Primer Seating

[AzMandella]

So being a newby I have been experimenting on primer seating . I purchased the PMA hand seater and really like it . Since I have not set up my reloading room , still drywalling and installing benchtops , I purchase a wilson decaping punch and base . So I decapped some 223 shells carefully so I could reseat the primers with the PMA tool . Question I have is when seating by feel are feeling for when the anvils touch or when the cup touches the bottom of the primer pocket ? Seems when the cup touches I get the primers about .004 below the rim . I am also using a primer pocket uniformer before seating the spent primers .

 

[mikecr]

Ideally, you would touch anvil to pocket bottom and then preload an additional 2-4thou(crush).
With uniformed pockets this should put cups at or below case head. If you don't provide this sensitizing, or if you over-crush to squish priming compound from between anvil/cup, you can hurt reliable & consistent firing.

Your tool is adjustable and sensitive to contact of anvil to pocket bottom. Or so you think.
You could measure a bunch of primers for unseated/loose height and group them.
Then you could take measurements of touch -vs- touch +.002", creeping into tool setting.

The ONLY tool that directly sets primers at desired crush is the indicated K&M.

 

[Caveman Jim]

Ideally, you would touch anvil to pocket bottom and then preload an additional 2-4thou(crush).
With uniformed pockets this should put cups at or below case head. If you don't provide this sensitizing, or if you over-crush to squish priming compound from between anvil/cup, you can hurt reliable & consistent firing.

Your tool is adjustable and sensitive to contact of anvil to pocket bottom. Or so you think.
You could measure a bunch of primers for unseated/loose height and group them.
Then you could take measurements of touch -vs- touch +.002", creeping into tool setting.

The ONLY tool that directly sets primers at desired crush is the indicated K&M.

I have a K&M precision primer seater, they are amazingly precise.

 

[wkdickinson]

Can you honestly attribute better scores to precise primer seating depth?

 

[Alex Wheeler]

Can you honestly attribute better scores to precise primer seating depth?

Rifle accuracy is based on groups not scores. Score shooters tune their rifles by shooting groups. It all revolves around groups. And yes, you can effect the groups size with the primer seating. Your scores will most likely come down to you wind calls more than primer seating. But scores are a poor way of determining the accuracy or a rifle.

 

[J.d. Popkes]

What was the post count last time we debated this?

some say they go by feel and they can feel half thou differences. Some say it doesn’t matter. Some (me), are interested in testing with primal rights CPS. Some have done great testing with conclusive results. Some people shoot 100 yards and some people 1000+, so that’s probably gonna matter.

I think it’s up to the individual, the type of shooting, the hassle they’re willing to put up with, and what that individuals tests show.

at least that’s what I remember

 

[BoydAllen]

I believe the guys that shoot the best, one of them is a bullet maker by the name of Sauter. You may have heard of him. He tested this with his rail and said that as long as the primer was bottomed in the pocket the results were good. At short range, I will take his word over just about anyone else's Also, I wonder what the shooting records of those are that claim otherwise. Seating by feel, my primers are a lot deeper (in un uniformed Lapua .220 brass than the deepest in the test that was linked to. One of the things that is not often considered is the available energy from the striker assembly. Many of the best short range competition actions have been known to be right on the edge, to the extent that working on this part of the most popular action had become somewhat of a cottage industry. My point is that if the firing pin has to do the work of finishing the seating of the primer, that energy is not available for crushing the pellet on the anvil. Be careful what and who you believe. Look at their actual shooting record. There is a LOT of bs on the internet.
Added a little later: What kind of statistics illiterate runs standard deviations on three shots?

 

[J.d. Popkes]

I believe the guys that shoot the best, one of them is a bullet maker by the name of Sauter. You may have heard of him. He tested this with his rail and said that as long as the primer was bottomed in the pocket the results were good. At short range, I will take his word over just about anyone else's Also, I wonder what the shooting records of those are that claim otherwise. Seating by feel, my primers are a lot deeper (in un uniformed Lapua .220 brass than the deepest in the test that was linked to. One of the things that is not often considered is the available energy from the striker assembly. Many of the best short range competition actions have been known to be right on the edge, to the extent that working on this part of the most popular action had become somewhat of a cottage industry. My point is that if the firing pin has to do the work of finishing the seating of the primer, that energy is not available for crushing the pellet on the anvil. Be careful what and who you believe. Look at their actual shooting record. There is a LOT of bs on the internet.
Added a little later: What kind of statistics illiterate runs standard deviations on three shots?

Short range

 

[wkdickinson]

Rifle accuracy is based on groups not scores. Score shooters tune their rifles by shooting groups. It all revolves around groups. And yes, you can effect the groups size with the primer seating. Your scores will most likely come down to you wind calls more than primer seating. But scores are a poor way of determining the accuracy or a rifle.

I understand your point and agree. You are a far more accomplished shooter, certainly much more knowledgeable about precision rifles than I and truly I enjoy reading your posts. However, the disciplines I shoot and have shot, are all won by "score", which as you point out is largely determined by your wind reading ability. But then again even if you are shooting for "group size" environmental factors play a very large role. My point was, not that primer depth doesn't effect group size, it likely does, but to what magnitude?

 

[BoydAllen]

Short range

Bart owns the current IBS 600 yard HG record which is .311 (5 shots). I seriously doubt that he seats those primers differently, but the next time I talk to him I will ask. Like I said, there is a lot of BS on the internet.

 

[mikecr]

I can't speak to record shooting, but I've seen gains with a few(so far) pretty accurate hunting guns.
I've found that Feds and Win primers like 2thou crush, and CCIs like 4thou.
Straight up difference in results otherwise(albeit small).
And that's been with different actions, different striking, different cartridges, but with pockets always set to correct depth.

I've also seen that I can optimize striking for a given primer, at my standard seating, for significant gain or loss. I can set striking to nearly double or half grouping while every primer fires just fine.
This concerns me more than primer seating.

Overall, I suspect that any primer still firing, even if terribly seated, works for underbore cartridges running extreme pressure loads. That it's a return diminished by that scenario.
But for hunting capacity cartridges, used for hunting shots, I believe it matters.

And I'll throw in at this point that grouping is PRECISION, and can be considerably disconnected from hunting/cold bore ACCURACY.
Here I see incredible precision, but 5 missed groundhogs in a row:

And here I see 5 hit groundhogs (great accuracy)

 

[BoydAllen]

I can't speak to record shooting, but I've seen gains with a few(so far) pretty accurate hunting guns.
I've found that Feds and Win primers like 2thou crush, and CCIs like 4thou.
Straight up difference in results otherwise(albeit small).
And that's been with different actions, different striking, different cartridges, but with pockets always set to correct depth.

I've also seen that I can optimize striking for a given primer, at my standard seating, for significant gain or loss. I can set striking to nearly double or half grouping while every primer fires just fine.
This concerns me more than primer seating.

Overall, I suspect that any primer still firing, even if terribly seated, works for underbore cartridges running extreme pressure loads. That it's a return diminished by that scenario.
But for hunting capacity cartridges, used for hunting shots, I believe it matters.

And I'll throw in at this point that grouping is PRECISION, and can be considerably disconnected from hunting/cold bore ACCURACY.
Here I see incredible precision, but 5 missed groundhogs in a row:
View attachment 1294660
And here I see 5 hit groundhogs (great accuracy)
View attachment 1294661

A lot of good information....thanks.

 

[Nealm66]

This is interesting. I’ve always used an rcbs primer seating die on a small partner press and I’ve done it for so many years with a lot of different rifle and pistol cartridges to the point where I can feel slight differences like a pocket getting loose etc. I’ve never changed the depth in all the years I’ve used it. The primers always seem to be at a good desirable depth but maybe I’m mistaken? My ammunition seems to always shoot very good but always open ears for improvement

 

[Alex Wheeler]

I understand your point and agree. You are a far more accomplished shooter, certainly much more knowledgeable about precision rifles than I and truly I enjoy reading your posts. However, the disciplines I shoot and have shot, are all won by "score", which as you point out is largely determined by your wind reading ability. But then again even if you are shooting for "group size" environmental factors play a very large role. My point was, not that primer depth doesn't effect group size, it likely does, but to what magnitude?

Primer seating can make a very big difference in accuracy. Seating by feel does work quite well, I am able to achieve my accuracy goals that way. But I have used tools that have such a poor "feel" you cant do a good job. In that scenario it would effect the accuracy enough that it would hurt anyone, and I think it would certainly show up in your scores as vertical points dropped. A lot of guys blow this off, but if they actually tested it themselves they would see how bad you can make a rifle shoot. You cant assume other guys are seating by feel the same way you are, their feel could be quite different. Out of the handful of guys that have tested this that I have talked to there are a couple common denominators. There is a window of crush that shoots best, its different for different primers, and not only is accuracy effected but so is poi. Seating by feel does seem to seat the primer close to where is wants to be which explains why we had had pretty good luck doing it, assuming your using a good tool and have developed a good "feel" for it. But if I was chasing a small group record I would 100% test for ideal crush and seat them to that number with a tool. You want to be prepared in case you get a perfect condition in that case.

 

[jackieschmidt]

In many of our 6PPC’s, after about four firings, the primer pockets are loose enough that much of this becomes a moot point.

The bullets still go in the group.

Of course, this is Short Range, where things that affect bullet performance at longer ranges do not come in to play.

Alex makes a good point about not relying on score to get the Rifle in a competitive tune. What we short Range Score shooters do is get the rifle grouping, or agging to a competitive level. When that plateau is reached, it is up to the shooter to guide it Into the X.

 

[Ccrider]

Even with Lapua 220 brass, you get a few primer pockets that you can feel are definitely loser and shallower. Do you shortrange his disregard the differences and say it does not matter?

 

[RegionRat]

So being a newby I have been experimenting on primer seating . I purchased the PMA hand seater and really like it . Since I have not set up my reloading room , still drywalling and installing benchtops , I purchase a wilson decaping punch and base . So I decapped some 223 shells carefully so I could reseat the primers with the PMA tool . Question I have is when seating by feel are feeling for when the anvils touch or when the cup touches the bottom of the primer pocket ? Seems when the cup touches I get the primers about .004 below the rim . I am also using a primer pocket uniformer before seating the spent primers .

If you have some basic inspection tools, you can check your primer pocket depth and primers to get an idea of what your seated depth is doing.

Nothing sounds wrong with -4 since the variations on allowable dimensions and the specs would shock you.

Till you get to run tests of your own, start out by trying to be consistent. Then try to set aside some time for your own tests once you have everything else optimized to where you could trust your results.

I find that I can adjust the seating depth to a fairly wide window before it affects me, and the PMA tool can be set to bottom the handle on the tool body and hit those depths well enough.

BTW, make sure your firing pin assembly and FP spring stay healthy and clean too.

Good Luck and in for your range report after your testing.

 

[AzMandella]

I do have good measuring tools . I have been in the steel and machining business all my life . 55yrs . Although I use vernier calipers at work I bought a Mititoyo digital caliper that measures into the 10ths . I took 10 new primers (CCI 450) and measured the thickness including anvils . They were very consistent 4 at .1200 4 at .1205 and 2 at .1195 . I then measured just the cups . Not very consistent not that it maters . I was just curious . Also I deprimed 5- 5.56 cases and used my pocket uniformer and they all measured out at .1195 afterwards . So 5/10ths crush to go flush . I then took the spent primers and bent them up and re squeezed then till they were at .1200 . I then pressed them in slowly adjusted my PMA primer tool and primed them till it came to a hard stop without forcing it . I then checked the primer depth and they were at .003 below the rim for all 5 cases . I also bought a K & M flash hole uniformer .

 

[mikecr]

So that's 0.0035" crush.
Should work well with that window of loose primer heights.
By that I mean not just firing, but firing more consistently.

 

[Lifesfordeath]

Would the accuracy one primer depth gage be a more precision tool to get an accurate repeatable reading? Then then increase or decrease depth in sucession to monitor results?