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Re: i need a presure signs tutorial!
Hey....me too. I've heard flattened primers isn't a great indicator. Not to hijack your thread, but here's my question and it may tell you what you're looking for. I hear that case web expansion is the better way to look for over pressure.
I was given some "magnum" brass recently, a few new pieces and some once fired with no load data on what was fired through them. Measuring with calipers, what I think is the case web (right in front of the extractor groove), the unfired new brass is all at .582 and the once fired is .586 to .589.
Is the once fired brass good to reload or have they been subjected to to much stress?
Hey....me too. I've heard flattened primers isn't a great indicator. Not to hijack your thread, but here's my question and it may tell you what you're looking for. I hear that case web expansion is the better way to look for over pressure.
I was given some "magnum" brass recently, a few new pieces and some once fired with no load data on what was fired through them. Measuring with calipers, what I think is the case web (right in front of the extractor groove), the unfired new brass is all at .582 and the once fired is .586 to .589.
Is the once fired brass good to reload or have they been subjected to to much stress?
Re: i need a presure signs tutorial!
For a bolt gun- sticky bolt lift, shinny/flattened spots on case head, ejector mark on case head, primer cup flattened around edges, crattering/folding around the firing pin mark on primer (but not always 100%). If you have a chrono, watch your speeds. When you get to pressure, velocities will often stop increasing, and sometimes decrease. Recoil will generally increase significantly more than the rounds before it during load work up.
Severe cases of pressure- hole in primer at firing pin, blown primer, case head seperation.
For a bolt gun- sticky bolt lift, shinny/flattened spots on case head, ejector mark on case head, primer cup flattened around edges, crattering/folding around the firing pin mark on primer (but not always 100%). If you have a chrono, watch your speeds. When you get to pressure, velocities will often stop increasing, and sometimes decrease. Recoil will generally increase significantly more than the rounds before it during load work up.
Severe cases of pressure- hole in primer at firing pin, blown primer, case head seperation.
Re: i need a presure signs tutorial!
Case head expansion is another way to check for pressure signs. Mike your case head and check its dimensions after firing. In extreme cases (no pun) the brass can actually flow into the extractor recess and will show obvious signs of deformation. Basically, check for flattened primers, extractor or ejector marks, the case head expansion, and compare the pressure signs the brass exhibits with the data you get from your chronograph or load manual. If you see these signs and are near max loads its time to back them off. Bullet seating depth can affect pressure too, seating too deep is a great way to inadvertently increase case pressure.
Case head expansion is another way to check for pressure signs. Mike your case head and check its dimensions after firing. In extreme cases (no pun) the brass can actually flow into the extractor recess and will show obvious signs of deformation. Basically, check for flattened primers, extractor or ejector marks, the case head expansion, and compare the pressure signs the brass exhibits with the data you get from your chronograph or load manual. If you see these signs and are near max loads its time to back them off. Bullet seating depth can affect pressure too, seating too deep is a great way to inadvertently increase case pressure.
Re: i need a presure signs tutorial!
Primers that are absolutely flattened in the case with a load that's under or at limit in a book is not usually a pressure sign, it's a sign of improper headspacing first and foremost. If this shows up, start looking back at the other under limit loads to see if they stretched a lot or have a case head separation impending too. Measure the base of the case, it will start to grow a lot.
If you're working a load up and see a nice round pin dent and round edge on the primer at the start, you will see the primer edges start to square up and the pin dent will look more like a splash crater as the load heats up.
A case head separation or a bulged/stretched case is a good indicator that the pressures are getting WAY too hot also.
Another thing to check is sticky bolt lift like was mentioned.
Additionally you're going to see ejector marks show up in the headstamp for something with a rivet type ejector. When you can see machining/tooling marks in the primers you are WAY hot already too.
I'll take some pics of some loads that are WAY too hot when I get home. Also some "limit" loads and some light stuff too.
A pierced primer can be caused by pressures too high but also by a rough or sharp firing pin. If the edge of the primer is nice and round but it's piercing primer cups and the load isn't near max chances are you have a rough/sharp pin, not an over pressure.
Primers that are absolutely flattened in the case with a load that's under or at limit in a book is not usually a pressure sign, it's a sign of improper headspacing first and foremost. If this shows up, start looking back at the other under limit loads to see if they stretched a lot or have a case head separation impending too. Measure the base of the case, it will start to grow a lot.
If you're working a load up and see a nice round pin dent and round edge on the primer at the start, you will see the primer edges start to square up and the pin dent will look more like a splash crater as the load heats up.
A case head separation or a bulged/stretched case is a good indicator that the pressures are getting WAY too hot also.
Another thing to check is sticky bolt lift like was mentioned.
Additionally you're going to see ejector marks show up in the headstamp for something with a rivet type ejector. When you can see machining/tooling marks in the primers you are WAY hot already too.
I'll take some pics of some loads that are WAY too hot when I get home. Also some "limit" loads and some light stuff too.
A pierced primer can be caused by pressures too high but also by a rough or sharp firing pin. If the edge of the primer is nice and round but it's piercing primer cups and the load isn't near max chances are you have a rough/sharp pin, not an over pressure.
Re: i need a presure signs tutorial!
I have been thoroughly enjoying my 22/6mm AI. You can easily push the 75 gr AMax's at 3900, but I keep them at 36xx with 49 gr of H4831 or H4831SC. The barrel is a 1:8 twist as well.
Bought the barrel & dies late last fall, so only three PD's fell to this round. Simply amazing watching a PD blown 20 feet in the air and 20 feet backwards, while shredding.
I have been thoroughly enjoying my 22/6mm AI. You can easily push the 75 gr AMax's at 3900, but I keep them at 36xx with 49 gr of H4831 or H4831SC. The barrel is a 1:8 twist as well.
Bought the barrel & dies late last fall, so only three PD's fell to this round. Simply amazing watching a PD blown 20 feet in the air and 20 feet backwards, while shredding.
Re: i need a presure signs tutorial!
2660 fps out of an 18" barreled AR10...
It's kinda hard to tell in the pic, but look at the .308 on the top case, and the FC on the bottom right case. You can see where they're dug in pretty good...
Chad helped me a lot on this. Actually my first time loading for a gas gun, started way to hot.
2660 fps out of an 18" barreled AR10...
It's kinda hard to tell in the pic, but look at the .308 on the top case, and the FC on the bottom right case. You can see where they're dug in pretty good...
Chad helped me a lot on this. Actually my first time loading for a gas gun, started way to hot.
