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Discussion Starter #1 (Edited)
I have and know chrono wont measure pressure...but. How would I measure to see if my loads are not exceeding the allowable pressure?
Question...we don't want to exceed 52,000psi correct?
Help.

Deuces
 

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I have a chrono. How would I measure to see if my loads are not exceeding the allowable pressure?
Question...we don't want to exceed 52,000psi correct?
Help.

Deuces
You can get software like Quickload that will estimate it for you based on powder type, caliber, velocity, case volume etc. As for pressure factory match ammo will be about 55k PSI typically.

I have quickload but don't use it very often to be honest. What I do is chrono factory ammo, measure the fired cases and then start working up my load. If I get to where I am running higher velocities than factory or seeing more case growth I will sometimes tone it down.
 

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Field expedient pressure testing methods are not enough for saami so I have read.

I look for signs that the firing pin has cratered the primer.

A hot load will flatten the primer but that's not necessarily a full on red flag.

Blowing out a primer from its pocket is.

Gas escaping around the primer can ruin the breech face or bolt face so watch out.

These are the basics as imparted to me.

Some more seasoned salts will hopefully chime in.
 

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I have a chrono. How would I measure to see if my loads are not exceeding the allowable pressure?
Question...we don't want to exceed 52,000psi correct?
Help.

Deuces
You can get software like Quickload that will estimate it for you based on powder type, caliber, velocity, case volume etc. As for pressure factory match ammo will be about 55k PSI typically.

I have quickload but don't use it very often to be honest. What I do is chrono factory ammo, measure the fired cases and then start working up my load. If I get to where I am running higher velocities than factory or seeing more case growth I will sometimes tone it down.

FWIW, this topic comes up a lot, the numbers are usually 2550-2650fps for a 168 or 175 match load. So if your handload is in there and you aren't seeing any primer leakage or excessive case growth I wouldn't worry about it. Plus if you want to run hotter loads, or heavy bullets like 190 grain sierras you can get a vented gas plug and go to town. Won't hurt a thing.
 

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Actually measuring pressure is not done by 'home reloaders', primarily just by large scale ammo manufacturers.

Inspecting the case bases is a good way to judge when pressure is excessive, some signs are:
Rims being chewed-up by extraction.
Deep imprint on the base from the ejector hole in the boltface.
Headstamp on the bases being flattened.
Primers being overly flattened.

With chrono, don't attempt to get the highest MV, best accuracy and function is usually at a lower MV.

Jay Kosta
Endwell NY USA
 

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I think the book, "ABC of reloading" has a section covering how pressure is measured. I read it in a book somewhere, and if I remember right it was that one.
 

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I believe that comparing results to reloading manuals makes more sense than trying to duplicate factory ammo. You don't have the same powder. You might have the same case. You don't know what the factory primer is. Usually you don't have their exact bullet.

Now if I have one (even better 2) manuals which show data for my barrel length, powder and bullet with a specific OAL, then I've got data to benchmark against.

Even so, primers make a difference. RAMMAC helped me a lot and ran VV N-135 data through QuickLoad for me. My results were a couple hundred fps higher than predicted. I still haven't proved it but suspect that the CCI #34 primers may have been the unknown variable.
 

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A chronograph measures speed, not pressure. You could have high pressure with low speed (using a fast powder) and the display would never tell you.

Quickload is a fun tool but plenty of people have won matches without it. If you plan on experimenting or using unique loads (cast bullets, subsonic, etc.) it's a good investment.

Though there are now some who say the below method isn't to be trusted. It's a healthy read and even if you don't do this method, there's good info in there.

http://shootersnotes.com/articles/when-are-pressures-too-high/

I also seem to recall Sierra offering a service where they would check your ammo. You just had to send them five loaded rounds. Might be worth a phone call or email to see if they will still do it.

Or, if you win the lottery, you could invest in an Oehler 43
 
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Some body mentioned the Oehler 43, it had a piezo electric sensor that you glued to the outside of the chamber, it would measure the stretch of the barrel and give you a pretty accurate chamber pressure. I don't think they make them any longer and guys that have them wont sell them.
you could build a crusher test gun, it would be a action with a barrel with a fixture right over the chamber, there's a hole in the barrel in the center of the chamber and a copper disc of a known thickness is clamped in the fixture over the hole in the chamber and when you fired the round it would crush the disc and you would calculate pressure by how much it crushed the disc, they used lead discs for lower pressure rounds and shotgun loads. this is known as "Copper unit of pressure and "Lead unit of pressure" they don't use them much any more.

Casey
 

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RSI currently sells a product that they call Pressure Trace II, it uses a pressure transducer and will display chamber pressures on a computer screen.



As for monitoring pressures, there is no real way to tell what your pressures really are, I use QuickLoad to estimate the pressures and I watch for a pressure ring on the inside of the case. If you see a ring develop on the inside of the case, about 1/8th of an inch above the bottom, after you fire your unknown load, then you're running pretty high pressures. That ring will also develop after several reloadings.
 
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Discussion Starter #12
Joesig and The TinMan, good stuff. Thanks for the link. Perfect.
Many thanks.

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Quickload is a fun tool...
It's not just a "fun" tool, it's the way several major manufacturers create their reloading manuals. It's not just a toy, it's a serious load estimating tool which, when setup correctly, will predict pressures and other data very well.
 
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It's not just a "fun" tool, it's the way several major manufacturers create their reloading manuals. It's not just a toy, it's a serious load estimating tool which, when setup correctly, will predict pressures and other data very well.
Please don't misunderstand me. I own it and use it. I agree it is a tool not a toy. I happen to enjoy using it, maybe more than I should. "Fun" should in no way be taken to mean that I take for granted its validity.
 
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Please don't misunderstand me. I own it and use it. I agree it is a tool not a toy. I happen to enjoy using it, maybe more than I should. "Fun" should in no way be taken to mean that I take for granted its validity.
I understand, I feel the same way about it and I also know that if you don't know how to use properly then your data can be really suspect.
 
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