Hidden Pressure Reading: A Method

[Mike Matteson]

A big A-Men to that !

That's why I do a run up on powder loads in .5gr increases for cases that hold about 70gr. Under that I only increase by .25grs. I will load 15 to 20 case with those increase. Go to the range and test them. Watching very carefully what the primers are telling me, and no heavy bolt lift or ejector marks starting to show. I kind of feel if you are seeing ejector marks or heavy bolt lift. The primer are already creator. I do run a larger target paper to see how the bullets are grouping. I don't expect much, because of the increase in powder for each load.
Now I haven't tested a load in a long time. My reloading area has be taken down. Have all kinds of new tools to reload with, and a bunch of changes going on. I have one new rifle and I think I will have second one about them. Another one at the smith's waiting for items to show up.
It's kind of like: Hurry up and wait. Must be back in the Army again.
I like the input.

 

[Mike Matteson]

I think primers are very difficult to read and the pressure indicator that I pay the least attention to. For the hand loader that doesn't have pressure testing equipment (most all of us) the pressure story is told by all of the indicators together. Not just one. Some rifles leave an ejector mark on all loads. This is why I start low in my load development. I want to see and feel the rifle at very mild loads and work up from there. Watching the velocity, bolt lift, case head, primer, and primer pocket. I think the best indicator is how the rifle feels as the pressure increases. When the bolt lift and ejection starts to feel different, the pressure is getting close to top end. Very well built custom rifles will hide the pressure felt on bolt lift. That rifle that shows ejector marks at mild loads will get to a point where the look of those marks becomes more pronounced. In other words when it starts to change its the point where you need to pay attention. As you work up watching your velocity increase nice and consistently with each increase in powder charge and you start seeing larger increases in speed with same increase in charge or more important a spike or larger jump in velocity, this is an indicator that you are starting to push pressure. But not if your velocity is low and all the other indicators show low pressure. If velocity is high and all the other indicators are saying top end that spike in velocity is likely a very good indicator that you are likely pushing the envelope.

So, my point is there are many things together that tell the pressure story. I pay most attention to how the rifle feels and the least to the primer. I pay attention to how all of these things change as I work up from mild. Starting too high deprives the shooter from feeling and seeing the changes.

Nice input. I do use a chronographs almost everytime no matter what. Also if you are loading above the high powder loading in a manual you know you are pushing the load. I have given out some loads that I reload for, but also make it known that these are load that have to be worked into, not just to to the top and start off.
I haven't come on to ejector marks without being a hot load.
I fully agree starting to high is a or can be a big problem. I have done that only once, and never again. I was using the manufactures reloading data too. Started off at the top end of their powder loads. First round down the tube, blow a primer out of the case. Never Again!!! Delt with Temp sensitivity powders and stay away from them too. 2nd time blowing a primer out of case.
Now I have or building a wildcat cartridge or on that line. I'll be watching very closely with them. Not much out there on them, but I can compare to other cartridges in those area to see what they have or are using.

 

[RockyMtnMT]

Then there are those combos or cartridges that create what I call phantom pressure. All the pressure signs with no velocity to go with it. The 6.5 prc is the most blatant example that I know of. If you use magnum primers in it, it will pressure out 250 fps and 4-5g earlier than when loaded with standard lr primers. I believe this comes from too quick of ignition burning too much in the chamber and not enough down the barrel. Low density loads can cause huge pressure issues. These are much more concerning to me than loads with acceptable powders, for the cartridge, that have been taken farther than they should.

It is not the end of the world if a loader works up a load to the point of "holy crap that was too much". You have to do very stupid things like go up another 5g past that point of difficulty opening the bolt or even a blown primer. If using a proper powder you shouldn't be able to get to a point of actual danger of catastrophic failure. Reminds me of a story we heard when we visited Wby. A guy called them angry that his Mark V had failed and shot the bolt through his neck. He couldn't believe that Wby had allowed a product on the market could allow this to happen and wanted to know what they were going to do about it. When asked how this happened he admitted that he confused his powder and accidently loaded pistol powder in his 300 Wby mag. He shot it the first time and had to beat the bolt open and knock the spent case out of the chamber before he could fire it again. It finally dawned on this angry man just how stupid he was when he disclosed that it was the ninth shot that caused the bolt to fail and go through his neck.

We got to see the procedure of proof loads. They are much higher than accidently working up to a blown primer. They completely fail the brass. But not as high as the dim wit that took 9 shots to drive a bolt through his neck.

 

[nksmfamjp]

I have to clear something up here, actions are built to withstand 3 or 4 times the amount of chamber pressure, some, like the Weatherby Mark V, are even stronger than this. The nominal rate of destruction is in excess of 200,000psi for CM actions or above, and a little less for SS actions of 416 material, this varies of course.
Now, actions are built to be used for myriad of cartridges, therefore the reason behind having a yield strength of 200,000psi or more.

That is an interesting statement and I'll take you at your word about this 200000 psi yield strength.

That said, I think you have a point here. I'm not an action designer, but if I were, I would design the action to handle bolt thrust as a fatigue loading. Ideally since a barrel is a pressure vessel loaded in a fatigue loading. I would look at is from a UTS standpoint, wanting a factor of safety of 4 for a largest diameter bolt face loaded by a 65000 psi cartridge. I would also consider fatigue whose analysis usually work around a 1 million cycle consideration….which tend to be close to a FOS or 4.

Of course you have to test. I guess I would have to pay someone with an Instron to test for single force loading to tell me bolt thrust at yield, and UTS failure. Also, what happens to my customer with each. Do they get a bolt in the face?
That probably requires firing one at the uts point and seeing if the case ruptures before you get a bolt in the eye.

Then of course, I need to test 1 million cycles of bolt thrust.

Are these custom action makers doing this? If not, what is the work around? I never see much evidence.

That said, I never chase blowing up my gun.

Back to the OP…..these hard bolt lift, ejector swipe, primer crater, brass marks…..those are all in the elastic zone of stress/strain for the action. You are pretty safe here for a few rounds, unless you have some kind of abnormal failure.

That said, don't load until you get gas in the eye, split cases or have to hammer a bolt open. Read the early signs and react to them.

 

[Rich Coyle]

Mike,

I'm with you on zero pressure signs.

 

[Muddyboots]

The funny thing about historically loading up into pressure is with new bullet designs today with higher BC's along with higher energy powders, you can achieve great loads without having to getting into oh crap territory. The second thought is get a bigger cartridge to actually achieve what you want. Personally, I accept what a specific cartridge can give me instead of trying to make it what it's not. If you want more velocity out of cartridge, get a longer barrel, get the longest action magazine COAL for the cartridge to allow bullet seating out further to gain case capacity. There just seems to be other means to increase a cartridge performance without sacrificing brass or your forehead.

This should be good for few pages.

 

[Mike Matteson]

Then there are those combos or cartridges that create what I call phantom pressure. All the pressure signs with no velocity to go with it. The 6.5 prc is the most blatant example that I know of. If you use magnum primers in it, it will pressure out 250 fps and 4-5g earlier than when loaded with standard lr primers. I believe this comes from too quick of ignition burning too much in the chamber and not enough down the barrel. Low density loads can cause huge pressure issues. These are much more concerning to me than loads with acceptable powders, for the cartridge, that have been taken farther than they should.

It is not the end of the world if a loader works up a load to the point of "holy crap that was too much". You have to do very stupid things like go up another 5g past that point of difficulty opening the bolt or even a blown primer. If using a proper powder you shouldn't be able to get to a point of actual danger of catastrophic failure. Reminds me of a story we heard when we visited Wby. A guy called them angry that his Mark V had failed and shot the bolt through his neck. He couldn't believe that Wby had allowed a product on the market could allow this to happen and wanted to know what they were going to do about it. When asked how this happened he admitted that he confused his powder and accidently loaded pistol powder in his 300 Wby mag. He shot it the first time and had to beat the bolt open and knock the spent case out of the chamber before he could fire it again. It finally dawned on this angry man just how stupid he was when he disclosed that it was the ninth shot that caused the bolt to fail and go through his neck.

We got to see the procedure of proof loads. They are much higher than accidently working up to a blown primer. They completely fail the brass. But not as high as the dim wit that took 9 shots to drive a bolt through his neck.

Stupid is, Stupid does! I know where a person used a shot bush for his powder load with a shotgun. That didn't work out so good either.
Whatever that man though he was doing repeating the problem 9 times. I don't want to be around him. The one time I had the temp problen. That was the only one round and 49 were unloaded or pulled the bullets out. I didn't repeat that with a 2nd round. The first one told me all I needed to know.
I haven't come across where I creator a primer because of the firing pin problem. When loading and over the manual call out of max recommend powder load. You are hot and pressure is building quickly. Your velocity are above the manual fps.
The other is I don't generally use Mag primers either. I can see it with powder loads in the 75+ and above that. There is plenty of rifles that load out to over 110 grs, not me and I am not going there.
Most of what I have seen here on ejector marks are loads that are a way over the manual call outs. They wonder why too.
A good discission on this again. New points seem to come up. So it's a dead item by a long shot. I feel I learn a little more each time this is brought up.
I'll take note on the PRC chambers and primers.

 

[VinceMule]

I never try and "make" a barrel do anything, ever.

I establish what is MAX pressure, back off 2.5g, then work up in .3g increments, three-shot groups, repeat and verify.

I find max pressure by working up in .5g increments, till I find pressure, will never load that Max pressure load again.

Very tight groups are usually achieved within 30 shots, and often much less If I have forehand knowledge that the same brand of barrel and bore dia was used with my same reamer. Change twist rate, change bore dia, use different bullet, etc, all bets are off, you start from scratch.