How important is primer pocket uniforming

[BLS700]

I've never uniformed primer pockets but I'm starting to wonder if i'm missing out. I'm only making hunting rounds now. Is it worth the time to do it?

[mehavey]

For bolt action/hunting precision, not "required"

For gas guns, I initially uniform as a matter of discipline/insurance, and each time thereafter as a mode of pocket cleaning.

Cheap insurance.

[Kayser]

I'm curious about the theory behind doing this for semi-autos. Is it a hedge against primers protruding above the case head, or is there some more voodoo reason? I've always just done a visual inspection of each case (against a bright well-lit background) after priming. It's pretty easy to see when they've got a nice deep seating. I do generally use a pocket cleaner though.

[mehavey]

The three service rifles all have floating firing pins that do bang up against the primer upon bolt closure
(the Garand being the most eye-opening). The farther I can "uniformly" get that primer away from the tip of that pin,
the better I sleep at night.

[hornady]

I am assuming you are talking about the flash hole and not the primer pocket.
For hunting in Pa, I would not waste my time with the flash hole. If thinking about getting into long distance match shooting, flash hole uniforming is one of many steps in producing extremely accurate rounds.

If indeed you are talking about the Primer pockets. I swag the pockets of any brass that may have a military crimped primer with the RCBS swag die. It is much more uniform than the burring type tools. If a primer pocket becomes over size over time there is not much you can do but throw the brass out.

[farmerboy]

most people believe for hunting rounds dont worry, for myself anything and everything I can do to make each and every round be uniform and ignite the same and get the most accurate round possible whether hunting, competition are just plinking I say to do it. Remember what youre really plinking for anyhow and if not accuracy you may as well shoot blind folded!!!

[temmi]

Given I do it for every rifle round I loade and have for 10 years...

I agree with mehavey.

But I still like to do it.

[Tim R]

If you are using comm brass, I have found the primer pockets to be pretty uniform. GI brass is another situation. I shoot three calibers in competition. '06, 308 and 223 which are shot in service rifles. I shoot GI brass, mostly Lake City and have found it is worth my time to uniform the primer pockets. I have some '06 and 308 L/C match brass and these seem to have pretty good and uniform pockets. Not so much with ball ammo brass.

[wncchester]

"Is it worth the time to (uniform primer pockets) it? "

It's a BR technique and some people seem to think that makes it a gold standard for accuracy but not me. Anyone who thinks reducing groups maybe 15 thou at 100 yards would be great should go for it tho.

[Unclenick]

Just to review the terminology, you can uniform primer pocket depth, uniform a primer pocket profile, and uniform the primer pocket vent (flash hole). In the common vernacular, only the first one is normally called primer pocket uniforming. The second is usually called primer pocket reaming or swaging, while the third is usually referred to as flash hole reaming. A fourth thing often done is flash hole deburring on the inside of the case, but that's on the other side of the web from the primer pocket.

Primer pocket depth uniforming is done with an end cutting tool that removes brass from the floor of the primer pocket around the vent. It doesn't cut the sides of the pocket or remove crimps. All it is concerned with is making the pockets uniformly deep. For the service rifles that is, indeed, creating a safety margin against slamfires.

For benchrest, primer pocket depth is uniformed on the theory that it makes the firing pin strikes more uniform, which does affect speed of ignition. Outside of benchrest, one is hard put to see the difference a few thousandths of pin strike depth makes.

Much more important for accuracy is that you be able to set the bridge in the primer. The bridge is the thickness of priming mix between the tip of the primer's anvil (that little inverted tripod you see looking at the business end of a primer) and the inside bottom of the primer cup. Federal says, first seat the primer until you just feel the anvil legs touch the bottom of the pocket. Then, for large primers the cup should be pressed in 0.003" deeper to correctly set the bridge. For small primers it is 0.002" deeper.

Setting the bridge to that specification will insure rapid ignition that is uniform shot to shot. Without it, ignition delays of tens of milliseconds can sometimes occur, and that's enough to let movement from trigger pressing, muscle contractions on the stock, and firing pin strike vibration to move the muzzle further off target before the bullet exits.

If you uniform your primer pocket depths, you set up a situation in which just one standard measurement tells you whether or not you have correctly set the bridge. Typically, primer touchdown occurs when the primer is about flush to 0.002" below flush with the outside bottom of the casehead. So, a correctly set bridge will have the primer 0.003-0.005" below flush. You can measure this with a depth mic or the depth probe on a caliper.

If you uniform your primer pockets, 0.005" is what you should strive for, while unmodified cases should average 0.004", which is what the primer seating tool built into the Forster Co-ax press produces. It's the only primer seating tool I know of that fixes primer depth. K&M also produces a tool that lets you feel touchdown, then has a dial indicator that lets you see how much further you are pushing the primer in to set the bridge. Slow going, but it makes uniforming primer pocket depth unnecessary if you have a bolt gun that isn't benchrest accurate.

[Ideal Tool]

Hello, everyone. I have been using the solid carbide Whotetail uniformer for both large and small pockets since the early 90's. Now, not every firearm I use these cases in is anywhere near benchrest accurate. However, this is what I have found: Cleaning pockets is very easy once it has been uniformed..simply twist tool and pocket is spotless. But an even more important benifit..It seems no matter how light a load, just about every time I clean the pockets. I am cutting brass..Now my tool has a built-in stop..it only cuts so far and nothing more..yet I am nearly always removing brass..firing pressure must be causing this brass to flow into case-web thickining and causing pocket to become shallower. My point being..if your not uniforming..how do you know just how deep your pockets are? As mentioned above, this is a concern with semi-auto loads.

[BLS700]

awesome post from unclenick. I'm referring to uniforming seating depth. I do flash hole deburring now. I'm shooting commercial (in this case) Win brass for a 30 06 fired out of a Thompson Prohunter.

[Steve in PA]

I do it for my hunting rounds. I am trying to reload the most accurate ammo I can, so why not do it??

[Sarge]

I've loaded a bucket of .223 & 30-06 for various autos (Rem 7400, Mini 14), some of it very accurate, and I've never encountered a problem. Used military brass on occasion, too. I don't fiddle with primer pockets or flash holes; don't reckon I'll start now.

[edward5759]

I shot a lot of bench rest and service rifle in the past.
I personalty like to uniform the primer pockets, for my own personal rifles.
When they make a flash hole, it ts not drilled into the case! It is punched. in the past like in the 1960s and 70s I would run into a lot that would still have the punch divit left behind on the inside of the case.
So I got in the habit of flash hole deburring on the inside of the case. and drilling a slightly larger flash hole.
I did it Just some us did it because we were after that elusive
.001 in the groups.

My wife says " When I was born I had a dull expression, no personalty and no humor and that is why I became an Engineer and Bench Rest shooter.

Edward5759

[Unclenick]

Edward5759,

Lake City flash holes are drilled. It's part of the mil spec. Norma advertising also boasts of drilling flash holes on their match brass (as well as lathe turning the extractor grooves). I think it's supposed to produce a more uniform diameter and eliminate that punch divot, but when you look in LC primer pockets you also see flash holes a lot further off-center than punched holes ever seem to be. And they still have plenty of drilling burr around the inside of the hole. I notice Fiocchi also produces a lot of pretty far off-center flash holes, so perhaps they are drilling, too. Norma seems to have figured out how to keep the drill centered.


Ideal Tool,

The web, according to SAAMI's on-line glossary, is just that portion of the brass which is the partition between the bottom of the primer pocket and the inside of the case. A lot of folks refer to the whole solid part of the head as the web, but if we stick with SAAMI's definition, then yes, pressure does push the web back into the pocket some. It also gradually flattens the whole head. I've had lower pressure .45 ACP cases make it through 50 reloads, and the legibility of the headstamp gets vague toward the end. The brass gradually flows into the lettering.

So, I don't know how much of your retrimming is finding brass from the whole head flowing back and how much is doming of the web. I suspect it's mostly the latter. It should be higher at the center than in the corners, where the anvil touches down, so I don't know how much it affects setting the bridge. It would make a good project to measure the effect over a known reloading history in a set of cases you clean in an ultrasonic rather than by recutting. You could get the center height of the dome with a depth mic (at least, a large primer pocket accommodates mine, but not a small one). But it's probably best to measure the actual touchdown height of primers and see how the average changes over time. That would tell you what's actually happening to the primer anvil position.

[4runnerman]

Plus one for Unclenick also. I do uniform also every time i reload. It is just a step in the process like farmerboy stated. I also trim,clean flash hole, chamfer inside and out. It is the proper way to do things. Anal ??? Maybe but every little step adds a percentage of accuracy to your shooting. Or like farmerboy (smart Guy) say put a blind fold on and just squeeze trigger. Plinking or bench shooting ,,you are still trying to hit something ,so try hitting it the best you can,,,Right????...

[BLS700]

Yeah I'm going to start. It won't add much and will make me feel better to know I didn't leave a step out from laziness and wanting to save a few bucks on buying the tool. Which leads to my next question then...which tool are you using?

[farmerboy]

I think most shooters, its a waste of time really. I know of alot if they can hit a pie plate at 100 yards they are happy and no need to stive for any better, Alot of people only shoot about 10 rounds a year and so precision is not their thing but for say a bench rest shooter or an individual such as myself who stives for the utmost in everything I do, Id say do all you can and leave nothing undone. Just my two cents but really to MOST it is a waste of time,

[Ideal Tool]

Hello, Unclenick. Yes I was refering to the portion between bottom of inside case & primer pocket bottom. I find this brass flow even in .22 Hornet cast-bullet loads..so even with this low presure it still flows. As to being high in center..it usually is near edges & rarely uniform..and not all cases show this at same time.

[Unclenick]

Interesting. It suggests you're seeing more overall head flow than actual web movement. Perhaps the gas flow through the vent is enough to protect it in most instances. I'm also wondering if having a lot of harder military brass has affected what I see. I'm using the Neil Jones tool, but the profile of the cutter is like your Whitetail, AFAIK.

[Slamfire]

The three service rifles all have floating firing pins that do bang up against the primer upon bolt closure (the Garand being the most eye-opening). The farther I can "uniformly" get that primer away from the tip of that pin, the better I sleep at night

That's why I ream my gas gun ammunition. Don't want any high primers.

For bolt guns, won't make a different.

One bud of mine, a NRA Camp Perry Long Range champ, he never cleaned his primer pockets. As for brass prep, he said, "load them and shoot them".

I have another bud, a F Class Champ, he always does the hoo-doo on his cases. I have some of his targets he shot with LC match, in my opinion he shoots equally well either way, but if he did not do the hoo-doo on his reloads, it would make a difference in his head.

[GWS]

Actually, there is another important reason to uniform primer pockets. I don't know about other progressives, but the RCBS Pro 2000 that I use, has a primer seater stop, that allows seating the primers exactly the same depth on each case.....it works....if you uniform the primer pocket depth on every case as a part of case preparation to make that possible. Easy on a Trim Mate or equivalent.

[murphjup]

Well I got my Sinclair Uniformer and I can tell you that my Hornady Brass 22-250 takes quite a few turns to bottom out the uniformer....

I had a problem with seating depth, the primers where not seating far enough...

Is this pretty normal the first time you uniform the pockets? It sure does look pretty when it's done...

Thanks all !!

[Unclenick]

Yes. Some of them can take quite a bit of elbow grease. Also, you'll find a small corner radius in the bottoms of the pockets, and the cutter takes that out, too. My Neil Jones tool has a hand crank, but even that can take awhile on some brass. I've also chucked other brands in my drill press, but that produced some edge chipping of the carbide cutter, so I decided a steel cutter would have been better for that rotation speed. A electric screw driver is probably slow enough.