Brass life
Posted: Wed Jan 28, 2009 8:34 pm
I thought I would pass on some interesting stuff on how long my 7-08 brass is lasting.
Two and a half years ago I installed new match barrels on both my M700 heavy and hunter guns. I deliberately set the head space short on both to have a .0005 light crush feel when closing the bolt on new WW brass cases. The theory being no initial stretch on first firing. I started out with 100 new Winchester cases for each gun and loaded them with my favorite match recipe of a 130 Sierra MK over 36.0 grs of Varget. This is a light , very accurate load that develops only about 2550 FPS. MV.
I am still using those same cases after loading and firing them each 15 times with the same load. OK....pause for a second. I am keeping a close eye on them for visiual signs of head failure, but they are still looking good (read safe). I am using the bent paper clip feel method to check for thin areas in the head, but feel nothing indicating imminant failure.They are smooth with no shallow areas. For their entire life I have only neck sized using a standard Redding necksize die, not the bushing type. The die is set to give a .002 shoulder bump for resistance free, snug chambering. Not once has it been needed to full length size a case to close the bolt.
I have had to trim them a total of three times with approximately .015 to .020 brass removed since new. The necks no doubt are somewhat work hardened, but still give consistant bullet pull or tension. The primer pockets still feel as tight as when new. Other than a run thru the tumbler every few loadings, no other techniques have been employed.
50 each gun of these cases are now loaded and when fired will be at 16 times. I have put them aside to be used for practice only and will continue to look over each one closely after firing. The entire lot will be trashed at the first sign of a bright ring or any crack. You wouldn't want to open the bolt at a match and have only the head come out. No calling alibies for this problem.
I do not consider this careless , or reckless loading behavior. I dont make a habit of stretching brass life to the max. In my many years of handloading I have had more than a few partial head seperations and three or four complete ones. In a bolt gun this is not a life or limb endangering event. First you will notice a bullet hole out of the group. A small waft of smoke will drift from the gas bleed hole or from the breech area of the action. Then you open the bolt , and hopefully the whole case is withdrawn. Sometimes only the head comes out. This will certainly mess up shooting a match. The few complete seperations I have had at the bench over the years resulted in easy removal of the body of the case.
I once had a complete head seperation while shooting a 7-30 Waters Super 14 Contender off the bench. The shot was way off the target. I opened the action and out came the head of a brand new Federal case. Nothing else was odd about the shot . The load was normal pressure, just a faulty case. The body was easy to pick out. However, the next shot showed a marking fully around the head of the fired case. The case that had failed combined with the normal frame flexing created a gap in the broken case and let alot of the hot gas out against the chamber wall and flame etched a ring into the chamber wall. All fired cases now have this light impressed ring mark into the head area. No big deal.
There is no doubt that the tighter match cut chambers combined with mild loads, quality WW brass and little resizing in between is leading to much increased case life.
On the flip side, my heavier ram loads using R-P brass and the exact same loading process show fatigue signs at ten to twelve loadings and get trashed.
Any one else getting long case life like this?
Two and a half years ago I installed new match barrels on both my M700 heavy and hunter guns. I deliberately set the head space short on both to have a .0005 light crush feel when closing the bolt on new WW brass cases. The theory being no initial stretch on first firing. I started out with 100 new Winchester cases for each gun and loaded them with my favorite match recipe of a 130 Sierra MK over 36.0 grs of Varget. This is a light , very accurate load that develops only about 2550 FPS. MV.
I am still using those same cases after loading and firing them each 15 times with the same load. OK....pause for a second. I am keeping a close eye on them for visiual signs of head failure, but they are still looking good (read safe). I am using the bent paper clip feel method to check for thin areas in the head, but feel nothing indicating imminant failure.They are smooth with no shallow areas. For their entire life I have only neck sized using a standard Redding necksize die, not the bushing type. The die is set to give a .002 shoulder bump for resistance free, snug chambering. Not once has it been needed to full length size a case to close the bolt.
I have had to trim them a total of three times with approximately .015 to .020 brass removed since new. The necks no doubt are somewhat work hardened, but still give consistant bullet pull or tension. The primer pockets still feel as tight as when new. Other than a run thru the tumbler every few loadings, no other techniques have been employed.
50 each gun of these cases are now loaded and when fired will be at 16 times. I have put them aside to be used for practice only and will continue to look over each one closely after firing. The entire lot will be trashed at the first sign of a bright ring or any crack. You wouldn't want to open the bolt at a match and have only the head come out. No calling alibies for this problem.
I do not consider this careless , or reckless loading behavior. I dont make a habit of stretching brass life to the max. In my many years of handloading I have had more than a few partial head seperations and three or four complete ones. In a bolt gun this is not a life or limb endangering event. First you will notice a bullet hole out of the group. A small waft of smoke will drift from the gas bleed hole or from the breech area of the action. Then you open the bolt , and hopefully the whole case is withdrawn. Sometimes only the head comes out. This will certainly mess up shooting a match. The few complete seperations I have had at the bench over the years resulted in easy removal of the body of the case.
I once had a complete head seperation while shooting a 7-30 Waters Super 14 Contender off the bench. The shot was way off the target. I opened the action and out came the head of a brand new Federal case. Nothing else was odd about the shot . The load was normal pressure, just a faulty case. The body was easy to pick out. However, the next shot showed a marking fully around the head of the fired case. The case that had failed combined with the normal frame flexing created a gap in the broken case and let alot of the hot gas out against the chamber wall and flame etched a ring into the chamber wall. All fired cases now have this light impressed ring mark into the head area. No big deal.
There is no doubt that the tighter match cut chambers combined with mild loads, quality WW brass and little resizing in between is leading to much increased case life.
On the flip side, my heavier ram loads using R-P brass and the exact same loading process show fatigue signs at ten to twelve loadings and get trashed.
Any one else getting long case life like this?