Flat Primer - ?

[Powerstroke]

So my better half has told me she would like to go cow elk hunting this year. Her M7 .260 has been hiding in the deep dark corners of my safe for the last couple of years just begging for a re-"build" I never have been able to get this one to shoot really well, but its always got the job done.

I decided to revisit the RL-19 with 130gr Accubonds as I've never tried this combo in this gun. It's a youth model 7 w/ a 18.5 inch tube.
With her behind the trigger, anything out to 350yds is going to end up as dinner on the table :grin:

I put a Leupy 12X on it and out we went this weekend with several different loads.
I'm looking for thoughts and or sugestions on what could have caused this - The third shot out of this group she called me over and said the bolt wouldn't open. I was able to open it, but definatly stiffer than normal. The primer was flattened beyond what I've ever seen since I've been loading myself. The other 3 primers looked fine.

NOTE: All four shots were what I'd call consistant for this gun - unfortunately I didn't have my chrony set up. This is also the best this gun has ever shot.
Remington Brass
CCI Bench Rest Primers
130gr AccuBond
46.0gr RL-19
COAL = 2.810 which is .020 back from the lands on this rifle.

 

[JD338]

Powerstroke

Nice shooting! Try a COL 2.800" and see if that doesn't tighten her up a little more. :wink:

Flat primer and stiff bolt are excessive pressure signs, as you already know. What is interesting is that is the only one.
Same make and lot of brass?
Possible slight over charge of that one load?
Was that shell warmer than the others, IE:in the sunlight, truck, pocket?

I would proceed with caution and reshoot. If it persist, back off the powder weight by .5-1.0 grains and try again.

JD338

 

[Greg Nolan]

Lots of possibilities. Like JD338 said. Load and brass. Maybe a fully resized piece of brass that didn't get trimmed back and is being crimped by the end of the chamber. Was the cartridge hard to seat with the bolt. I only say that because it happened to me. I had a real tight chamber and it caused some issues. Good luck.

 

[SJB358]

I would think it would be the same thing Greg mentioned, maybe one piece of brass was just a hair long and was crimped in the chamber during firing. Your groups look pretty good for a rifle not shooting that "well"! JD mentioned that maybe it was left out in the sun, or maybe allowed to get warm before firing. With it being only a one time thing, I wouldn't sweat it too much. A Chrono would probably tell you what is happening. Good luck buddy, can't wait to see pictures of the wife and the 260 over an elk. Scotty

 

[OU812]

Do you recall if 1 of the primers was seated slightly deeper than the rest? With my 350 rem mag some times with new brass I will have a primer seat deeper than the rest and will flatten the primer a little bit while the rest are just fine. Something to look for.

 

[Powerstroke]

Thanks Guys -
I'm still slightly puzzled out of the thousands of rounds I've loaded over the years to see this. I'll flatten a primer every now and again slightly, but usually working on loads and pushing that edge - this one was far from it and *really* flattened.

All four bullets came directly from the box and were shot back to back - Original bag of Remington brass & same can of powder.
My Wife said the bolt closed as normal ??, All on brass that has been shot 4 to 5 times - I will add that these are neck sized and not full length.

I'm about to chaulk it up to a widget glitch? I use a Lyman 1200 DPS 3

I'm definatly going to load some more and take the chrony this time.
Actually had a group with the 125gr Partitions that showed some promise as well.

Thanks again !

 

[Powerstroke]

Update -
And sure enough ( I think )
I threw all the cases in the tumbler before I went to bed last-night.

That one case is .010 over max length & there is a small but noticable ding in the case mouth.

 

[SJB358]

Glad you figured it out. Now, lets see some of the 125gr PT groups! Those seem like they would be dandies in any of the 6.5's! Scotty

 

[JD338]

Sounds like you solved the "case". :lol:

Give us an update on the next tripto the range.

JD338

 

[DrMike]

Powerstroke,

I recently had the same thing happen on a 7mm RM that had one neck slightly longer than another and a seemingly miniscule ding in the neck. I witnessed the same effect of high pressure and an excellent group! Sounds as if you worked the problem out.

 

[257 Ackley]

Mark -
I found R19 gave me the best accuacy for the 130 AB with close to the same recipe as you; Nosler brass and Federal 210M primers are about the only difference. Groups were under .5 inches with an OAL of 2.805. It isn't blazing fast at 2895 average, but gave me the ability to hold dead on out to 300 yards when sighted in 2 inches high at 100 yards. Good luck, I know we have discussed what to do with that rifle for a while.