Primer pocket depth

[Lukas_K]

Have encountered this for the first time, would like to hear more experience.

 

After several reloads on SAKO brass, the primers seat deeper and deeper. I uniformed the pockets before the first reloading cycle and only kept cleaning them. Now after 9 reloadings, the primers seat slightly below the brass face (can be felt when you run a finger along the base). Noticed after having a few misfires on the last range trips which I believe to be caused by that.

 

What caused this kind of wear on brass? Can it be prevented? Primers seat tight, they´re just getting below the rim.

[Jagged 77]

I can only surmise as I've never had this particular issue but firstly I'd check how deep you set your primer pocket uniformer, then I'd look at your primer pocket cleaning technique - are you removing any brass? Also how much pressure are you exerting when you seat the primer - if too much you could be crushing them in.

 

One thing I'd suggest you do immediately however is to take one of these cases and section it length ways. After 9 firings you could have caused brass to flow away from the web area (and maybe away from the base where the pocket sits). Even if the primer pockets were ok you should be on the lookout for wear signs in the brass regardless and be prepared to scrap if necessary.

[henryo]

I normally end up seating primers one or two thou deep anyway. It means you can't set the round off by closing the bolt hard. I've never had a problem but you could if you had a short firing pin?

 

Just a few ideas:

 

The rounds that misfired, do they have light strikes?

 

Is the firing pin definitely hitting hard? Bolt doesn't need a clean?

Also sounds silly but if you don't have the bolt completely all the way down it takes the momentum out of the firing pin and (probably) won't fire.

 

I think as Jagged is suggesting excessive headspace would contribute to the problem if you're resizing the body.

 

Are you using standard/weak primers with ball powders (they don't catch as well) in cold conditions?

[Lukas_K]

I believe I´ve eliminated other suggested causes. These primer pockets are simply deeper by almost .5mm in some cases as compared to freshly prepped (1x fired factory) cases. I´m scrapping these 100 cases anyway - talking .308W here, so that´s no big deal.

 

I´ve cleaned the pockets after each firing with a brush, and the cases were annealed after every 2nd firing. I just thought they would last longer, and that when they would start to fail... let them split the necks, loosen the primer pocket so the don´t actually hold the primer, but this was the last thing I expected.

[henryo]

.5mm is almost 20 thou that's crazy

 

BTW I find that if you are using an RCBS primer pocket brush it does take material out of the brass. The uniformer is better as it has a stop so shouldn't cut further than any rubbish.

 

Personally I use the uniformer the once and then an ultrasonic clean is good enough

 

All the best

H

[Lukas_K]

Thanks for tht advice, I´ll probably change my cleaning routine for this next batch of brass and see how that goes.