Loading up to 36 grains of cfe223 with 90gr tnt

[RobUrban]

Thank you all for the information. Will definitely think about all this information in the future reloading. I agree with all the comments that this was not a smart reloading decision and would reccomend no one try this stupid test again. It does seem reloading for the grendel could be more troublesome without being able to rely on the typical pressure signs. Would anyone have a guesstimate a what pressure you would begin to see more severe pressure signs?

[Klem]

Would anyone have a guesstimate a what pressure you would begin to see more severe pressure signs?

Any pressure above safe pressure.

You might not see any warning signs and then suddenly you're in the hospital as they try to save your eyesight.

[lazyengineer]

One handy thing today is most modern manuals and web-based data sets from powder manufactures will list the pressure with the load, which is useful! As stated, SAAMI for Grendel is 52,000 PSI. So for me at least, I basically look at what they list, and don't exceed that.

As to sign: for reference, SAAMI for .223 Rem is 55,000 PSI, and at least in .223 you'll never see pressure sign there in an AR15.
NATO 5.56 is max 62,000 PSI. The Federal Lake City XM193 and XM855 that I've shot, are going to be loaded up to (but to some degree below), that spec. Pressure sign in an AR starts showing up with that ammo (flat primers and some headswipe).

So to answer the question on when does pressure start showing up on brass in an AR15 in Grendel - I'm going to guess somewhere between 55,000 PSI and 62,000 PSI. And from what I can tell, the bolt lugs on a Grendel are not rated to handle that. So... as stated by others - the bolt lugs on your Grendel were apparently exceed by around 4000 PSI during the testing done. That's a lot. There's some manufacturers tolerance, but I'd say you're lucky nothing broke yet.

This is also why I say Federals printed velocity of their Preditor loaded TNT 90's at 3000 fps is suspect. They get to hand-formulate the powder specifically, so maybe - but I'm going to guess that's only in a 24" BBL to the tightest of tolerances shooting down hill with a tail-wind and rounded up... I can't get anywhere near that in any of my guns.

[A5BLASTER]

Thank you all for the information. Will definitely think about all this information in the future reloading. I agree with all the comments that this was not a smart reloading decision and would reccomend no one try this stupid test again. It does seem reloading for the grendel could be more troublesome without being able to rely on the typical pressure signs. Would anyone have a guesstimate a what pressure you would begin to see more severe pressure signs?

I think the better way to word your question would be. At what velocity would someone start to see severe pressure signs?

My answer to that is. If your seeing 50 to 75 fps faster per same barrel length are out of a shorter barrel length then what book data are well established velocity data from this fourm is showing.

You should probably stop.

Now if your running a bolt action grendel. 50 to 75 fps faster is most likely safe but in a ar grendel once you start passing up book data speed with the same length barrel are a shorter barrel. Your probably right on the edge are already past it.

Just my thoughts.

[lazyengineer]

By the way, who made your bolt? Because if nothing else, it's pretty good proof-level testing of the equipment, and the bolt held - so there's that!

[Klem]

F-Class shooters using 223 over-pressure their rounds on a regular basis. They cannot get to 1,000yds without exceeding SAAMI. What makes this possible are thick, solid, quality bolts, actions and chambers. Cheaper actions like the Rem 700 are catered for by PTG offering an after-market dedicated bolt. The standard Rem .075" firing pin is replaced by a smaller .062" hole and pin with less clearance around the pin. This imparts more support to the primer and less gap for primers to donut and break off disks inside the bolt. The downside is the narrower firing pin is it more prone to primer piercing. Thick primers like the CCI450 are compulsory. That said I have seen a few pierced primers over the years. That, and sticky bolts are the typical overpressure signs. Flattened primers are par for the course.

A typical 80gn load is pushed out of 30" barrels at 90K lbs (Quickload). This goes on every weekend until the barrel needs changing. Using neck-sizing only the brass lasts quite a few reloads. Do that in a relatively fragile AR15 and you turn your gun into a hand grenade. The OD of an AR chamber is .975" compared to the OD of a Rem700 chamber at 1.25". That's a lot more steel supporting any over-pressure. A Grendel is a larger case than the 223 so that's a wider chamber machined into the barrel which means less supporting steel. Comparing the bolt lugs are chalk and cheese. All this means in an AR you are unlikely to see convenient overpressure signs before it's too late.

If you want to test your gun to destruction you should clamp it, remote fire and stand behind safety perpex, like the pro's do.