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Discussion Starter #1 (Edited)
Guys,
Ammunition type is key to getting acceptable 5.56MM terminal performance on flesh & bone targets. The poor terminal performance of the original Vietnam era 10.0" Colt CAR-15 was well known but much of that was due to the then-standard ammunition of that era: M193 55gr. FMJBT. Back in the '60s, my cousin's 101ST LRRP group shot a VC in the sternum with a CAR-15 and had something unusual happen: (1) entry hole with (2) exit holes dropping him like a stone. It caused such an uproar, COLT/Remington/other reps were taken out in the field to view the body first hand. But it was probably just a fluke that the M193 round fragged. M193 will not normally frag when fired from a 10.0"/10.3"/10.5" barrel. Current ammunition types are much better suited for use in short barrel weapons (below). Commercial ammunition modeled after the 5.56MM 70gr. OPTIMIZED brown tip loading is my choice for terminal performance no matter what barrel length I use. AR15/M16/M4 5.56MM barrel length is a tool box: use what works for your application. I have 10.0" to 24" uppers available. But due to long term hearing loss, I rarely fire 5.56MM without a suppressor attached. With a can on the end, a 10.0" to 18" upper is about the limit for ease of use. And 5.56MM accuracy has come a long way due to improved ammunition. The 18" full heavy 1x7.7 Krieger CLE turned for me is proven capable of head shots out to 750yds. in good conditions firing BHA MK 262 MOD 1 ammunition. FWIW.

Here is MV data at 10 ft. from a 10.0" Colt 1x7 LWT M4 barrel with M4 can with several useful loads at approx. 80 degrees F. Mostly use M193 for practice, BHA MK 262 MOD 1 or 77gr. SMK handload for accuracy, and any of the 70gr. TSX loads for terminal performance. The 77gr. SMK loads yield best accuracy and the 70gr. TSX loads yield best terminal performance (both by very wide margins).

Edit: I added MVs from 14.5" Colt 1x7 M4/16" Colt 1x7 M4/18" Krieger SS 1x7.7 where possible:


LC M193 55gr. FMJBT--------------------------------------------------------------: 2638 FPS-----(2985 FPS in 14.5"/3278 FPS in 18")
BHA MK 262 MOD 1 77gr. SMK OTM------------------------------------------: 2351 FPS-----(2577 FPS in 14.5"/2641 FPS in 16"/2825 FPS in 18")
77gr. SMK over MAX listed 5.56MM NATO charge of TAC (handload): 2434 FPS-----(2663 FPS in 14.5"/2824 FPS in 18")
MK 318 MOD 0 62gr. SOST-------------------------------------------------------: 2496 FPS-----(2937 FPS in 18")
SWA 5.56MM 70gr. TSX-----------------------------------------------------------: 2456 FPS-----(2629 FPS in 14.5")
5.56MM OPTIMIZED 70gr. Brown Tip------------------------------------------: 2506 FPS
SSA 5.56MM 70gr. TSX------------------------------------------------------------: 2575 FPS-----(2748 FPS in 14.5"/2802 FPS in 16")
70gr. TSX over MAX listed 5.56MM NATO charge of TAC (handload): 2543 FPS-----(2733 FPS in 14.5"/2787 FPS in 16"/2957 FPS in 18")

Here are some recovered water-shot test bullets fired from 10ft. with 10" Colt: The MK 318 MOD 0 SOST fragmented quite nicely while the M193 yawed/flattened but did not frag. And the 70gr. TSX expanded to 0.48" across the petals while retaining 100% weight.



Business end of the 5.56MM 70gr. TSX bullet after water-shot expansion tests. Minimum expansion velocity is 1800 FPS in water, slightly less on flesh & bone targets:




Business end of 62gr. TSX, 70gr. TSX, & 180gr. TTSX after water-shot expansion tests:



5.56MM 70gr. TSX hunting handload fired from Colt 14.5" [email protected]: 0.43" (5) shot Group. I hunt deer/pigs/etc. with this handload (70gr. TSX over MAX published 5.56MM NATO pressure TAC handload). Work up your handloads slowly; err on the side of safety. The 5.56MM 70gr. TSX bullet is designed to work thru expansion so is NOT overly dependent on high impact velocity to work well like fragmenting bullets.



5.56MM 77gr. SMK OTM accuracy handload for 10.5" 1x7 SS Noveske:



Colt 10.0" 1X7 LWT M4 barrel used for MV/Water Shot Fragmentation-Expansion testing above:

 
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Discussion Starter #3 (Edited)
That krieger is smoking fast, my 7 twist white oak is maybe 2700fps with Mk262.
Fellow shooters with 24" & 26" 1x7.7 SS Krieger barrels chrono the BHA MK 262 MOD 1 at over 3000 FPS unsuppressed. Others also report that the 18" Douglas SPR barrel makes virtually the same MV as this 18" Krieger/CLE. Putting a can on an AR15/M16/M4 barrel will add approx. 20-30 FPS; will get a firm number on that next time I do chrono testing. A properly installed can will also usually allow a barrel to shoot tighter just as a poorly installed can will cause a high quality barrel to shoot shotgun patterns. Issues with a QD mount are the usual culprit. Be sure you are firing actual BHA MK 262 MOD 0/1 cartridge. Does not matter whether it is the mil-spec, SECONDS, or the first quality commercial (below): they all make virtually the same MV. Once the ammo leaves the original box, it is very hard to tell which is which. Several guys have said the same thing as you on MV but we eventually found they were actually firing BHA's AMU load which is about 80 FPS slower but 0.1" to 0.3" more accurate @100yds from the 18" Krieger. The BHA 5.56MM 77gr. SMK AMU load and the SWA 5.56Mm 77gr. SMK load are (2) of the most accurate mag length 77gr. SMK loads I have tested in the 18" Krieger and they both make virtually the same MV within 10 FPS at approx. 70 F.

 

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The southwest load for 77s is 23.2-23.4 grains 8208, or at least it used to be. I'm in CA so I wouldn't know anything about cans except that I want one when I move out of this commie hellhole.
 

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Discussion Starter #5 (Edited)
The southwest load for 77s is 23.2-23.4 grains 8208, or at least it used to be. I'm in CA so I wouldn't know anything about cans except that I want one when I move out of this commie hellhole.
Pulled down & measure at 23.8gr. of a Hodgdon EXTREME stick rifle propellant and it is very thermally stable just as advertised. It was measured to vary by only 18 FPS (5 shot average) from -10F to +135F in the 18" Krieger. It is one of only a small handful of mag length 5.56MM 77gr. SMK loads that I feel is capable of 0.5 MOA or better accuracy at 100yds. when fired from an accurized SPR length AR15/M16 in trigger-pull conditions from a solid concrete benchrest with a BR quality tripod. That level of accuracy is very hard to realize in the field but using the most accurate factory ammunition/handload you can work up for that specific barrel to start with helps keep them tight.

 

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Yeap that's 8208, they use H4895 for their 308 loadings. SWA is good stuff. Thanks for posting this I love reading actual data.
 

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Discussion Starter #7 (Edited)
Yeap that's 8208, they use H4895 for their 308 loadings. SWA is good stuff. Thanks for posting this I love reading actual data.
IIRC, the SWA guys posted that they have used H4895 & IMR 8208 XBR propellant in their 5.56MM 77gr. SMK loading. It seems to be win-win either way but I think 8208 has a slight edge for LR accuracy use: slightly better ES/SD at the cost of a very slight reduction in thermal stability. Might just be lot-to-lot variation though. Will work up an over-mag-length 80gr. VLD over 5.56MM pressure 8208 load next chance I get. Here is the over-mag-length 80gr. VLD over 5.56MM TAC load fired off the tool box of my 4WD at 750yds. in good conditions. The over-mag-length 80gr. VLD really shines at LR over the mag length 77gr. SMK. when the wind picks up. And I think swapping to 8208 will reduce/eliminate any vertical stringing due to thermal variation of the propellant caused by varying barrel temperature/OAT.



Here is the 18" 1x7.7 SS Krieger set up I was firing that day:

 
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