Inconsistent pressure signs from H4831

[EMorr]

As the title of this post alludes to I have had some inconsistent results when using H4831 powder in my current combination. The combination that I am currently working with is the Hornady 208 grain Match BTHP bullet sitting on top of 57.5 grains of H4831 inside of Federal 30-06 cases (these cases have been fired 4 times previously and were just annealed prior to this loading) primed by CCI #200 primers, the bullets are seated to an OAL of 2.650 at the ogive, which is nowhere near the lands of my rifle. All of the bullets were weight sorted and seated to within 2 thousandths of an inch of each other, the only thing I did not do with this batch of reloads was sort the bullets by bearing surface length.

I first started developing this load last year and have slowly been stretching the distance I’m shooting at. As I don’t have the opportunity to shoot as much as I would like sometimes a few months can pass between range sessions, due to the greatly varying weather conditions between ranges sessions I always start with a few rounds with lower powder charges and work my way back up to my max charge of 57.5 grains looking for pressure signs along the way. I have never had an issue with pressure until yesterday when I saw very inconsistent pressure signs from my brass.

As always I started low yesterday and worked my way up to my max charge, when I reached my max charge about half of the brass showed no pressure signs and the other half showed a fair amount of over pressure. After a few rounds showing over pressure I stopped shooting that load as I did not want to wreck my rifle or worse hurt myself. Yesterday the temperature at the range was 107 degrees and the initial load development for this combination was done in cooler conditions with a temperature of only 75 degrees. I realize that no powder is 100% temperature stable and I may have reached the tipping point for this combination at 107 degrees and I can accept that, the next step I plan on taking is to re-start the load development looking for a max powder charge that will not show pressure signs at these higher ambient temperatures.

My questions to the experts here is why do you think I am seeing pressure signs on some cases, such as ejector swipe and sticky bolt lift on some cases where other identical loads fired moments earlier show no pressure signs on the cases? Now for some pictures.

For the moment I have become an internet retard and cant get the picture of the brass to imbed, as soon as i can pull my head out of my ass I will post pics of the brass.

After removing my head from my ass here are the pictures. the first pic is of the brass that i saw not pressure signs from, i know the primers are cratered but that is from an over-sized firing pin hole, the last pic of Nosler brass is from a known safe load and also have primer cratering.

These are the pieces of brass that had a sticky bolt lift and ejector swipe.

Cratered primer in Nosler brass from safe load for reference.

 

[B3dlam]

Re: Inconsistent pressure signs from H4831

How are you measuring you powder it might just be that some of the rounds had slightly more powder then the other rounds and therefore generated higher pressures and since you are running a very hot load anyways you have less margin of error with your powder charges.

 

[turbo54]

Re: Inconsistent pressure signs from H4831

I the ejector mark visible only, or is itraised? Can you catch a fingernail or sharp tool on it?

If it is visible only, you're on the edge of "high" (not necessarily "over") pressure. If it's raised, you are officially "over"...unless...

Are you certain that EACH case is equally cleaned of any/all sizing lube? Residual lube will cause this really easy.

Also, cases whose shoulder is bumped back too much can do this. If your sizing is in question, try neck sizing only to see if the condition repeats.

 

[EMorr]

Re: Inconsistent pressure signs from H4831

The powder was dropped from the Lee perfect powder measure to within a few tenths of a grain of my max load and then hand trickled to the exact load on a Frankford Arsenal digital scale that was calibrated and checked against a balance beam scale for thoroughness before I began loading so I’m confident the loads were consistent.

The Ejector marks are slightly raised and the cases were all clean and lube free so I’m sure I am over pressure, I will look into how consistently my dies are bumping back the shoulder back but for now I will just re-work the load and pick a smaller max charge. Thanks for to both of you for the quick replies.