User Panel
User Panel
User Panel
|
Posted: 3/24/2024 6:03:44 PM EDT
Picked up a BCM Mk2 upper with their ambi MK2 charging handle and took it out for the 1st time today.
Put about 100 rounds through it mostly suppressed. First-it was extra gassy suppressed with a Sandman S. I figured with their 'fancy' channel like area's around the gas tube and the MK2 charging handle appearing to somewhat seal the rear of the upper it would be much less gassy. This can is not near as gassy on other rifles. The upper did ship with a liberal coating of oil inside and out. I tried to remove what I could with a rag. Maybe that's why it's gassy? Second-suppressed it would not always lock back on the last round. Once, IIRC, out of 2 or 3 mags it locked back. I think the Larue lower uses an H2 buffer. I ran the last 20 rounds unsuppressed and it did lock back. Ejection was at 2'ish with a can and 4'ish without. To top it off the can was stuck on the newly installed forward controls designs muzzle device. Had to put my knee on the lower and use 2 hands to get it removed. That's a 1st for both sandman cans (have a K & S). Anyone have one of these MK2 uppers and run it suppressed? Is this just the way these are?  Attached File Attached FileGas tube:  Attached File Attached File |
|
|
|
TN, USA
|
Posted: 3/24/2024 8:38:02 PM EDT
[#1]
You need to adjust your buffer on your own. I don’t know how long that barrel is. Unless you install an adjustable gas block you are going to get gas when suppressed; it’s inherent to the design of an AR.
What did you think would change with this upper versus another? |
|
|
|
Posted: 3/24/2024 9:15:14 PM EDT
[#2]
I understand I'll get gas but this is much more gas than other uppers with the same can.
|
|
|
|
|
Posted: 3/24/2024 9:21:31 PM EDT
[#3]
Quote HistoryOriginally Posted By DuneShoot: I understand I'll get gas but this is much more gas than other uppers with the same can. ...so the gas port is a larger diameter. This is entirely unsurprising given thst BCM bills themselves as "mil-spec plus" in their branding and design mindset. It is overgassed for reliable function with shitty cheap ammo most people put through their rifles these days. Your options are to live with the gas, install an adjustable gas block, or an adjustable carrier. |
|
|
|
|
Posted: 3/24/2024 9:27:04 PM EDT
[#4]
Quote HistoryOriginally Posted By LeadBreakfast: ...so the gas port is a larger diameter. This is entirely unsurprising given thst BCM bills themselves as "mil-spec plus" in their branding and design mindset. It is overgassed for reliable function with shitty cheap ammo most people put through their rifles these days. Your options are to live with the gas, install an adjustable gas block, or an adjustable carrier. |
|
|
|
TN, USA
|
Posted: 3/24/2024 9:28:20 PM EDT
[#5]
BRT tube will be your least invasive option and cheapest.
|
|
|
VEN
|
Posted: 3/24/2024 9:36:40 PM EDT
[#6]
The aero adjustable has blocks are pretty good. I've used those and superlative. Both work well on heavily used guns.
|
|
|
|
Posted: 3/24/2024 9:45:48 PM EDT
[#7]
I don't have one of these upper receivers. For the rifle that I have that I run suppressed I have a Bootleg adjustable bolt carrier group. It works very well on that rifle running a Rugged Razor can, gas is minimal. I also have the PRI Gas Buster charging handle and I think that also helps control ths gas in the face we all dislike.
|
|
|
|
|
Posted: 3/24/2024 10:06:36 PM EDT
[Last Edit: NemesisMind]
[#8]
Not related to your post, but can you share about that optic setup? Looks like two prism optics.
|
|
|
|
|
Posted: 3/24/2024 10:19:01 PM EDT
[#9]
BCM uses a 0.076 gas port on their 16" mids. It's a pretty middle of the road gas port size, not the best for suppressed use but far from the worst. I'm running an RC2 on mine (16" BFH mid) with their T0 buffer (which a 3.8 ounce A5 buffer). Runs great, no complaints from me. I think some of the complaints about gas can be lube related. I've noticed if I just use oil, particularly on the rails, it gets pretty smoky. Since switching to Super Lube on the cam pin and carrier rails I haven't noticed it as much. Super Lube seems to stay put better and not get flung all over the place.
As far as your Sandman sticking to the new mount goes that's not unusual. Mine sticks pretty good when hot, but once it's cool it'll usually come right off. I use my Surefire brush to clean the inside of the mount off once and while and that seems to help. |
|
|
|
USA
|
Posted: 3/24/2024 10:26:07 PM EDT
[#10]
BCM, used to get a lot of flack for having small gas ports. Especially with their 14.5 middy. That seems to have driven them the other way.
obviously your sandman being stuck doesn't have anything to do with the upper, and nor does it being over sprung/buffered that is causing the failure to lock back. I would be hesitant to throttle the gas too much, and you need to do it conjunction with buffer decrease anyway. was ammo different? I know for example Winchester seems to be a lot more gassy, or at least more irritating. |
|
|
NC, USA
|
Posted: 3/24/2024 10:52:19 PM EDT
[Last Edit: BULLDAWG_556]
[#11]
I have a MK 2 upper that had cut to 13.7 and pinned a NOX. I left the gas port alone. I played with lots of combos but factory BCM spring and H2 stock is best for suppressed (Sandman S and Polonium K) and H unsuppressed.
Geissele Super 42 and Sprinco blue is too much spring for unsuppressed. It will run, just not lock back on the last round. Oh, not overly gassy, but I had to switch out the BCM carry handle, I recommend Radian or Geissele ACH as the BCM did push gas to the face. |
|
|
|
Posted: 3/24/2024 11:34:31 PM EDT
[Last Edit: TGWLDR]
[#12]
|
|
|
|
|
Posted: 3/25/2024 7:00:11 AM EDT
[#13]
Quote HistoryOriginally Posted By NemesisMind: Not related to your post, but can you share about that optic setup? Looks like two prism optics. It's the PA SLX dot and magnifier. For my eyes I can either focus the reticle OR the target but not both. The dot was just returned from ebig fixed. Battery clip/holder was loose. May swap to EoTech. |
|
|
|
|
Posted: 3/25/2024 7:03:11 AM EDT
[#14]
Thanks all for the suggestions. I will play around with different ammo, buffers, and charging handles and see how it goes.
|
|
|
|
OH, USA
|
Posted: 3/25/2024 8:36:03 AM EDT
[#15]
I run a BCM MK2 ELW14.5" on my main rifle. Same charging handle, but I run a BRT gas tube and VLTOR A5 buffer (a5h2). I run a Surefire RC2 mini 5.56 3/4 of the time and this setup doesn't gas me out. Only time I've ever had failure to lockback issues is while shooting PMC Xtac 5.56 unsuppressed. In that case, I switched to a lighter buffer (A5h0). Ran that until I was out of that particular ammo.
|
|
|
TX, USA
|
Posted: 3/25/2024 10:43:37 AM EDT
[#16]
Quote HistoryOriginally Posted By BULLDAWG_556: I have a MK 2 upper that had cut to 13.7 and pinned a NOX. I left the gas port alone. I played with lots of combos but factory BCM spring and H2 stock is best for suppressed (Sandman S and Polonium K) and H unsuppressed. Geissele Super 42 and Sprinco blue is too much spring for unsuppressed. It will run, just not lock back on the last round. Oh, not overly gassy, but I had to switch out the BCM carry handle, I recommend Radian or Geissele ACH as the BCM did push gas to the face. I have a Mk.2 14.5" BFH on a Larue lower. I have a Geissele Super 42 H1. I've only shot unsupressed with Federal 62 grain .223, but I've had zero problems. It actually shoots extremely smooth. I'm super impressed with the combo. |
|
|
|
Posted: 3/25/2024 11:17:52 AM EDT
[#17]
Quote HistoryOriginally Posted By PaulRad: I run a BCM MK2 ELW14.5" on my main rifle. Same charging handle, but I run a BRT gas tube and VLTOR A5 buffer (a5h2). I run a Surefire RC2 mini 5.56 3/4 of the time and this setup doesn't gas me out. Only time I've ever had failure to lockback issues is while shooting PMC Xtac 5.56 unsuppressed. In that case, I switched to a lighter buffer (A5h0). Ran that until I was out of that particular ammo. Don't I need a longer buffer tube for this buffer? |
|
|
|
USA
|
Posted: 3/25/2024 11:44:28 AM EDT
[#18]
Quote HistoryOriginally Posted By DuneShoot: Don't I need a longer buffer tube for this buffer? Yes, you’ll need an A5 length tube. |
|
|
NC, USA
|
Posted: 3/25/2024 2:07:18 PM EDT
[#19]
Quote HistoryOriginally Posted By jdk1: I have a Mk.2 14.5" BFH on a Larue lower. I have a Geissele Super 42 H1. I've only shot unsupressed with Federal 62 grain .223, but I've had zero problems. It actually shoots extremely smooth. I'm super impressed with the combo. I forgot to add, my fail to lock is with 75 grain PPU Unsuppressed Suppressed it will run everything I agree very smooth shooter and is my #2. 1st being a 10.3. |
|
|
MI, USA
|
Posted: 3/25/2024 5:22:29 PM EDT
[#20]
Quote HistoryOriginally Posted By jd2395: The aero adjustable has blocks are pretty good. I've used those and superlative. Both work well on heavily used guns. I have an Aero AGB and it's been good. I did make sure I took the adjustment needle thing out and put some Lucas Red n Tacky on the threads to avoid carbon lock and that has worked great. Just don't lose the tiny spring and or ball bearing detent. |
|
|
MI, USA
|
Posted: 3/25/2024 5:26:45 PM EDT
[Last Edit: Tiribulus]
[#21]
Originally Posted By DuneShoot: suppressed it would not always lock back on the last round. ... unsuppressed and it did lock back. |
|
|
|
Posted: 3/25/2024 5:36:43 PM EDT
[#22]
Quote HistoryOriginally Posted By Tiribulus: I don't understand this. It should be the opposite. Unless it was slamming hard enough to throw the bolt forward past the catch? I need to run it again with different ammo and buffer. |
|
|
|
|
Posted: 3/25/2024 9:52:36 PM EDT
[#23]
If you don't want the Mk2 upper itself I'll buy it from you.
|
|
|
|
|
Posted: 3/25/2024 10:11:34 PM EDT
[#24]
Quote HistoryOriginally Posted By TheTacticalCoyote: If you don't want the Mk2 upper itself I'll buy it from you. Need to try it a few more times. |
|
|
|
|
Posted: 3/26/2024 3:30:17 AM EDT
[Last Edit: Brok3n]
[#25]
I love my BCM MK2 14.5, been running it since 2020 but not suppressed. That's what my piston PWS Mk2 will be for. What FSC muzzle device are you using exactly?
eta: I use a Springco Blue spring and BCM H2 buffer with Lantac BCG and BCM extended A2X flash hider. |
|
|
|
|
Posted: 3/26/2024 5:47:44 AM EDT
[#26]
Quote HistoryOriginally Posted By Brok3n: I love my BCM MK2 14.5, been running it since 2020 but not suppressed. That's what my piston PWS Mk2 will be for. What FSC muzzle device are you using exactly? |
|
|
|
|
Posted: 3/26/2024 6:46:11 AM EDT
[#27]
Quote HistoryOriginally Posted By DuneShoot: THIS ONE. Quote HistoryOriginally Posted By DuneShoot: Originally Posted By Brok3n: I love my BCM MK2 14.5, been running it since 2020 but not suppressed. That's what my piston PWS Mk2 will be for. What FSC muzzle device are you using exactly? Every mount I’ve tried besides a DA 3 prong sticks on my Sandman K, including the FCD 6315km. Fwiw I use a carbine spring and H buffer. My 14.5 BCM runs like a champ. |
|
|
|
|
Posted: 3/26/2024 8:55:04 AM EDT
[#28]
Quote HistoryOriginally Posted By DuneShoot: It may end up in the EE! Need to try it a few more times. A different upper receiver won't help your issues. |
|
|
|
AZ, USA
|
Posted: 3/26/2024 9:36:00 AM EDT
[Last Edit: -Shaggs-]
[#29]
I've got a MK2. 14.5" Midlength. Whole rifle though and it has the MK2 ambi charge handle like you have. Mine was also heavily coated in oil when received. Gave it a really good cleaning and put a Dead Air micro brake on it. I also run a Sandman S. I didn't have any issues with gas. Ran suppressed and unsuppressed. I even ran a Geissele charge handle for comparison. The BCM seems a little better IMO. I only ran one kind of ammo but I did run two different kinds of mags. Magpul and Lancer. All ran fine and all locked back when empty, suppressed and non.
My lower has the MK2 recoil mitigation system though. Says its a 3.8oz buffer and the receiver extension is 3/4" longer than a carbine extension. So maybe that has a little something to do with it? I've also had my can get stuck on the brake at times. Usually it happens if I let it completely cool before trying to remove it. So I try to take if off when its still a little warm. Pic just cause, ha. 
|
|
|
SC, USA
|
Posted: 3/26/2024 10:19:46 AM EDT
[#30]
Some comments...
1) I would always shoot a new upper at least a couple hundred rounds unsuppressed first to make sure everything is running well and correctly/consistently before adding the variable of a suppressor. If it won't lock open unsuppressed, I'd figure that out first before even messing with a can. 2) Any time a new lower comes into my possession, one of the first things I do is verify buffer tube length and put in a known-quantity buffer spring (Sprinco white in my case, for carbine tubes)... I don't care how quality the make of the lower is known the be; I've still found buffer spring variability from one manufacturer to another. (Exception being a high quality complete rifle from a known manufacturer, they should build the whole thing right as a package, but that isn't what is happening here). This allows, at a minimum, diagnosing of any potential issues with one less variable in play. I always end up sticking with the Sprinco whites anyway. 3) In my opinion, the charging handle has virtually zero bearing on gas to the face. The latch area where the gas is supposedly coming out doesn't even get dirty. I honestly wonder how this idea even got started. The gas is coming out of the chamber/ejection port. To reduce it, you need to either slow down the unlocking via more buffer system spring or weight, or reduce the total gas going into the system through gas port reduction, lower backpressure can, or some combination of the three. I'd get it going without the can first and foremost. |
|
|
|
Posted: 3/26/2024 10:21:25 AM EDT
[#31]
It sounds like your issues are related to the gas system and not the actual upper receiver?
|
|
|
|
TX, USA
|
Posted: 3/26/2024 8:29:54 PM EDT
[#32]
Quote HistoryOriginally Posted By LeadBreakfast: ...so the gas port is a larger diameter. This is entirely unsurprising given thst BCM bills themselves as "mil-spec plus" in their branding and design mindset. It is overgassed for reliable function with shitty cheap ammo most people put through their rifles these days. Your options are to live with the gas, install an adjustable gas block, or an adjustable carrier. With wolf and tula no longer an option, what brand is the shitty cheap ammo these days? |
|
|
|
Posted: 4/13/2024 1:38:58 PM EDT
[#33]
Swapped optics and ran it again today with a heavier buffer. It locked back every time.
Still a bit gassy and the oil from BCM is still burning off. You'd think after a few hundred rounds that oil would be gone. Would like to find a BCM complete lower with their new heavy buffer system.  Attached File |
|
|
|
SC, USA
|
Posted: 4/14/2024 7:42:16 AM EDT
[#34]
The stuff that comes on it from the factory is a packing preservative, not lubricating oil, and should be removed as much as possible before shooting.
|
|
|
|
Posted: 4/14/2024 7:48:08 AM EDT
[#35]
What product is best to use to remove it?
|
|
|
|
SC, USA
|
Posted: 4/14/2024 7:56:46 AM EDT
[#36]
I just use normal gun cleaning products, but depending on the gun, sometimes I've had to spend a bit of time scrubbing.
|
|
|
|
Posted: 4/14/2024 9:21:28 AM EDT
[#37]
I had better luck running a standard upper with a charging handle designed to divert gasses and an h2 adjustable gas block combo. The MK2 just didn't have that much benefit for me as a lefty.
|
|
|
|
TN, USA
|
Posted: 4/14/2024 11:18:29 AM EDT
[#38]
Quote HistoryOriginally Posted By DVCNick: The stuff that comes on it from the factory is a packing preservative, not lubricating oil, and should be removed as much as possible before shooting. It’s not. It’s G96 gun oil that BCM has used for almost 20 years now. OP just has unrealistic expectations. The guns need oil. There will be blowback with a suppressor on. Buffer and spring selection on your own lower is a generalized solution that won’t fit every upper gassing. |
|
|
Win a FREE Membership!
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.
