Primer seating

[VA-XBolt]

I'm feeling the bottom then applying an exact amount of crush measured by dial indicator on the f class products stand.

OK, that makes sense. And yet another tool I didn't know existed. I do like the idea of the F Class stand, if noting else, so that I can easily move the CPS around on my bench. The addition of the crush indicator is a bonus.

Jerry will be turning case heads to uniform the extractor groove before long 🤣

As long as that doesn't turn into yet another tool I need to buy... LOL

[jvw2008]

Hmmm I might need to get a mini lathe after all. Chuck up a le wilson shell holder backwards and feed the cases one at a time into the cutter.

Naw. Just need to talk to Mr Blake about an accessory for the autoDOD.

[VA-XBolt]

Hmmm I might need to get a mini lathe after all.

Please NO MORE TOOLS.. My bench is already overrun!

[mnbogboy]

I habe always seated with a press, it is easy to over do it and sink them in a measurable amountbdeeper.
Once I added an extension to the press handle and put an indicator pinon the end of it. That press was mounted parallel to the wall. If you brought the indicator to the same spot on the wall and measured the primer depth, you could become very repeatable as far as "crush" goes! With no long range to test results a test should be able to conduct with simple chrono results.

[mnbogboy]

I always measured case head to primer cup. Adding 2 to 4 thou of crush is easy in a press. Consistency by "feel" is harder to accomplish.

[missippyman]

I'm not a benchrest shooter but I have always used the standard rule, listed in all of the manuals that I have, along with more than a couple writers in Handloading magazine. I seat all of my primers to .001 to .002 below the case head. I have not had any problems once I got this method down.
Not to say any of you are mistaken, just how I learned to seat primers. I had a couple primers fail to ignite way back when I started reloading but not since then.
My suggestion is find the process that suits you and stay with it.

[DHuffman]

[quote author=missippyman link=msg=143005 dat
I'm not a benchrest shooter but I have always used the standard rule, listed in all of the manuals that I have, along with more than a couple writers in Handloading magazine. I seat all of my primers to .001 to .002 below the case head. I have not had any problems once I got this method down.
Not to say any of you are mistaken, just how I learned to seat primers. I had a couple primers fail to ignite way back when I started reloading but not since then.
My suggestion is find the process that suits you and stay with it.
[/quote]

I certainly won't argue with the last sentence of your post. Seating to .001 to .002 below the case head is basically a "good enough" measurement and it's obviously making them go bang.

I realize what I'm doing is not for everybody and I'm not trying to to get anybody to throw down the money on the tools to measure primer crush just sharing what I've learned.

The whole process is not about making the gun go bang reliably it's about wringing consistently smaller groups out of a gun by optimizing the ignition timing.

To adequately test a difference in crush a load must be tuned as good as you can get it. Powder, seating, neck tension and primer preference. Before I had a chance to test it on paper at 600 yards I was crushing .0035" after winning the 2022 Long Range Rendevouz in June with a small amount of that lot of bullets i put together a test of 3 shot groups at .002" - .006" which revealed .003" shot smallest and not just by a little. .002 & .004 were good and .005 & .006 were starting to open up.

Proof enough for me it matters for benchrest accuracy. I'll add the picture in a few minutes from my phone

[DHuffman]

Like I said I was crushing between 3 & 4 thou at the Rendevouz sure wish it had been 3 LOL

[DHuffman]

Those are the same brass bullets and powder used at the Rendevouz, same charge weight, same seating depth. Shot at 600 yards. Only difference is primer crush.

Interesting to note also the smallest group has the largest SD / ES and the largest group has the smallest.
Chasing single digit chrono numbers ican be a waste of components and barrels. The target tells the truth.

[DHuffman]

All measuring below flush measures is below flush!

If you accurately measure primer pocket depth then accurately measure a primer cup then seat the primer then you can measure below flush and do the math and figure crush or lack thereof.

[LeadHammer]

Man those results are actually insane.
I need a different method of doing my primers I guess.

[DHuffman]

Man those results are actually insane.
I need a different method of doing my primers I guess.

While it is only one test I like how it goes from small to smallest then back to small then it scatters then groups up bigger.
Typical "node" behavior that actually lends legitimacy to the test in my opinion.

[LeadHammer]

Man those results are actually insane.
I need a different method of doing my primers I guess.

While it is only one test I like how it goes from small to smallest then back to small then it scatters then groups up bigger.
Typical "node" behavior that actually lends legitimacy to the test in my opinion.

Very interesting data for sure. Looking forward to more tests.

[DHuffman]

After using this procedure awhile I think the next time I uniform a set of pockets .121" would be my target depth on the pockets.

With .003" crush I'm getting a few @ .006" below flush. I don't really know that it matters but it seem the less you take out of the pocket the better for longevity.

I want to update this statement a little. I kept my original .122-.123 depth cut the same because I realized the variance in below flush was in the primer itself or rim thickness variance. I could sort primers by thickness as well as identify these cases that keep coming up with a bigger below flush and match them to thicker primers  but no I'm not doing all that LOL this is working IMO

This is however on Lapua brass with CCI 400s on my Alphas with BR4s the same depth is getting most primers with a .002-.003 BF with a few at .001-.002 and a very few outliers at flush to .001 above flush. With the same pocket depth this is likely the thicker cup on the BR4 compared to a 400

I was thinking about going a thou deeper on the alpha case but decided against it because if I wanted to run a different primer with a thinner cup I could end up with an even deeper BF

So for now I'm sticking to the original .122-.123 uniformed depth.

The Centurty 21 uniforming tool is by far the best I tried but I've heard the PMA tool for Lapua brass is as good or better at uniforming depth without cutting sidewall.   

 

[jvw2008]

6mm BRA and 6mm Dasher Alpha/Lapua Brass:

For Alpha I use the 21st at 0.122 which is simply a skim of the bottom of the pocket. As Dave just reported, there is less pocket variance in the Alpha. This uniformity is consistent with Alpha across the board. IMO it is simply the highest precision made brass I have found.

 Many top shooters today (mainly F Class) such as Eric Cortina, recommend leaving primer pockets alone - ie. don't uniform. Based on my dimension measurements of multiple brass offerings I don't agree with his advice. Eric doesn't use Alpha, he uses Lapua. Personally, if there was any brass out there that I would consider not uniforming pockets it would only be Alpha.

Lapua is, comparatively, still extremely good and in some areas possibly better than Alpha's offering. If Lapua had Alpha consistency I would lean towards the Laupa just for its slightly larger case capacity.

Early on in production Alpha unfortunately had some batches of brass that didn't hold primer pocket size well with multiple firings. True to their commitment, the company went back and did a reformulation of their brass composition and have now labeled it OCD brass. If anything they may have over corrected for hardness since most of us find the Aplha pockets are more difficult to cut with a uniforming tool. At this point in my use of the Alpha OCD brass, I could not say how long these pockets will hold up, but I'm pretty sure it will be just as long as the Lapua pockets.