bet on bullet comaparitor being the same

[Mag 300]

I have a bet and what better place to ask ,
once you have the ogive dimension for a certain rifle say 6 mm you can use the comparitor measurement to load other rounds using different mfg of bullets like lapua 105 berger 108 once you have the measurement for the rifle to the 6 mm comparitor loading another mfg bullet should be the same distance off the lands

Thanks for the input.

 

[BOLTRIPPER]

Re: bet on bullet comaparitor being the same

maybe prolly no...

1st off ....how much money we talkin 'bout on the bet ?

.....and as you well know the ogive on some bullit makers jump about a bit.......

 

[Ted_D]

Re: bet on bullet comaparitor being the same

the same diameter of the ogive would be in the same place. But you may or may not have more bullet out of the case

 

[Victor N TN]

Re: bet on bullet comaparitor being the same

One key to answering the question is where does your seater die plug touch against your bullets? If the seater die doesn't touch it at nearly the same place as the comparitor, the measurements may be slightly off. If they contact at the same point, then the readings SHOULD be the same, no matter what bullet. But most bullet seater plugs will make contact with the point of the bullet before it does the ogive. At least, unless you have a special plug made or make your own.

 

[Mag 300]

Re: bet on bullet comaparitor being the same

Ted yu may have more bullet out of the case but the measurment of the ogive is the same for two different bullets then they will be the same off the lands of the same rifle
Bill

not talking OAL but comaritor that measured the area that is .244 for a 6 mm to the base of the cartridge

 

[18Echo]

Re: bet on bullet comaparitor being the same

I've measured the ogive on two seperate lots of Sierra 175MK's and it was different. Couldn't figure out for the longest time why my last two rounds were so off. then I pulled one from the old box and got one from the new box and they were different. I think they were off by .002 or .003.

 

[Victor N TN]

Re: bet on bullet comaparitor being the same

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 18Echo</div><div class="ubbcode-body">I've measured the ogive on two seperate lots of Sierra 175MK's and it was different. Couldn't figure out for the longest time why my last two rounds were so off. then I pulled one from the old box and got one from the new box and they were different. I think they were off by .002 or .003. </div></div>

Sierra is known to have several different machines running into the same bin. I was told by someone that was there that they usually run 168 SMKs on as many as 6 machines and have them running into the same bin. Bullets taken from that communal bin all go into the same boxes.

I learned back in the 1980s to seperate Sierras into groups. Advise I would pass on to you now. At least if you plan on being serious about groups or shot placement.

 

[Pirate-69]

Re: bet on bullet comaparitor being the same

I think Bill's question is one have been wondering about also. Lets say Bill's 6MM gave a comparitor measurement to the ogive of 2.610" for a 100 grain bullet and he wants to back it off the lands 0.010". He would set his die so the bullet was seated with a ogive measurement of 2.600". Now, if he wanted to shoot a 65 grain bullet in the same rifle and also shoot it 0.010" off the lands, all he has to do is to adjust his die so the loaded 65 grain round ogive measurement is also 2.600". This is because the ogive length in a rifle will be constant regardless of the bullet fired but the COL can vary because the ogive is not located at the same place on all bullets.

Am I understanding this correctly??????? If not, please help me understand.

 

[Victor N TN]

Re: bet on bullet comaparitor being the same

If I read it correctly, I believe you are correct.

You need to remember another variable. If it is in a high powder burning case every 300 to 500 rounds you will need to check the length to the lands again. In a calm cartridge like a 6PPC the lands will move back as much as .005" in 400 to 600 rounds.

Just something else to keep in mind.

 

[18Echo]

Re: bet on bullet comaparitor being the same

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 18Echo</div><div class="ubbcode-body">I've measured the ogive on two seperate lots of Sierra 175MK's and it was different. Couldn't figure out for the longest time why my last two rounds were so off. then I pulled one from the old box and got one from the new box and they were different. I think they were off by .002 or .003. </div></div>

Sierra is known to have several different machines running into the same bin. I was told by someone that was there that they usually run 168 SMKs on as many as 6 machines and have them running into the same bin. Bullets taken from that communal bin all go into the same boxes.

I learned back in the 1980s to seperate Sierras into groups. Advise I would pass on to you now. At least if you plan on being serious about groups or shot placement. </div></div>

Group into Length to ogive or by weight? I weighed my first box of 175SMK's and they were all 175.

 

[Victor N TN]

Re: bet on bullet comaparitor being the same

I have a labratory balance that lives in a plastic house on a granite base. I promise they aren't that close. They usually run +/- 1.75 grains in a group of 100 pieces. (3.5 grains from lightest to heaviest.)

But the best way to seperate them is by base to ogive length. OAL will give you up to .020" differences.

 

[Mag 300]

Re: bet on bullet comaparitor being the same

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Victor N TN</div><div class="ubbcode-body">If I read it correctly, I believe you are correct.

You need to remember another variable. If it is in a high powder burning case every 300 to 500 rounds you will need to check the length to the lands again. In a calm cartridge like a 6PPC the lands will move back as much as .005" in 400 to 600 rounds.

Just something else to keep in mind. </div></div>

Victor

Thanks I did not think of that
Bill

 

[jr81452]

Re: bet on bullet comaparitor being the same

the short answer is: not likely. the ogive is not a fixed point in any sense. it is in fact "The pointed, curved nose of a bullet". the ogive is the entire section between the full caliber shank and the meplat. as such, most comparators measure to a nondescript "datum point". the diameter of that datum point will vary greatly from the diameter of the throat of your rifle. thus the comparator measurement you get for a specific bullet is not the actual distance to your lands but rather a relative distance. since the datum diameter's location on the length of the ogive is different for every make of bullet, and that diameter has no actual relationship to your lands, it is highly improbable that both bullets seated to the same comparator measurement would have the same actual distance to the lands.

here is an easy test. use a magic marker to blacken a bullet, then seat that bullet in an empty case so that you know it will seat well into the lands (just seat it long and push the bullet into the case the rest of the way with the bolt). upon extraction of said test round from the rifle you will notice the lands have worn of some of the black marker where they touched. now take out your comparator bushing and put it on the bullet. if it touches at the exact same place as the worn off marker, then don't ever sell it because you have found the holy grail of comparators. if not, then i rest my case and you have lost your bet.