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

[YZ-80]

Perhaps an over simplification, but sometimes you just never know what can happen with any given rifle and when a few parameters line up to create the perfect storm, they just do. Case in point is my 6.5-284 with a 130 Accubond and H4831sc. I should easily be able run that up to 53.5 grains. Heavy bolt lifts and extractor marks in the Hi 51's/low 52's dictated otherwise. I ended up backing off to 51.4 grains before the pressure signs resolved. Luckily, it was a great load.

 

[436]

Firing pin?

 

[codyadams]

Seems pretty obvious, the loads are way over pressure..... 0.7 grains is not near enough of a drop for a component change of brass and bullets. In a case that size I generally drop 3ish grains or more from max I established with similar weight bullets any time I do a major component change like brass, and do a gross work up in .3-.5 grain jumps just to establish my pressure/velocity range and where I find max pressure. In that scenario, worst case is you shoot 10 or so extra bullets.

Changing brass manufacturers, and changing bullets, and then dropping only .7 grains is asking for trouble. Then to shoot and blow 3 primers....you may have etched your bolt face, or possibly even set lugs back slightly depending on how over pressure you were.

Please be safe man! That was minimum 75,000+ psi inches from your face, 3 times.

 

[bomberodevil]

Did anyone say head space yet? and double check your scales

I have the RCBS Chargemaster and a Franklin Arsenal electronic scales, and I weigh every charge on both scales. If it's more than a tenth off, it goes back into the hopper. It's possible they are both off, but they'd have to be both off on the same load.

 

[PlumberEd]

It appears that you have learned what most of us have learned about reloading…there are no smart shortcuts. Fortunately before a catastrophic event. I learned the hard way that anytime I change a component in an established load to drop 8ish% from max and work backup. Better to waste a few components than to cause yourself unwanted trouble.

 

[tim_w]

Check what the h2o vol is of both the Hornady and Nosler cases you have. That might point to the issue.

What did the new nosler cases measure for headspace in your chamber compared to your firformed Hrdy cases?

Personally, swapping components like that I would have dropped 2 or 3 gr min. Then worked up.

I would be checking that bolt face for flame cutting.

 

[Muddyboots]

We ALL have had a tough reloading lesson to swallow at one time or another. The lesson learned on new load component is an easy trip wire for even the "experienced". There is another lesson learned which is as several of us have stated, strongly recommend bolt face and lugs be evaluated by a smith before any load development proceeds.

I also learned similar lesson but it was extremely heavy bolt lift from starting too close to max. It happens and its what we do next is most important.

Hope the rifle is fine and you can get it going with the 143ELDX.

 

[skipglo]

Good point. I forgot to mention, I take 8-10 measurements with the Hornady gauge and a fire-formed case from my rifle to measure the CBTO with every different bullet I use, and then start at .030" off the lands for hunting loads. I'll re-measure it this weekend, but my CBTO was 2.218", COAL at the lands was 2.876", and the COAL after backing out .030" was 2.846". I also trim every case to SAAMI prior to loading.

I seat with coal of 2.80, 41.5 grs H4350. Several hundred rounds, zero pressure signs,
.250 groups and better when I do my part. You either compacted the load or are into lands is my only thoughts. Edit: last minute thought....Did you check your powder scale?

 

[Highlander44]

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?

As mentioned earlier, could be brass.
I had a surprise when doing some cold weather load testing. My load was close to recommended max, and shot well all fall. On a very cold winter day- it blew primers….
I reached out to my engineer buddy, and he told me this is due to rigidity in the metal of the barrel in the cold?
I didn't see that one coming, but the results were there.
Mike

 

[pdog shooter]

I had the exact problem, same caliber, powder, brass and bullet. Buddy had same problem. Well below max powder charge with chrony to verify. Did not check volume but weighed less than Peterson brass. Problem stopped when we stopped using nosler brass. No problems with nosler brass in 22-250. How does that primer cup get out of the pocket with the bolt closed?
Peterson "fat" brass can cause that problem also but it is much easer to diagnose.

 

[25WSM]

I just cant wrap my head around the part when you though it was ok to shoot the second shot. And the third shot? You know the definition of insanity? Not saying you are insane here. But did you really expect the third time would be better? You blow a primer like the ones in your pics and you pull the plug right now on that load. And yes the difference in powder capacity is probably what caused your issue. Plus the fact that you didn't start low and work up. These are golden rules of reloading that can never be deviated from. It's probably the number one rule every reloader learns when he starts. Your situation just confirms this as a must. Thanks for sharing. If it keeps only one more person from a world of hurt it was worth your effort to post this. Safety first.
Shep

 

[bomberodevil]

As mentioned earlier, could be brass.
I had a surprise when doing some cold weather load testing. My load was close to recommended max, and shot well all fall. On a very cold winter day- it blew primers….
I reached out to my engineer buddy, and he told me this is due to rigidity in the metal of the barrel in the cold?
I didn't see that one coming, but the results were there.
Mike

I'm in Phoenix so cold is a relative term! The temperature was probably in the upper 60's, so maybe 30-40 degrees cooler than the warmest ambient temp I may shoot at, but not cool enough that I would think would alter the metal.

 

[azsugarbear]

Lots of things that could be causing high pressure. One I did not see mentioned is same vs. different lot of powder. Some lots burn faster than others - even with the same powder. There are lots of possibles causes for a pressure spike that have been given. Just start eliminating them one by one. At any rate, reduce powder chrge and shoot over chrony to get an idea of where you are at. Best of luck.

 

[bomberodevil]

I just cant wrap my head around the part when you though it was ok to shoot the second shot. And the third shot? You know the definition of insanity? Not saying you are insane here. But did you really expect the third time would be better? You blow a primer like the ones in your pics and you pull the plug right now on that load. And yes the difference in powder capacity is probably what caused your issue. Plus the fact that you didn't start low and work up. These are golden rules of reloading that can never be deviated from. It's probably the number one rule every reloader learns when he starts. Your situation just confirms this as a must. Thanks for sharing. If it keeps only one more person from a world of hurt it was worth your effort to post this. Safety first.
Shep

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.