High Pressure - Don't know why

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zogg54

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Out to the range Saturday with my very first hand loads for my savage 111 7mm Rem mag. Recipe from the Hodgdon reloading website: 139 grain Hornady GMX, in a 2.499 case with 67.5 gr (starting charge) of H1000 powder, with Federal Premium "match" large magnum primer.
Pulled the trigger, boom! Hmm, very difficult to get the bolt open. Primer has been blown completely out of the case, and the pressure was so great it jammed the ejection plunger into the bolt face and broke the spring. My very first hand load created with brand new RCBS gear.
Some of the old boys at the range with lots of experience had a look at my shells and said everything looked good. One guy took one of my shells and pulled it apart and said everything was to spec perfectly (weighed & measured). I pulled the bullets and remeasured the powder weight and everything was dead on to spec.
At this point I have to wonder, if the powder I bought is what the label says it is. I purchased the powder brand new in a sealed container from a retail store. Any idea what might be happening here? I will really appreciate any insight others may have.
 
I was going to mention about the measuring of powder but I read your friend double checked. Because if you use a digital scale they can be affected by some types of lighting with ballasts and it throws off the reading slightly.

Was there a crimp placed on the bullet, perhaps it was too tight causing excess pressure at the neck?
 
There's no way a tight crimp could cause that kind of pressure.
I was wondering about the data as solid copper bullets usually have lighter loads than lead core but the data is indeed for a GMX specifically (only 139gr data on the Hodgdon site).

There has to be something else going on or Hodgdon accidentally posted some way over spec data on their site.
Is there any possible way it was the wrong powder? Do you have other kinds of powder for other cartridges or is H1000 the only powder you have?
Have you measured the bullets with a micrometer? Maybe they where off-size. Unlikely since there aren't any GMX bullets near that size that would chamber (a .308 bullet in a case wouldn't fit the neck/throat of the chamber).

I can't find any Hornady or Hodgdon recalls for anything involved. A super-mega-ultra hot primer is still unlikely to cause that extreme of a pressure spike.
What was the brand of case? Was it new or fired before?
 
Pulling apart one shell after the fact doesn't really prove much, it just shows that shell is ok. Its way more likely you messed up with your first reloads then powder manufactures putting the wrong powder in the can.

My guess is you over charged a case. Do you have a scale check weight?
 
As hickstick_10 said it may have been one case that was over charged.
Did you check the powder level in each shell before seating the bullet?
I always have a small flashlight on my loading bench to do this. Just today while loading some .303 British I caught an aberrant over charge in one case by doing this. I have no idea how it happened since I was measuring the charges individually on a balance beam scale and it was a ~10% over charge; not a double charge (wouldn't have fit). First time it's happened to me and good reinforcement to keep doing my checks.
 
do you have any other loading data to cross reference to?

unfortunatly there is no such thing as solid be all end all data, chamber, brass, powder lot, air temp, air density can all change (although slightly) power burn rates and pressures reached.. all data says is in that day in their barrel with that powder lot, that it worked fine

id be surprised if you hit that sort of pressure with a start charge from a manual, but stranger things have happned..

possibly bore obstruction? to much oil etc?
 
zogg54 said:
Recipe from the Hodgdon reloading website: 139 grain Hornady GMX, in a 2.499 case with 67.5 gr (starting charge) of H1000 powder, with Federal Premium "match" large magnum primer.
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Couple of things to suggest:

Did you verify that recipe with other sources to make sure there wasn't a typo on an single web-site? Recipes from different sources will often be close if not exact. If you see one that is "way off" question it.

Are there any recall notices for lots of H1000?

What was your overall length and were you jump starting or jamb starting with regard to the leed?
 
That is odd. I would make a few loads for pressure testing. Start 8 grains or so less than your current load, and work up one grain at a time, one cartridge per load, and fire from the bottom to top.

Check each case for pressure signs, sticky bolt lift, etc, and work your way up. If you get pressure signs then stop, but if you don't get anything unusual, I would say it was just an accidentally overcharged case.

Something else to check for, recheck your reloading manual to double/ triple check you have the powder weight and bullet combo correct.
 
Hornady 9th Edition reloading manual lists 61.9 gr as the minimum charge of H1000 powder, 72.8 gr max load. Their data was compiled using Hornady/Frontier brass and Winchester Large Rifle Magnum primers. Assuming that there were no flaws in your loading procedures, I would reduce the charge to 62.0 gr and work up from there by 0.5 gr at a time while watching for pressure signs. Also, what brand of case were you using?
 
I pulled the bullets and remeasured the powder weight and everything was dead on to spec.
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I'm using balance beam type scale perfectly zeroed and read at eye level.
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Hornady 9th Edition reloading manual lists 61.9 gr as the minimum charge of H1000 powder, 72.8 gr max load
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People gotta read a little harder :)

Two things:

1) You only mentioned the case trim length, not your seating depth/COAL. What COAL were you aiming for? Were you maybe seating super close to the lands? Or maybe seating super deep?

2) I also think you should check your scale against some check weights (do you have any?) or against someone else's scale. If you don't have a good check weight and don't know anyone else nearby with a scale you can check against, clean up a few pennies and measure their weight as accurately as possible, then take them with you to the range next time and get one of those old-timers to check their weight for you. $.04 should be about 64 gr or so. Or mail 'em to one of us. I have like a dozen digital scales by now, including a lab scale accurate to .02 gr. Plus I'm poor and could use the extra cash. ;)

3) Has this rifle showed any problems with factory ammo?
 
I am using the RCBS scale that came with the kit. I have read many posts saying they are excellent scales and weighed bullet from the box was dead on to the indicated weight. @BlaclLabelBrad, Interesting that you have found those stats in the Hornady manual. Id say you have come the closest in discovery what has gone on here. That is a pretty big contrast to what Hodgdon is saying in their reloading data. Was that for the 139 gr GMX bullet?
 
Year ago or so the rifle had the exact same problem with Hornady super performance factory loads. Had to send the gun out east to get fixed, and the store that sold me the ammo pulled it all from the shelf. I read here and there on the internet of a few people having the same problem. As far as seating depth goes, I set my die to the case, backed off a quarter turn, locked the ring. Then I placed a factory round in the holder and set the bullet based off of a factory load. These hornady bullets are quite long so my COAL was longer but the start of ogive was the same as the factory load. When I compare the crimp rings between the bullets it looks as though the same amount of bullet seated into the case.
 
I have read many posts saying they are excellent scales
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Doesn't matter.. they might be fantastic scales, but that won't help if your particular scale is borked. You already know you have an issue somewhere. You should check everything.

and weighed bullet from the box was dead on to the indicated weight.
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Better.. but a check weight or comparison against another scale is best. :)

zogg54 said:
@BlaclLabelBrad, Interesting that you have found those stats in the Hornady manual. Id say you have come the closest in discovery what has gone on here. That is a pretty big contrast to what Hodgdon is saying in their reloading data. Was that for the 139 gr GMX bullet?
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Yes, I have the same 9th Edition manual right here. For 139 gr GMX, H1000 lists loads at 61.9 gr, 64.7 gr, 67.4 gr, 70.1 gr and 72.8 gr. Your loads are 5 gr short of Hornady's listed max load. Right in the middle.

Then I placed a factory round in the holder and set the bullet based off of a factory load
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Well.. how much, and of what type, was the powder in the factory load? Rhetorical question. You don't know..

What do your calipers say for COAL? The Hornady book lists 3.290" for the 139 gr GMX.

EDIT: People are gonna say COAL is bunk.. but remember that you *already* have a problem that's been observed. Now we're just trying to find out why
 
Since this has happened twice, once with factory ammo. I wonder if its got a bore that is a bit too tight and possibly not the greatest chamber.
It's the only thing that makes sense to me with that load and that bullet.
I know I wouldn't be shooting it again without some serious investigation of that rifle, not worth the risk.
 
SND said:
Since this has happened twice, once with factory ammo. I wonder if its got a bore that is a bit too tight and possibly not the greatest chamber.
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I actually think this is probably the right answer. If there's something out of 'normal' specs in the rifle, then vanilla loads as tested in another rifle might wind up being super hot.
 
SND said:
Since this has happened twice, once with factory ammo. I wonder if its got a bore that is a bit too tight and possibly not the greatest chamber.
It's the only thing that makes sense to me with that load and that bullet.
I know I wouldn't be shooting it again without some serious investigation of that rifle, not worth the risk.
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Yes, gun is done for now. Going to the Savage rep for repair and or analysis. This was my first rifle and up until now I have been content to say savage has proved exceptional value. However, I've had a couple of people tell me that savage is not great in the barrel/chamber department. Now, we may be able to chalk that up to anecdotal evidence but this issue has me concerned with going to a savage again. I have decided that I will now purchase a sako A7 in 7mm rem mag.
 
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