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Bullet seating die question

This may be a dumb question, or I'm the only one who doesn't know the answer, here goes anyway.

I seat bullets using a micrometer seating die, Forstner in my case, where I back off the mic, seat, measure CBTO, adjust mic, re-seat, measure CBTO to double check, done.

Is there a system out there with a seating "stem" that's calibrated so it seats the bullet at the exact same point on the ogive as the CBTO gauge? My line of thinking is if the seater is referencing the exact same point on the ogive as the gauge, there's no need to measure over and over again.

I know, too much time on my hands :)

Chris

Re: Bullet seating die question

Reply #1
This may be a dumb question, or I'm the only one who doesn't know the answer, here goes anyway.

I seat bullets using a micrometer seating die, Forstner in my case, where I back off the mic, seat, measure CBTO, adjust mic, re-seat, measure CBTO to double check, done.

Is there a system out there with a seating "stem" that's calibrated so it seats the bullet at the exact same point on the ogive as the CBTO gauge? My line of thinking is if the seater is referencing the exact same point on the ogive as the gauge, there's no need to measure over and over again.

I know, too much time on my hands :)

I've experimented with this on my LE Wilson dies. By the time I get the stem hollowed out enough to seat off the ogive the sidewall is too weak and bells out.

@Fuj has modified some Lee dies to accomplish this and should chime in.

@jvw2008 and I have discussed this at length concerning the inline type dies and agreed it could be done by for instance by boring a 6mm die to accept a 7mm seating stem leaving enough sidewall in the stem so it would not bell out. I haven't attempted it as of yet though.   
Dave



Re: Bullet seating die question

Reply #4
Odd - the link works for me when I just tested it. Yes it is Bob Greens comparator system.

Re: Bullet seating die question

Reply #5
I recall seeing that comparator a while back.

I can see where it would solve the problem of repeated measurements if bullets are grouped appropriately. I'm not sure if it's a labor saving device; essentially it's piece work done up front to avoid piece work done later.

I have noticed though, when I get a handful of bullets in a row that all measure the same CBTO on the first seat, they always need the same mic adjustment to get to the correct seat on the second seat. This works only if the die is reset to the starting point for every first seat of course.
Chris

Re: Bullet seating die question

Reply #6
Sounds like you’ve got that technique down. 😊

Re: Bullet seating die question

Reply #7
The world awaits Fuj's tweak to Lee dies :)
Chris

Re: Bullet seating die question

Reply #8
I recall seeing that comparator a while back.

I can see where it would solve the problem of repeated measurements if bullets are grouped appropriately. I'm not sure if it's a labor saving device; essentially it's piece work done up front to avoid piece work done later.

I have noticed though, when I get a handful of bullets in a row that all measure the same CBTO on the first seat, they always need the same mic adjustment to get to the correct seat on the second seat. This works only if the die is reset to the starting point for every first seat of course.

Exactly on all of that, you can either put in the work before or put in the work as you're seating them!
Dave

Re: Bullet seating die question

Reply #9
I've got 2 of the Bob Green Comparators, one for 6mm and one for 7mm. It was pretty effective and worth the effort on the 105 Bergers but not necessary on any of the custom 103-105 bullets I shot this summer. No variance between the seater stem datum and the ogive.

I sorted some 180 & 184 Bergers with the 7mm and the variance in them was not worth the effort either.
Dave

Re: Bullet seating die question

Reply #10
my opinion and my opinion only... the neck and shoulder and probably half way down the case is flexible to some extent... and when you seat the bullet I think it actually compresses the case a little as you put down pressure on the bullet when seating it... once the mouth accepts the bullet the case relaxes a little and starts to return back to the size and shape it was before you started to seat the bullet... once you get the bullet seated all the way in and remove the down force on it it relaxes the rest of the way and returns to what ever size its going to be... this is where annealing and consistent neck tension plays a major role... if neck tension and case flex is the same on each case you should get really close to the same seating depth for each round minus what ever minor variance there is in the bullet itself... a few wees ago I was loading 184 berger hybrids in Peterson brass.. all had been annealed and sized with a fl forster competition die... bullets seated with a forester competition seating die... I measured cbto on 20 of them and they were all within .0005 with one pull of the handle...I credit a lot of that to the Peterson brass being very consistent... and the 184 bergers being consistent as well... but also mmy annealing did its job and my fl die did its job along with the seater...with Hornady brass I usually see 2 to .003 variance in seating depth and to be honest I don't sweat it... I cant tell the difference in that variance and being dead nuts on on my targets...  like I said just my opinion... 
Grant

 

Re: Bullet seating die question

Reply #11
Grant and I often disagree on seating depth consistency and I'll be the first to admit Grant has got things figured out and shows off some damn fine groups anyone would be proud to shoot. His reloading skills are top notch and his program definitely works for him. I agree wholeheartedly on neck tension and in my opinion consistent accuracy can't be had without consistent neck tension. I proved it to myself after having little success in MT all summer then changing my sizing procedures to get my neck tension light and consistent to do much better late summer and fall.

I'll also say that sub .5 MOA groups 3 shot groups inside of 400 yards are certainly not easy but are much less sensitive to exact seating depth and being centered in the sweet spot of the seating depth node. When we start talking  about 5 or 10 shot groups at 600 or 1000 the same load that's in the " node " but not centered in the sweet spot and the same load that may be seated to within .002 -.003" may still shoot MOA or even sub MOA but I doubt these rounds will ever likely shoot sub .5 MOA on 5 or 10 shot groups at that distance.

The exception being if by chance a person happened to get 5 or 10 rounds seated exactly alike in the sweet spot of the node together in the ammo box and just by chance happened to shoot those 5 or 10. Think of it like the ammo box lottery, 5 or 10 perfect rounds just happened to be lined up in the same row/rows in the box then the next 5 or 10 happen to have a few that are not the same.

This may be one of those instances where we all have different expectations and goals as well as define accuracy differently. I'm not knocking anyone's program, techniques or results here and as my friend Grant said....My opinion and my opinion only.
Dave

Re: Bullet seating die question

Reply #12
It's downright funny how a group of culls can make a one-holer from time to time :)

Chris


Re: Bullet seating die question

Reply #14
when testing my load for finalizing I do post a 3 or five shot group on here... sometimes its the best group I shot for the day and sometimes it isn't.... rest assured it isn't the only one I got lucky with.... :)   I call a load good when I can shoot 2 or 3 groups of 3 or 5 today and do it again tomorrow or the next day... i try to share what works for me and if it works for someone else that's cool... if it doesn't that's cool too... and its great to see others get the results their looking for their way... i shoot a lot... and have tried about every way i have read about... but in the end i had to find my own way....and it meets my expectations … i would love to sit down out here in my cornfield with my friend dave and shoot.... im sure i would learn a few things.... he might too...  lol
Grant