11.5 barrel - AR15.COM

Posted: 2/3/2016 9:47:31 AM EDT

I currently have a 14.5 inch elw bcm barrel and love how the weights is distributed on the barrel. I am now looking at 11.5 inch sbr setup from them. Would it be wise to go with the cold hammer forged barrel for 11.5 vs the elw. What would be the pros and cons to this barrel setups.

I also read that the Government profile barrels have a .750 gas block diameter, lightweight and enhanced lightweight barrels use a .625 diameter gas block. When running these suppressed would one have more gas blowback then the other. Would one run better then the other being sbr and suppressed.

Posted: 2/3/2016 10:26:04 AM EDT

[#1]

You'll often get varying answers to this. For me I went with hammer forged BCM the first time in 11.5. My next will be the LW. For paper punching at the range I don't see benefit of paying an extra $75 again for hammer forged over standard for a second one.

Posted: 2/3/2016 11:04:43 AM EDT

[#2]

The lightweight barrel will heat up and cool more quickly than the gov profile barrel. This might give you a more consistent POI when shooting suppressed vs. unsuppressed.

While the the gov profile will take longer to reach the same temp as the LW, it will remain hotter for longer, obviously.

ETA - the amount of gas blowback in the system should be determined by the gas port diameter, and not the barrel diameter at the gas block.

FWIW, I would opt for the 11.5 govt.

Posted: 2/3/2016 1:31:44 PM EDT

[#3]

How is the gas port sizing on the BCM 11.5" barrels?

Posted: 2/3/2016 2:11:10 PM EDT

[#4]

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How is the gas port sizing on the BCM 11.5" barrels?

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Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

Posted: 2/3/2016 3:23:45 PM EDT

[#5]

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Quoted:

Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

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Quoted:

Quoted:
How is the gas port sizing on the BCM 11.5" barrels?

Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

Which adjustable gas block would fit under the kmr handguard? Would a jp work.

Posted: 2/3/2016 3:56:18 PM EDT

[#6]

An adjustable gas block is going to add back the weight that you save on the ELW barrel. I love my 14.5" ELW, but when it came time for a new barrel on my 10.5", I went with a lightweight Faxon Firearms barrel (they're about $125) and a Baby Govnah gas block (about $30), which only comes in 0.750" diameter.

I think this results in an overall lighter setup, and on the 10.5" barrel, the distribution of the weight is negligible compared to an ELW or similar profile.

Posted: 2/3/2016 3:56:59 PM EDT

[#7]

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Quoted:

Which adjustable gas block would fit under the kmr handguard? Would a jp work.

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Quoted:

Quoted:
How is the gas port sizing on the BCM 11.5" barrels?

Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

Which adjustable gas block would fit under the kmr handguard? Would a jp work.

Unsure. A clamp on SLR sentry 7 just fit but I recently swapped it to a SLR set screw Sentry 7 for more clearance.

Posted: 2/3/2016 7:53:49 PM EDT

[#8]

Quote History

Quoted:

Which adjustable gas block would fit under the kmr handguard? Would a jp work.

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Quote History

Quoted:

Quoted:
How is the gas port sizing on the BCM 11.5" barrels?

Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

Which adjustable gas block would fit under the kmr handguard? Would a jp work.

FWIW I just installed a Superlative Arms piston kit under a BCM KMR. It is close but it fits. If you go to their website they have a diagram with the measurements. Anything that size and under should fit.

ETA: They sell adjustable blocks. Here is the link and you can see the diagram as well.

Posted: 2/3/2016 8:34:32 PM EDT

[#9]

I have a 11.5 elw bcm upper that will serve a sbr when my form 1 clears (currently sitting as a pistol). It will be run suppressed when the suppressor is out of jail. I just placed a slr set screw gas block on the barrel and yes it does fit under the krm rails without any issues. The barrel is drilled so the set screw will help index the gas block correctly. It was a sentry 6 premium in a melonite finish (not 0.45 spacing one) and it is really light. It was 1.28 ounces if I remember correctly when I weighted it.

Posted: 2/4/2016 11:23:18 AM EDT

[#10]

Quote History

Quoted:

Which adjustable gas block would fit under the kmr handguard? Would a jp work.

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Quote History

Quoted:

Quoted:
How is the gas port sizing on the BCM 11.5" barrels?

Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

Which adjustable gas block would fit under the kmr handguard? Would a jp work.

I have a SLR Sentry 7 on my 11.5 KMR and it fits perfect.

Posted: 2/4/2016 2:27:13 PM EDT

[#11]

Quote History

Quoted:

Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

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Quote History

Quoted:

Quoted:
How is the gas port sizing on the BCM 11.5" barrels?

Have always read it is on larger side. I have run an adjustable gas block on mine from day 1 and it is turned down a good bit.

No adjustable on mine but I do run an H3 buffer. Runs perfect.

Posted: 2/4/2016 3:52:06 PM EDT

[#12]

How's the gas blowback with the h3. Ill be shooting lefty and the gas blow back is a concern. Have you ran it suppressed?

Posted: 2/5/2016 4:35:35 PM EDT

[#13]

I have the bcm 11.5 lightweight standard barrel.
accuracy is not as good as a couple of 16 lightweight colt barrels I have
it was really overgassed out of the box with standard front sight post. H3 didn't help a whole lot.
now it has a sentry clamp on adjustable 4 clicks open and runs smooth. went back to H1 buffer with no change to gas.
my kmr10 fits over it good with no worries of contact
if I were to do it again, I would only get that barrel for an A1 style build
using a trekt on it now, no change to gas. adjustable gas and gasket charging handle help a bunch

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