Recently had my M4SDK approved, wanted to share a little info I’ve found regarding compatible muzzle devices.
In the months leading to my cans approval I was researching what muzzle devices would and would not work with the M4SD/K series of cans. I had a hard time finding much info, and now that I have the can I’ve found that some info out there is incorrect.
I had BCM comp that did not fit either of my M4SD’s, the comp came on a factory BCM 16" ELW-F upper straight from BCM. I have since sold it so I cannot get you measurements.
Griffin muzzle devices require a NATO specification blank firing adapter groove to attach. The BCM comp did not have a NATO spec groove and the griffin guys tried to get BCM the tweak the comp design shortly after it debuted. I’d be curious to know if BCM quietly got on board or if the tolerance stack between the comps and the cans might permit some cans to fit on some comps. None of my 3 GA cans fit either of my 2 BCM comps.
This mirrors my experience with M4SD not fitting BCM gunfighter comp. Early/older version. Several years ago I also asked BCM to modify the groove to fit; I’m glad I’m not the only one! I am also interested to know if BCM changed the spec, or if it’s a case of tolerance-stacking. I like the Mod 0 as a good middle ground between a FH and brake.
I used a drill and a bolt/washer/nut as a lathe to spin the MD and made the groove on mine wide enough. It didn’t take much.
Edit: After checking the BCM site, I see that the mod 0 is now advertised to accept a BFA/FH-mounted suppressor. I have no idea how long that has been so. I will try to get my hands on a newer version and test for compatibility.
I have an M4SDII, 30SD, and an Optimus with an A2 mount. I’ve had fitting issues with random A2’s. Some were very loose & some didn’t fit at all.
I have about 5 or 6 BCM MD’s and all of them fit great.
For the best fit; however, I use the MD’s from GA. They offer the most positive latch engagement with least amount of wobble.
The answer is “some but not all”. The GA A2 mounted cans interface with the A2 style MDs on the two raised “lands” on the MD and latch into the BFA groove.
The lands need to be at the same distance apart to interface with the can properly. The BCM A2X does not. The lands on the BCM A2X are further apart so the forward bearing surface on the can will not line up with the front land on the A2X.
I sold my upper that had a BCM A2X otherwise I’d have taken a picture for comparison.
(Apologies for the cell phone edited pics)
Griffin Armament, and perhaps others, make extended A2 compatible mounts that work with their A2 mounted cans. (See pic)
I have a 6315 and my M4SDII fits, but it was very tight; difficult to get on and off, even when clean. I put the MD in a drill and used 600 grit, then 1200 grit sand paper to reduce the OD of the 6315. The reduction was small, maybe .0001". I couldn’t measure it with my calipers, but the can works fine now.
I also have one BCM Gunfighter Mod 0. The BFA groove was too narrow for the gate to lock. Again, I modified the MD so the silencer works. I used a bolt, nut, and some washers to hold the MD and spun it in a drill. I made the BFA groove wider with a file. It didn’t take much. The OD of my BCM MD is good.
Sample size of 1 of each, so…
I have several A2s and each works fine with the M4SDII.
As a side note, the M4SD-K is a great can also. It is approximately .75" shorter than the full size version. I wouldn’t call it a true mini at 5.75". However, I think it shines on 11.5-12.5" barrels. I can’t tell a difference between it and the M4SDII in performance, only length/weight. I like it better than the full size version.
