New brass showing pressure signs.

[birdie]

??? I fired my new lapua brass yesterday in my 22-250 and showed signs of high pressure. I used the same loads that I used in my nosler brass that did not show pressure signs. I full length size . Just wondering why the difference. Loaad was 52 grain sierra with 34.5 gns of h-4895 and federal 210 primers. Any input would be greatly appreciated. thanks.

[Samdweezel05]

I would check case capacity difference between the two and also check the thickness of the neck. Could be more neck tension on the new Lapua brass.

[earl39]

I agree with Sam. Could also be tight necked chamber if the Lapua is slighty thicker in the neck. Check and see if a bullet will drop back into a fired case. If snug then it is a tight neck chamber at least for the Lapua brass.

Gary

[birdie]

How do you check case capacity?

[Samdweezel05]

A simple way I do it is with water. I don't really care what the number is I just want to know if they are the same. I Fill each case with water (need to have a spent primer in it so the water doesn't run out) and dump the water in a balance beam scale. You could use powder but I was always afraid that depending on the powder you used you could get different results depending on how the powder sat in the case.

[helotaxi]

Water is the standard method for checking case capacity, but simply weighing the cases will give you an idea of relative capacity. A heavier case of the same external dimensions must have thicker walls and therefore must have lower capacity.

[Senderofan]

Check that neck thickness out...like stated above. I got pressure signs using Lapua brass...switching from Rem or Federal...and it turned out to be the necks. Just needed to turn them.

Wayne

[Nor Cal Mikie]

What's your definition of high pressure? Cratered primers? Could be as simple as brass not fire formed to the chamber. Case being pushed forward against the shoulder of the chamber by the firing pin. When fired, slams back causing cratered primers. First time fired brass (in that chamber)?
Will the fired brass chamber without too much force to close the bolt?
Could be a real easy fix, Mike.

[tammons]

Different manuf cases have different capacities.

Some Lapua brass compared to say compared to 308 Winchester etc has a smaller capacity.

If you are running at the ragged edge then that is probably the issue.

I just weigh an empty case then fill it with H20 and weigh it again.
A drop of soap helps with tension or whatever thay call it.
Use a dropper or a syringe.

That gives you the capacity in H20.

[bigedp51]

Reading brass for pressure between brands is "ball park" guesswork.

Below are two brands of .303 British ammo, the Greek HXP ammo looks like it was loaded hotter but actually they are both loaded to the same pressure.

http://i122.photobucket.com/albums/o254/bigedp51/privihxp.jpg

The Greek HXP brass is thinner and softer and the Prvi brass is thicker and harder so comparing brands for pressure is guesswork at best.

The brass alloys can be diffrent, the heat treatment can be diffrent and case wall thickness can be diffrent.

http://i122.photobucket.com/albums/o254/bigedp51/brasshardness.jpg

[birdie]

In respopnse as to what I consider excessive pressure a very experienced freind sat next to me at the range. The thing I noticed was the sound of the report. He looked at the primer and it was very flat compared with the nosler loads. I have had that same sharp sounding report 2 yrs. ago with nosler brass and a hot load. That load blew my extractor and spring and ball out of the bolt of another mod. 12 22-250. I know by the sound and condition of the primer. I have been working a lot and have not checked case capacity. I did however check brass thickness on lapua vs nosler and they are identical.thanks birdie...

[GaCop]

How was the bolt lift on those rounds? Did you measure the case just above the extractor groove? .005" expansion at that point compared to an unfired case would indicate high pressure. Try dropping the powder charge a few tenths to see if the problem goes away. Was the powder the same lot number as the other loads that shot fine?

[birdie]

Bolt lifted hard. Powder was same lot. Case measurement above extractor groove was .003 larger on the lapua brass vs. the nosler. Also head space was expanded about .002 measuring with my hornady coparator.