Blown primers when firing a fast string in a Benchrest competition.

[geordiesniper]

I recently shot in a 1000yd benchrest match in Heavy Gun class here in the UK. We shoot 4 relays of 10 shots with a bit of a break between relays to allow the barrels to cool down. My rifle is in .284 Winchester and weighs about 19 pounds (anything above 17lb is in Heavy Gun).
The problem I had is on the third relay, and firing quickly on the 7th shot I didn't realise the primer blew and I continued until on the 9th shot then I couldn't raise the bolt handle.
I managed eventually to remove the bolt with a few taps of a hammer and found a crushed primer in the raceway and 2 loose primers also fell out.
The question is has anyone had this problem when firing 10 shots rapidly in any calibre and any idea why this happens. I am a bit puzzled that it didn't happen on the first two relays and am presuming that maybe the load of 54.3grains of RS70 using a Berger 180gr Hybrid with a 5 thou jump and a Mv of 2910fps (which shown no problems firing slowly in testing) was because I was machine gunning them then the chamber heated up and raised pressures thus blowing the primer out.
I guess the obvious thing is to reduce the load or reduce weight and shoot in Light Gun
This is the first time in 20 years of shooting that I have had primers blown.
Any info would be appreciated.

 

[ShootDots]

I do not know what RS70 is, but if it is in the same burn rate range as H4350 as your charge would be light for H4831SC, I am guessing it is H4350 or it's equivalent. If it is, you are running VERY warm. I have a "straight" .284 shooting 180 Hybrids and a I have a load at 51.4grs giving me a velocity of 2835. You run a 2900+ load with H4350 and it's a wonder you did not lose primers from the first shot! But I do not know where SR70 sits on the burn rate chart.

 

[Dusty Stevens]

Hot dirty barrel is my guess with a load teetering on too hot. A perfect storm that has shown up just in time for you to back off before summer hits and you dont get that far in a match.

 

[geordiesniper]

I do not know what RS70 is, but if it is in the same burn rate range as H4350 as your charge would be light for H4831SC, I am guessing it is H4350 or it's equivalent. If it is, you are running VERY warm. I have a "straight" .284 shooting 180 Hybrids and a I have a load at 51.4grs giving me a velocity of 2835. You run a 2900+ load with H4350 and it's a wonder you did not lose primers from the first shot! But I do not know where SR70 sits on the burn rate chart.

RS70 equates to Reloader 22 or Vihtavouri N165. On reflection my blown primers are a combination of a dirty barrel and my loads where on the warm side. So I will try a lower Mv of 2820fps approx and use 4831SC and N165. Thanks for your replies. Good shooting.

 

[dkhunt14]

RS70 equates to Reloader 22 or Vihtavouri N165. On reflection my blown primers are a combination of a dirty barrel and my loads where on the warm side. So I will try a lower Mv of 2820fps approx and use 4831SC and N165. Thanks for your replies. Good shooting.

Usually if you are on the warm side with a load the load will get more pressure as the barrel fouls and warms up. Try lighter loads. My guess is if you had primers come out the case you probably ruined the brass. Matt

 

[geordiesniper]

Usually if you are on the warm side with a load the load will get more pressure as the barrel fouls and warms up. Try lighter loads. My guess is if you had primers come out the case you probably ruined the brass. Matt

Hi Matt. Yes I didn't realise my loads where on the warm side as I have always been careful (plus it never gets too hot in the UK lol). But I got caught out well and truly at the weekend so will go down a few grain or two using RS70 and I know a few good safe loads using 4831SC and N165.
Yes the brass is ruined on the blown primer cases but the others that didn't blow are still usable after checking their dimensions against full length resized brass. Thanks for the input and good shooting. Les

 

[Laurie]

For American forum members, Reload Swiss RS70 is a Nitrochemie manufactured powder that shares the same characteristics as Nitrochemie's / Alliant ATK Re17 and Re33, but with an intermediate burning rate. The manufacturer shows it as having the same burning rate as Re22, but it should produce higher MVs as it is made with Nitrochemie's advanced EI deterrents infusion treatment. On paper / in QuickLOAD it regularly produces the highest MVs for cartridges that suit H4831, Re22, N165 etc, but I've yet to hear if the actuality delivers on the promise and more important whether it's consistent enough. We've had it for a couple of years in the UK although it's only been widely available for 12 months or thereabouts.

 

[dragman]

Had the same problem one time with a savage target action .284 I used to have. blew one and it stuck the next cartridge because the other primer was smashed in the raceway. I was right on the limit of pressure and running a string to test for vertical when it happened.

 

[fguffey]

I managed eventually to remove the bolt with a few taps of a hammer and found a crushed primer in the raceway and 2 loose primers also fell out.

Blown primers when firing a fast string in a Benchrest competition.

Blown primers or loose primers? There is no way to direct pressure to the primer, pressure that effects the primer pocket effects the flash hole meaning when the case head is hit with high pressure the case head upsets. For reloaders with no place to start .00025" case head expansion is considered normal for factory ammo. That leaves you with a case head that has expanded and loosened the primer or the primer was loose when you started and nothing happened to tighten the primer pocket when you pulled the trigger.

Then there is the remote possibility for this problem happening to someone else, someone else could have sized a case that was too short for the chamber from the shoulder to the case head; added to that someone else could create the problem with reduced loads, meaning the case head did not seat the primer against the bolt face when fired. With a reduced load the primer could have backed out when fired without bolt face support.

F. Guffey

 

[geordiesniper]

Blown primers or loose primers? There is no way to direct pressure to the primer, pressure that effects the primer pocket effects the flash hole meaning when the case head is hit with high pressure the case head upsets. For reloaders with no place to start .00025" case head expansion is considered normal for factory ammo. That leaves you with a case head that has expanded and loosened the primer or the primer was loose when you started and nothing happened to tighten the primer pocket when you pulled the trigger.

Then there is the remote possibility for this problem happening to someone else, someone else could have sized a case that was too short for the chamber from the shoulder to the case head; added to that someone else could create the problem with reduced loads, meaning the case head did not seat the primer against the bolt face when fired. With a reduced load the primer could have backed out when fired without bolt face support.

F. Guffey

Blown primers!

 

[fguffey]

Blown primers!

Therefore the primer pocket expanded and the flash hole increased in diameter and the case head was crushed. If the reloader did not measure the diameter of the flash hole and or primer pocket and had no way to measure the diameter of the case head there is not way of determining what caused the problem.

Then there is the reading of the primers and brass that is considered soft.

F. Guffey

 

[billshehane]

Pretty simple-- TOO MUCH POWDER !

 

[fguffey]

http://www.lhs-germany.de/fileadmin/dateien/dokumente/Pulver/2013/Burning_Rate_Chart_LHS_2013.10.pdf

The powder is listed under Reload Swiss and they claim it compares with Hodgdon Super-performance.

His primers fell out now someone should determine when they fell out and why. When I test a receiver with

Pretty simple-- TOO MUCH POWDER !

It does not take me long when looking at the case to determine I had "TOO MUCH POWDER", there was that one time I changed a 150 grain bullet out with a 200 grain bullet. I was told the receivers were suspect, after testing I determined there was nothing suspect about the 4 receivers.

F. Guffey

 

[243winxb]

Same lot number/type of bullets? If the new lot has thicker jackets, pressure would go up http://benchrest.com/showthread.php?49336-Berger-bullet-failure-test

 

[ridgeway]

Check your ignition system. Remove firing pin, make sure no gunk built up inside. Check or replace firing pin spring. Had a similar issue where blanked primers to the point they fell out of new brass. Took me awhile to pinpoint the issue, which was a weak firing pin spring. This was in a custom action. Issue popped up out of the blue.

 

[geordiesniper]

My primers went in nice and tight and the brass was new, and I know now that the load was too hot for that particular days temperature plus add in the mix of barrel fouling = blown primers.

I have also just checked the old primers and they show signs of cratering and they can also be inserted into the fired cases with simple finger pressure and fall out so the cases will be binned.

Thanks for all of your comments and good shooting.

 

[bruce moulds]

2910 fps in a 284 with a 180 gn bullet is the giveaway.
the bird in the cage down the mine is shooting fast and hot, presenting the tip of the iceberg.
keep safe,
bruce.