David LaPell
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When shooting your reloads, how do you determine the PSI pressure? I read alot about it, but is there a way to measure it?
How do you determine pressure?
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David LaPell
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When shooting your reloads, how do you determine the PSI pressure? I read alot about it, but is there a way to measure it?
mstuhr
Member
Hi Dave,
PSI is all but out of the question with out equipment.
If you are shooting a revolver you can get some idea by extraction. Also your primer will tell you alot too about pressure. They will flatten or crater around the firing pin strike with hot loads.
A good manual is the best thing a guy can do and when sneaking up on a max load watch your primers and extraction.
I know, if I look, I can find examples and post a picture or two.
I was out earlier today reclaiming some brass from my bowling pin loads. They were from unpublished data, and over the edge some. I made a primer change and they went nuts. I took the 25-2 out and got my brass back.
In the 1911, I had so much slide speed that the recoil would snap the gun back and up,the bullet would nose dive and the slide slam closed and tie everything up. That is with a 22# recoil spring, 20# mainspring and a square bottom firing pin stop. Some of these primers show no indentation at all.
I'll try to get you some pictures.
Here we go.
OK, if the pictures are in the order I posted them you will see a normal fired round in the first picture. There is nothing building up around the pin strike, nothing sharp or flattened. This was a normal factory equivalent 230 grain load.
The next is a cratered load. You can see the ring of material starting to build up around the pin strike. Signs like this are a good place to stop and back up and an indication of high pressure.
The third picture is a pierced primer. Pressure forced it back into the firing pin and ruptured the primer. When you see this you know you have done something wrong and need to stop. Another sign I could not find is carbon blow by around the primer. That can be from overstressed brass too, but none the less cause for concern.
The last picture is a load that the primer flowed back into the firing pin hole. I'd say the U in auto was at the top of the chamber and whatever flowed into the hole was sheared off when the gun unlocked. This is just a bad thing all around.
None of these rounds really show an excessive amount of flattening. They are magnum primers so that probably helps. A flattened primer may not pierce or even crater all that much but it will flow to the outer edges of the primer hole.
I hope these help you.
These are not recomendations as to how far you can go. I found my way here through a component change. I have shot this load quite a bit for the last two years with a different primer and other than what I'd call minor cratering it has been fine.
I would say any of the above signs in your fired casings should concern you if you see them.
Good luck and be careful!
Mike
PSI is all but out of the question with out equipment.
If you are shooting a revolver you can get some idea by extraction. Also your primer will tell you alot too about pressure. They will flatten or crater around the firing pin strike with hot loads.
A good manual is the best thing a guy can do and when sneaking up on a max load watch your primers and extraction.
I know, if I look, I can find examples and post a picture or two.
I was out earlier today reclaiming some brass from my bowling pin loads. They were from unpublished data, and over the edge some. I made a primer change and they went nuts. I took the 25-2 out and got my brass back.
In the 1911, I had so much slide speed that the recoil would snap the gun back and up,the bullet would nose dive and the slide slam closed and tie everything up. That is with a 22# recoil spring, 20# mainspring and a square bottom firing pin stop. Some of these primers show no indentation at all.
I'll try to get you some pictures.
Here we go.
OK, if the pictures are in the order I posted them you will see a normal fired round in the first picture. There is nothing building up around the pin strike, nothing sharp or flattened. This was a normal factory equivalent 230 grain load.
The next is a cratered load. You can see the ring of material starting to build up around the pin strike. Signs like this are a good place to stop and back up and an indication of high pressure.
The third picture is a pierced primer. Pressure forced it back into the firing pin and ruptured the primer. When you see this you know you have done something wrong and need to stop. Another sign I could not find is carbon blow by around the primer. That can be from overstressed brass too, but none the less cause for concern.
The last picture is a load that the primer flowed back into the firing pin hole. I'd say the U in auto was at the top of the chamber and whatever flowed into the hole was sheared off when the gun unlocked. This is just a bad thing all around.
None of these rounds really show an excessive amount of flattening. They are magnum primers so that probably helps. A flattened primer may not pierce or even crater all that much but it will flow to the outer edges of the primer hole.
I hope these help you.
These are not recomendations as to how far you can go. I found my way here through a component change. I have shot this load quite a bit for the last two years with a different primer and other than what I'd call minor cratering it has been fine.
I would say any of the above signs in your fired casings should concern you if you see them.
Good luck and be careful!
Mike
Pisgah
Member
Any decent reloading manual will contain a treatise complete with phots of the visible signs of high pressure. It's good stuff to know. But it is very important to note that often by the time obvious signs begin to appear you are WAY overpressure. If you're not willling to spend money on testing equipment -- the prices have come way down for such, but are still too rich for me -- your safest bet is to use manuals from established sources which have done the testing for you. With experience and plenty of common sense you can -- at times -- safely venture slightly out of limits for some certain guns and loads, but it takes a long, long time with plenty of study before you have much of a safety factor in doing that.
nitesite
Member
For a fee, some of the powder companies will pressure test your handloads for you.
That is the only way I know of to get PSI data.
That is the only way I know of to get PSI data.
Skip Sackett
US Veteran
Manuals CANNOT tell you what pressure you will develop using ANY load, period. They can only tell you what their loads developed in their equipment. That is the reason you are supposed to start low and work your way up.
Their conditions are/could be designed for "worst case scenario". Tight chamber, small bore, biggest bullet, yada yada.
As far as determining pressure in your firearms at home, can't be done. I have toyed with the idea of sending some rounds to White Labs but still, they will only tell me what those rounds run in their equipment.
I use the original "tea leaves" of primer condition, extraction, felt recoil, intensity of the report.
That's what I do, you do what you want!
Their conditions are/could be designed for "worst case scenario". Tight chamber, small bore, biggest bullet, yada yada.
As far as determining pressure in your firearms at home, can't be done. I have toyed with the idea of sending some rounds to White Labs but still, they will only tell me what those rounds run in their equipment.
I use the original "tea leaves" of primer condition, extraction, felt recoil, intensity of the report.
That's what I do, you do what you want!
dennis40x
US Veteran
Pressure is not a bad thing in fact it is a needed thing but it can be too much of a good thing. There have been various methods that handloaders/reloaders have utilized over the years to determine pressure. Those methods let it be said are not universally agreed upon or may not be valid to a certain excitant. The dilemma is you don’t know what you don’t know. One may obtain various hand loading manuals and examination of the loading tables presents conflicting maximums and minimums. It is what it is.
leon riverrat
Member
I recently had some heavy 38 special loads tested by an independent lab to determine pressures for Lil'gun powder as well as 2400 and 4756. These loads all produced pressures in excess of 30,000CUP but showed none of the commonly sighted signs of excess pressure such as cratered primers or hard extraction. 20,000 CUP is the SAAMI limit for the 38 special.
The tested loads gave higher velocities by some 100 to 150 fps than were obtained in my personal guns since the test barrel was longer and no cylinder gap was present.
The tested loads gave higher velocities by some 100 to 150 fps than were obtained in my personal guns since the test barrel was longer and no cylinder gap was present.
Shadow1006
Member
Primers really can't tell you much as they don't talk! The primer used for the large pistol @ 18K psi is the same primer used in the 50K CUP revolver. As you see there are two desticntively different measuring methods...CUP vs. PSI with no direct corellation.
Not all primers are the same hardness or softness of the cup as they are made by different manufactures. It is said the federal primers have soft cups and CCI has harder primer cups.
The only way to be sure is to have them measured on lab quallity equipment. Everything else is a "guesstiment"!
Not all primers are the same hardness or softness of the cup as they are made by different manufactures. It is said the federal primers have soft cups and CCI has harder primer cups.
The only way to be sure is to have them measured on lab quallity equipment. Everything else is a "guesstiment"!
DonD
Member
I've said it before on this forum but with this post, it bears repeating.
Reading primer signs, case head expansion etc. is not reliable. By the time the signs are really clear, you've gone too far.
John Linebaugh told me that he had rounds producing 70,000 psi slide right out of the chambers of revolvers, no primer pressure signs, no nothing. Dangerously overpressure.
So unless you want to purchase a reliable pressure testing rig or like to live dangerously, trust reputable reloading manuals and work the loads up for YOUR gun. Don
Reading primer signs, case head expansion etc. is not reliable. By the time the signs are really clear, you've gone too far.
John Linebaugh told me that he had rounds producing 70,000 psi slide right out of the chambers of revolvers, no primer pressure signs, no nothing. Dangerously overpressure.
So unless you want to purchase a reliable pressure testing rig or like to live dangerously, trust reputable reloading manuals and work the loads up for YOUR gun. Don
I know John Linebaugh as a friend. Obviously, he is right. But...my heavy loads have shown flattened, cratered or pierced primers and difficult extraction, split case heads, etc. Extraction is influenced by the amount of lube on the cylinder walls, so wipe the oil off of your cylinder walls before you load up.
I use loads from the manuals, or, for instance, Hodgdon web data. It is free and correct. I don't load heavy any more unless I'm after dinosaurs... and they are rare in Florida.
sonny
RidgwayCO
Member
Absent a pressure-measuring device, I think the best way for the handloader to check pressures is with QuickLOAD software.
For every load you enter, the program computes the pressure in PSI. Then when I test a load, I carefully compare the actual velocity with the projected velocity. If it's lower, then I assume the actual pressure is lower. If it's higher, then I assume the actual pressure is higher. Of course, I always check the maximum computed powder charge with reputable reloading manuals, just to be safe. I mean this is software written by humans, not the Gospel.
Is my method precise? Not particularly. But it gives me more than just a guess about pressures, and I feel it's better than reading primers. Primers are too easily misread because they're too hard, too soft, firing pin problems, etc. etc.
For every load you enter, the program computes the pressure in PSI. Then when I test a load, I carefully compare the actual velocity with the projected velocity. If it's lower, then I assume the actual pressure is lower. If it's higher, then I assume the actual pressure is higher. Of course, I always check the maximum computed powder charge with reputable reloading manuals, just to be safe. I mean this is software written by humans, not the Gospel.
Is my method precise? Not particularly. But it gives me more than just a guess about pressures, and I feel it's better than reading primers. Primers are too easily misread because they're too hard, too soft, firing pin problems, etc. etc.
