chrono results - .223/.308 - some interesting data

[bsumoba]

So ran some chrono on my loads that are shooting sub-MOA and got the following. See below.

I hope this helps some of ya'll out.

Here is a summary/analysis of the data:

• Chrono was placed about 12 feet from muzzle
• Used the same 55gr Blitz and FMJ in both the M&P15 and Larue. There was a 2" barrel difference, but looking at the velocities, there is a 400fps spread with the Blitz and a 245fps difference with the FMJ. Anyone have similar experiences like this with the same load in two different rifles?
• Baseline which was 77gr SMK Black Hills Match ammo was giving me some pressure signs. Slight flattening, but not enough to be too concerned about.
• Velocities in general are all on the low side with the M&P15. It is more than likely that Im using a low charge weight node. The baseline was about what I expected the velocities to be with 77gr Black Hills, so I know the chrono is working well and its just my charges. I may try to work up a higher charge weight, but I am VERY content with the accuracy and dont intend on shooting this out far as this is more of a 300 or less rifle with it being a carbine 16"'er.
• Velocities with the Larue are as expected. I think I am good with these loads and comperable to factory ammo and velocities you should be getting with certain grain weight bullets.
• Velocties are as expected with my LR-308 using 175gr SMK and 43.5gr Varget. No pressure signs and velocities are right where they need to be for this combo. I am extremely happy with this. While chrono'ing, I was getting 1/2"-3/4" MOA on my shots! Could probably go to 1000 yds with this. Running quick numbers with my ave velocity, I am getting a 37.7 MOA drop at 1000 yds or close to 400 in drop...maybe not. LOL. I would probably have to load my upper end node which was 44.1gr, but was getting slight primer flattening at this charge and would prefer not to run this regularly.

M&P15 Sport - 16" factory barrel

BASELINE: 77gr SMK / Blackhills Match Ammo
2604
2578
2578
Average (fps) 2586.66
Extreme Spread (fps) 26


25gr H335 / 55gr Blitzking / OAL: 2.230" / LC Brass
2636
2661
2612
Ave (fps) 2676
ExtSpread (fps) 183


25gr Benchmark / 55gr Hornady FMJ / OAL: 2.250" / LC Brass / Lee factory crimp
1st shot - error
2578
2749
2752
Ave (fps) 2693
ExtSpread (fps) 174

23gr Varget / 77gr SMK / OAL: 2.260" / LC Brass
2359
2306
2331
2310
Ave (fps) 2326.5
ExtSpread (fps) 53

23.5gr CFE223 / 77gr SMK / OAL: 2.260" / LC Brass
2189
2164
2182
2182
Ave (fps) 2179.25
ExtSpread (fps) 25

24.1gr CFE223 / 68gr HPBT / OAL: 2.230" / LC Brass / Factory Crimp
2314
2310
2211
2263
Ave (fps) 2274.5
ExtSpread (fps) 103


Larue PredatAR - 18" LW-50 barrel

BASELINE: 77gr SMK / Black Hills Factory Match Ammo
2688
2677
2704
Average (fps) 2689.666667
Extreme Spread (fps) 27


25gr H335 / 55gr Blitzking / OAL: 2.230" / LC Brass
3144
3058
3051
Ave (fps) 3084.33
ExtSpread (fps) 93

25gr Benchmark / 55gr Hornady FMJ / OAL: 2.250" / LC Brass / Lee factory crimp
2911
2962
2943
Ave (fps) 2938.66
ExtSpread (fps) 51

22gr 8208XBR / 77gr SMK / OAL: 2.260" / LC Brass
2629
2666
2624
Ave (fps) 2639.66
ExtSpread (fps) 42

24.0gr W748 / 77gr SMK / OAL: 2.260" / LC Brass
2699
2688
2645
Ave (fps) 2677.33
ExtSpread (fps) 54

22.5gr 8208XBR / 68gr HPBT / OAL: 2.230" / LC Brass
2609
2650
2629
Average (fps) 2629.33
Extreme Spread (fps) 41


LR-308 - 20" JP Supermatch Barrel w/ Thermal Dissipator

43.5gr Varget / 175gr SMK / OAL: 2.800" / LC Brass
2677
2599
2624
2645
2650
2661
Average (fps) 2642.666667
Extreme Spread (fps) 78

[74c5]

I'm still working up to optimum on a couple .223 loads but, noticed the spread dropped to about 20fps on 77 gr Nosler CC when installed into cases that I had forgotten to cham and debur. Wasn't going to shoot them until I saw what the velocities were in the ones done to the same load but properly prepped cases.
Maybe some of the nodes want a crimp?

[huckberry668]

400fps difference is a little extreme but it's a Lothar Walther 50 barrel so it's apparently true.

Barrel length has a lot to do with velocity as well as barrel bore dimensions and quality. If I remember right, the same 308Win round out of a 26" 10-twist Savage 10FP bore has about 60fps less velocity than out of a 24" FN A3G (12" twist chromed bore).

16" barrels don't yield good velocity results for 223/556 rounds. So do most other high power rifle rounds. There is still a lot powder to burn apparently. I chrono'ed my 16", 18" and 24" AR uppers 2 months ago so i know the scope dope and I had similar results but not as drastic.

Just 2" longer gets it to the finish line much faster. this is one of the reasons why I like 18" ARs more and more nowadays...

All handloads, same headstamp, trimmed off datum (all within +- .002" OAL), sized to .001"~.002" under Go-Gauge and no other prep. Shot out of the same lower 10-12 feet from the chrono. average of 5 shots. These are mid level loads according to the published load data.

Load: Nosler 55 FMJBT H335 Fed 205.

1. Stag 16" 2H freefloated - Avg 2800fps.
2. Stag 18" 3GH upper - Avg 2960fps.
3. Armalite 24" T upper - Avg 3029fps.

Load: Nosler 55 FMJBT IMR4895 Fed 205.

1. Stag 16" 2H freefloated - Avg 2772fps.
2. Stag 18" 3GH upper - Avg 2930fps.
3. Armalite 24" T upper - Avg 3032fps.

Load: SMK 69 BTHPM Varget Rem 7.5

1. Stag 16" 2H freefloated - Avg 2612fps.
2. Stag 18" 3GH upper - Avg 2718fps.
3. Armalite 24" T upper - Avg 2829fps.

Load: SMK 69 BTHPM IMR4895 Rem 7.5

1. Stag 16" 2H freefloated - Avg 2697fps.
2. Stag 18" 3GH upper - Avg 2808fps.
3. Armalite 24" T upper - Avg 2905fps.

[bsumoba]

400fps difference is a little extreme but it's a Lothar Walther 50 barrel so it's apparently true.

Barrel length has a lot to do with velocity as well as barrel bore dimensions and quality. If I remember right, the same 308Win round out of a 26" 10-twist Savage 10FP bore has about 60fps less velocity than out of a 24" FN A3G (12" twist chromed bore).

16" barrels don't yield good velocity results for 223/556 rounds. So do most other high power rifle rounds. There is still a lot powder to burn apparently. I chrono'ed my 16", 18" and 24" AR uppers 2 months ago so i know the scope dope and I had similar results but not as drastic.

Just 2" longer gets it to the finish line much faster. this is one of the reasons why I like 18" ARs more and more nowadays...

All handloads, same headstamp, trimmed off datum (all within +- .002" OAL), sized to .001"~.002" under Go-Gauge and no other prep. Shot out of the same lower 10-12 feet from the chrono. average of 5 shots. These are mid level loads according to the published load data.

Load: Nosler 55 FMJBT H335 Fed 205.

1. Stag 16" 2H freefloated - Avg 2800fps.
2. Stag 18" 3GH upper - Avg 2960fps.
3. Armalite 24" T upper - Avg 3029fps.

Load: Nosler 55 FMJBT IMR4895 Fed 205.

1. Stag 16" 2H freefloated - Avg 2772fps.
2. Stag 18" 3GH upper - Avg 2930fps.
3. Armalite 24" T upper - Avg 3032fps.

Load: SMK 69 BTHPM Varget Rem 7.5

1. Stag 16" 2H freefloated - Avg 2612fps.
2. Stag 18" 3GH upper - Avg 2718fps.
3. Armalite 24" T upper - Avg 2829fps.

Load: SMK 69 BTHPM IMR4895 Rem 7.5

1. Stag 16" 2H freefloated - Avg 2697fps.
2. Stag 18" 3GH upper - Avg 2808fps.
3. Armalite 24" T upper - Avg 2905fps.

What do u mean by its a LW? Is there a reputation for LWs?

[huckberry668]

Lothar Walther barrels are legendary. I believe your barrel is polygonal rifled. Which is why the velocity is so much higher with only 2" longer. Bench rest it. I wouldn't be surprised if you get sub half moa groups out of it and heck of a barrel life with easy cleaning.

[bsumoba]

Lothar Walther barrels are legendary. I believe your barrel is polygonal rifled. Which is why the velocity is so much higher with only 2" longer. Bench rest it. I wouldn't be surprised if you get sub half moa groups out of it and heck of a barrel life with easy cleaning.

In fact, I am getting 1/2" MOA easy with both 8208XBR (my temperature insensitive choice) and W748 (my more accurate choice and one ill choose if not going to extreme temperature environments).

[huckberry668]

Temperature sensitivity has never been a problem for me... but then again, i don't push my loads beyond max or shoot bench rest comp where 1/10MOA groups are required.