Primer seating "Depth" vs primer "Crush"

[Ruger15151]

Hey guys


I have a question that I haven't seen addressed on any of the forums (accurateshooter, etc)

There are several primer seating tools that sets consistent primer seating depth. However, if your rim to primer pocket dimensions are different or the primers vary in height, you will get different crush even though all are seated at the same depth.

I have read on this form that many top shooters seat by feel.. meaning.. they seat to the bottom of the primer pocket then squeeze a bit more to set the crush.

In your testing, is consistent seating depth or consistent crush the most important factor?

 

[piie]

if you can believe this guy...

 

[WSnyder]

I haven't seen addressed on any of the forums (accurateshooter, etc)

There have been at least two recent threads here about it.

YouTube Witch Doctor primers, he has two videos.
The discussion:

Primer Seating Depth

I recently watched and The conclusion seamed to be that seating primers 9 thousandths below flush was close to optimal Which tools does the group here think are capable of seating primers consistently to 9 thousandths below flush consistently with a reasonable margin of error? What's an...

forum.accurateshooter.com

 

[BoydAllen]

I suggest that you do your own testing. Over the years I have talked to a number of top shooters and one common denominator is that all of them do their own testing.

 

[searcher]

Hey guys


I have a question that I haven't seen addressed on any of the forums (accurateshooter, etc)

There are several primer seating tools that sets consistent primer seating depth. However, if your rim to primer pocket dimensions are different or the primers vary in height, you will get different crush even though all are seated at the same depth.

I have read on this form that many top shooters seat by feel.. meaning.. they seat to the bottom of the primer pocket then squeeze a bit more to set the crush.

In your testing, is consistent seating depth or consistent crush the most important factor?

Everyone has their own idea on this - but I'd say very slight crush. The whole idea of the crush is to ensure that the primer has ultra-solid contact with the base of the primer cup. You mention the difference in measurements from base of cup depth and that is why seating to the same depth doesn't cut it. If one of the primers has any free space under it after seating, that is not good. The crush all but eliminates primer "creep". If one reams or cuts their pockets as I do, not as much crush is required - only enough to set the "teets" on the bottom of the primer. If one is using less than desirable brass and the pockets are not uniformed - more crush is warranted. Consistency is key - so I think if using uniformed pockets - one could get by with no crush - as long as the primers were all set the same. I always add just a bit even with the trued pockets.

 

[Doom]

The video with Keith Glasscock is an excellent example of how a test should be organized and analyzed. In his case the results are pretty clear. His analysis of velocity data (mean and standard deviation) is how chronograph data should be analyzed. To Boyd's recommendation no one test is ever considered to be definitive. To reach a consensus such a test would need to be repeated multiple times with repeatable results.

Unfortunately, far too often we run a single test and fail to even analyze the results properly.

 

[BoydAllen]

I have posted this a couple of times. A technician at CCI told me that they recommend seating so that the bottoms of the anvil feet are flush with the cup. This takes a lot of pressure. I have seated a primer with more than my usual firm pressure and carefully removed it, the feet were almost, but not quite flush (20X magnification, between the jaws of a dial caliper). IMO there has been a LOT of assuming going on on this subject. The best research that I have seen on this is a couple of videos on Youtube by a real, highly competitive benchrest shooter.

 

[Field_2_Fork]

I have posted this a couple of times. A technician at CCI told me that they recommend seating so that the bottoms of the anvil feet are flush with the cup. This takes a lot of pressure. I have seated a primer with more than my usual firm pressure and carefully removed it, the feet were almost, but not quite flush (20X magnification, between the jaws of a dial caliper). IMO there has been a LOT of assuming going on on this subject. The best research that I have seen on this is a couple of videos on Youtube by a real, highly competitive benchrest shooter.

Care to share the YT channel? I can't find much on their that is BR related, as in almost nothing. Maybe I'm not looking in the right places? Much appreciated.

 

[BoydAllen]

He has done a couple of videos on primer seating.

https://www.youtube.com/user/DBCHeadoc/videos

 

[Uncle Ed]

The primer should be seated with a slight crush with the base of the primer touching the bottom of the primer cup. This ensures that no forward movement of the primer anvil when fired.

Ignition occurs when the firing-pin indents the cup, crushing the pellet against the anvil-tip. To work properly, the anvil’s ‘feet’ have to be anchored on the case pocket floor and its tip barely separated from the priming compound, or just nudging it. So, the primer should be seated to a snug fit within the pocket putting the anvil’s feet squarely on its floor and positioning the tip against the pellet.

RELOADING BENCH

LARGE RIFLE PRIMER PERFORMANCE BY LAURIE HOLLAND​

http://www.targetshooter.co.uk/?p=1471

 

[WSnyder]

Care to share the YT channel? I can't find much on their that is BR related, as in almost nothing. Maybe I'm not looking in the right places? Much appreciated.

The thread I linked above will take you to a previous discussion and the links to two of his (Witch Doctor) primer seating test videos right there in the first post.