I had a partial case head separation using a 1.8oz buffer

[LRRPF52]

My thoughts:

1. Bill Alexander (in conjunction with Lapua) designed the 6.5 Grendel case with the thinner web area to increase powder capacity, knowing that the hardness of Lapua brass could handle it assuming shooters were loading to 50,000 psi average pressure and 52,000 psi average maximum pressure. (Lapua also suggested a shorter neck than used in the 6mmPPC and "6.5"-PPC, which A) also increased powder capacity, B) improved reliability in full-auto, and C) reduced the defect wastage rate in mass production.

2. This all assumes that the feed cones of barrels are matched to this case design. As Bill mentioned in his post I reposted on Page 2, Post #36, of this thread: “Feed cone on the rear of the barrel was changed to support the web correctly…. If you use the cone set up from a 5.56 it does not support the web correctly.” Feed cones for 5.56 in M16s are set up to help the smaller-diameter .223 Remington case find its way into a smaller-diameter chamber mouth. Since the 6.5 Grendel case is fatter and the bullet tip has much more leeway to find the larger-diameter chamber, the same feed cone geometry is unnecessary.

My position takes a little bit from everybody's input and the truth lies somewhere in the middle. Got no problem using Lapua brass as long as my barrel's feed cone area is properly set up to support that web area. Also, I would have no problem using Lapua brass in an "unsupported" chamber, as long as my loads are not above max book. I suppose the converse of my position is: If I don't know my barrel properly supports the 65G case web area, I'd use Hornady brass with its thicker web and accept the reduced capacity. Safe reloading practices are a given.

We have to be very careful of the “somewhere in the middle” positions though, because reality could exist outside of any of the proposed hypotheses.

If the chamber isn’t supported, the barrel needs to be replaced. Over time, an unsupported feed cone area will build a failure node into all the brass fired through it even if they don’t fail like this one did on initial firing.

The problem becomes exacerbated if the brass is sized excessively, work-hardening and misshaping that web area.

This is a common reloading mistake that new and old hand-loaders are prone to making if they aren’t watching headspace and case web management from load-to-load.

The biggest indicator that it has happened is bulging/belting or case head separation.

Another possibility is a chamber cut that isn’t square to the bore, along with lack of support.

It will bias the alignment of the cartridge so that one side of the case body will be fine, whereas the other will bulge out: