Whats the big deal about alittle pressure?

[cst]

I know a few years back people were complaining of broken lugs from faulty metallergy and over pressure...

Knowing that the Grendel was designed for 52k psi as the max pressure...what are the dangers or risks that can occur when you load slightly above that threshold? In search of higher ballistics, I bet more than 3rd of the loads on the Grendel handbook are at or alittle above the max pressure.

Ive personally push 123 grs.scenars over 2k rounds through 2 different guns above 2530-2590fps with and without suppressors with no broken bolt lugs yet(thanks Precision Firearms for great bolts!!!!)

Besides needing to keep an extra bolt in the field(everyone should with any AR BTW)..what else can go wrong with prolonged over pressurized rounds? And I'm not talking about something so hot that your blowing primers every 10 rounds...I mean going over the threshold to say a theoretical 56Kpsi or even 60K psi?

[rwh]

Often high pressure comes with increased ES and larger groups. I've broken lugs with loads that were a full grain below the published max load. Pressures can spike more than you'd expect as you go over max. Hot loads can also produce higher gas port pressures, which can cause failures to eject and is harder on the brass. It's not like loading to 56K or 60K is going to turn a grendel into a 6.5x47 or 260 remington. I don't see any reason to push the pressure boundary just for another 50-100 feet per second.

[Klem]

Not a lot if you know what you are doing. If you don't...damage and injury.

52K lbs is the line in the sand that the industry has determined is the safe maximum peak pressure. For .223 it is 55K, for military 5.56 it is higher at 62,366K.

F Class shooters push their .223 rounds 50% past SAAMI peak pressure in order to reach 1,000yds and still be competitive against the 308 guys. To do this they use strong actions and quality stainless match barrels. Tool makers like PTG come to the table selling bolts with smaller diameter firing pins and firing pin holes to support the extra pressure. Your brass gets hammered and barrel wears out quicker but for people who change barrels every year regardless it doesn't matter. I can confirm group sizes are the same as if they were under SAAMI.

If you are prepared to take responsibility for catastrophic failure and the injury risk that goes with that then you can expect the symptoms of mild over-pressure. Fewer reloads for your brass, early fire-cracking in the leade/throat, stress on the barrel and bolt and heavier recoil.

+1 for rwh advice. Every calibre has limits.

[ah1whiskey]

in the very tight case volume of ar type rounds , i would be VERY careful.

the smaller the case volume the less margin for error.

[cst]

ive been doing searches going back a couple years on this site and looking thru the reloading handbook and anytime you see loads for CFE223 and heavier bullets, forexample...alot of the loads are above 31grs...My concern is that many of the loads published and talked about online are all on the border of being around that max threshold..

There is an old thread with D. fortier and his range reports of 123scenar AA loads that are over 2600fps on a 20" barrel..http://www.65grendel.com/forum/showthrea...id+fortier.

52K psi is the documented max pressure for the grendel but based on everyones experiences over the years...bouncing off this line in the sand is not necessarily a receipe for disaster?....

Most of the powders that are available today that will allow the Grendel get a decent velocity are temperature sensitive to some degree...Ideally we want to create loads according to the max temperature we are going to shoot so we dont overpressure the gun at extreme conditions(on the hotter end). I'm trying to use my loads that are year round and developing a load at 95deg will suck alot of velocity when it hits 50deg.

[JASmith]

CFE223 appears to be poorly modeled in Quickload.

It is very difficult to squeeze in enough of that stuff to get to 52ksi with 123gr bullets. One is likely to see bullets being pushed back out a bit just after seating before getting enough psowder in to get decent pressures. Onset of bullet rejection appears to happen at or above the QL calculated 108% fill.

[LRRPF52]

The Grendel was meant to have a Maximum Average Pressure of 50,000psi.

The AR15 was engineered around a cartridge almost nobody shoots in it anymore, the .222 Remington, with a 50,000psi MAP incidentally.

Bolt thrust on fatter cartridges in constrained pressure containment systems can cause things to stretch the more you hammer away outside of the MAP. Barrel tennon threads with the barrel extension have come unscrewed on people who have put fatter cartridges in the AR15, then pushed into 55-60ksi territory, and fired brass dimensions are all over the map. Eventually, chambers can form a ring in them at the weak spot, and you start to see problems with extraction.

As the pressure increases, so does the recoil impulse.

I personally like mild recoil, pushing high BC pills at moderate velocity with a tight twist in the rifling. Downrange performance exceeds what I expected by at least 500 yds so far. Keeping the pressures down also leaves a nice buffer room for factory and hand loaded ammo.

True or false?

All of my hand loads produce the exact same peak pressure in the chamber......false

If I find a load that is on the edge for MAP, and push slightly over it, none of them will really go that high that are on the upper end of the margins.....?????????

If I'm on the edge of an accuracy node, pushing pressures, conditions can combine with the outliers to drift out of the accuracy node, while stressing the gun and spiking pressures........true