Sezting Dies, OAL gage & Variable Seating Depth

[audredger]

Rifle is a Remington Tactical 308. Trying to work up a predictable cold bore one shot load for our local "Turkey Shoots".
Range is at a known distance between 50 to 150 yards. Last year I won a ham and this year I want the bacon!

Using the Hornady OAL gauge I determined where the 150 gr FB Berger's where touching the lands. Carefully adjusted the RCBS competition seat-er to give me a .003" jump. Then proceed to load ten for a test run. When I go back and check the using the Hornady comparator; my seating depths vary by several thousandths.

A bit of investigation reveals that the hole in the Hornady comparator is .290" in diameter, where the RCBS die contacts the bullet the hole is .250" and on the Redding die it is .180"

I know that Berger makes there bullets as best they can but there are variations with in a lot. By measuring at one datum point and, seating from another; am I not exaggerating the variations in the bullets?

Should I open up the hole in the comparator to say .307, (land diameter) then, build a seat-er that presses at .307?

 

[jhelmuth]

I'm no expert by any definition... so take this for what it's worth...

Rifle is a Remington Tactical 308. Trying to work up a predictable cold bore one shot load for our local "Turkey Shoots".
Range is at a known distance between 50 to 150 yards. Last year I won a ham and this year I want the bacon!

Using the Hornady OAL gauge I determined where the 150 gr FB Berger's where touching the lands. Carefully adjusted the RCBS competition seat-er to give me a .003" jump. Then proceed to load ten for a test run. When I go back and check the using the Hornady comparator; my seating depths vary by several thousandths.

A bit of investigation reveals that the hole in the Hornady comparator is .290" in diameter, where the RCBS die contacts the bullet the hole is .250" and on the Redding die it is .180"

Realize that consistent "pull" (torque) on your press arm will add to the variance(s) as well. So you might want to use a torque wrench style press arm if you want the most consistent "pull".

For .308, I would give it a bit more jump (around 0.010") - but that is just me and YMMV...
I do not think a variation of 0.002" in jump would make a critical difference in a cold bore shot (but what do I know?) unless you were already at the lands (or real close).

I know that Berger makes there bullets as best they can but there are variations with in a lot. By measuring at one datum point and, seating from another; am I not exaggerating the variations in the bullets?

...yes - kinda. You are measuring a delta from the 2 "tools" (along with your own "error").

Should I open up the hole in the comparator to say .307, (land diameter) then, build a seat-er that presses at .307?

You could... but I would not. Because [1] your tooling to do so would need to be of very high quality and caliber (which most folks would not own to do so) and [2] it's not necessary. You can simply find the delta in the measuring and "adjust" for that tolerance.

 

[jhelmuth]

Oh yes... and the quality of your dies are also a component in the deltas too. I would also consider a competition seating die as well.

 

[fdshuster]

audredger: Before the match, try the first shot fired from a dirty barrel without any thought of the barrel being "cold". My first shot out of a clean barrel always has a point of impact slightly different from the point of aim, whereas the difference between "cold" and warm is not noticable.

At our local match's the clean versus dirty factor is considered so important that a fouler shot is permitted (into the dirt backstop), before we fire for score.

In my experience with the 308, it is very forgiving in bullet seating depth. It's something that is just not critical, and I use a jump of .020" for all load combinations.

 

[jonbearman]

The difference in the seater plug diameter shouldn't matter as long as it isn't deforming the bullet. You might have to sort by ogive length and sinclair and others make a tool for sorting bullets by ogive or bearing surface. Every bullet can be slightly different giving you different seating depths.I agree with frank that .020 is a good place to start off the lands.I usually seat even further off like at .030 and get good results.The .308 isn't fussy like a 6ppc or a 6br. Just jump them and don't worry about being so close ,you will drive yourself nuts as like I said ogive's do vary without a doubt.Try it and let us know what your target results are.Be safe above all!

 

[audredger]

Thank you all.... some additional info; both the RCBS and Redding dies are "competition" dies. All testing is from a fouled barrel. I also coat my bullets and treat my barrel with HBN.

The chamber is a factory chamber with a long lead. I cannot get it to shoot VLD's worth a damn unless they are real close to the lands and thus that is where I have started this development.

 

[jonbearman]

Use the hybrids if you can get them.I have a similar remmy which shoots lights out with believe it or not 168 grain hornadys using blc-2.I would give them a try you may be pleasantly surprized as the 150's never shot that great out of mine either.