6.5CM 127gr LRX oddity

[wesc]

Question for those of with significant experience reloading. I have a 16.5” proof CF 6.5CM on an ARC nucleus. I was working up a load for the 127gr barnes LRX. My initial ladder from 38.3-41gr of H4350 didn’t show any promising loads until 40.7 and 41.0gr.

At this point I was already well above the published barnes data (stops at 40.4gr) but I had zero pressure signs on the primer, bolt lift, rim. I did a little reading and found others had made their way to 43+gr and some started their ladder at 41.5.

So I Loaded a ladder from 40.4-42.5:

40.4-2565
40.7-2612
41.0-2646
41.3-2656
41.6-2696
41.9-2704
42.2-2685
42.5-2679

no pressure signs, 1 finger bolt lift. That said, I’ve never seen a consistent drop in velocity with a pressure increase. In addition, I feel that these velocities are probably a bit higher than what I should be getting from this barrel. Wasn’t going for speed, was just trying to find a node. I’ve got a few here but I’m a bit hesitant to load them given this data. That said I still haven’t loaded 10k rounds so I’m sure there is something to learn here.

 

[wesc]

Also, virgin peterson brass-full length sized, CCI BR-2 primers FWIW

 

[Supersubes]

It helps to look at several sources for data. For example Hodgdon list the h4350 max with a 130 accubond with a 24” barrel at 39.2gr/60k psi/2687 fps. That is an absolute joke, and anybody who’s loaded creedmoor knows it . Their instrumentation was flat broken that day. Look at their 140 amax data. Same thing, just out in left field. Compressed at 40 grains, and slow despite 60k psi. Then go to the 142 smk data. Two grains higher charge than the 130, 1.5 grains more than the 140, faster than both, same pressure.

If you start low and work up and look closely for pressure signs, you can take the max listed charge with a grain of salt.

Sounds like Barnes data is out in left field as well. I’d expect you to be in the 42-43 grains pretty easily. What you’re seeing with the drop in velocity probably has to do with the small sample size.

 

[straightshooter1]

Also, virgin peterson brass-full length sized, CCI BR-2 primers FWIW

What's the COAL you're loading to?

 

[straightshooter1]

Sounds like Barnes data is out in left field as well. I’d expect you to be in the 42-43 grains pretty easily. What you’re seeing with the drop in velocity probably has to do with the small sample size.

I agree; should be able to go 43+ . . . but as usual, approach higher pressure loads with caution.

 

[wesc]

Not sure on COAL. I’m at 2.207 on the ogive which is 0.050 off the lands (or at least the jam length).

 

[Steel head]

It helps to look at several sources for data. For example Hodgdon list the h4350 max with a 130 accubond with a 24” barrel at 39.2gr/60k psi/2687 fps. That is an absolute joke, and anybody who’s loaded creedmoor knows it . Their instrumentation was flat broken that day. Look at their 140 amax data. Same thing, just out in left field. Compressed at 40 grains, and slow despite 60k psi. Then go to the 142 smk data. Two grains higher charge than the 130, 1.5 grains more than the 140, faster than both, same pressure.

If you start low and work up and look closely for pressure signs, you can take the max listed charge with a grain of salt.

Sounds like Barnes data is out in left field as well. I’d expect you to be in the 42-43 grains pretty easily. What you’re seeing with the drop in velocity probably has to do with the small sample size.

I’m well over Hodgdon book date for my 260 and 130’s.
that data is silly.
Op, you really should be able to get at or near 43 with H4350 and 130 class bullets.

 

[straightshooter1]

Op, you really should be able to get at or near 43 with H4350 and 130 class bullets.

And maybe even 44 gr if he loads longer. Like, if COAL is at 2.840, 44.0 grs is about 103.8% of case capacity and estimated pressure is getting very close to SAAMI max of 63,091 psi. @ 90°F. Of course, these are ballpark numbers, especially with regards to his particular rig.

 

[wesc]

Thank you gentlemen. I appreciate the info. I had reviewed some other data and felt the 120-130gr loads seemed a bit light (when compared to the loads I used to load for 140 and 147 ELD-Ms) but I figured it was related to differences between leaded bullets and monolothics. That said, in absence of pressure and with the info here I’m more confident I’m safe. The sample size argument makes sense wrt the drop in velocity.

I’ve got a few nodes to trial here and it’s a hunting rig so I’m not going to split hairs when I find something that works well.

thanks again for the wisdom