frustrating problem with 6mm PPC loading!

[flexible]

Hi everyone, flexible here. Been a pistol reloader for decades and a newbie rifle reloader.
This spring I started shooting matches in Heavy Varmint 6mm PPC.
Bought 200 cases of Lapua 220 Russian already neck turned to .262.
Over the season about 30% of the rounds wouldn't chamber without a hit from a rubber mallet.
The season ended with this issue so i broke down the last 30 rounds and redid all my measurements, chambered the resized brass (chambered with a slight amount of resistance). I loaded dummy rounds to make sure it wasn't overall length.
They chamber with only slight resistance.
Did a complete set of 20 rounds.
SAME PROBLEM!
A couple of guys from the BR group were practicing and they suggested i check the trim and redo the neck turning.
Any ideas?
Using Redding bushing dies and 29 grains of N133
thanks

 

[R.Morehouse]

Definitely check the case length and make sure your loaded round 258/260. Are you jamming the bullets into the lands?......How is your extraction?

Regards
Rick

 

[LHSmith]

Ditto on checking case length (brass only -no bullet). Were the cases subjected to stn. stl. pin cleaning where the case mouths may have been peened increasing the outside neck diameter.

 

[flexible]

Just took the deprimed cases out of the tumbler. sampled almost 20 cases.
Case length 1.485 to 1.488
Outside case mouth: .260 to .261
bullets are lightly touching the lands, extraction is fine.

 

[LHSmith]

Also have you been cleaning the throat area to preclude a carbon ring from forming? Did the problem start AFTER the cases had been loaded several times?

 

[flexible]

Sorry just noticed the question about cleaning and yes SS pins in liquid tumber

 

[LHSmith]

Outside case mouth: .260 to .261

Loaded round measurement is what matters.

 

[flexible]

yes, the cases only have 2 to 3 'generations' on them. The original fireforming and then 1 or 2 reloads

 

[jimmymac]

There could be more than one thing going on here. Are you certain it is truly a 262 neck?

What is the wall thickness of your brass? A good number to shoot for in a 262 neck is .0083 wall thickness to provide enough loaded round clearance using most any 6mm bullet. Are you measuring your loaded round OD with a caliper or a micrometer? Can you take an unsized case and slip a bullet in there by hand? There should be little to no resistance.

Have you compared the dimensions of your freshly fired brass against your sized brass? You could easily have a sizing die problem.

 

[Bill K]

I would guess with your comment of using a rubber hammer to push the bolt closed, this is a AR and you are striking the bolt assist.
AR's need to have the case FL sized, the base of the case and shoulder set back ( you may need a small base die) and the cases trimmed to specs to function without a hitch in feeding and chambering.
And make sure you necks are trimmed also to fit your neck/chamber area with a seated bullet.

 

[Bronsin]

Take 3 fired cases and send them to Harrell's to get the correct sizing die for your chamber, That Redding die isn't cutting it.

 

[flexible]

Nope, not an AR; it's a bolt.
I'll mesure the neck wall thickness later today.
I'll try seating a bullet by hand.
It's driving me crazy because 70% of the rounds i loaded functioned perfectly.
I did a visual inspection of the chamber but I'll use a chamber brush later.
Crazy thought, since it's charge of 29 grains of N133, could that be 'slightly' stopping the bullet from seating as deep as the dummy rounds?

 

[flexible]

I had my custom Whidden dies delivered 2 days ago but haven't had time to set them up.
I've got to come up with a set of fixes, like:
1. set up the Whidden dies
2. measure every step of the way
3. makes lots of runs to the range before it gets too cold.

 

[Schippergreg]

Stop tumbling in ss pins. You’re probably penning the necks. Take a case and re chamfer and debur it. Then seat a bullet and get an accurate measurement of the loaded neck diameter.

 

[TIMO]

I never tumble my bench rest brass, I do plenty of other rifle brass with SS pins, though. I can see where peening may result if left in too long during the process, never heard of case necks growing or any ill affect from the SS pins other than some getting stuck in the flash hole and all the carbon is removed from the inside of the case neck. For the particular rifles or pistols that I tumble the brass in SS pins or media I full length size after that process prior to loading so I guess I don't see any growth, but I also do a cursory inside and outside chamfer as needed and check overall case length.

Just my .02

Tim

 

[flexible]

might have found the culprit, just measured the overall length and it was 2.2, definitely on the long side.
No idea how that crept upwards.
I'll do some more work.
thanks

 

[LHSmith]

You do your COAL measurements with a tool that measures to the ogive? Right?

 

[flexible]

Hornady Lock & Load, use a bullet comparator too

 

[Jefferson]

also the base might need a better resizing die

 

[Eric Leonard]

If the sized brass chambers easy then it won’t with a bullet seated it sounds like a neck clearance issue