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Slightly loose fitting primer pockets

kelbro

Silver $$ Contributor
Has anybody been noticed or been able to measure a variance in load performance when using brass with slightly loose primer pockets? I'm not talking about primers that you can push in with your thumb :).

Quite often I'll notice that some primers seat much easier than the rest of the batch. I haven't really tracked them to see if that variance shows up on target.

I hate to toss good cases but I also prefer to keep my loads as consistent as possible.
 
For the pockets to be loose, means the base is stretched from running with too high pressure.

As to wether or not ... it needs to be tested.

Mark the 'loose' ones, put them aside. Load a batch from the 'loose' and from the normal, and let the target tell you.

I'm no expert, but a looser pocket should make zero difference to anything, assuming that you full length size so that the case volumes remain the same. That primer is held in place by the bolt face on ignition, and will only drop out after firing when the pocket has been stretched too much to hold it.

More important is to fiigure out why some are stretched and some not, so you can avoid the stretched condition.

Maybe you ran a test with an over-pressure load, and didn't notice it because you were only looking at the primer which looked ok.

I've read about White River primers being a bit more difficult to seat, that suggests they are microscopically larger in diameter, if the 'loose' feel is bothersome.

For me, the 'loose' makes no difference in my reloads in my rifle. I've got some brass in the batch that fired a bit hot in load development, and the primers seat easier in those, but I can't shoot the difference.
 
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With a bolt action, a single primer that is looser than others shouldn't be a big problem because the bolt stops the primer from blowing out. Loosening primers might be useable until you begin to see leaks around the primer after it is fired. However, I tend to take loosening primers as an indication of the brass getting close to it's useful life.
As Big5ifty indicated, if you load close to Pmax, it happens much sooner.

With an AR, loose primers can become a big problem because the bolt moves backward. I had a loose primer pop out and drop into the action. That isn't what you need and it can cause some real problems. If you are shooting a semi, err on the side of caution.
 
Whether or not loose primers caused by expanded primer pockets cause issues on the target are the least of your worries. At some point hot gases are going to start escaping around that loose primer and start etching the bolt face. Replacing brass that has loose primer pockets is far less expensive than replacing a bolt or having said bolt welded up and machined back to spec.
 
When I start feeling a difference in seating pressure, I start checking cases with a go-nogo pocket gage and weed them out. I dont run them hard and use very tight fitting primers so its rare I have to cull brass with oversize pockets
 
You did not mention the primer brand you are running. I will say I was using REM7 1/2 for a long time but currently using CCI450.
I grabbed a couple thousand 7 1/2 last year maybe, used a few and they sure seemed to go it a lot tighter that I recall my prior batch and definitely more tight than the 450's I have. Food for thought.
I like to hand prime so I can feel the pocket/primer. DO not have one of those force pack presses so I do not have empirical date for you.
 
My post was deleted and rightfully so! I learned of this practice years ago and was dumbfounded that anyone would try it, and I should have posted that it was an attempt at being humorous but I did not. I learned of this when hearing of early 1000yd shooters had so much prep time with win mag and ultra mag cases (not Lapua) and it was toast because of loose pockets and they wanted one more firing. We have it so much better now with all the good tough brass that is around!
Sorry Boss!
 
Ironically I just shot my three best ever 100 yard groups with my 20VT using some LC brass that had 8 firings on it and had been marked "LOOSE primer pockets" TRASH by me the last time I loaded it. I was in a hurry, the brass was sitting there, and well...I loaded it again. No issues and all three groups were 4 in a tight touching group and one right next to it or half out. It shocked me. I only have an 18 power on it and for some reason it was shooting amazingly well that day with 40 grain Vmax.
 
kelbro said:
Has anybody been noticed or been able to measure a variance in load performance when using brass with slightly loose primer pockets? I'm not talking about primers that you can push in with your thumb :).

Quite often I'll notice that some primers seat much easier than the rest of the batch. I haven't really tracked them to see if that variance shows up on target.

I hate to toss good cases but I also prefer to keep my loads as consistent as possible.
Click to expand...
I've got some Federal .308 cases with 11 firings on them that I use every so often, and like you mention, some primers seat much easier than others. Since there's no apparent gases leaking onto my bolt face, I'll keep using them until they're just very loose with gas leakage or I start to see case head separation signs. I've not see any related variation in velocity or on POI's with them where they still produce groups under .5 MOA using moderate loads.

I'd say you're good to go until you start to see some gas leakage. IMHO
 
kelbro said:
some primers seat much easier than the rest of the batch
Click to expand...
Not seating the primer straight? OR a variation in primer and/or pocket.
It may take 5 firings, till pockets become loose. Load at or near maximum PSI.
More so if using the same brass to workup the load to maximum.

SAAMI as minimum & maximums of both.
 
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243winxb said:
Not seating the primer straight? OR a variation in primer and/or pocket.
It may take 5 firings, till pockets become loose. Load at or near maximum PSI.
More so if using the same brass to workup the load to maximum.

SAAMI as minimum & maximums of both.
Click to expand...
I need a SAAMI primer pocket go/no-go gauge!
 
Different makes of New Brass can have slightly different size pockets. As can primers be different diameters. This was the very reason I bought a CH trimmer with the chamber style case holders. I can square the base on new brass, then recut the primer pockets to be uniform with the CH primer pocket uniformer. It is a one time prep for my match brass that is then finished preped and fire formed then sorted by the exact same water capacity. It is how I get down to .10 group size area with trued actions with match barrels.
Accuracy comes from consistency in the builds and the consistancy in the loading and each of the components. Never take a label at face value, measure. Just for example, there is only one 30 cal 110 RN bullet that is .308 all the rest are .306 or .307 so check, do not assume just because the box says .308.
 
I took my 30.06 to the range Saturday, the brass is on its last life primer pocket wise but its a hunting rifle so the batch should make it another year or two. I deliberately looked for 5 pieces of brass with very "lose" pockets, found a couple where I couldn't even feel the 21st century priming tool seating the primers.

They shot exactly as good as the other loads, now when looing for the rifle/loads max pressure id say tighter might be better but that was my fault as I knew what was going to happen lol but as said above the the looseness is one thing but as soon as they start leaking its a problem for your hardware.

oops.jpg
 
From the ; "There always has to be one in the Crowd " ! I currently have over forty re-loads on my Practice Brass . They have been shot for the last five years with only Rem 7- 1/2 BR primers . Half and half of 185 Juggs , and 200 Hybrids . A "Moderate" Competition load , keeping the velocity in the 2650 - 2670 range for both bullets . Yeah ; I know . That's a little soft for the 185's , but they shot well there .
After a bunch of research about primers , and primer pocket expansion , I learned that the Unis-Ginex primers were a bit larger in diameter , so as some of my Brass reached that point of no return , I got a pack of the Ginex primers , and then went in like "New Brass"....After some testing , I also learned the change in primers ; to the Ginex , for the "worn-out" pockets , there was also a loss of , on average 40FPS in velocity with the same load set-up . SOoooo.....If you go that route , know you will have to adjust the Load to regain the lost velocity , or just add a few "clicks" "UP" !
But doing this does give you at three or four more firings on those expensive cases , and "PRACTICE" is still Practice !
 
I use the go/no go gauge on my brass as part of my reloading steps. When one sticks to the no go, I put it to the side and then run those through a correction tool made by Henry temple that I have to tighten them back up and usually they last several more firings before retiring them altogether.
 
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