6BR Tuning

[jpmimproved]

Got a Borden action with my first 6BR and working up a load that I am having some issues with. Lapua brass, 105 JLKs, rem 7.5 primers, H4895. All rounds were seated to the lands.

The issue I am having is that I am seeing ejector marks/swipes even at very low charges, and flattened primers at “relatively” low charges. And a couple pierced primers. Accuracy has been pretty good for my abilities, so trying to figure out where to go from here. Was looking at 27.0-27.2 gr for a node, but had a pierced primer/flattened primers at 27.6. Let me know your opinions.
Red circles at ejector marks, green is flat primers, black is pierced primer.

 

[JFrank]

I have no idea why your having pressure at such low charges but 27.0-27.2 is not a node to work with.

 

[coj0502]

Have you checked your neck clearance?

 

[jpmimproved]

I can slide a bullet into the fired case by hand, the pressure ring gives a some resistance, and the bearing surface has a slight drag.

 

[jpmimproved]

I have no idea why your having pressure at such low charges but 27.0-27.2 is not a node to work with.

I agree, I’m not super excited for it either. No node really showed up in testing to my eyes.

 

[Walt Krafft]

I would try Varget. It is a little slower and lots of shooters have good luck with it. N140 also deserves a try.

 

[gambleone]

Is your scale weighing your powder accurately?

 

[jpmimproved]

Is your scale weighing your powder accurately?

I use a charge master to dispense, then fine tune on an Ohaus lab scale. Both are calibrated and are +-0.1 grains from each other.

 

[BartsBullets]

Got a Borden action with my first 6BR and working up a load that I am having some issues with. Lapua brass, 105 JLKs, rem 7.5 primers, H4895. All rounds were seated to the lands.

The issue I am having is that I am seeing ejector marks/swipes even at very low charges, and flattened primers at “relatively” low charges. And a couple pierced primers. Accuracy has been pretty good for my abilities, so trying to figure out where to go from here. Was looking at 27.0-27.2 gr for a node, but had a pierced primer/flattened primers at 27.6. Let me know your opinions.
Red circles at ejector marks, green is flat primers, black is pierced primer.

Any Idea how fast the bullets were going? I’ve had some lots of H4895 that were nuclear. Just a thought.

 

[Northridge]

one thing to check that may appear of topic but important is measure a loaded round and make sure you don't have a close to zero tolerance as this can cause strange pressure everywhere regardless of charge. sometimes a primer combination can do this try another type of primer..

Shawn Williams

 

[Kracken McGraw]

Those primers still look rounded and not flat even at your highest charge, except for that one circled in green.

 

[Gary C]

jpm,
I have shot a few loads out of a stock Savage with starting with 28 gr IMR 4895 using a Berger 108 and Fed match small rifle match primers and Laupua brass.
I had groups in .2-.4 and decided to increase the charge in .3 increments and went up to 29.1 with no signs of pressure. Best group was .232 and i have twenty loaded at this charge to test further.
These were shot at 40 Deg. F.
I don't know the comparison in the H-IMR 4895 but I wouldn't expect a huge difference.

 

[Belly Benchrester]

I would try Varget. It is a little slower and lots of shooters have good luck with it. N140 also deserves a try.

29.2 N140 hammers in my 6BR with a 108 berger

 

[david kieffer]

I would bet you started with residue in your chamber. The two cases that show ejector marks are at the lowest charge , The first fired ??? . Any residue , oil , cleaning solvents ect will show pressure .

 

[JEFFPPC]

I would say first 2 things that need MEASURED is the diameter of a loaded round vs your neck diameter and the length of your cases.

 

[jpmimproved]

Those primers still look rounded and not flat even at your highest charge, except for that one circled in green.

this was part of the reason I was a little lost because the flattened primers were sporadic.

I would bet you started with residue in your chamber. The two cases that show ejector marks are at the lowest charge , The first fired ??? . Any residue , oil , cleaning solvents ect will show pressure .

I fired 14 rounds at 26.4 grains cleaning about every 5 rounds, being sure to dry patch a couple times after. Could still have left oil behind though, would explain the erratic pressure signs. Ejector marks are at all charge weights pretty much, even though the picture doesn’t show it

I would say first 2 things that need MEASURED is the diameter of a loaded round vs your neck diameter and the length of your cases.

Loaded neck diameter was .0015” greater than unfired brass. Were you referring to after firing neck diameter vs loaded?

one thing to check that may appear of topic but important is measure a loaded round and make sure you don't have a close to zero tolerance as this can cause strange pressure everywhere regardless of charge. sometimes a primer combination can do this try another type of primer..

Shawn Williams

Zero tolerance as in headspace? Making sure I understand the terminology.

 

[foxguy]

Borden Action, Custom Barrel. you didn't say?
Is your chamber cut as a No turn .272 for Factory brass. I would guess 50% or better of the custom Barrels are .268 Chamber and the Brass has to be turned for that chamber.

 

[jpmimproved]

Krieger no turn neck

 

[Walt Krafft]

What is your loaded round neck diameter? What is it after firing?

 

[Kracken McGraw]

Mr. Kieffer above was referring to having excess oil in the chamber above and you were referring to patching dry the barrel. I just wanted to make sure you were on the same page as what he was suggesting.