When are Pressures Too HIgh?

[JASmith]

I'm preparing for a wildcat project and that brings to focus the question of how to determine whether the pressures are reasonable or a getting to be insanely high. In other words, how can one tell when loads are in the 50 ksi range preferred for the AR-15 frame, 59 ksi for sane bolt-rifle loads, and 63 ksi for "insane" bolt rifle loads.

I did some searching and developed some thoughts on how this might be done, with the conclusion that I will need to wait until someone implements a proper pressure barrel to get actual pressure measurements. The nut on my Savage barrel will probably make a strain gauge problematic, so that relatively precise method doesn't appear to be in the cards.

I did, however, come up with a revival of an old method that gives a clue of the behavior of the case in the chamber. In effect, case head expansion gives a clue about the ratio of chamber pressure to current brass strength. So, the method can help one can get a rough idea of when the bounds of sanity for a particular cartridge and chamber are being approached. At the same time, when comparative loads with 'kind of' known pressures are tested in concert with the developmental loads, we can get an idea of when the pressures are in the AR-15 bolt friendly levels too.

I documented these thoughts in a discussion at http://shootersnotes.com/articles/wh...ures-too-high/. While the reviews prior to posting have been positive, I plan to post a link and request for comments in both Ammoguide.com and in 65Grendel.com to see whether folks think this is a crazy idea.

Comments are welcome!

Cheers!

[mongoosesnipe]

I alway watch my primers I try to always load below the level where primers flatten out though honestly I advise mild loading unless you are really stretching a gun out but I am also a big fan of using the right gun for the job you could load one case to a dangerous level to shoot out to 1000 or you could shoot a mild load in a bigger gun especially if your building a bolt gun there it in not a great idea to load a Grendel to shoot to 1500 similarly 338 lapua is overkill at 100 on anything short of a brown bear

[Bill Alexander]

If the large metal fragments from the gun exploding go more than 50 yards you probably need to back the load off!

[bwaites]

If the large metal fragments from the gun exploding go more than 50 yards you probably need to back the load off!

Wow, I always used the 100 yard rule, I guess I'm running on the ragged edge! LOL

[Dogue]

If the large metal fragments from the gun exploding go more than 50 yards you probably need to back the load off!

Or switch to a billet upper.

Wow, I always used the 100 yard rule, I guess I'm running on the ragged edge! LOL

Just drop .5 grain and load 'em up.

[ricsmall]

If the large metal fragments from the gun exploding go more than 50 yards you probably need to back the load off!

Never used that measuring stick before, may have to rethink my loading practices!LOL

[hm2 clark]

I sure dont know as much as some other reloaders here but when (1) the primer backs out or (2) the bolt is difficult to lift, I discontinue that load and go down to the next lowest load.

[JASmith]

The idea described in the paper should help one find out that he is approaching a tight bolt or primers backing out because these are signs that the pressure is uncomfortably high for the brass and, if an AR15, way too high for the bolt.

In other words, we want to keep the primers from backing out or the bolt from getting hard to lift.

[Von Gruff]

I also use my chrono in conjunction with primer condition etc. Like most sensible handloaders developing a load, I use carfully weighed charges in encrements that are compatable for the case size and note velocities as there is usually a comparable rise in velocity per charge increment and if there is a reduction in velocity increment arround where I expect the velocity ceiling or max loading to be, then that, along with the primer apearance has my attention. I dont want to be getting into the sticky bolt lift area as that is way too high in my estimation.