prvi priming problem

you are looking at the wrong tool to fix the percived problem.
you need a primer pocket UNIFORMER...non adjustable...sinclair

you can radius the mouth of the pocket with a bunch of tools the most practical are crimp removal tools the ad a nice radius to the top of the pocket.


grahame said:
what I'm going to try is to chuck my RCBS pocket reamer into my mini lathe and then Dremel the face a little...hopefully this will dig into the radius at the base of the pocket. i.e to remove some of the tool chamfer.....it will taper more of the mouth of course...grahame
Click to expand...
 
The Op may have 2 issues with his military brass.

First, the primer pocket might be too much conical, second, the primer pocket bottom radius might be important, both making thet he can't seat properly.


One must remember that a primer pocket is put in shape by the hammering of a punch while the exterior of the case is in a fixed and adjusted volume defined by an exterior matrix and a drawing punch at dead center in the inside. The punch guide fully close the volume the the punch hit the raw case. Brass is pushed away from the punch and finish the case head by filling the volume allowed by the tools.

To remove that punch (forming the primer pocket and finishing the case head in a fixed volume) (therefore with a very high material pressure), the punch HAS TO be conical and with a round edge to limit wear and help material to flow. The more angle, the lower the effort on the punch, the easier to eject the punch, the higher cycling rate of manufacturing.

Keep in mind military ammo manufacturers use priming machines that push an enormous lot on the primer cup to force it into the primer pocket. The more "cup swagging" into the (conical) primer cup, the more sealing against immersion without varnish. Please notice that as long as the mixture is not stressed in between anvil and cup it won't bang.

(if the drawn raw case is to thick at the head, the primer pocket will not be deep enough, so primer WILL 150% bang at the priming machine)


As far as I know of, primer pocket uniformers are "only" 1 cut mill bit. They are not designed to cut on side to change the cone into a cylinder. Even using a drill press can be a PITA to correct this issue with the various uniformers I own.

Hope this help.
 
"As far as I know of, primer pocket uniformers are "only" 1 cut mill bit. They are not designed to cut on side to change the cone into a cylinder. Even using a drill press can be a PITA to correct this issue with the various uniformers I own."
being a straight end mill config they will cut the sides if smaller than the tool
 
rsmithsr said:
"As far as I know of, primer pocket uniformers are "only" 1 cut mill bit. They are not designed to cut on side to change the cone into a cylinder. Even using a drill press can be a PITA to correct this issue with the various uniformers I own."
being a straight end mill config they will cut the sides if smaller than the tool
Click to expand...


Mines do not.

In case of too much conical shape of the primer pocket, which SHALL be corrected because of very hard priming or impossible priming with my tooling, all my uniformers do get stuck inside the pocket one depth or another, whatever the rpm, lube and feed speed.

No pressure screw ever handled the torque (ie old sinclair hexagon bar, 2 carbide bits, pressure screws). I had to go with bigger, shouldered carbide bits direct in chuck. Still a PITA on the brass handling side.

Furthermore, as these cutting tools are "free fingers/hand use" , I mean they have no guidance to keep milling end on axis with the primer pocket, one would, after many use, should the bits also cut on side, enlarge the normal primer pocket on a regular basis.

Once again, with my tools, that did not occur even on training cases that have seen hundreds of shots ... and cleaning.

Just gave a look with a magnifier, there is no sharpening on the side, no cutting edge, no clearance angle. Mines can't cut on side. And they get stuck.

I am very interested in the brands /models you own that are ALSO cutting on the side. Here, just having a mill bit ground to specific diameter is already $$$$$$$$$.
 
I solved my problem...it was the small radius at the bottom of the primer hole that was causing the bulged or not seated enough primer....But first , I measured my #34 CCI primers at an average over ten primers at 0.126"....I found on Accurateshooter.com an table giving primer thicknesses of : CCI .118" , Fed .118" and .117" , Rem at .119" and lastly Win at .121" i.e all a bit thiner than my #34...I think this tells me that (if) the Rad at the primer hole is a bit generous , then seating the .126" primer is going to be a challenge. So , I put my RCBS primer pocket reamer in my mini lathe and using my Dremel i removed the chamfer off the nose of the tool....i.e it now has 90 degree edges to the cutting bits...i tried it out on some new prvi and it works...primers now seat fully. Grahame
 
I have done some measuring and fixing of my problem...I measured my primer pocket depth to exactly .130" I then measured 10 of my CCI #34 primers for seating depth , they varied in thickness from .1259 to 1.270"...since i cannot get my primer to seat fully i think to radius at the bottom of the pocket is the issue...So , I put my RCBC primer pocket trimmer in my laithe and spun it up and using my dremel / cutting disc i removed the nose chamfer off the trimmer i.e now a 90 deg nose....retrimmed the prvi and now I can prime perfectly.
 
I forget to say that I found a table under Accuratshooter.com that gave some dimensions of other makes of primers :: CC! .118" , Fed .118 and .117" Rem .119" and win .121". grahame
 
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