LMT Enhanced BCG Compatibility

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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Dr.Phil
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LMT Enhanced BCG Compatibility

Post by Dr.Phil » Tue Oct 05, 2010 5:19 pm

I'm in the process of planning a 300 BLK build and plan on using the AR platform as the host.
My question is what type of dwell time will be generated with the following setup?
Noveske 10.5" utilizing a pistol length gas system, a TBAC 30P-1 can and pushing 220 grain SMKs @ 1,045fps.
(Handloads will be used and powder canidates so far are Accurate No.9, H110 and A1680.)

The purpose of the inquiry is to determine whether or not I will be able to utilize LMT's Enhanced BCG.
Image
I have been using one of these BCGs for years in my 14.5" 5.56mm upper and really like the performance.
LMT does not recommend using it with barrels less than 14.5" in length utilizing a carbine gas system.
LMT states that their enhanced bolt carrier is incompatible with barrels shorter than 14.5" because there isn't enough dwell time to allow for the slower unlocking of the bolt created by the elongated cam path.
Good link to a thread that discuses this in detail.

Noveske uses the pistol length gas system on the 10.5" 300 Whisper barrel to increase the dwell time while running sub-sonic loads.
This permits the action to cycle properly while using such a low pressure cartridge.
I'm hoping that the dwell time in the gas system will closely approximate that of the 14.5" barrel in 5.56mm.
Link to previous thread related to 300 Whisper ARs and barrel length...

Worst case scenario, I throw the BCG from my 14.5" upper into the 300 Whisper to see if it works.
I really prefer to not use the bolt in a different upper though.
In addition to that, I would really like to know more about the dwell time of different setups.
Any thoughts on this are much appreciated.
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Re: LMT Enhanced BCG Compatibility

Post by 300Blk » Tue Oct 05, 2010 9:40 pm

No one can say without trying it.

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Stickman
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Re: LMT Enhanced BCG Compatibility

Post by Stickman » Tue Oct 05, 2010 11:19 pm

silencertalk wrote:No one can say without trying it.


I'm holding on ammo, but I'll try it when it arrives. I've got an unfired enhanced LMT BCG to use for it.
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Re: LMT Enhanced BCG Compatibility

Post by Dr.Phil » Wed Oct 06, 2010 9:45 am

Thanks Stick!
I'll also try it out as soon as I can get my hands on a Noveske Barrel.

Nice Photo by the way... :)

Was hoping to get some more info than "No one can say without trying it."
I realize that you can't say definitively, but I was looking for more of a discussion on pressure at the port location / dwell time and how these compare to current 5.56 uppers.
This would help to more accurately gauge whether or not the features of the LMT Enhanced BCG would be of any benefit.

The design of the bolt would definitely still be relevant due to the design of the locking lugs, extractor, and fully supported bolt face.
It comes down to timing as it pertains to the bolt carrier.

AFAIK
The pistol length gas system allows for the gas to be directed to the BCG when it is at its peak.
The 300 / 221 pressure curve charts that I've seen indicate that with the pistol length gas setup, this pressure is similar to that of a 5.56 with a carbine length gas system.
Since the 300 BLK projectiles are moving at a much slower velocity than a 5.56, the dwell time should end up being similar to a carbine length barrel with a carbine length gas system.

With all of that said, my Wild Ass Non Scientific Guess would be that it will work.
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Re: LMT Enhanced BCG Compatibility

Post by rob_s » Wed Oct 06, 2010 10:41 am

Dr.Phil wrote: Was hoping to get some more info than "No one can say without trying it."
I realize that you can't say definitively, but I was looking for more of a discussion on pressure at the port location / dwell time and how these compare to current 5.56 uppers.
You do realize how few people there are in the world, let alone the interweb, let alone this site, that really have the functional knowledge and experience to engage in that kind of discussion intelligently, right?

Trial and error would be the rule of the day, especially on what some are terming an "experimental cartridge" like the 300 BLK. and it's such an easy thing to try. Unless the inability to run the LMT BCG would totally eliminate the 300 BLK from your consideration?
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Re: LMT Enhanced BCG Compatibility

Post by 300Blk » Wed Oct 06, 2010 11:00 am

If you are just shooting recreationally, use the LMT group and assume it will work, unless you see a problem in actual shooting. If it does not, get an AAC bolt carrier group. Or a known mil-spec verified BCG and an AAC green extractor kit.

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Re: LMT Enhanced BCG Compatibility

Post by firefighter509 » Wed Oct 06, 2010 11:49 am

silencertalk wrote:If you are just shooting recreationally, use the LMT group and assume it will work, unless you see a problem in actual shooting. If it does not, get an AAC bolt carrier group. Or a known mil-spec verified BCG and an AAC green extractor kit.

Not to change subject but your making your own BCG'S now ? You going to put the skull an x rifle on it? 8)

Feel free to use this subject as if it were your own!!!!
Last edited by firefighter509 on Sat Oct 09, 2010 8:18 pm, edited 1 time in total.
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Re: LMT Enhanced BCG Compatibility

Post by Dr.Phil » Wed Oct 06, 2010 2:36 pm

rob_s wrote:You do realize how few people there are in the world, let alone the interweb, let alone this site, that really have the functional knowledge and experience to engage in that kind of discussion intelligently, right?
Since RSilvers did all the development on this product I concluded that it was within reason to think that he would have knowledge of this.
Without this knowledge, he would have just been cutting barrels, chambers, and port sizes at random until he tested something that worked well.
While this may indeed be the case, from an engineering standpoint it would be both inefficient and potentially unsafe.

In this case, if I read between the lines correctly on RSilvers response, it appears that trying to match the port pressure and dwell time of the 5.56 was part of his design.
He understandably does not wish to divulge any information that may be proprietary or potentially dangerous and this is very evident when looking through all his posts regarding the 300 BLK.

Yes of course just try it and see in this case is an adequate solution.
Fortunately for me, it sounds like Stickman has an upper already and is just waiting for ammo to test out this parts combination.

I look forward to all the excitement that will undoubtedly come from the 300 BLK release.
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don't tell them where they know the fish."
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Re: LMT Enhanced BCG Compatibility

Post by 300Blk » Wed Oct 06, 2010 5:03 pm

I feel there is no way to predict without testing it. Plus we are not sure what LMT really means and if what they say is literally exactly correct or if they just simplified it for explaination.

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Re: LMT Enhanced BCG Compatibility

Post by Stickman » Wed Oct 06, 2010 10:25 pm

Dr.Phil wrote: Fortunately for me, it sounds like Stickman has an upper already and is just waiting for ammo to test out this parts combination.

Not much in the way of ammo, but its here. I'll see if I can get the LMT enhanced BCG a try, but its not going to be with many rounds.
Stick

I've done work photography work with 45 or so manufacturers within the firearm community, my images have been used for catalogs, magazines, covers, etc. I have also shot work for the US Military. I am prior service and a full time LEO.

I now also shoot and write for Military Times. My primary focus will stay with weapons, accessories and related equipment reviews. Manufacturers can reach me through any of the boards. Have something new? Let me know.

http://www.flickr.com/photos/stickgunner

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