Question on primer seating depths

[Plecotus]

I've now broken my reloading cherry and am seeing some success, albeit with new Lapua Palma brass in .308. I've just prepared some GGG .308 brass and have a question about primer seating depths.

My method has been: Clean cases>>>remove primer crimp using a countersink>>>>>>>apply a K&M primer uniformer>>>>>>size cases>>>>>>>insert primer (CCI 250) using a handheld Lee New Autoprime.

I've primed a few cases but the primers seem to be seated much deeper in the pockets than they should be...around .009 - .0012" from the top of the primer to the case head. This seems too deep to me. Am I correct in thinking that this is too deep and wondering if I've crushed the primers against the bottom of the pocket? I'm tempted to de-prime and take a look at them but thinking that in de-priming, I might crush them anyway so I wouldn't know whether it was inserting or removing them that's the problem.

Any thoughts most welcome.

[Maggot]

I've now broken my reloading cherry and am seeing some success, albeit with new Lapua Palma brass in .308. I've just prepared some GGG .308 brass and have a question about primer seating depths.

My method has been: Clean cases>>>remove primer crimp using a countersink>>>>>>>apply a K&M primer uniformer>>>>>>size cases>>>>>>>insert primer (CCI 250) using a handheld Lee New Autoprime.

I've primed a few cases but the primers seem to be seated much deeper in the pockets than they should be...around .009 - .0012" from the top of the primer to the case head. This seems too deep to me. Am I correct in thinking that this is too deep and wondering if I've crushed the primers against the bottom of the pocket? I'm tempted to de-prime and take a look at them but thinking that in de-priming, I might crush them anyway so I wouldn't know whether it was inserting or removing them that's the problem.

Any thoughts most welcome.

I think you might have felt them being crushed and the primer seater should not normally push them too far. Neither should the pocket uniformer go deeper than you need unless its collar has slipped. Often the way you find out about this is with a light strike but never say never. Check the setting on your uniformer chap.

[rox]

This seems too deep to me. Am I correct in thinking that this is too deep and wondering if I've crushed the primers against the bottom of the pocket?

I see about 0.011" to 0.012" below flush with Murom primers in GGG Imperial pockets that are swaged only. About 5k like this have functioned flawlessly. Oddly enough the same primers in GGG commercial brass sit about 0.0045" below flush, so it seems that the Imperial pockets are deeper - perhaps GGGs primer cups are deeper too.

Unfired primers in GGG Imperial ammo also sit at about 0.0045" below flush, but they don't appear to be bottomed-out, so will seat to 0.007" or 0.008".

Based on my experience (about 5k rounds) your primers are bottomed-out and not crushed. Everything is as it should be - they should function reliably and be a good basis for excellent ammunition.

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[Plecotus]

That's really useful. Thanks guys. I think I need to get a bit more practice with th "feel" of the correct seating depth. Out of interest, rox, do you know the depth of the pockets on your GGG brass and the thickness of the Murom primers? I think I remember reading somewhere that some Murom primers were quite a bit thinner than their CCI equivalents.

[Mattnall]

Does it still go bang? = no problem.

[rox]

That's really useful. Thanks guys. I think I need to get a bit more practice with th "feel" of the correct seating depth. Out of interest, rox, do you know the depth of the pockets on your GGG brass and the thickness of the Murom primers? I think I remember reading somewhere that some Murom primers were quite a bit thinner than their CCI equivalents.

0.1300" Depth of primer pocket (GGG 'Imperial').

0.125" Height of Murom Primer (before seating).
0.011" Depth of seated Murom primer below flush.
0.120" Height of Murom Primer (after seating - deprimed).

The Murom primer has quite a curved cup which can flatten during firm seating, hence the difference in height. You can see it in the photo below (left is a new, unseated primer, right is one that was seated and de-primed).

Now, the interesting thing was that the pocket of once-fired GGG Commercial was also 0.130" deep - backing-up my previous comparisons which suggested that there was no difference between the two apart from the headstamp. I'm therefore not sure why the primers appeared to seat so much shallower. I've verified they are bottomed out and re-applied similar seating force in case the cup had sprung-back, but still only saw 0.007" below flush compared with 0.011" in Imperial. Suspecting that the Imperial crimp (swaged not cut) could be causing a difference in reading the face of the case head, I've just cut it out to remove any burr, but I still see around 0.010" to 0.011" below flush.

Anyway, as Mattnall says, if they go bang, and are bottomed-out, they'll work great. That's been my experience anyway.



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[Pete]

Squeeze gently until it stops............

Pete

[Plecotus]

Hi Folks,

Sorry for the late reply. Work got in the way of a lot of things and a family bereavement hasn't helped either. I think I have the hang of this now. I do think I have the feel of correct seating depth and checking a random sample of my loads, primers are consistently around .003 below the case head. I'm getting single digit SDs now too so I think it's all coming together.

Thank you for all the advice. It really is much appreciated.

[snayperskaya]

That's really useful. Thanks guys. I think I need to get a bit more practice with th "feel" of the correct seating depth. Out of interest, rox, do you know the depth of the pockets on your GGG brass and the thickness of the Murom primers? I think I remember reading somewhere that some Murom primers were quite a bit thinner than their CCI equivalents.

0.1300" Depth of primer pocket (GGG 'Imperial').

0.125" Height of Murom Primer (before seating).
0.011" Depth of seated Murom primer below flush.
0.120" Height of Murom Primer (after seating - deprimed).

The Murom primer has quite a curved cup which can flatten during firm seating, hence the difference in height. You can see it in the photo below (left is a new, unseated primer, right is one that was seated and de-primed).

Now, the interesting thing was that the pocket of once-fired GGG Commercial was also 0.130" deep - backing-up my previous comparisons which suggested that there was no difference between the two apart from the headstamp. I'm therefore not sure why the primers appeared to seat so much shallower. I've verified they are bottomed out and re-applied similar seating force in case the cup had sprung-back, but still only saw 0.007" below flush compared with 0.011" in Imperial. Suspecting that the Imperial crimp (swaged not cut) could be causing a difference in reading the face of the case head, I've just cut it out to remove any burr, but I still see around 0.010" to 0.011" below flush.

Anyway, as Mattnall says, if they go bang, and are bottomed-out, they'll work great. That's been my experience anyway.



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I used Murom primers in some PPU 7.62x54r cases the other day and some appeared to be seated very deep and on measuring the height of some of the unseated primers there was some that measured 0.118", I measured those in another pack and they were all 0.125" high so must have been a few that slipped in somehow.

The problem I'm having is really shallow primer pockets in some once fired Sellier and Bellot 54r brass I've got, even with Sellier and Bellot primers I can't get the primer below flush and some I tried were proud.I think I need to set about them with a primer pocket uniformer as the pockets only seem to be around 0.122" deep.

[Maggot]

Bin murom and use Magtech