I loaded up 10 rounds to tst what i thought was a good load. 5 out of the 10 lost the primer (just fell out) the other five showed all the pressure signs ofaway to hot load. although on paper at 300yds i could easily tell which ones had kept the primers, 4 out of the 5 went into a 1/2" group with the 5th making it a 3/4", while the other 5 were closer to 2 1/2". this was supposed to be a final comfermation that the load was good, so i could start loading up the rest of 145 rounds for this weekends match. Im shooting the 6brx, 107 sierra's inthe lands. this load was 33gn varget, with wsrm primers. i guess i'll load the rest at 32.5, bu tthe velocity on that charge was only 3003fps, and the 33gn wa 3030fps. what do you think?
pressure again
- Thread starter goldy1
- Start date
When the primer falls out, you're a single step away from catastrophic case-head failure. Those cases have had the entire web and case-head section permanently expand so much, that the primer pocket remains at a too large diameter to hold the primer even after the rest of the case has reduced in size after the pressure drops, hence the primer falling out when you open the bolt. Having this happen to single round in a batch is very worrying. Having it happen five times means you have a serious problem with this combination, and also means you continued using a load that was potentially dangerous four times too often. I don't want to sound preachy, but if you saw that problem with one cartridge, you should have stopped there and then, taken the rounds home and pulled the bullets. There are more than a few shooters who have carried on this situation who subsequently wished they didn't as they ended up with wrecked rifles - then, there are a smaller less lucky number who also did it and who are now one-eyed!
You've got to now do four things - 1. check the powder charge weight employed was actually the same as tried before - ie not what you might have remembered the previous load to be; 2 if it was definitely the same (likewise, brass, bullets, powder lot etc) look at every aspect of how you loaded that batch and what if anything might have been done differently; 3 ask yourself about ambient temperature in your range sessions (was it hotter when the primers blew?); 4 if absolutely nothing has changed buy a set of scale check weights to ensure that you're loading the weights you think you are. (Not electronic scales by any chance?)
In the absence of overwhelming evidence of some mistake or change that definitely caused the pressure increase, drop the charge and do so by more than 0.5gn. In your shoes with this problem and a 33gn charge I'd go down 1.5gn at least and see how that looks. It's no good either thinking it's 'only' giving x fps MV and I should be getting X+50 or x+100 fps. Every barrel is different and some produce dangerous pressures at lower MVs than others will happily produce every day.
You've got to now do four things - 1. check the powder charge weight employed was actually the same as tried before - ie not what you might have remembered the previous load to be; 2 if it was definitely the same (likewise, brass, bullets, powder lot etc) look at every aspect of how you loaded that batch and what if anything might have been done differently; 3 ask yourself about ambient temperature in your range sessions (was it hotter when the primers blew?); 4 if absolutely nothing has changed buy a set of scale check weights to ensure that you're loading the weights you think you are. (Not electronic scales by any chance?)
In the absence of overwhelming evidence of some mistake or change that definitely caused the pressure increase, drop the charge and do so by more than 0.5gn. In your shoes with this problem and a 33gn charge I'd go down 1.5gn at least and see how that looks. It's no good either thinking it's 'only' giving x fps MV and I should be getting X+50 or x+100 fps. Every barrel is different and some produce dangerous pressures at lower MVs than others will happily produce every day.
IMHO, most of the loads posted on the Internet are way to hot. Be careful and take them with a grain of salt. I don't shoot 6BRX but I do shoot alot of 6BR and my loads are always below what I read.
A 107 in a 6BRX is only 3003fps? That's cook'n. I think 2950 with a 105VLD is a full load in a 6BRX and 107/108's are going to be less than that. The gun's telling you to take a full grain out of that load.
Pressure is real and in your face, results on target is what this whole thing is all about, but, muzzle velocity is nothing more than a good mathematical thing to know.
When you pick bullet and cartridge, the ballistics are fixed. Run a good safe load and she'll hammer for you.
Just my load philosiphy,....
Mike
A 107 in a 6BRX is only 3003fps? That's cook'n. I think 2950 with a 105VLD is a full load in a 6BRX and 107/108's are going to be less than that. The gun's telling you to take a full grain out of that load.
Pressure is real and in your face, results on target is what this whole thing is all about, but, muzzle velocity is nothing more than a good mathematical thing to know.
When you pick bullet and cartridge, the ballistics are fixed. Run a good safe load and she'll hammer for you.
Just my load philosiphy,....
Mike
goldy1: My standard load for my 6BRX is 33 grs. of Varget, 107 SMK, seated to just touch, BR4 primers, and of course, Lapua brass. Barrel is a Krieger with a .237" dia., .272 no turn neck. Oldest 20 count box of brass has 18 loadings & still trouble free. Chronographed velocities average 2930 fps. Not suggesting you should try my combination, just saying what works in mine, proof that they are all different. If it were me, I'd reduce the powder charge and seat the bullets off the lands a bit. As always advice from Laurie is the first to be considered.
Keith Glasscock
Gold $$ Contributor
Trying to get maximum velocity rarely (in my limited experience) gets you where you really want to go.
You might be right on the high node, but moving down to the next lower node might get you a better score. Sometimes, a cartridge might be capable of more velocity, but it just can't quite get to the next node safely. I have a friend running the Dasher. He runs at 2950 fps. His scores at 600 yards are downright amazing. Last night - 200/13X (again!)
If I were a betting man, I would guess that the 1" or less of improved wind drift from the extra 80 fps won't make 1 point difference in your scores when averaged over 50 matches. On the other hand, I wouldn't want to test that theory. It sounds like the 33.0 grain load is downright unsafe pressure wise. I'm not sure what you should do, but I would reduce more than half a grain.
Just my opinion, YMMV
Good luck, and safe shooting!
You might be right on the high node, but moving down to the next lower node might get you a better score. Sometimes, a cartridge might be capable of more velocity, but it just can't quite get to the next node safely. I have a friend running the Dasher. He runs at 2950 fps. His scores at 600 yards are downright amazing. Last night - 200/13X (again!)
If I were a betting man, I would guess that the 1" or less of improved wind drift from the extra 80 fps won't make 1 point difference in your scores when averaged over 50 matches. On the other hand, I wouldn't want to test that theory. It sounds like the 33.0 grain load is downright unsafe pressure wise. I'm not sure what you should do, but I would reduce more than half a grain.
Just my opinion, YMMV
Good luck, and safe shooting!
+ 1 on that Mike. I briefly ran loads close to the 6BR/105 loads widely listed with moly coated bullets and after a while decided to use far more modest numbers and uncoated bullets. My resulting 105gn Berger VLD match load was 'only' producing 2,785 fps (from memory) and performed very well indeed for all practical purposes. It also helped get 4,500 rounds out of the barrel. (The rifle is now waiting for rebarrelling which in turn awaits a 6BR-DX reamer arriving from the US.)
Laurie,
York, England
In every cartridge that can get loose primer pockets, I try to find the exact threshold.
Then I back off a safety margin based on the tolerances in my system.
Typically 4% for just me.
Vernon Speer said 6% for writing load books.
But this is 6mmBR, and I can't get loose primer pockets with 6mmBR, just pierced primers. So I back off a safety margin from the exact threshold of pierced primers in 6mmBR.
Then I back off a safety margin based on the tolerances in my system.
Typically 4% for just me.
Vernon Speer said 6% for writing load books.
But this is 6mmBR, and I can't get loose primer pockets with 6mmBR, just pierced primers. So I back off a safety margin from the exact threshold of pierced primers in 6mmBR.
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