD in small increments until the rifle stops cycling, then move it back a few thou until it does. I suspect you will find a big difference in felt recoil. However, the powder used is not suitable for your current set up and you will likely go from no operation to harsh operation... but better then it is now

For the 308, starting loads of H4895 worked really well in all my rifles I tested wrt to operation. When you get the entire system balanced, your ejected brass is going to go in a 4 oclock direction and land in dinner plate type circle. It will take some fiddling to sort out.

On the upside, this is also when you will see the best accuracy.

Good luck.

Jerry
 
Mystic Precision said:
You need to slow that bolt down ALOT. Harsh recoil is the BCG slamming into the rear of the buffer tube. It hurts you and upsets the rifle harmonics. It also destroys the brass and tears up the rims. Get an adjustable gas block.

A BCG moving faster then desired will cause irratic extraction and often, no ejection. That then translates to a BCG slamming forward faster then desired.

Simple test, move the gas block FORWARD in small increments until the rifle stops cycling, then move it back a few thou until it does. I suspect you will find a big difference in felt recoil. However, the powder used is not suitable for your current set up and you will likely go from no operation to harsh operation... but better then it is now

For the 308, starting loads of H4895 worked really well in all my rifles I tested wrt to operation. When you get the entire system balanced, your ejected brass is going to go in a 4 oclock direction and land in dinner plate type circle. It will take some fiddling to sort out.

On the upside, this is also when you will see the best accuracy.

Good luck.

Jerry
Click to expand...
Hey Jerry
I ordered an Adjustable Gas Block. As for H4895. I have some as well as some IMR 4064. I will try some faster burning powder as you say. I'll update as parts and loads are developed. :)
 
Mystic Precision said:
You need to slow that bolt down ALOT. Harsh recoil is the BCG slamming into the rear of the buffer tube. It hurts you and upsets the rifle harmonics. It also destroys the brass and tears up the rims. Get an adjustable gas block.

A BCG moving faster then desired will cause irratic extraction and often, no ejection. That then translates to a BCG slamming forward faster then desired.

Simple test, move the gas block FORWARD in small increments until the rifle stops cycling, then move it back a few thou until it does. I suspect you will find a big difference in felt recoil. However, the powder used is not suitable for your current set up and you will likely go from no operation to harsh operation... but better then it is now

For the 308, starting loads of H4895 worked really well in all my rifles I tested wrt to operation. When you get the entire system balanced, your ejected brass is going to go in a 4 oclock direction and land in dinner plate type circle. It will take some fiddling to sort out.

On the upside, this is also when you will see the best accuracy.

Good luck.

Jerry
Click to expand...

Hi Jerry
I tried making dummy rounds.
168 gr BTHP set to 2.775" which is spec. The second last round from the (XCR-L) pistol mag never feeds. Random jams as well. It will not feed with Magpul mags.

I have tried the suplerlative arms adjustable gas block. With it fully open and and with varied H4985 loads it will not lock back the bolt. I noticed the bolt catch barely grabs the bolt locking lugs when I manually lock the bolt back. I am comparing this to an AR-15 that I have and the bolt catch nearly covers the bottom 1/3 of the bolt face. The BCL barely is contacting. I am about ready to give up on this McGowen/BCL build of mine. It hasn't been much fun. Do you think a Stag 10 would be a better receiver?

Thanks and hope the shooting is going good.
 
if the bolt is cycling all the way back but the bolt is not catching, then you may have a mag follower issue. Sounds like the mag you have is not fitted properly if the bolt is skipping over the rd.... did you open the rear of the mag to allow the follower to hit the bolt latch better? You likely have to tweak the feed lips to get the case presentation to be correct for the bolt.

On my BCL, open the bolt on the empty mag leads to 100% bolt lock... and it locks open when firing. So I suggest you look at the interaction of all the parts and fix as needed.

I am running a BCL right now. Debugging the beast but it is very accurate. I got it used and have changed several parts and will have one more area to tweak.

with OAL, set to what the rifle will feed. maybe it needs to be shorter to account for a bullet nose shape.... maybe a bit longer. Make up some dummy rds and cycle them. Adjust as needed to get the rifle cycling properly. The 'spec' is whatever works in your particular rifle.... and it will change with different bullets.

If you cycle a dummy rd and the bullet tip hits just under the chamber, shortern the OAL until it feeds. If you can get some Sierra 168 or 175gr MKs, see if these cycle better. Might just be the nose shape on the Noslers don't suit your rifle.

As you can read from other threads on the STAG, I do not see them immune to proper fitment and set up. An AR is an AR... sorting out all the various bits is necessary to get them running well.

Jerry
 
As stated above... brass ejection is NOT a good way to judge rifle function, and neither is 'sliding the gas block forward to limit the gas'. That's just dumb, and doesn't give you any measurable method of understanding how much gas is getting into the bolt carrier assembly.

Hand-loading for a semi-auto rifle has a tremendous amount of factors involved - especially pressure curves etc. to properly function the rifle with safety, and ultimately accuracy in mind. Have you tried shooting the rifle with factory ammunition at all?

Before messing around with a hand full of things, take it back to the basics, and try to isolate each issue.
 
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