primer pocket question
- Thread starter canuck
- Start date
M
mike in co
Guest
yes and you may find that the depth of the pocket changes as you fire the brass...
4
4 Liberty
Guest
You can use anything that fits without taking any brass off.
M
mike in co
Guest
Boyd Allen
Active member
It is not that it is not desirable, but that given that primers vary in thickness, even if we uniform pocket depth, properly seated primers will vary in depth. Also, how many shooters have actually proven definitively that their accuracy has been improved by uniforming pocket depth? I think that in most cases it is simply a matter of doing everything that is possible to cases in the hopes that accuracy will be improved. Another example would be turning case necks for use in factory chambers. Years ago I tested this, and found no improvement in accuracy. On the other hand, a light cut does no apparent harm, other than increasing an already generous clearance. There are things that do help accuracy, and there are things that are commonly done that IMO do not.
Would flashhole chamfering fall into the don't bother category?
Boyd Allen
Active member
Depends. There was a test of Lapua brass (6BR if memory serves) that indicated that anything done to the flash holes degraded accuracy slightly, but those are drilled holes. For punched holes, that may have various issues at their inside edges, I would definitely chamfer, and make every attempt to do it minimally and uniformly.
With Lapua brass, I found accuracy improved when I stopped flash hole reaming, cutting, or messing with it. The hole is .059" for a reason....
M
mike in co
Guest
the problem i see with some reloaders is failure to seat the primer to the bottom of the primer pocket.
a uniform pocket depth makes it much easier to seat to the bottom of the pocket.
add a small crush and you are done.
if you do not seat to the bottom of the pocket, the firing pin must move the primer to the bottom of the pocket and then ignite the primer...
since it used energy moving the primer to the bottom of the pocket, you have a less uniform ignition.
none of this is new , it has been discussed multiple times.
primer pockets can change depth in use.
if consistency is your goal , then do things that promote consistency.
i seldom see double digit es's
a uniform pocket depth makes it much easier to seat to the bottom of the pocket.
add a small crush and you are done.
if you do not seat to the bottom of the pocket, the firing pin must move the primer to the bottom of the pocket and then ignite the primer...
since it used energy moving the primer to the bottom of the pocket, you have a less uniform ignition.
none of this is new , it has been discussed multiple times.
primer pockets can change depth in use.
if consistency is your goal , then do things that promote consistency.
i seldom see double digit es's
Wayne Shaw
Active member
I use the tool to SQUARE the pocket. The edges have a radius, and I think the pocket should have a square bottom. Usually by the time the tool starts to hit where the flash hole is, I quit. Primers seem to seat better for me.
Lee Martin
Active member
With Lapua brass I never prep the pocket. Instead I use an RCBS primer pocket cleaner to knock out the carbon:
Never had a need to touch the flash hole.
-Lee
www.singleactions.com
Never had a need to touch the flash hole.
-Lee
www.singleactions.com
Well, Lapua brass is expensive for a reason. Actually, compared to most other brass, it's quite expensive. However, it's also the most long lasting and is literally ready to load.
Not so with something like Lake City. Take a look inside the cases sometime. Lapua has a nice flash hole which appears as if it's drilled. Lake City looks like it was shot with a small caliber rifle and there are often large ugly burrs on the inside.
I haven't tested flash hole de-burring alone as it relates to precision groups but I have spent some time fine tuning my cheap brass to include careful trimming, chamfering, flash hole de burring, primer pocket uniforming, annealing, and sizing in attempt to make a silk purse out of a sows ear. There is definitely an improvement in performance with carefully prepared brass but I can't say what percentage (if any) is attributable to improving the flash hole.
I would say it makes sense that a flash hole without a bit ugly burr would better and since it's only an additional two or three seconds time on my case prep machine, I do it with cheap brass. I already have the case in-hand from chamfering so sticking it on the deburring tool for a second or so is no big deal and I only have to do it once.
But, since Lapua is so well made, it's not necessary to dress it up to this extent. And, as you pointed out, messing around with a perfect flash hole is not likely to improve things.
Bottom line: If your flash hole has a big burr, get rid of it. If not, leave it alone. Now you have my two cents.
Doug Casner
New member
Lake City brass
Lake City brass the primer pocket and headstamp was punched into the head by a big horizontal press. Operation called heading. Ran a bunch of them. That was 20 years ago. I don't know what they do now. Doug
Lake City brass the primer pocket and headstamp was punched into the head by a big horizontal press. Operation called heading. Ran a bunch of them. That was 20 years ago. I don't know what they do now. Doug
F
Fretka
Guest
I recently prepped a blue box of Lapua .220 and noticed that the cutter for the flash hole would not spin smoothly indicating some small amount of "punch of drill flash" left over from manufacture. IME it is a step worth doing but YMMV.