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Micrometer Seater useful?
- Thread starter nksmfamjp
- Start date
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lancetkenyon
Well-Known Member
It would. But what are you going to do with the ones you deemed "out of spec"?
lancetkenyon
Well-Known Member
But seating stems do not seat off the ogive. They seat down from the point. And if your BTO varies, it is not giving you a true measurement from the ogive which is where the bullet contacts the lands.
In all honesty, the Hornady or Wilson comparators don't quite measure from the ogive, but very close. Much more so than measuring with a seating stem.
Mikecr
Well-Known Member
No, it won't.
Base to ogive (BTO) is base length + bearing length + high ogive datum.
The only part of this related to CBTO is ogive datum, as affected by ogive radius.
Seating stems do contact ogives (the ogive is the entire bullet nose), pushing at their own datum.
That stem datum is then affected by ogive radius, and there is a measure for this that helps with consistent seating:
It's a Bob Green Comparator (BGC).
Seating stems contact low on ogives for the steepest angle to push against. An angle too shallow (higher on the ogive) would wedge too much.
There is 'some' wedging anyway which varies with seating force, and this is reduced through stem bedding.
But consistent and moderate to light seating force leads to less seating variance.
I qualify ogives with a BGC, match pre-seating forces with an instrumented mandrel die, and my stems are bedded to specific bullet.
I always measure CBTO, with every round, and it's rare that I need to go back and adjust the micrometer with re-seating.
Last edited:
MagnumManiac
Well-Known Member
This is one of the MOST IMPORTANT aspects of consistent seating and distance to lands affecting outcomes.
This is why we bed our stems for ONE bullet in ELR, of course sorting ogives precisely must be done.
As @Mikecr says, ogive variance and measuring LOW on the ogive is key here.
Cheers.
Rflshootr
Well-Known Member
When I load, I go about it in a slightly different way. I seat all the bullets .010 long. Then I go back and measure each round with a Sinclair nut gauge, make an adjustment to the micrometer and re-seat each individual round. No time wasted in boring bullet sorting any more. It also removes the chance of putting a bullet in the wrong pile while sorting and having different bags or containers with each length bullet.
MarkInPA
Well-Known Member
Thought maybe people might be interested in the link to this tool. Looks like Bob has it on sale for $250.00.
Bob Green's Rifles
Complete Bench & Varmint Rifles Precision Barrel Installation Superior Custom Dies and Tooling Specializing in craftsmanship
greensrifles.com
nksmfamjp
Well-Known Member
- Joined
- Jan 5, 2004
- Messages
- 3,466
I think I get it. If I'm fine with my variation one time through the seater, the micrometer is not required. If I want to seat in 2 steps for perfect oal, the micrometer is required.
That said, how does +/-0 coal compare to +/-0.001 coal on target?
That said, how does +/-0 coal compare to +/-0.001 coal on target?
They are also better when loading different bullets for the same cartridge including between multiple rifles and when conducting seating tests.
Mikecr
Well-Known Member
I don't think Bob understands the tool's real potential.
He seems unmotivated to innovate a universal version, and I'm sure he's not selling many at $250 per cal.
The tool allows you to compare the distance between 2 ogive datums. One at rifling contact, and the other at seater stem contact, at the same time. Variance in ogive radius shows up with this.
Where ogive radius matches, ogives/datums are 'qualified'
Until you've qualified datums, they should be considered an abstract that you could not credibly act on.
This is one of a few reasons why BTO(base to ogive) measure, is in itself, useless.
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