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338LM Peterson brass, primer pocket!?

JGSprecision

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I cannot get these primed without crushing.
Uniformed no change, .2085 reamer no change. Depth seams ok. Same primers and priming tool as usual. Never had this issue.
Have tried WMLR (really bad) and CCI250 (not as bad).
Supposed to loosen up after first firing but dunno how to a get a first fire.
 
can chamfer a tad yes a rcbs tool will make a wider chamfer and the lymans have diff angles do some experimentation and find a cure or maybe someone else has an easier idea, I use a chamfer toll for military brass
 
I'm trying adding some chamfer right now.
I have an RCBS swager, the large goes in after reaming but it would press in some chamfer. Does feel like I'm pushing a long bore. WLRM are almost impossible to get flush, worse than CCI.
Too bad because I have alot of them and they added 20fps lol
 
More testing... tried a swage2 tool, absolutely no difference.
Had some S&B once fired, loaded 5 shot 5 same primers same tools.

I'm out of ideas.
 
ebb said:
I would bet Peterson would have more info on what the problem is and how to fix this than the general public. Maybe talking to them would be best.
Click to expand...
That probably would have been the typical path but after trying this/that/reaming/swaging I feel like I signed up for the ride, its completely possible that its something I'm doing wrong.

I did a bunch of pin measurements, these pockets are 0.209 dia x 0.128 deep. So no mater the primer they are of a usable size. I'm having some doubts about my press's ability to get things seated flush (feels like its bottoming out.
That could be be due to my 45-70 shell plate converted to 338LM (because a 338LM doesn't exist), shell plate isn't holding it tight enough to the press. I bought a shell holder for 338LM to use my RCBS bench primer but its MIA :(
I did find a major malfunction and the reason they've been hard to chamber, some dummy seated them 0.060 into the lands (DOH). Bullet comparator and print math got me close but the old jamb test showed I needed some more.
The running theory is I'm crushing not flush primers when chambering. I've pulled bullets on previously seated rounds and the primers have been igniting.

So I have a stack of the corrected bullet seating depth rounds to test.
I've crushed primers- these are not getting that kind of force.
 
Last edited:
And my theory is panning out. Proper seating depth = bolt doesn't crush primer, at least for 1 quick shooting session. I can't seem to get full depth on the press, might be time to see why.
They are extremely close to flush.
 
I have been loading 338 LAP for way over a decade, but have only used Lapua brass. But in the beginning, I had to call RCBS and get a different shell holder. I have loaded the whole time on an RCBS Rock Chucker, it is doable but should be taller. You have to hold the bullet on top of the case mouth and slide them both together in at an angle to get them in the press. All that to say, if you have press issues get one big enough that you don't have to do the angled slide. My mentor eventually got a Redding big boss, or an Ultra mag press I can't remember which so research presses and get one big enough to do the job with out gymnastics involved.
 
ebb said:
I have been loading 338 LAP for way over a decade, but have only used Lapua brass. But in the beginning, I had to call RCBS and get a different shell holder. I have loaded the whole time on an RCBS Rock Chucker, it is doable but should be taller. You have to hold the bullet on top of the case mouth and slide them both together in at an angle to get them in the press. All that to say, if you have press issues get one big enough that you don't have to do the angled slide. My mentor eventually got a Redding big boss, or an Ultra mag press I can't remember which so research presses and get one big enough to do the job with out gymnastics involved.
Click to expand...
My Lee is like that with my 338 edge
I gotta fiddle around when seating Bullets
 
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JGSprecision said:
That probably would have been the typical path but after trying this/that/reaming/swaging I feel like I signed up for the ride, its completely possible that its something I'm doing wrong.

I did a bunch of pin measurements, these pockets are 0.209 dia x 0.128 deep. So no mater the primer they are of a usable size. I'm having some doubts about my press's ability to get things seated flush (feels like its bottoming out.
That could be be due to my 45-70 shell plate converted to 338LM (because a 338LM doesn't exist), shell plate isn't holding it tight enough to the press. I bought a shell holder for 338LM to use my RCBS bench primer but its MIA :(
I did find a major malfunction and the reason they've been hard to chamber, some dummy seated them 0.060 into the lands (DOH). Bullet comparator and print math got me close but the old jamb test showed I needed some more.
The running theory is I'm crushing not flush primers when chambering. I've pulled bullets on previously seated rounds and the primers have been igniting.

So I have a stack of the corrected bullet seating depth rounds to test.
I've crushed primers- these are not getting that kind of force.
Click to expand...
That’s exactly why I have gauge pins for primer pockets and necks.
 
ebb said:
I have been loading 338 LAP for way over a decade, but have only used Lapua brass. But in the beginning, I had to call RCBS and get a different shell holder. I have loaded the whole time on an RCBS Rock Chucker, it is doable but should be taller. You have to hold the bullet on top of the case mouth and slide them both together in at an angle to get them in the press. All that to say, if you have press issues get one big enough that you don't have to do the angled slide. My mentor eventually got a Redding big boss, or an Ultra mag press I can't remember which so research presses and get one big enough to do the job with out gymnastics involved.
Click to expand...
Buying Lapua brass would have saved headache. I ordered a K&M Pocket correction tool, from measuring my 50BMG one it would have fixed my issue with radii in the bottom corner of the pocket.
I'm doing them in a Hornady LNL AP which was never meant to happen. I have 2 50BMG ammomasters here but I really enjoy the LNL AP.
I'm familiar with how to cheat long loads, I like the Hornady seaters with the sliding neck bushing. I slide the bullet in that bushing then get my fingers out of the way right before the neck comes up.
This whole load is budget components setup to break in a new 110 Precision. 1000015468.jpg20250709_193450.jpg20250709_192606.jpg
Using some old Winchester Magnum Rifle powder that seems to work like 4831 but its a super fine ball powder. Midway 250gn seconds SPBT bullets , Not going for any records just a decent working load.
 
SKWERLZ said:
That’s exactly why I have gauge pins for primer pockets and necks.
Click to expand...
Its a great method , time tested!
One needs a precision 0.210 sleeve with a mic body mounted on the back and a selection of pins, then you get a true depth and diameter reading.
 
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