Internal ballistics question

[wmitty]

Before I realized the relatively large range of case weights (and volumes) of various .223/5.56 brass I damaged a bolt face on a 788 Remington while using formed .223 brass in a .222 with what turned out to be an excessive charge of H335. I now weigh the brass and segregate cases into groups based on weight, while not sorting headstamps. The question I am asking is can the internal shape of cases of different manufacturers significantly affect chamber pressure in cases of the same weight?

[fredj338]

At max loads, everything matters. I doubt your 222 was an internal cap issue but a neck thickness issue from formed brass. Did you ream the necks? The diff in internal cap between diff manuf is not much in 223, maybe 1-2gr max. That isnt likely over pressure unless your load was already border line over pressure with a faster powder.

[charlie b]

If cases are sized the same and weigh the same then they should have the same interior volume. You can always check. Get some fine sand and fill each case. Level off. Weigh it.

For a while I also shot .222 with 5.56 brass in a Contender. It worked but I have no idea what velocities were or if I was over pressure. There were no signs of excess pressure, but, that doesn't mean they were not.

I finally got tired of the forming process and had the barrel reamed to .223.

[M-Tecs]

Case volume across the 223 - 5.56 is surprising consistent.

Good actual data here: https://www.6mmbr.com/223rem.html You can compare volume to weight on the chart. For comparison reference a 222 Rem is listed at 27 H2O volume.

You're going to have a hard time getting enough H335 into a .222 too do damage. Even compressed loads are relatively low pressure.

fredj338's pointed out tight neck's as a possible issue.