11.5" Chrono Numbers

[AT Armor]

We chrono'd a few different rounds today in a new gun, BCM 11.5 SBR, SOCOM RC mounted. The numbers came in a bit lower than expected. Such as:

Federal XM193 2766 fps
SSA 70gr TSX 2295 fps
BH 50gr TSX Optimized 2931 fps
SSA 77gr SMK 2178 fps
SSA 55gr TSX 2470 fps

10 rd strings, average fps. 700ft elevation, 60 deg. The barrel has less than 200 rds on it. All are 5.56 loads.

These are lower than (unverified) velocities for these loads I have seen reported in other reputable places for an 11.5. The XM193 is within 100fps of said reports, but the others are quite a bit slower.

Does anyone have any comparable data for any of these?

These velocities put frag ranges for the XM193 at 25 yards and the 77 SMK comes out of the bore slower than the frag threshold. Tolerable for expansion ranges for the BH50 and SSA 70, (153 and 218 yards respectively). Not great, but ok as these are my two SD rounds.

 

[kaltesherz]

I have the exact same set up (11.5 BCM w/ 556 RC) so I appreciate the numbers- but damn, those are pretty low.

 

[kaltesherz]

BTW were the SSA 5.56 or .223?

 

[WDPD8207]

I was thinking about buying the 11.5" BCM upper and running an AAC mini 4. Do you feel the velocities would increase or be lower with the can?

 

[kaltesherz]

I was thinking about buying the 11.5" BCM upper and running an AAC mini 4. Do you feel the velocities would increase or be lower with the can?

Just an FYI, I ran this combo for awhile and had insane muzzle flash, now I'm running a SOCOM 556 RC and it's taken care of the issue.

 

[WDPD8207]

Just an FYI, I ran this combo for awhile and had insane muzzle flash, now I'm running a SOCOM 556 RC and it's taken care of the issue.

Ok, good to know. I'll look into the SOCOM 556 RC. Thank you.

 

[kaltesherz]

Ok, good to know. I'll look into the SOCOM 556 RC. Thank you.

I've also heard the SOCOM Mini is great about reducing flash (several have said it's on par with the full size RC) but I only have experience with mine. Added bonuses being even less blowback than the Mini4 and a much better / cleaner locking mechanism. It's my 3rd 5.56 can and miles above my other ACC cans.

In defense of the Mini4, it is small, durable, and I had no issues with it's noise suppression.

 

[AT Armor]

BTW were the SSA 5.56 or .223?

All 556, all recent production (and we had it properly stored beforehand).
I will chrono the same with a 14.5 in the next couple of weeks, will see where it is compared to reported velocities from the other sources.

 

[03humpalot]

Interesting. Out of curiousity how are you determining the fragmentation ranges? Its something I need to do here soon at work.

 

[AT Armor]

Interesting. Out of curiosity how are you determining the fragmentation ranges? Its something I need to do here soon at work.

Brother I used data from manufacturers or second hand reported data from reputable sources, some older data posted by @DocGKR as well.

Any other first hand chrono data from similar setups (11.5 suppressed) would be appreciated.

11.5 chrono velocities / Frag or expansion velocity required / threshold range
Federal XM193 2766 fps / Frag threshold 2700 fps / 25 yds
SSA 70gr TSX 2295 fps / Expansion threshold 1800 fps / 218 yds
BH 50gr TSX Optimized 2931 fps / Expansion threshold 2300 fps / 153 yds
SSA 77gr SMK 2178 fps / Frag threshold 2300 fps / 0 yards

I freely admit this could be chomped up, but I think it is in the ballpark. I know the raw velocity chrono numbers are correct since I was the one that did the chrono, other than that if anyone has anything that will refine these, please come up on the net.

 

[03humpalot]

Gotcha appreciate it.

 

[Kevin 149]

A can will generally increase velocity slightly vs. the same gun minus the can. I have chrono data at home I can post later, if my memory serves it's in the 10-20 fps range on a 10.5"

 

[Kevin 149]

I posted the below on LF a few months ago. It was using an LMT 10.5" and can.

December, 2012, 40 degrees outside, No idea what the relative humidity nor barometric pressure was. I was at the range, so therefore it was perfect! Rifle is a factory LMT 10.5", can is a Yankee Hill.



Eight round string w/unknown manufacture M193 ammo, was 2668 fps with can, and 2653 fps without; a whopping 15fps faster with the can.



With my own training handloads. I load any cheap 55fmj and AA2230, a little slow deliberately, results are:

(5 round string) 2552 and (10 round string) 2575 fps with can; and

(5 round string) 2544 and (10 round string) 2559 fps without

(5 round string) can is 8 fps faster and (10 round string) can is 16 fps faster.



If a little bit really is a lot, that right there's a good argument to always have a can; 'cuz a can has more death power!



By comparison, the same date & time, a factory 16" LMT was at 3119 w/the M193 and (5 rounds) 2919 and (10 rounds) 2923 with the same handload.



Hope this helps.