How does primer seating depth affect velocity spread?

[Jakeonthekob]

Sorry for another noob question but what effect does variances in primer seating depth make in shot to shot consistency?

For example, if you have 5 rounds seating 0.001 inches in, 5 rounds 0.002 inches, etc. what could you expect velocity and SD wise? Of course assuming everything else is as close to exactly the same.

Also, what depth do you all seat your primers at?

Thanks!

 

[longgunJR]

Tagging, id like to learn about this too

 

[Supersubes]

Seat to the bottom of the pocket, not to a specific depth. I’ve never been able to demonstrate any difference between virgin and uniformed pockets, seating with a high end adjustable tool or a run of the mill tool. A tool with enough leverage to let you feel the primer bottom out will be sufficient.

 

[whatsupdoc]

Dont think most reloaders have the proper measuring equipment to test this. You also stated "Of course assuming everything else is as close to exactly the same" right there is the the problem.

Can you guarantee that everything is the same.?

And finally are you that competent a marksman that .002 of primer seating variation will adversely affect your shooting.

 

[Jakeonthekob]

Dont think most reloaders have the proper measuring equipment to test this. You also stated "Of course assuming everything else is as close to exactly the same" right there is the the problem.

Can you guarantee that everything is the same.?

And finally are you that competent a marksman that .002 of primer seating variation will adversely affect your shooting.

Just a theoretical question. I know we are all limited by equipment, tolerances, etc. But I wanted to know if there could be a big difference in velocity.

I think you can just measure primer seating depth using the end of your calipers no?

 

[longgunJR]

The back of the calipers don’t have enough surface area to measure primer depth, unless you’re super tedious with it. For an accurate measure you can’t beat a proper depth mic

 

[brianf]

ill say that i dont know

on the flip side:

if the primer is off the deck .001
but the flash hole/base in that are is .001 thinner
making the total distance from primer to powder the same

does if matter?

using quality brass with a clean pocket and primer flush is about all we can as for.

total component tolerance in addition to fluctuations in primer/ powder/ brass are just too much to worry about

IMO

 

[whatsupdoc]

Just a theoretical question. I know we are all limited by equipment, tolerances, etc. But I wanted to know if there could be a big difference in velocity.

I think you can just measure primer seating depth using the end of your calipers no?

Sure you can measure the depth with calipers, but how accurate will your measurements be as the best calipers typically have a .001 error tolerance and you are looking for .001 variance.

Just push the primers in until they bottom out and look for consistency elsewhere.

 

[Sheldon N]

For example, if you have 5 rounds seating 0.001 inches in, 5 rounds 0.002 inches, etc. what could you expect velocity and SD wise? Of course assuming everything else is as close to exactly the same.

Also, what depth do you all seat your primers at?

No idea what velocity difference you'd see, if any. A lot of the BR guys are pretty emphatic that inconsistent primer ignition will reduce accuracy at distance. That encompasses everything in the firing system... pin/spring/firing pin fall etc.

I seat around 0.004 below flush and don't worry about it.

 

[MtnCreek]

I don't have any proof to back this up, but I believe consistently seated primers will give more consistent velocities. I seat till the primer touches the bottom of the pocket and then apply a little more pressure. Some brass needs the pocket uniformed to get a consistent feel. May be hocuspocus but I believe...