Primer Pocket Problems?
Introduction - Priming Tool Problems
Here at the V Shop, we handle a lot of reloading equipment. We speak to many enthusiasts across all shooting disciplines. Our customers are generally very keen and do an awful lot of research. Priming tools are extremely popular as shooters are looking to increase consistency and rapidity without sacrificing safety.
We have only had two priming tools returned. The first one was a very inexpensive, low end tool and it was no surprise. Too many plastic components in critical areas. We no longer stock that priming tool. The second however, was an RCBS Automatic Priming Tool 9460. Considering how many we have sold and how happy customers are with the tool this came as a shock. We sell a lot of these and would sell more if we could get stock. This is a robust tool designed for the loader who has hit some volume issues and needs to the speed of their priming process. The buyer initiating the return complained that his results using the tool were inconsistent, with some primers seating perfectly, but others not completely seating. We processed the return and carried on. Was this truly the end of the story, or just the beginning?
Primer Pocket Cut Too Deep
Last month, I was processing a large lot of RWS brass for research into another V Shop article that will appear on the site in a month or two. A part of the case prep, I was using a trusty Sinclair Primer Pocket Uniforming Tool. I use the tool to lightly clean and square up primer pockets. I usually do not take off much brass during this process, mostly just primer crud. I have done this for many years for my TR and MR ammunition and it is just a habit. I was several hundred RWS cases into the batch. I grabbed the next case, inserted my uniforming tool, and gave it a twist. Nothing happened. I repeated the process and I still had no contact with the bottom of the primer pocket. None at all. Miles away. Not even close.
I started to examine the case more thoroughly. Then I saw it. The head-stamp read PPU. Somehow, a single PPU case had been included in the RWS batch. Now I do not know the exact dimensions of the Sinclair Primer Pocket Uniformer, but it has to be between SAAMI min and SAAMI max. The PPU brass was well over. I tossed the case in the bin, following my first instinct. What I should have done in hindsight is first measured how deep that primer pocket was cut. I am sure that CIP dimensions are close to SAAMI because theoretically shooters switch between European and American primers all the time.
Perhaps they should stop doing that.
Pay Attention to Your Primer Pockets and Primer Dimensions
Last year, I met an F Class Shooter on Century at the 600 Yard Point. He had a fine pair of 260 Remington Rifles with matched glass and matched stocks. They appeared to be very well built rifles. This gentleman had a nice set up. We started talking about Peterson Brass as you do. I had just taken delivery of my first batch of Peterson Brass and was very keen to talk to anyone about it.
The gentleman informed me of the typical depth of the Peterson Primer Pocket to the thousandth of an inch, and then went on to tell me that not all batches of his favourite primer were not ‘tall’ enough to work properly in Peterson Brass. Of course we all of know the height of our primers, and the depth of our pockets batch by batch. How else could we ever get 1/4 minute groups?
I explained that I only uniformed my pockets using a fixed tool. The F Class Shooter cut his primer pockets to uniform depth with an adjustable tool so that they were compatible with the batch of primers he was working with, then seated accordingly. I don’t do this for TR, but may consider it for 1200 Yard MR ammunition in the future.
Not Enough Information to Draw a Conclusion
When the priming tools were returned, I focused on the Customer Service aspect and promptly processed refunds. These sales were made on Amazon and e-bay, where customer communication is restricted. In hindsight, I should have asked specifically what Primer/Case combination was causing the problem, and I would do this for any customer who just reached out and asked.
My suspicion is that due to component shortages, and high prices, shooters are not able to obtain their old favourites and are driven to alternative brands. Due to the variance in tolerances across manufacturers, some incompatible combinations are going to be encountered.
I cannot be sure, but I think that it may be possible the customers experiencing the problems with the priming tools were encountering these combinations.
If you are going to be using a ‘new’ primer/case combination, please hand seat the first few primers so that you get a feel for the relationship between this components. To do this properly, you will need a hand priming tool with enough depth capability. The tool should give enough ‘feel’ to allow you to determine when you have managed to seat the primer. You could also use one of the hand priming devices which have a built in dial indicator, if you can find one. In the case of the second customer return, I suspect that the RCBS tool was too ‘precise’ to actually seat and was limited to max SAAMI depth to avoid crushing primers and making the priming process unsafe.
Even if you are not trying to compete against the fellow next to you getting 1/4 minute groups, take a moment to think about where your primer is in relation to your firing pin and how you can ensure that this dimension is correct and as consistent as possible from round to round.
Testing by F Class Shooters Shows Primer Seating is More Important Than Once Thought
Too achieve consistent powder ignition, and therefore velocity, it makes sense that the primer flash should be as consistent from shot to shot. First, are the primers in a batch all more or less the same? Second, is the force at which the primer is hit by the firing pin the same from shot to shot? Third, is the primer seated properly? Fourth, is the primer pocket in the batch of cases all the same?
At first, we were all happy if a round went bang. Then we wanted an entire box to go bang. Then we started to think about how most of our loaded rounds would go into a group and there would only be a few flyers. Now, we want them all in the middle.
If you are shooting bottleneck cases like the 308 Winchester, the case will be resting on the shoulder (or some point near there) when the firing pin hits the primer. There are a few factors that can effect this distance. If the cases are not consistently sized, the distance from the firing pin to the primer could vary from round to round. If the primer pockets in the batch of cases are not all the same depth, then even if the primer is seated correctly (just touching, no crush) the force from the firing pin hit will not be consistent from round to round. This won’t help your SD’s.
If you are shooting a rimmed case like the 303 British, you are in another world. Unless you have adjusted your loading technique to headspace at the shoulder, you will probably be counting on head space at the rim. The distance from the top of the rim to the bottom of the primer pocket is important if you are trying to get consistent firing pin hits. There is no easy way to change this. Using a primer pocket uniforming tool might work if your rim thicknesses were consistent, as the tool indexes from the bottom of the rim.
The easiest way to achieve consistency is to use good brass if you can get it. New thinking seems to put primer pocket uniforming out of favour. I do it out of habit, but some say that it is unlikely to leave a square flat surface at the bottom of the primer pocket. The new thinking is essentially to get good brass with uniform pockets in the first place.
Some F Class Shooters, like the fellow that spoke to me, measure their primers when they get a new batch. I suspect some sort through their primers by weight as well using a good scale. If you know the depth of your primer pocket and the height of your primer, then you will theoretically know how deep the primer should be when it is seated. This can be a good quality control check (look for high ones or low ones).
So, use good brass and good primers when you can. If you do this, many of your variables will be sufficiently controlled so that you don’t have to worry about them, and making great ammunition will be much easier. Good brass is more expensive, but requires less time to prepare and can last longer. Case weights and primer pockets are more consistent as an added bonus.
If for some reason you have trouble finding quality products and have to make do, spend the time to learn what you are working with. Do a bit of measuring and have a think. Don’t try and seat a short primer in a deep pocket…
Good Luck and Good Shooting