Blown primers on 6.5 CM-Problem Solved on page 6!

[Lefty7mmstw]

I don't mind checking the headspace once in a while, I know it does shrink or erode over time. The dummy cartridge is a great idea too.

I'd worry about it on something like a 7rum a lot more than a creed... even then, usually you don't have that much forward erosion, but you burn the rifling flat for the first couple inches over time.

 

[Tulsa Reiner]

I know, I should have stopped immediately, that was really sloppy of me. I'd never had a blown primer before, after many years of hand loading. I guess it wasn't sinking in what the issue was at first. I knew there would be different characteristics between the manufacturers of brass, I just wasn't expecting that big of differences. I knew before to start low, and I thought I was low enough. Lessons learned!

Thanks to you all for your feedback. It's never too late to learn and hopefully my mistakes will help someone else down the road.

Bomber: another thank you for sharing your experience. It reinforced my rule to always drop back to at least 5%-10% below published maximum charge whenever a component is changed. Then I increase my charges by 0.2 grain increments while chronographing and watching for pressure signs. It seems like I always find my best node well before reaching the max charge, so I stop there. I quit chasing maximum MV years ago.
This one really snuck up on you. Fortunately it didn't bite you.

 

[Rosebud]

I'm doing some load development on a 6.5 CM Christensen Arms Mesa, with a 22" barrel. This rifle has approximately 300 rounds, and has been easy to develop loads for. I have developed loads for Nosler 140 AccuBond at 2734 fps with 41.2 grains of H4350, with 3-round groups at sub .400 moa, and SD of 6. I also have a load with Nosler 140 grain BT, 41.0 of H4350, .360 moa, an IMR 4350 load below .400 moa. All of these loads had zero pressure signs, and MV in the low to mid 2700 fps.

Today I try some load development with Hornady 143 ELD-X, H4350, Nosler brass, Federal 210 primers. I begin at 41.1 grains of powder, with intent of going to 41.8 in 0.10 increments, shooting for accuracy. Hodgdon site has 41.8 of H4350 as their max load.

At my first load at 41.1, I blow the primer. Thinking that was an fluke, I fire two more, both with blown primers. This is below my 140 grain AccuBond and BT loads that have zero pressure signs, and 0.7 grains below the Hodgdon site max loads. I pulled the rest of the loads and reloaded, starting at 40.3 grains of H4350. I can't believe that 41.1 grains of H4350 is over pressure. Any thoughts?

Not one to gloat but I believe that is the 1st thing I asked about.

 

[bomberodevil]

Not one to gloat but I believe that is the 1st thing I asked about.

You were absolutely correct! I had the math correct in one location but wrong in another page of notes. I didn't double check my work.

 

[Stonyman88]

Problem solved. Re-measured my CBTO and COAL, today's measurements were within .003" of last week's measurements. Still scratching my head on how this load was so much hotter than a couple of loads I've already developed with pretty much the same system.

Was looking through my notes page from last week, and there it was. I inadvertently added my .030" off the lands back into my math! I was on the lands! Stupid and sloppy math, my fault completely.

Double and triple check your math! Thanks to all who passed along great advice and tips.

Glad you found out the mistake, looked at the page before I read your info, and couldn't figure out what was what. Kept thinking you just figure it out, but then read the comment, Just a tip, only write down the distance to lands with the fired brass with the seed in it, and note it as Lands for what ever rifle it is and the seed your using, I keep these in a old prescription bottle, round, and case, If I use another seed, I put that in a bottle by it self with a sticker, now all you have to do is check new seeds if you change. Sometimes it's so difficult to keep or remember everything for sure. thanks for the info

 

[JAYgs8163]

Still though, "start low and work up"!!! Glad you found the error in your math!

 

[Lenny Foffa]

Along with head space , I would also check the length of the case and compare it to the true exact length of your chamber. If you case is too long, you could be causing the mouth of the case to gouge into the bullet when you close the bolt. That will cause higher pressure. Measure everything carefully. Can we assume, you did not mess with the flash holes at all???

 

[Buckys]

Problem solved. Re-measured my CBTO and COAL, today's measurements were within .003" of last week's measurements. Still scratching my head on how this load was so much hotter than a couple of loads I've already developed with pretty much the same system.

Was looking through my notes page from last week, and there it was. I inadvertently added my .030" off the lands back into my math! I was on the lands! Stupid and sloppy math, my fault completely.

Double and triple check your math! Thanks to all who passed along great advice and tips.

Thanks for posting the solution and retitling your post.

 

[General RE LEE]

On a side note, I know first hand Nosler brass is thicker than Hornady. Keep that in mind when doing load development.

 

[bomberodevil]

On a side note, I know first hand Nosler brass is thicker than Hornady. Keep that in mind when doing load development.

I'm dumping the Hornady, I'll use Nosler brass for practice rounds with SST and use Lapua brass for the Accubonds and the ELDX. I'll buy another 100 pieces of the Lapua soon and phase out the Nosler. Reduce my variables.

 

[General RE LEE]

I'm dumping the Hornady, I'll use Nosler brass for practice rounds with SST and use Lapua brass for the Accubonds and the ELDX. I'll buy another 100 pieces of the Lapua soon and phase out the Nosler. Reduce my variables.

I actually like Hornady brass. I get better velocities cause I'm not hitting pressure as soon as harder brass. Lapua brass is definitely good stuff, but Hornady has worked great for me and I get multiple reloads in 6.5 CM. It's also cheaper and matches Hornady load data.

 

[bomberodevil]

I actually like Hornady brass. I get better velocities cause I'm not hitting pressure as soon as harder brass. Lapua brass is definitely good stuff, but Hornady has worked great for me and I get multiple reloads in 6.5 CM. It's also cheaper and matches Hornady load data.

I do too, but I have a lot more reloads through my Hornady brass, and I just want to get down to one brass manufacturer per cartridge. For the 6.5 CM, it will be Lapua.

 

[tim_w]

Not sure harder brass has much to do with hitting pressure sooner. Brass with reduced internal volume yes. Not always the same thing.

 

[bomberodevil]

Glad you found out the mistake, looked at the page before I read your info, and couldn't figure out what was what. Kept thinking you just figure it out, but then read the comment, Just a tip, only write down the distance to lands with the fired brass with the seed in it, and note it as Lands for what ever rifle it is and the seed your using, I keep these in a old prescription bottle, round, and case, If I use another seed, I put that in a bottle by it self with a sticker, now all you have to do is check new seeds if you change. Sometimes it's so difficult to keep or remember everything for sure. thanks for the info

My final notes are a little neater than my worksheet notes, this is how I track my measurement.