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Ogive to base measurements.
Posted: Sun Feb 06, 2011 2:05 pm
by ovenpaa
As part of an ongoing project to measure the point where the Ogive meets the lands back to the base of the bullet I built a little fixture this morning. This is for 7mm Berger 180's. Using an off-cut of aluminium I bored a .290" diameter hole reducing to 5mm with a 45 degree step at around where the ogive would meet the lands, there is also a chamfer on the start of the bore to make sure the bullets are not marked in anyway.
The fixture is bolted to the base of a Sinclair fixture used for checking bullet run out. I will need to make a slightly longer mast as the standard one is barely long enough. The plan is to build some little dedicated fixtures on granite blocks with interchangeable fixtures for whatever bullet is needed.
Apologies for the crap pictures from my iFone.
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 3:52 pm
by spud
:) :) :)
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 4:18 pm
by ovenpaa
I just measured a group of 180 VLD's and they were all within a tenth of a thou. One thing I did notice was the mast which is made out of 8mm stainless flexes slightly so new ones will be 10mm x 130mm
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 4:29 pm
by spud
ive just weighed a 1000 of the same bullet dave all same batch number there was .3 grains differnce betwean highest and lowest 18.0 dead to 180.36 extreme ranges
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 4:30 pm
by Robin128
COAL varies as a function of your measurement to the ogive of each round, right?...what about then the varying capacity of the cartridge? IE pressure.
Or was that too stupid a question... even for me... :lol:
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 4:32 pm
by Robin128
You are attempting to keep distance to lands constant?
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 4:43 pm
by spud
Robin128 wrote:COAL varies as a function of your measurement to the ogive of each round, right?...what about then the varying capacity of the cartridge? IE pressure.
Or was that too stupid a question... even for me... :lol:
personally i will weigh every casde and h20 it after fireforming for further segregation
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 5:33 pm
by dodgyrog
Some people will go to the far end of a fart!
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 5:45 pm
by ovenpaa
It all helps when the only bit we are interested in is 5" across at 1000 yards or more.
There are many steps you can take to get to the ultimate loaded round, some I take some I don't, the important things are repeatability and feeling good about what you have done, it is one less worry at the firing point.
Re: Ogive to base measurements.
Posted: Sun Feb 06, 2011 5:48 pm
by dodgyrog
I like stalking up close and personal! 1MOA works for me.
Each to his own.