Re: LMT Enhanced Bolt Carrier
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: country888</div><div class="ubbcode-body">What barrel length are the best for these? Web site says 14' & longer.</div></div> They don't guarantee it to work on anything under 14.5".
This is due to the extra dwell time the Enhanced Bolt Carrier adds.
It is designed around an M4 MILSPEC configuration with a 14.5" barrel.
Depending on how big the gas port is on your barrel, it can work all the way down to a 10" 5.56 NATO barrel.
There are two versions of the LMT Enhanced Bolt Carrier.
The older one just has three exhaust ports where the dust cover notch is.
The newer design also has a tiny hole behind the three gas ports to further smooth out the cycle.
I own both and when I received the new version I called LMT to inquire about the new port.
The tech guys said that they added it to try and make it work better on the SBR setups.
I put a Full Auto model of the new version on my suppressed 14.5" upper and noticed less "gas face".
I put a Semi Auto model of the original version on my suppressed 10" Noveske 300 BLK upper and it works flawlessly.
The big improvement that it provides on the 300 BLK is in taming the full power supersonic loads.
Since this product was not designed with the 300 BLK in mind, I did a lot of research into whether or not it would work prior to investing in another one for that project.
The easiest way to understand how the LMT Enhanced Bolt Carrier works is to think of a standard AR and how the standard volume / duration of gas impacts the operation.
In a traditional M16, there is a 20" barrel and a rifle length gas system.
This configuration as designed by Eugene Stoner permits the cartridge to depressurize prior to the bolt unlock sequence.
In an M4 configuration, the shorter 14.5" barrel and carbine length gas system delivers the full load of gas over a shorter duration and earlier than a standard rifle configuration.
This is why you have things like the CRANE "O" ring under the extractor in the M4 configuration.
They are needed to generate enough force to extract a cartridge that is still partially pressurized.
The LMT Enhanced Bolt Carrier Group was designed for the Enhanced SOPMOD program and directly addressed the requirements outlined in the program.
The main problem is the shorter the barrel, the tougher it is to get that balance of gas and dwell.
As the gas block is moved closer to the chamber, the gas is delivered to the bolt carrier earlier in the cycle.
The length of barrel from the gas block to the muzzle determines the duration that the gas system is pressurized.
The final component is the size of the gas port and this determines the pressure of the gas system.
The LMT Enhanced Bolt Carrier adds an additional variable by delaying the unlocking of the bolt.
The conclusion that I ultimately came to regarding what will and what will not work with the LMT Enhanced Bolt Carrier is this:
As long as the setup that you are using resembles the volume and dwell time of the M4, it will work fine.
The 300 BLK does this very well because the slower moving bullets allow for much longer dwell times than the 3000 fps projectiles of the 5.56 NATO cartridge.
