Benchmark Data & 24” Barrel

[Harpoon1]

CZ 527 American 6.5 Grendel 23.5” barrel
Benchmark/ Hodgdon Data
Starline
CCI #41
70f/@ sea level

ChargeMaster Lite
MagnetoSpeed
1 shot per charge

Speer 90 TNT 2.225” COAL

29.0/2762
29.2/2742
29.4/2795
29.6/2809
29.8/2846
30.0/2828
30.2/2842
30.4/2879
30.5/Hodgdon Max/2.200 COAL
30.6/2896
30.8/2894

Edited: “31.2/ 2952” is the Speer data Max. I can’t recall why I stopped with the previous charge weight, instead of going up at least to the Speer max, maybe just a simple oversight, IDK?

No pressure signs on the brass, all the rounds impacted into a less than 2 MOA concentric group

Nosler 90 Varmegeddon FB Tipped/2.260” COAL

29.0/2730
29.2/2754
29.4/2778
29.6/2782
29.8/2835
30.0/2861
30.2/2882
30.4/2901
30.5/ Hodgdon Max
30.6/2923
30.8/2935

Again, no pressure signs, and all rounds impacted an approximate 2MOA concentric group.
Interesting that there was no speed inversion with this bullet, compared with the TNT data.

Hornady 95 Vmax/2.230” COAL

28.2/2515
28.4/2627
28.6/2617
28.8/2630
29.0/2649
29.2/2695
29.4/2668
29.6/2709
29.8/2735
30.0/2771 Hodgdon Max/compressed

Again, no pressure signs, here we saw 2 disitinct vertical groups about an 1” apart. Both groups combined, measured edged to edge, still around 2MOA

Nosler 100 BT/2.260” COAL

28.2/2699
28.4/2682
28.5/ Nosler data max load w/100 BT/93% case fill
28.6/2722
28.8/2716
29.0/2745
29.2/2776
29.4/2811
29.6/2830
29.8/2849
29.9/Hodgdon Max
30.0/2854

More of the same, no pressure signs and another 2 MOA concentric group. I like it!

Benchmark has a temperature sensitivity rating of 0.44

Some others for comparison

H4895 0.23
8208 XBR 0.59
A2520 0.74
AR Comp 0.77
PP Varmint 0.89
TAC 0.91
CFE 223 1.70

[FLshooter]

Thanks for posting
I am going to try to data for the 90 TNT. Good bullet for Florida hogs.

[Harpoon1]

Thanks for posting
I am going to try to data for the 90 TNT. Good bullet for Florida hogs.

My pleasure.

You’ll get a kick out of this. I ended up trying your muzzle crowning technique after all. Chopped 4” off the RAP Grendel. Worked like a charm! Can’t beat the price.

It’s a “truck gun” for me, and now has what I think is a better balance @ 18”. And also the first real “live fire” test with the new “reduced” spring ASC mag. Jaw dropping. It’s like it’s an entirely different gun, ran great.

[tdbru]

Harpoon1,
interesting data. i didn't realize H4895 had half of the temp coefficient of BenchMark. where did you find that info? did any other powder that is in the usable range of the 6.5G have a lower temp co?
thanks,
-tdbru

[s3silver]

Harpoon1,
interesting data. i didn't realize H4895 had half of the temp coefficient of BenchMark. where did you find that info? did any other powder that is in the usable range of the 6.5G have a lower temp co?
thanks,
-tdbru

Although not as popular, varget is pretty stable also and is what I mainly use since I have quite a bit of it.

[Harpoon1]

Harpoon1,
interesting data. i didn't realize H4895 had half of the temp coefficient of BenchMark. where did you find that info? did any other powder that is in the usable range of the 6.5G have a lower temp co?
thanks,
-tdbru

[ATTACH=CONFIG]15710[/ATTACH]

[Harpoon1]

Harpoon1,
interesting data. i didn't realize H4895 had half of the temp coefficient of BenchMark. where did you find that info? did any other powder that is in the usable range of the 6.5G have a lower temp co?
thanks,
-tdbru

[ATTACH=CONFIG]15711[/ATTACH]

[Harpoon1]

Harpoon1,
interesting data. i didn't realize H4895 had half of the temp coefficient of BenchMark. where did you find that info? did any other powder that is in the usable range of the 6.5G have a lower temp co?
thanks,
-tdbru

Think I stole it from Klem!

Just got a keg of A2460, based off this chart. In the Western Powders Manual, it’s almost identical to TAC in speed and supposedly 1/3 as temperature sensitive.

Varget is the most stable listed in the Grendel range but kind of slow. Only got 2263 FPS with 26.8 grns (Speer Manual max) and 120 Gold Dots. The manual claims 2420 FPS with a different case/primer, same length barrel. IDK?


[ATTACH=CONFIG]15712[/ATTACH]

[FLshooter]

My pleasure.

You’ll get a kick out of this. I ended up trying your muzzle crowning technique after all. Chopped 4” off the RAP Grendel. Worked like a charm! Can’t beat the price.

It’s a “truck gun” for me, and now has what I think is a better balance @ 18”. And also the first real “live fire” test with the new “reduced” spring ASC mag. Jaw dropping. It’s like it’s an entirely different gun, ran great.

Glad that it worked out for you. I’ve never felt the need to chop down a barrel. But I have recrowned some older barrels that have sat around for a long time and gotten rusty.

[s3silver]

Varget is the most stable listed in the Grendel range but kind of slow. Only got 2263 FPS with 26.8 grns (Speer Manual max) and 120 Gold Dots. The manual claims 2420 FPS with a different case/primer, same length barrel. IDK?

Yea, it is kind of slow. I worked up to 28.8gr 2.250” col with 123 eldm and get about 2420 fps out of my 22” barrel. The same load does about 2350 out of the 16” barrel. It’s a little bit on the hot side but shoots good out to 500 meters.

For your 18” rap, h4895, benchmark, or 8208 would probably work better.

[CJW]

Nice job Harpoon, thanks for the post.