Odd Pressure Issue

[eshorebwhntr]

I would get your rifle over a decent chrono and see where you are really stepping out at. I would also do a load run up with another powder and check the things like brass length, neck thickness vs/ chamber width, etc. that could net you way more pressure than anticipated. Are you sure you are off .030" or might you be resting your bullet on the rifling??
Check everything and you will find your issue.... I'd bet you a wooden nickel it isn't the primer. The pierced primer is the effect of something else garfed up...

All brass is new RP 8mm Mag, FL sized, trimmed to 2.840, primer pockets uniformed (depth), inside/outside deburr, flash hole deburr, and neck turned to .311 finish diameter, then resized with a .308 neck bushing. Gun is built with a .313 neck diameter.

When first starting with the 168's here recently I took the firing pin assembly out and seated a bullet long and worked down in .005 increments until I got an easy bolt fall. I've also made my own Hornady gauge and used the LNL tool. Both gave me the same length to the lands. Within .002-3. I then set the loaded round back .030 back using a micrometer die and checked the measurements. All were from the ogive.

I think I'd stop putting more powder in this , until I came up with a reason for this thing blowing fire out of the wrong end. I see all the primers have the same markings stamped in them from the bolt. Is this existing pressure cutting, or is the bolt face that messed up. Since the gun has been sitting for a while , is the barrel rusted or pitted, is the powder correct , or has it been contaminated? If it were mine I'd send it to a good gunsmith and have it bore scoped, headspaced. If it all checked out , I'd start with new reloading supplies. k Redden

I felt the same. I didn't think having too little powder in a round was causing an issue. Especially only half a grain in a +70gr charge. But I loaded up 75.5 gr which is in the middle of the Berger book recommended range and it gave the same result. Primers smoked at random. Not a big deal. It was easy enough to try.

The gas leaking by is starting to leave a ring on the bolt face around the FP hole.

The gun was shot about 50-70 times last fall with 180 VLD's practicing before going on a mule deer hunt. It was then cleaned with bore tech, dry patched out, and stored with a light coating of colloidial graphite which Gre-Tan sends out with all of their builds. I hope it hasn't pitted or rusted a Krieger SS barrel in that time and I really don't have good way of telling if it did.

I try to keep good track of my reloading supplies. It was not a new can of Retumbo but I really don't feel it was contaminated either. I've got some new cans of H1000. I only want to change one thing at a time right now. That will be the next thing I try.

Yes, sir, I did read that last post. None of us can be sure what caused your specific problem. It could be lots of things, not the least of which might be enlarged primer pockets. The point I was trying to make there was that when the powder charge begins to burn the primer gets pushed back against the bolt face and everything in the chamber begins to swell. The case swells to fill the void provided by the head space which in turn pushes the base of the cartridge back against the bolt face and, essentially, reseals the primer. That all happens in an instant. If the charge is too small, even though the bullet may exit the barrel "normally", the pressures may not be great enough to maintain a seal on all the remaining cartridge components and pressure leakage past the primer is a possibility. I'd just hope that you don't get caught up in a post hoc ergo propter hoc scenario that leads to false assumptions.
In your situation I'd find some new brass, prepare loads somewhere in the mid range of the reloading manual recommendations, and try again.

I understand. Just wanted to make sure you knew that I did try jumping up into the middle of the range per the Berger manual at 75.5 gr and got the same exact result.

I have some left over Norma 300 HH I could fireform and give a try if need be. I don't see why this RP 8mm neck turned stuff shouldn't work though.

I've loaded up 5 rounds with the same 75.5gr Retumbo charge and some CCI 250 primers. As best I can tell all the variables are exactly the same other than the primer.

I appreciate all the time and help you guys have provided. I'll keep this updated as I work through the issue.

 

[barefooter56]

All brass is new RP 8mm Mag, FL sized, trimmed to 2.840, primer pockets uniformed (depth), inside/outside deburr, flash hole deburr, and neck turned to .311 finish diameter, then resized with a .308 neck bushing. Gun is built with a .313 neck diameter.

When first starting with the 168's here recently I took the firing pin assembly out and seated a bullet long and worked down in .005 increments until I got an easy bolt fall. I've also made my own Hornady gauge and used the LNL tool. Both gave me the same length to the lands. Within .002-3. I then set the loaded round back .030 back using a micrometer die and checked the measurements. All were from the ogive.



I felt the same. I didn't think having too little powder in a round was causing an issue. Especially only half a grain in a +70gr charge. But I loaded up 75.5 gr which is in the middle of the Berger book recommended range and it gave the same result. Primers smoked at random. Not a big deal. It was easy enough to try.

The gas leaking by is starting to leave a ring on the bolt face around the FP hole.

The gun was shot about 50-70 times last fall with 180 VLD's practicing before going on a mule deer hunt. It was then cleaned with bore tech, dry patched out, and stored with a light coating of colloidial graphite which Gre-Tan sends out with all of their builds. I hope it hasn't pitted or rusted a Krieger SS barrel in that time and I really don't have good way of telling if it did.

I try to keep good track of my reloading supplies. It was not a new can of Retumbo but I really don't feel it was contaminated either. I've got some new cans of H1000. I only want to change one thing at a time right now. That will be the next thing I try.



I understand. Just wanted to make sure you knew that I did try jumping up into the middle of the range per the Berger manual at 75.5 gr and got the same exact result.

I have some left over Norma 300 HH I could fireform and give a try if need be. I don't see why this RP 8mm neck turned stuff shouldn't work though.

I've loaded up 5 rounds with the same 75.5gr Retumbo charge and some CCI 250 primers. As best I can tell all the variables are exactly the same other than the primer.

I appreciate all the time and help you guys have provided. I'll keep this updated as I work through the issue.

eshorebwhntr,
Check the neck wall thickness on the cases that have the primer issue. Make sure they are turned to what they are supposed to be. To little clearance can cause these pressure signs also. What were your seating the VLDs to on or off the lands? That MAY be a good distance to start with for the 168s. Use lowest powder charge listed for the bullet/powder/ cartridge combination you are testing. That you dont indicate any pressure signs using the VLDs that you have now is a bit puzzling.

 

[eshorebwhntr]

I backed them down to .030 jump and intended to start playing with seating depth once I determined my charge weight.

The necks were turned down with a K&N kit until it cleaned up the surface of the neck and made it concentric. I then resized it with a .308 bushing, seated a bullet, and measured the loaded round diameter to be .310, giving .003 clearance with about .002 "tension". Kinda what I've always done with neck turn chambers on my other rifles. .003 seems to work well.

Also I've found this thread while digging around a little this morning...

bad primers--etched bolt face(picture) [Archive] - Benchrest Central Forums

 

[barefooter56]

I backed them down to .030 jump and intended to start playing with seating depth once I determined my charge weight.

The necks were turned down with a K&N kit until it cleaned up the surface of the neck and made it concentric. I then resized it with a .308 bushing, seated a bullet, and measured the loaded round diameter to be .310, giving .003 clearance with about .002 "tension". Kinda what I've always done with neck turn chambers on my other rifles. .003 seems to work well.

Also I've found this thread while digging around a little this morning...

bad primers--etched bolt face(picture) [Archive] - Benchrest Central Forums

Yeah. I was going to go there next on the primer issue. It dosen't seem to be only happening with a single manufacturer either. Wonder if they are making the primer cups thinner to save money since they are mostly brass. Don't know. Lets try reversing the testing and doing the seating depth first then the load since the seating depth directly affects the powder capacity of the cartridge case. Use the 'lowest powder charge listed while doing this. Other suggestion would to be get some cerrosafe and make a cast of the chamber to confirm the neck diameter of the chamber. Process of elimination ,one thing at a time.

 

[Lefty7mmstw]

Can you slide a bullet into a fired case??

what does the mouth of the case look like when you pull it???
does it have a bit of crimp like radius?? Or straight in diameter from shoulder to mouth??

 

[eshorebwhntr]

I'll look tonight at the case mouth. Pretty sure it is more or less straight. I'm sure I could push a bullet through the neck but I doubt if it is loose enough for the bullet to fall through under its own weight. Probably still a little tension there.

 

[Lefty7mmstw]

I'll look tonight at the case mouth. Pretty sure it is more or less straight. I'm sure I could push a bullet through the neck but I doubt if it is loose enough for the bullet to fall through under its own weight. Probably still a little tension there.

you should be able to start a bullet in and let her drop through... If you've got tension on bullets with a fired case neck, the case is not releasing the bullet well. too tight a chamber neck for your brass dimensions...

 

[eshorebwhntr]

you should be able to start a bullet in and let her drop through... If you've got tension on bullets with a fired case neck, the case is not releasing the bullet well. too tight a chamber neck for your brass dimensions...

I respectfully disagree. I've shot this rifle with that neck dimension for 5 years without issue using everything from factory RP STW brass, Qual Cart STW brass, and Norma fireformed 300 HH brass. All rounds finished out at .310-.311 and all shot without issue.

I also have 2 other rifles, a 7 Mag (.313 nk) and a 6.5 SAUM (.296 nk), all built by Greg Tannel that have similarly "tight" necks. I run both of those at .310 and .293, respectively, without issue for years.

I know no one wants to believe it's a bad batch of primers but I keep going back to that for a few reasons.

I bought this lot of 2000 F215's from a local gun store back in 2008 or 2009 to my best recollection. They've sat since then and I'd been using up what F215M's I had. I ran out of them recently and decided to use what I had and pulled the 215's from '09 out. Then this problem appeared that we've been discussing.

I also own a 6.5 SAUM. The last batch of ammo I worked up showed 2 rounds that started to display this same characteristic. Again, first time I've seen it using a proven load by myself and many others with this cartridge.

So across 2 platforms, in 2 totally different cartridges, with the only commonality being the primer, I've had this issue come up.

I've already got 5 rounds loaded up with CCI 250's to try hopefully tomorrow or Saturday. If that fails, I'll keep going down the list but for now it's the easiest thing to try.

 

[barefooter56]

I respectfully disagree. I've shot this rifle with that neck dimension for 5 years without issue using everything from factory RP STW brass, Qual Cart STW brass, and Norma fireformed 300 HH brass. All rounds finished out at .310-.311 and all shot without issue.

I also have 2 other rifles, a 7 Mag (.313 nk) and a 6.5 SAUM (.296 nk), all built by Greg Tannel that have similarly "tight" necks. I run both of those at .310 and .293, respectively, without issue for years.

I know no one wants to believe it's a bad batch of primers but I keep going back to that for a few reasons.

I bought this lot of 2000 F215's from a local gun store back in 2008 or 2009 to my best recollection. They've sat since then and I'd been using up what F215M's I had. I ran out of them recently and decided to use what I had and pulled the 215's from '09 out. Then this problem appeared that we've been discussing.

I also own a 6.5 SAUM. The last batch of ammo I worked up showed 2 rounds that started to display this same characteristic. Again, first time I've seen it using a proven load by myself and many others with this cartridge.

So across 2 platforms, in 2 totally different cartridges, with the only commonality being the primer, I've had this issue come up.

I've already got 5 rounds loaded up with CCI 250's to try hopefully tomorrow or Saturday. If that fails, I'll keep going down the list but for now it's the easiest thing to try.

Let us know what you find out! The primer"failures" that are out there seem to be of more recent production than 2009. BUT the whole industry has been a zoo trying to keep up for a long time. Production issue? Quality issue? Cost "saving" issue? Just bad luck? Who knows.

 

[just country]

Evening, I got online looked up Powder Residue around primer pockets
found some good info

Go to Shooting Illustrated/problems with primers
wwwshootingillustrated.com
articles 2012/2/16/problems-with-primers

The articles and others will come up for infolightbulb
Articles by Richard Mann-Thursday ,Feb. 2012

just country

 

[eshorebwhntr]

Good article and reference material. Like I said, the main reason I'm thinking it's the primers in this case is because the rifle has been fine for some time now and this problem arose with the most recent batch of ammo loaded for it.

 

[Lefty7mmstw]

I respectfully disagree. I've shot this rifle with that neck dimension for 5 years without issue using everything from factory RP STW brass, Qual Cart STW brass, and Norma fireformed 300 HH brass. All rounds finished out at .310-.311 and all shot without issue.

I also have 2 other rifles, a 7 Mag (.313 nk) and a 6.5 SAUM (.296 nk), all built by Greg Tannel that have similarly "tight" necks. I run both of those at .310 and .293, respectively, without issue for years.

I know no one wants to believe it's a bad batch of primers but I keep going back to that for a few reasons.

I bought this lot of 2000 F215's from a local gun store back in 2008 or 2009 to my best recollection. They've sat since then and I'd been using up what F215M's I had. I ran out of them recently and decided to use what I had and pulled the 215's from '09 out. Then this problem appeared that we've been discussing.

I also own a 6.5 SAUM. The last batch of ammo I worked up showed 2 rounds that started to display this same characteristic. Again, first time I've seen it using a proven load by myself and many others with this cartridge.

So across 2 platforms, in 2 totally different cartridges, with the only commonality being the primer, I've had this issue come up.

I've already got 5 rounds loaded up with CCI 250's to try hopefully tomorrow or Saturday. If that fails, I'll keep going down the list but for now it's the easiest thing to try.

you asked for ideas... I've given you mine... To disagree is fine, but if you don't have play in the neck you are essentially crimping the bullet and holding it when fired. You WILL have higher pressures than a looser chamber neck.

We've been using 215's for decades and the only failures they've ever produced was with beat up or incorrectly dimensioned brass. I hope you find your problem but I will be unfollowing this thread.

 

[eshorebwhntr]

Well, 5 shots this morning. Only change was to CCI 250's

 

[barefooter56]

Well, 5 shots this morning. Only change was to CCI 250's

Looks like you found your answer. Load doesn't look to bad on pressure either. Top of primer is flat but edges are still slightly rounded. You may want to contact FEDERAL with the lot number of those 215M
primers and see if they have had the same issue (s) reported by other shooters.