OK, I could really use some help here.  I am seating 77gr SMKs using a Redding Competition Seating Die.  I made a dummy round and seated to the proper depth (i.e. fits in mag and matches published data), then confirmed OAL using a Hornady Comparator Set . Proceeded to seat my batch with the Competition Seating die set to the same depth.  Checked them all when finished and I have about 7 thousanths variation.  I realize that if the Seating Die and the Comparator attachment to the calipers are not the same I.D. then normal variations in the ogive of the bullet will result in variations, but I thought the whole point of both the Competition Seating Die and the Comparator Set was that they would both be made to engage the ogive of the bullet at the proper location (where it will first engage the barrel's rifling) to give excellent consistency.  What am I missing here.  Are they two just that far off.  Is this normal.  

So in summary should I:
1)  Just seat them all as I have done with my die and assume that they are all sized to an overall length that will allow them to have the same jump to the lands.
2)  Make another pass at them with the seating die and adjust the seating die's depth for each round so as to make sure their OAL (as measured by the Hornady Comparator) is the same.

Thanks guys!!!

You can try running a few of them through the dir again and make sure to press the die all teh way down using some force.

Ok, so my understanding that the two should match (die and comparator) is correct then??   Thanks for the reply!

It's not the die it's the press. I'm waiting for camera battery to post in what will be a Gateway thread. Look for fix tomorrow.


eta: this is assuming your using Hornady AP press. I made a fast read through your post and caught the word Hornady. Realizing know it's your comparator.

Ok. I will look for it!  Thanks.

Update: I went back and measured some rounds from a batch I worked up a few months ago with the comparator.  They are all very consistent... within 1 thousanth of each other.  This is what I would expect.  Same setup as this time.  Not sure what is the issue with this batch.....

What I meant before is if you were not paying attention, putting different pressure when pulling the handle on your press can effect what you are describing.

Ok, maybe that's what I'm running into....

Thanks

It may be worth while to remove the seating stem from your new die. Check to see that the 77gr bullet tip is not bottoming out inside the seating stem. I've had to modify a couple of the seater's I use for 77gr and higher by drilling out a small amount of material so the bullet would seat off the ogive.

Excellent idea, thanks!  
I did make it to the range today and the newest batch did group almost exactly the same as the older batch...maybe just dumb luck.  I will try the seating stem inspection though since that would definately lead to the mismatch with the comparator!...thanks!

BTW, I did rerun all the rounds through the seating die one more time before crimping and ensured consistent force on the arm of the press.  This helped a bit, but there was still some variances.

What is your powder charge? Are you crunching the powder as you seat?

See this thread.
Hornady OAL issue solved.

Not compressing the powder...using 23.1 grs of Varget. Load it with a drop tube and it gets in there pretty efficiently.