223, 55 grain loads chronographed

[sloughfoot]

xtremevel provided the ammo and asked me to record the average velocities of various 55 grain 5.56 Mil-Spec loads and commercial .223 loads with 55 grain bulletes. I also chronographed a couple of my reloads.

I fired them out of a chrome, 20 inch, 1X7 Colt barrel and a chrome, 16 inch, 1X9 Bushmaster barrel.

The velocities listed are 20 inch/16inch. Ten shot strings were used for both barrel lengths.

Olympic 5.56 3135/2917 (no ES available) (changed from 223)

American Eagle .223 3104/2929 (ES 40)

LC77 5.56 3206/3029 (ES 100)

Precision Cartridge .223 3055/2810 (ES 140)

TC 67 5.56 3190/3058 (ES107)

PMC Bronze .223 2678/2665 (this is suspect, but I did not have ammo to recheck. ES was 205 with this load)

WCC94 5.56 Q3131 3248/3109 (ES 38)

Silver Bear .223 3044/2890 (ES135)

55 FMJ, my reload with 26.2 748 3126/2969 (ES 89)

55 SP, my reload with 26.2 748 3046/2870 (ES90)

There is virtually no difference between the velocities of the Mil-Spec and the commercial loads except for the PMC. I don't know what happened there but I would like to retest that load because there was a condition change while shooting that string.

 

[XtremeVel]

Thanks for the great work Dean !

I can get you more of the PMC for a retest. I'd have to check, but I'm pretty sure it will be the same lot.

That Twin City from 1967 is a good example on ammo life. That stuff was stored poorly for over 2 decades (forgotten in back of a car in northern Indiana parked in a unheated barn). Now that is is being stored properly, I am confident it has another 40+ years of life left. Next time instead of sorting thru for the best looking rounds, I will give you some of the worse,with the most growth on them.

Thanks for including your Q3131 also. I had always heard highly of it, but never broke down and tried any because of the price. Also, I was never sure of the difference, if any, of that and the Q3131A.

 

[U.S. Patriot]

Nice report, I want to build a 20" A2.

 

[Titanium Man]

Awesome work!! Thanks

 

[SmileDocHill]

Is ES some kind of standard deviation? Difference between highest and lowest?

 

[sloughfoot]

ES is Extreme Spread. The difference between the highest velocity in the string versus the lowest velocity in the string. For this type of test, I think 10 shot strings produce valuable data.

What I think may have happened with the PMC is that the machine did not properly "see" one of the bullets over the screen. It read a super low velocity for one or two bullets, which distorted the data for the string. Unless PMC's QC for powder charge is poor. I really don't think so and I hope I can retest the PMC ammo. The hi was 2798 and the lo was 2593. Can't be right, but it is what was recorded. Maybe a cloud or maybe a insect?

SD is Standard Deviation and the PMC showed a a SD of 51 which matched 3 other loads. The best SD for the day was the American Eagle, which was 12.

Maybe I should have mentioned that it was 95 degrees, but I was shooting under a cover so nothing got real hot. There was a light breeze.

All strings were fired with a rifleman's cadence, one shot every 3-4 seconds, aimed at the NRA 100 yard bullseye target. Of the 100 shots fired with the 20 inch rifle, 92 stayed inside the 9 and 10 ring. The 8 went into the 8 ring. Very acceptable accuracy for the intended use of the ammo.

Also, I changed the table because I just realized that Olympic is Greek 5.56 military ammo.