Home Forums Hunting & Shooting Ask The Gunwriters Safe Pressures?

There has been a bit of discussion about safe pressures and how to "work up a load". Most people look at the base of a fired cartridge to determine "traditional reloader pressure signs". That, and measuring the case expansion, is the way I used to do it.

Attached is a photo of two fired cartridges. Using "traditional reloader pressure signs", I'd not be concerned with either one. The one on the left has a flatter primer but they are the same load, fired in the same rifle.

Do any of you see anything that would make you say the pressure was too high or would the load be OK?















BTW, based on piezo pressure testing of the same ammunition, it was significantly beyond pressure levels I'd be comfortable with. Memory is they were 80K+.

Are they the same brand of primers?

Not all primers are made from the same material. Softer primers can flatten more relative to other primers.

I use velocity these days to give an indication of safe pressures. If my velocity is too high then that indicates my pressures are up. I was shooting a rifle last Sunday and most 140gn bullets were getting around 2900fps. But the first 6.5mm 140gn Ballsitic Tip went over 2960fps so I didn't bother shooting the other two. Pulled them when I got home.

Did you chrony the loads? Did the case on the left have the same velocity as the others? Or higher?

That brass doesn't look like it has been subjected to 80K+ PSI.

I always take the load up until I get the very first sign of an ejector mark or a slight resistance on the bolt handle and prefer to use new brass. That way whatever load I settle on (will be accuracy) I will know just how far it is from being too high pressure for THAT BRASS.

A good top load would have the brass do 5 reloads before the primer pocket got a bit loose.

The brass is always the key. For an example, anneal a case head then work up from very very mild loads and with pressure testing equipment. In that case pressure testing equipment will show very mild pressure with loads that loosen the primer pocket.

It looks to me that the head stamp on both cases are smeared which would say high pressure to me.

I was told they were identical loads.

They were "proof" loads that looked so good, to me, I ran a Piezo pressure test on the ammo. Photos don't do justice to the actual thing. When I looked at the brass I thought: "If I was reloading, I'd think I was approaching safe limits. I'd certainly not think I had exceeded them."

This was what made rethink my position on "working up loads".

That night I pulled bullets from my favorite 25-06 load. It was a good bit faster and used more powder than the reloading manual said was "maximum".

Since then, I go by velocity and traditional pressure signs.

The gain of 50-150 fps just isn't worth the risk...to me.

We did measure velocity on the loads. I don't remember anything more than normal shot-shot variation. I no longer have the actual data.

Agreed! Exactly my point!

Given that there are no signs of excess pressure, and 80K is well into the pressure that causes cartridge brass alloy to flow, I find the 80K+ figure suspect. And if that is what 80K+ PSI loads look like, I fail to see what the risk is.

😏🍿🍿🍿

We have agreement that there are no signs of excess pressure. That is my point. The piezo test was either done in my shop (meaning I did it) or at an adjacent military test facility. I don't recall. Either way, it was a measurement conducted on calibrated transducers to SAAMI specifications. I have no reason to disbelieve it.

No popcorn needed. My intent is informative as opposed to argumentative.

No observations, just a couple of questions. One concerns the chamber. Do you recall if it was a match chamber or an off the shelf rifle? What was the cartridge? Thanks.

Will just comment that the reason SAAMI limits the maximum average pressure of ANY cartridge to 65,000 PSI is not that they're chicken-schidt, but because pressures can increase considerably in warmer temperatures, even with today's most temperature resistant powders. Just because some load creates "only" 80,000 PSI in the typical 70-degree testing doesn't mean something bad can't happen in different conditions..

Many years ago when chronographs were still expensive and rare, dad and I had the opportunity to throw some lead across a friends early model Ohler. We were at a range half way across the state of Wyoming in the dead of winter, and temperatures were 30 below zero.

Dad was shooting his .270 Winchester, and his top load of 130 Nosler Solid Base clocked in at 3300 fps.

For some reason he never shot that same load in "normal" temperatures, let along in the summer.

The cartridges in the photo were fired in a bolt action rifle. Other cartridges, from the same batch, were fired in the Piezo system. The temp for the pressure test was close to 70 degrees (controlled laboratory).

The pressure measurement was made in a SAAMI spec. pressure test barrel. The cartridge was .308. The rifle the cartridges (shown) were fired in was built on a Remington action. I would assume that rifle had a "match" chamber, but am not certain.

We, in the USA, are lucky to have SAAMI. I believe SAAMI is what has kept government regulation out of our ammunition industry.

I shudder to imagine Slow Joe et al in charge of a "Federal Proof House" which must approve everything we do/use.

Playing with the maximum might feel like you’re getting the most, but once the pressures are crossing the line, you ought to think, “ Is the extra 100 FPS worth losing my dominate eye?”

If 65,000 psi in your 308 doesn’t provide the velocity you need, get a larger cartridge and keep getting a larger cartridge until you get the desired cartridge.

I don’t understand the concept of Intentionally shooting 89,000 psi ammo!

It’s all fun and games until it isn’t.

Originally Posted by HuntnShoot
Given that there are no signs of excess pressure, and 80K is well into the pressure that causes cartridge brass alloy to flow, I find the 80K+ figure suspect. And if that is what 80K+ PSI loads look like, I fail to see what the risk is.

This sends a chill up my spine.....
Charlie