I often hear when developing max loads, to look for "signs of pressure."
What are these mystical, so-called signs of over pressure?
Thanx.
What are these mystical, so-called signs of over pressure?
Thanx.
- Thread starter garandman
- Start date
Exploding receivers. 
Several common ones come to mind, not necessarily in order....
abnormally flattened primers
ejector marks on case head
sticky bolt
bulging near base of case
sometimes cratered firing pin strikes on primer---I believe this may indicate other things too, such as oversize firing pin hole
excessive kick from rifle
There may well be others
I was just poking fun while I was uploading a pic.
Here are two large rifle primers punched out of a 308 load workup with Varget from this week. Everything in these two cartridges was the same, EXCEPT that the one on the right was 0.6 grains higher powder charge. See how much flatter it is at the edges while the one on the left still has a round edge? The flattened one on the right was just barely over Hodgdon's book max. That's a tell. Ignore the craters(big splashed up edges around the firing pin strike) in my pic, my Remington has an oversized firing pin hole.
If I see flattened primers develop as the powder charge goes up I know I'm at the limit. In some cases when I first started reloading I got flattened primers even on starting loads. Figured out I was bumping the shoulders back too far on my brass and the excessive headspace that resulted gave the primer more room to back out on firing which flattened them. Setting my sizing die fixed it.
I use a decapping die to push spent primers out before resizing, it takes more time but allows me to feel if there's a difference in tension holding the primer. If the primer just drops out when the pin the load was over pressure. You could check this when repriming sized, cleaned cases too, if the primer slides in easy with absolutely no resistance the pocket is loose which is a good indicator of high pressure if you're using good brass. With Federal I sometimes get loose pockets when I'm obviously not over max because the brass is soft from the factory. Winchester and Lapua only seem to get loose when I abuse it.
I also check the case head right before the extractor groove before and after firing with a caliper. If the case head shows expansion I'm at the limit. The case head is harder than the shoulder/neck area and shouldn't expand under normal loads. As above, Federal brass is exempt from this as it sucks to start with.
Last one for me is bolt lift. If the bolt is harder to lift than normal after firing there is a pressure problem. Usually I can see this when the brass comes out. Usually if the bolt is "sticky" there will be an ejector mark on the rim where the caliber is stamped, seen as a round indent from the ejector plunger and/or a smear on the head or web of the case where it stuck to the chamber from overpressure.
Sometimes the perfect load ends up being overpressure, and it bums me out. When it does, this helps me feel better and find the strength to move on:
Here are two large rifle primers punched out of a 308 load workup with Varget from this week. Everything in these two cartridges was the same, EXCEPT that the one on the right was 0.6 grains higher powder charge. See how much flatter it is at the edges while the one on the left still has a round edge? The flattened one on the right was just barely over Hodgdon's book max. That's a tell. Ignore the craters(big splashed up edges around the firing pin strike) in my pic, my Remington has an oversized firing pin hole.
If I see flattened primers develop as the powder charge goes up I know I'm at the limit. In some cases when I first started reloading I got flattened primers even on starting loads. Figured out I was bumping the shoulders back too far on my brass and the excessive headspace that resulted gave the primer more room to back out on firing which flattened them. Setting my sizing die fixed it.
I use a decapping die to push spent primers out before resizing, it takes more time but allows me to feel if there's a difference in tension holding the primer. If the primer just drops out when the pin the load was over pressure. You could check this when repriming sized, cleaned cases too, if the primer slides in easy with absolutely no resistance the pocket is loose which is a good indicator of high pressure if you're using good brass. With Federal I sometimes get loose pockets when I'm obviously not over max because the brass is soft from the factory. Winchester and Lapua only seem to get loose when I abuse it.
I also check the case head right before the extractor groove before and after firing with a caliper. If the case head shows expansion I'm at the limit. The case head is harder than the shoulder/neck area and shouldn't expand under normal loads. As above, Federal brass is exempt from this as it sucks to start with.
Last one for me is bolt lift. If the bolt is harder to lift than normal after firing there is a pressure problem. Usually I can see this when the brass comes out. Usually if the bolt is "sticky" there will be an ejector mark on the rim where the caliber is stamped, seen as a round indent from the ejector plunger and/or a smear on the head or web of the case where it stuck to the chamber from overpressure.
Sometimes the perfect load ends up being overpressure, and it bums me out. When it does, this helps me feel better and find the strength to move on:
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