6.5 Sherman Short & Berger 156

[Kramer93]

I have a 6.5 Sherman Short that I'm trying to figure out a load for. I'm currently using the newer ADG brass 1x fired, federal gm210m's, Berger 156 EOL's, and I'm trying out a couple different powders. It's a Defiance anti action with a 22" Bartlein barrel, around 175 rounds on it. Ran a couple ladder tests on a labradar today, and I'm a little surprised by the results. I've seen a bunch of people saying they use around 58gr of H1000 and end up around 3000 fps. I've also heard Retumbo is an option, but to use 1gr more, so I tried that today. I'm just wondering if this is normal for a 22" barrel, if I just have a slow barrel, or if I should run another ladder test with more powder. It seems to be running slow for the amount of powder I'm using, especially with H1000. Here's the chrono results.

H1000
58.0 - 2742
58.2 - 2769
58.4 - 2774
58.6 - 2815 *very light ejector mark
58.8 - 2795
59.0 - 2807 *light ejector mark
59.2 - 2840
59.4 - 2840 *light ejector mark
59.6 - 2834 *light ejector mark
59.8 - 2843 *slightly heavier bolt lift

Retumbo
58.8 - 2809
59.0 - 2807
59.2 - 2818
59.4 - 2852
59.6 - 2869
59.8 - 2857
60.0 - 2870
60.2 - 2882
60.4 - 2887 *ejector mark
60.6 - 2899 *ejector mark & slightly heavier bolt lift

Do I run another ladder test with retumbo up to 61.4 ish, or try to find a different powder? The retumbo test put all 10 into a dime size hole at 100, so accuracy shouldn't be much of an issue, I guess I was just expecting more velocity for that much powder.

 

[Deadman Pointers]

It does seem a little slow... I have a 7.5tw 20" Proof barrel and @ 57.5gr of H1000 I see 2800 fps. N568 didn't give decent speeds...

 

[J_D]

OP, How is this working out?

My 6.5SS barreled action arrives today. I have dies, H1000 and N560, and going with Berger 153.5 LRHT's.

 

[Kramer93]

OP, How is this working out?

My 6.5SS barreled action arrives today. I have dies, H1000 and N560, and going with Berger 153.5 LRHT's.

I think I was getting false pressure signs because the brass was a little long at the shoulder. This barrel did speed up some, too. Ended up bumping the shoulders back another couple thousandths, and I'll have to check my notes, but if I'm remembering right, it is running the 156's at 2940 with 60.4gr of retumbo and no pressure signs. I might try N565 if I can find some. I think N560 might be a little bit fast for top velocity.

 

[J_D]

I didn't plan on full velocity to preserve barrel life.

 

[Kramer93]

I'd probably start with H1000. It's been plenty accurate in my rifle, just didn't have the speed I was looking for. I started with some of the 30° shoulder brass, and fireformed it to 40° with 56gr of H1000 and a 129gr hornady interlock. Those shot between .2-.3" at 100 yards. No idea on speed, but the accuracy was there for sure.

 

[J_D]

Rich said to use 54 gr of H1000 on new brass to preserve primer pockets and 57gr to start my ladder with. The new brass doesn’t need forming, it’s good to go and I am getting 100 once fired brass with the BA.

 

[Kramer93]

I started a little higher due to the lighter bullets, and the fact that I was using it for hunting while fireforming the old 30° brass. I agree that 57gr is a good place to start a ladder test if you're not looking for speed. The newer 40° brass is good stuff for sure. I fired one piece 10x to torture test it, and it's still holding up. I'll need a new barrel before I go through the brass that I have.

 

[Kramer93]

Cracked open a new bottle of retumbo from a different lot number to load some hunting ammo for this year, loaded some up at 60.2gr, and it ended up going 2970fps with some pretty bad ejector marks. This lot number seems to be significantly hotter than the last I was using, but accuracy is still there. I pulled the rest of them, and will be doing another ladder test. Here's the three rounds I shot with this new bottle of powder. Not real excited that I have to reduce the powder charge. Hopefully it shoots similar groups afterwards.

 

[J_D]

I'm hoping to get some ammo loaded this weekend and just have a few details to sort through myself.