Primer depth for accuracy

[Skeptic123]

I'm trying to find anyone's actual testing experience regarding primer seating depth. With the Accuracy One primer seating gauge and the Primal rights seating tool, among others, it is possible to mostly control or at least ascertain what each rounds seating depth is. But.....does it really make any difference in accuracy. Does .001 more or less crush translate to more accurate loads? Does it affect ES or SD? Is it quantifiable? Thx.

 

[caihlen]

Talk to Alex Wheeler. He did some serious work on this.

 

[BoydAllen]

Out to 300 yards short range group competition produces the highest level of accuracy. I pretty confident that well over 95% of those competitors seat primers by feel, using hand tools.

 

[garandman]

I'm getting 0.25 - 0.40" @ 100 yard in 2 calibers just mashing 'em deep.

 

[OmegaRed]

Yes - but .001 increments no. You will find a range though like bullet seating. Good thread from a few months back. Uniformity of primer pockets is worth mentioning as a starting point.

 

[potatojudge]

You'd need to uniform primer pockets, which is no biggie, then sort your primers by height, which kinda is, then keep them sorted as you prime brass looking for the same amount of crush fit using something like a K&M seater with depth gauge.

For a procedure that's not proven to be helpful, that's an obnoxious amount of time, work, and organization. At the level of 99.99% of shooters, myself definitely included, seat by feel.

 

[Nick Caprinolo]

I never understood all the hoopla about primer depth. If the primer pocket is unified and the primer is set against the bottom of the pocket, it would seem that they are all seated the same.

The primer is designed to go bang and transfer all its energy into the little hole in the case. How can a few thousandths make any difference. As stated above, most everyone seats them as deep as they will go.

 

[OmegaRed]

I never understood all the hoopla about primer depth. If the primer pocket is unified and the primer is set against the bottom of the pocket, it would seem that they are all seated the same.

The primer is designed to go bang and transfer all its energy into the little hole in the case. How can a few thousandths make any difference. As stated above, most everyone seats them as deep as they will go.

Not disagreeing or being argumentative, but in that same line of thinking then why does a few thousandths of firing pin fall matter? But it's accepted that it does.

 

[garandman]

Not disagreeing or being argumentative, but in that same line of thinking then why does a few thousandths of firing pin fall matter? But it's accepted that it does.

"A few thousands " is not the same criticality everywhere in the entire systems of both gun and ammunition universally. For instance, some guns like a lot of bullet jump to lands. Some like 2b jammed into the lands.

The fact that a few thousands of firing pin fall can be significant has no direct connection or indication of causality that a few thousands of primer seating depth matters.

 

[newbieshooter]

Bart did some testing years ago?

How Much Primer Crush?

Just acquired the 21st Century priming tool that has 0.00125" travel per click. Very pleased with my purchase. I'm priming 6.5x47 Lapua cases with CCI 450 primers. I found that generally the primers "bottomed" at 27 clicks back from the tool head being fully "closed". From there, I screwed the...

forum.accurateshooter.com

 

[BoydAllen]

Yes - but .001 increments no. You will find a range though like bullet seating. Good thread from a few months back. Uniformity of primer pockets is worth mentioning as a starting point.

Bart Sauter reported that he did some testing. I believe that it was probably done at his home basement slot range, using a rail and he said that his results showed that as long as primers were bottomed that they shot well, I do not believed that he found any problems with compressing them some. The recent post that I remember about primer seating depths involved a small sample shot at long range under less than perfect conditions.

IMO most shooters do not have a set of flags, have their rest situation optimized, and may not have the use of a top level bench. Almost none take advantage of the obvious advantages of tuning at the range, but lacking much of this, they obsess on minutia that will get lost in conditions, if it has any real effect at all. Fix the obvious stuff first. Under the best conditions people shoot hundred yard aggregates under .200" with primers seated by feel.

 

[gunsandgunsmithing]

I think for most of us, seating by feel is as good as it gets but there are people that just dont do well with anything less than being able to quantify what "feel" means. Nothing wrong with that..just one example of how we arent all wired the same.

 

[Ccrider]

Bart Sauter reported that he did some testing. I believe that it was probably done at his home basement slot range, using a rail and he said that his results showed that as long as primers were bottomed that they shot well, I do not believed that he found any problems with compressing them some. The recent post that I remember about primer seating depths involved a small sample shot at long range under less than perfect conditions.

IMO most shooters do not have a set of flags, have their rest situation optimized, and may not have the use of a top level bench. Almost none take advantage of the obvious advantages of tuning at the range, but lacking much of this, they obsess on minutia that will get lost in conditions, if it has any real effect at all. Fix the obvious stuff first. Under the best conditions people shoot hundred yard aggregates under .200" with primers seated by feel.

Or in other words, as oft said, it don’t matter if you can’t shoot the difference.

 

[garandman]

Or in other words, as oft said, it don’t matter if you can’t shoot the difference.

I like to say "The only way to see if it'll actually work / matter in your gun is to try it in your gun. With guns, there really are few universals."

 

[jimmymac]

...this is along the same vane as the need for a $1000 scale. Most guys can't shoot the difference. Meanwhile the old BR shooter down the way is throwing charges without a scale and shooting small.

 

[jimmymac]

Different game.

 

[DaveTooley]

The next thread will be "HELP I'm having misfires"

 

[OmegaRed]

Bart Sauter reported that he did some testing. I believe that it was probably done at his home basement slot range, using a rail and he said that his results showed that as long as primers were bottomed that they shot well, I do not believed that he found any problems with compressing them some. The recent post that I remember about primer seating depths involved a small sample shot at long range under less than perfect conditions.

IMO most shooters do not have a set of flags, have their rest situation optimized, and may not have the use of a top level bench. Almost none take advantage of the obvious advantages of tuning at the range, but lacking much of this, they obsess on minutia that will get lost in conditions, if it has any real effect at all. Fix the obvious stuff first. Under the best conditions people shoot hundred yard aggregates under .200" with primers seated by feel.

I agree - most SR benchrest shooters reloading skillsets are honed through a lot of practice and technique. I'd surmise most competitive SR shooters primer seating "feel" is very consistent in the same way as their powder throwing technique is. Take an average joe and that same powder thrower is probably a lot more inconsistent.

I should also say always read these posts as if they are being asked in relation benchrest shooting of some sort since they are dealing with some nitty gritty aspect of reloading, but your point is well taken that it may not matter if they don't start with the foundations of accuracy.

 

[DaveTooley]

Primers are a primitive explosive device. They have to be seated to a depth that seats the anvil against the priming compound in such a way to sensitize them to respond to the firing pin strike setting off the explosion. I have had some Wolf LR primers that where I would get hang fires, click-bang, unless absolutely crushed. I err on the side of more pressure is better when seating primers. I seat mine to the bottom. Give the case a half a turn and hit it again. Just my routine.

 

[Bill Norris]

Primers are a primitive explosive device. They have to be seated to a depth that seats the anvil against the priming compound in such a way to sensitize them to respond to the firing pin strike setting off the explosion. I have had some Wolf LR primers that where I would get hang fires, click-bang, unless absolutely crushed. I err on the side of more pressure is better when seating primers. I seat mine to the bottom. Give the case a half a turn and hit it again. Just my routine.

I agree it is a good thing to seat that primer as deep as it will go. Leaving it .002 or .003 thousandths off the floor of the primer pocket just makes no sense to me.