Home Forums Hunting & Shooting Ask The Gunwriters Safe Pressures?

I agree. Just because you can't see it...

I use Winchester large rifle primers in ALL my cartridges. They all look like the pic on the left. WLRPs are known to be soft.

Buford,
Interesting post for sure. I know you've spent years studying the science of ballistics. One thing I also notice when shooting a high-pressure round is that I definitely notice muzzle blast to be "sharp" as well as recoil to be more "snappy" if there's such a thing. Accuracy also diminishes. In your pictures above, I'd be curious to know if chamber finish had an effect on the reason for not showing bolt swipe indications.

The rifles were secured in a fixture and the pressure test system is also mounted to a fixture so I can't comment on recoil. I didn't notice anything abnormal about the muzzle blast but normally "doubled up" on hearing protection when shooting inside.

I don't have any way to intelligently reply to your question on chamber finish but think it was whatever was normally done when building the rifles.

My whole point for posting this was to provide information:

I thought I could recognize pressure signs.

Later experience with actual SAAMI pressure testing procedures taught me different.

I suspect most handloaders that "see pressure signs" are already above SAAMI recommendations. Note that they are "recommendations" and not laws.

How much pressure each shooter is willing to accept, and the way way they determine that, is totally up to them.

What I am saying there, Charlie, is that if there are no signs of high pressure, one hypothesis is that there isn't high pressure being exerted. It's possible that the pressure testing equipment is poorly calibrated or flawed in some other way.

The problem with high pressure isn't high pressure. It is the results of high pressure. If those results don't occur, either the pressure isn't high, or it isn't a problem.

That doesn't mean I would just load and shoot more of those. I am saying that thousands of guys over several decades have loaded and shot millions of those. Let's not pretend this hasn't happened, and then turn into Pollyannas. Let's deal with reality.

Buford
You statement is right on with my testing and experience...I thought I could recognize pressure signs.
Later experience with actual SAAMI pressure testing procedures taught me different.

Charlie

Huntnshoot
I greatly respect your ideas and opinions. Sharing ideas and opinions are what makes the Campfire a great place. But, I want to say in the most respectful way, sir, I dont agree. I think it's best I refrain from further discussion on this particular thread as I dont think I can bring anything to the table.
Thanks
Charlie

Is the cat alive, or is it dead?

Over the last 20 years on 100 gun forums, I have learned the code words for the threshold of an effects of pressure problem, "long brass life".

Shooters have to learn not to hot rod cartridges. They laugh and say it's part of being a looney. It's not. If they truly were looneys, they would use the need for speed as an excuse to buy another rifle.

If they cannot afford another firearm, increasing pressure to dangerous levels with their existing rifle is an accident waiting to happen. The best case is you end up with a broken rifle and can no longer shoot. I don't think we need to talk about the worst case scenario.

I know what speed certain cartridges get with certain weight bullets.

If I need bullets to go faster than what that cartridge is known to safely get, I simply go with a bigger case. I came to that conclusion some time back, trying to achieve a velocity goal with a .30-06 AI. It was a stretch, but I finally realized the .300 WinMag would easily do what I wanted....

I’d guess the load on the right is from a clean bore. The load on the left looks to be cratering of the primer.( apparently excessive pressure in this case but definitely not always the case.) Nothing definitive however because you don’t have enough of the whole picture. Experienced reloaders know they have to couple that information ( primer appearance) rwith a chronograph reading, a reference to a loading manual, shooting conditions, knowledge about powder characteristics in all weather conditions, rifle behaviour and the rifle history. Given all of that, you would be able to guess that was an overpressure situation.

Any one of these indicators alone is pretty much worthless IMO, and I’m not sure when in history primer appearance became the traditional source of gauging the excessive pressure of a load. I don’t have the greatest memory but in the last 25 years of reloading I don’t recall primer appearance being touted as the sole source of pressure estimation in anything I’ve read. Could be before my time however.

akaSawDoctor,

Did you read my column on primer appearance and pressure-guessing? It's still listed above the recent threads on this forum, and generated a LOT of debate:

https://www.24hourcampfire.com/ubbt...ch-column-primer-flattening#Post13673133

Sensible. I think that some people believe that they can push the envelope because they have been reloading for a long time and consider themselves experts. Both in and out of the service, I have seen at least 10 rifles and several handguns come apart when they came across my bench.

6x45mm testing

This happened before Christmas. I was testing some 6x45mm loads. The first 20 shots (10 shots x two different powders) with some 85 gr Noslers were uneventful. The velocities varied from 2715 to 2767 fps. That's on the money for the 6x45mm.

When I started with the third powder, things seemed off. The velocities had climbed, and were hanging around 2800 to 2820 fps, so I stopped shooting them. I checked the cartridges, but nothing seemed wrong. No shininess, crated or pierced primers. At this point, the velocities were up a tad, but in my estimation, not dangerous.

I tried a fourth powder.

The first two shots chronoed at approximately 2850 fps. Alarm bells went off, so I stopped shooting the fourth powder.

Foolishly, I tried the fifth powder. The first shot chronoed at 2917 fps. Full stop. The increased recoil, primer appearance and velocity told me that there was something wrong. Probably too much powder. The combination of the three told me I had problems, so I went home.

I disassembled the loads and weighed them on three different scales - a Lee Safety scale, Ohaus 10-10 and the Lyman 1500

It did not take long to discover that there was something wrong with my Lyman digital scale. This was the scale I used to put the loads together.

When I turned it on, the display read 23.2 grains with nothing on, or around it. I let it warm up, calibrated it and weighed the powder. The display showed an amount less than the original charge weight. I threw the first powder load on my Lee and the Ohaus. The charge weight was supposed to be 25.8 grains, but showed 26.3 grains on the two beam scales.

I weighed the rest and they varied from 0.4 to 0.7 grains higher than what the Lyman told me.

I went to my computer and did some number crunching. It suggested that my pressures were around 60KPSI - but the software will have a bit of skew. It's a small case, so small differences can have a big effect. Was it only 60KPSI or could it have been higher?

Now, to my point.

I would not use primers as the sole indicator, because, at first, they seemed normal. It wasn't until later that I discovered there was too much powder in the cases. There was no cratering or pierced primers with the second or third loads. The trouble started with the fourth load - measuring 2800 to 2850 fps. Maybe 0.4 or 0.5 grains above max. The fourth load showed cratering. The fifth powder load, the one that measured 2917 fps, was 0.7 grains above what I considered was the max.

There were three things that told me I had problems. The combination of primer condition, the 2917 fps chrono display, and the increased recoil. You can see the case with the pierced primer. That was the fifth load. The two cases from the fourth load are beside it.

I have never used primer appearance as an indicator of pressure the reason being it depended too much on other factors -such as headspace- than it does on actual pressure.

Instead, I pay attention to muzzle speed. Given the use and adequate powder-cartridge-bullet weight combination and barrel length, I consider I am within safe pressures if I am within reasonable speed limits. To determine what is a reaonable speed limit I refer to manuals which publish pressuure tested loads, the experience of knowledgeable authors like Mule Deer, and my own brains.

New powders that seem to hold pressures longer could change the picture and move the speeds another 100fps higher -Re26/270WCF/150gr is a good example- but I yet have to lay my hands on any.

I don't see any practical advantage in getting those 100 extra fps and when I thought I needed them I shot larger cartridges.

Alvaro

I hadn’t read it up until now. Good article and a little bit more to add to the tool box. Thanks John.

Great article, MD. Wish I had seen it earlier. I'm a big fan of Hatcher's Notebook.

BTW, on primers backing out, I saw definitive proof of this when measuring "barrel time". We instrumented a fixture with an oscilloscope and energized it with a 9v battery such that firing pin contact with the primer completed the electrical circuit. In addition, we setup high-speed video with good backlighting so that we could observe the firing pin movement and projectile exit. I think we shot the video at 10K frames/second but it may have been higher.

The firing pin came out, impacted the primer, bounced (don't know if this bounce was specific to this fixture or normal), primer backed out, case backed into breach block and obturated.

It was fascinating video to watch. Not only were we fascinated by it but the engineers for a major ammunition manufacturer were, as well.

Crimping the primer pockets, in this instance, greatly reduced or removed the primer backout.

I operate under the premise that metal fatigue is cumulative but failure of a rifle action happens all at once, sometimes with no indications of a problem other than velocities or powder charges that indicate you're operating above the range that's safe. In other words like someone already said, high pressure isn't a problem until it is. Somebody correct me if I'm wrong about that.

And I've seen it happen. It wasn't my rifle but my son who was 12 at the time had been shooting the same rifle with the same loads about 30 minutes prior. That will get your attention.

And the guy who owned the rifle was more experienced than most on here and didn't hot rod his loads.

Metal fatigue is indeed cumulative, yet when metal lets go it is sudden and mostly without warning

Absolutely spot on. That is why G meters are installed on aircraft and service life gets adjusted depending on that.