Seating by ogive or COAL?

[newbieshooter]

Nice to see you're using my pictures again without referencing the person that took the time to make that image...me.

I see attribution in the file name when you mouse over the image.

 

[Ned Ludd]

I see attribution in the file name when you mouse over the image.

View attachment 1541137

The fact remains that there is no visible reference to the originator of that image (me) unless you do the mouseover. Something that isn't obvious and permanently visible doesn't qualify as a valid reference by any standard. Why someone would think it's OK to swipe another member of this forum's work and pass it off as their own is beyond me. That is plagiarism and pure laziness. If someone wants a particular image, it would be proper to ask permission to use it first, then reference the originator in a very clear and obvious manner...every single time the image is used. Better yet, just spend the time to make your own image, like I did.

 

[Tesoro]

I now go the lazy route and get excellent results for my purpose ( <moa at 1000). I shoot closed tipped 6mm DTAC bullets and just sort by bto to cull out the occasional wild one. No cbto measurement, I just seat so the bottom of bearing surface just above the neck shoulder junction. Use a powder load that is in top 1/3 of the increasing velocity curve before it levels off, and then finish polish with a tuner. As throat erodes I tweak the tuner to make up for it. Been working well so far at 1000 yds on my hillbilly targets! I pay more attention to uniform neck tension than I do a few tho diff in ogive to lands.

 

[Straightshooter1]

Nice to see you're using my pictures again without referencing the person that took the time to make that image...me.

When one puts the pointer over the picture is shows you as the source. Not good enough?

 

[Eagle Six]

When one puts the pointer over the picture is shows you as the source. Not good enough?

I realize you are asking a question to Ned, however as a member and following this thread I would have no need to place a pointer over the image and would have assumed you were the creator without you providing a credit line or quoted the original post. I offer this as food for thought.

 

[Straightshooter1]

I realize you are asking a question to Ned, however as a member and following this thread I would have no need to place a pointer over the image and would have assumed you were the creator without you providing a credit line or quoted the original post. I offer this as food for thought.

Hmmm??? All kinds of pictures from all kinds of sources are posted without people assuming the poster was the creator. As I understand it, it's plagiarism if the poster was in some way passing them off as their own and/or profiting from it. In this case, I'm in no way profiting from it nor is it on a website different from where it came. I would think that if Ned cared so much about credit for his illustration, he would have put his name right on it, which I will do on my copy for any future use by me, since the file name doing so is apparently not enough.

 

[wkdickinson]

Let me throw you another curve ball. I have been having more success getting smaller rounder groups with lower SD and ES by seating to a seating depth inside the case. I see more consistency on paper by controlling the internal ballistics of the case. With a seater die that is made for the profile of the bullet I am using, I try to control the seating depth and not worry about jump to lands/ CBTO or the COAL. I check the bullet base to ogive and keep that under 0.002" variation. There is a risk that the bullet profile may vary between individual bullets such that the distance between the comparator contact point and the seater contact may vary more than 0.002" but I have not seen that as a huge problem with the .224 and .243 Berger's I am shooting. More variation in length on the bullets seems to occur from the seater stem contact point to the tip.

Ned has posted images of what I am talking about recently.

I have long wondered about this exact concept! In reality, is it really bullet jump that makes the difference, or are we actually varying the case volume, by how deep we seat the bullet in the neck. If that is not what is happening, how then do we explain how the same CBTO continues to work even as the lands move?

 

[JFrank]

I’ve not been able to connect any change in fps to a change in seating depth.

 

[Ned Ludd]

When one puts the pointer over the picture is shows you as the source. Not good enough?

Make your own images, please do not use mine. I can't be any plainer than that.

 

[RCE1]

I would say, in terms of accuracy, the ogive would be important. However, if you're dealing with a magazine there will be some OAL limitations.

 

[wkdickinson]

Several years ago I was having a problem with inconsistent CBTO with my 6 Dasher. I was using a Whidden "Micrometer" seating die, with the correct seating stem for Berger 105 Hybrid bullets. No mater what I did I could not get consistent CBTO (0.005 - 0.040"+). Logic told me this was impossible, because the seating stem didn't move. So I made a new compartor insert as close to the diameter of the mouth of the seating stem as I could. When I measured my loaded rounds - they were within 0.001" of each other.

I then I randomly selected 30 bullets from the remaining lot (400/500) and first measured the BTSS. Then measured the BTO and subtracted it from BTSS. The results mirrored the problem I'd been having with CBTO inconsistency.

I don't shoot Berger 105 Hybrids anymore - just my experience.

 

[JFrank]

A similar practice myself, I colored the bullet with a sharpie then used the Wilson seater stem to mark the spot where it made contact. About .0174 ish so I just use a 17 cal insert in my Hornday comparator to monitor seating after setting the depth by ogive. I qualify bullets by btss first followed by bto before finally sorting OAL similar to the Bob Green tool so I should pay homage to BG I suppose.

 

[jelenko]

What is 'btss'?
Thanks

 

[ISS]

Easy near universal answer: .020" off the rifling origin. Probably answered here.

ISS

 

[JFrank]

What is 'btss'?
Thanks

Base to seater stem contact point.

 

[gunsandgunsmithing]

@Dave M.

 

[wkdickinson]

What is 'btss'?
Thanks

"Base To Seating Stem"

 

[DiffEQ]

For plinkers (i.e. 223, 6.8, 6.5G, etc on my Dillon 650), COAL, only QC checking a random selection along the way.
For accuracy, B2O, and the neck tension better be the same, or you will experience "spring back". When that happens, the B2O measurement can vary 0.002" - 0.005", driving you nutz in the process. If it's annealed and I experience a significant increase in force needed to seat the bullet (feel, no gauges), I'll pull it, dump the powder, salvage the primer and scrap the case.

 

[Tesoro]

"Base To Seating Stem"

ooh a new one for the list of 'B' acronyms. !!! How come noone is talking about jamming which negates all the above?

 

[Wild Bill IV]

if you think about the firing pin pushing the case into the chamber, up against the shoulder before finally igniting the primer, you might conclude the best way to maintain the exact same bullet to barrel lands configuration would be to measure and control the distance from bullet ogive to shoulder datum, rather than OAL or BTO.

That is a good point!!
However, if you keep the sizing die set at one constant point, and watch press loading, the base to datum will stay consistent and CBTO will be easier to measure!! I set my FL die for 1/2 thou shoulder setback!! Done it for 48 years and haven't had any problems!!! I still use a dummy case/bullet with makers to locate the lands!!! This distance is called RIFLE SEATING DEPTH!!! And yes, it changes with throat erosion from plasma ejection!!! I KNOW, FORM-FIT-FUNCTION as an ENGINEER!!! CONSISTENCY IS THE KEY TO PRECISION!!! ACCURACY IS IN THE SKILL OF THE SHOOTER!!! I never use COAL as a gauge!!!