Pressure question

[deadwolf]

Assuming all things equal, what would cause pressure signs in once or twice fired, reloaded brass, and no pressure in new brass reloaded with the same load?

I am really scratching my head in this one, and while the question is simple, I’ll give you the back story...

I reloaded some Federal and Winchester 300 wsm brass (on its second reload) with a middle of the road powder charge and working up in .5 increments as usual. I had a hard bolt lift on extraction with the first round fired. This happened with a couple more shots with a different bullet combo as well. Measured all the brass again thinking maybe the shoulder wasn’t bumped back far enough somehow and confirmed it was all bumped back plenty far. Pulled a few bullets and double checked the powder throws. All good there as well. Now this may sound like an add for Bertram Brass at this point, but we loaded up the same recipe in new brass and everything shot exactly as we expected. We did achieve the velocity we expected with a little lower charge weight, but I’m going to conclude that’s due to the thicker Bertram brass.

But here I am questioning how in the world we had such pressure so low in the work up.

Anyone have an idea?


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[section8mainiac]

I have ran into a similar situation. Weigh each pice of brass. Also measure the case volume before resizing and after using water.

What is the pressure sign exactly?

Same primers?

 

[granite7]

Did you trim after resizing or check case length?

 

[deadwolf]

Did you trim after resizing or check case length?

Yes, always.

Trim, chamfer, deburr, double check length


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[deadwolf]

I have ran into a similar situation. Weigh each pice of brass. Also measure the case volume before resizing and after using water.

What is the pressure sign exactly?

Same primers?

On the brass itself there was a slight ejector mark, coupled with a hard bolt lift and difficult extraction (hard to run the bolt backwards)


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[Kraze]

What powder, charge weights, primer? You're using both Winchester and Federal brass to work this load up? And maybe now Bertram brass as well? If I was you, I'd pick one to work up a load. Case capacity can vary between brands, I wouldn't mix and match.

 

[deadwolf]

The Bertram was brand new and not used for the load work up. I had Hornady eldx 178s and 200s, each in different brass. Planning on only using the Bertram now and scrapping the others. I was using the Winchester and federal because it had been factory ammo and fired in the rifle, then planned to use it to reload and not pay for new brass. It still doesn’t explain the pressure in both federal and Winchester rounds, as they had been loaded once before.


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[Kraze]

Ah gotcha. Still might help to know what the loads were for the two different combos. Some people have a different definition of a "middle of the road" charge than others lol.

 

[Wrench]

Brass flow to the neck. Weight oddities, low neck tension and compressed loads allowing the bullet to grow the case length. ....to think of a few.

 

[deadwolf]

Brass flow to the neck. Weight oddities, low neck tension and compressed loads allowing the bullet to grow the case length. ....to think of a few.

Neck tension is .002 under, I wouldn’t think that would be too light??

The 200 eldx was a slightly compressed load, them suckers are long in a short mag

Can you explain the brass flow to the neck?


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[Wrench]

When you fire high pressure loads there's a flow of brass that moves towards the shoulder and neck.

Ifyou Google brass flow and doughnut it should do a much better job explaining it than I can.

.002 with a compressed load could be moving under recoil.....and possibly without. Measure you oal and then ban the case around and measure again. Let a few sit for a few days....and measure. They can grow from the powder push.

 

[section8mainiac]

A few more questions:

1. Did you resize the new brass before loading!

2. Did you wipe all oil/lube off after resizing?

3. Did you notice any pressure signs on the primers?

 

[deadwolf]

A few more questions:

1. Did you resize the new brass before loading!

2. Did you wipe all oil/lube off after resizing?

3. Did you notice any pressure signs on the primers?

1. No (and the resized brass had the same shoulder measurement as the new brass)

2. Always, my brass goes back in the tumbler again after sizing

3. No


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[4ester]

Same lot of powder?

How many rounds down the tube since cleaning? Carbon ring?


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[rayporter]

^^

can you mic the neck diameter of the loaded rounds?

 

[deadwolf]

Same lot of powder?

How many rounds down the tube since cleaning? Carbon ring?


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Different powders, RL17 with the 200s, RL26 with the 178s

When we saw pressure with those rounds we loaded some new Sierra TGK GameChanger 165s with RL 17 (new Bertram brass) and no pressure signs, though we had 3187fps with a charge weight 3 grains under max if I remember right. Which was faster than expected.

Maybe 30 rounds since cleaning


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[deadwolf]

^^

can you mic the neck diameter of the loaded rounds?

Out of town right now so not able to measure