Thread: Measuring COAL

What's the views on measuring COAL when reloading. I've always been taught to measure to the ogive, instead of the tip of the projectile. Have found there can be a lot of variance when measuring to the tip, especially with lead or plastic tipped projectiles. Was just wondering, for the people chasing real tight accuracy if they're missing out on tighter groups by measuring this way.

The reasoning behind this is when reloading for my rifles, the difference between 3/4 - 1 MOA and 1/4 MOA is only 5 thou seating depth of the projectile. Or are people still getting good accuracy measuring to the tip? And at the same time, I know 3/4 to an inch is fine for probably 80 % of shooter, was just a thought I had to myself while mucking round at the reloading bench the other day.

Interesting that 5 thou makes such a difference, I knew it was important but didnt realise that such a small amount would be that significant. When seating do you try get them all to exactly the same length eg 2.850 as opposed to 2.852? Would you worry about a 2 thou difference in seating depth? I measure to the ogive not oal.

hells bells Batman......I chuck a previously loaded round in to set up the seating die and go to it..... but Im a hunter not a shooter so 1" is more than fine. all my loads are 1mm short of magazine length.

Originally Posted by Benj

Interesting that 5 thou makes such a difference, I knew it was important but didnt realise that such a small amount would be that significant. When seating do you try get them all to exactly the same length eg 2.850 as opposed to 2.852? Would you worry about a 2 thou difference in seating depth? I measure to the ogive not oal.

Engineer by trade so bit anal I guess you'd say. I was surprised as well. Was testing some loads the other day, I get the speed I want below pressure signs then start at max mag length and increase seating depth 5 thou at a time till I hit the grouping I want. For example 2.220" for 300 wsm magazine, then 2.215, 2.210 etc.

I know neck tension will change your seating depth, so I measure everyone off the press and adjust accordingly. Only normally 3-4 in a batch of 50 that feel slightly different when seating, and can normally feel if they're a little harder to seat, adjust mic a little to seat deeper.

Originally Posted by Micky Duck

hells bells Batman......I chuck a previously loaded round in to set up the seating die and go to it..... but Im a hunter not a shooter so 1" is more than fine. all my loads are 1mm short of magazine length.

@mickey Duck yea I know, not for everyone. I just enjoy tinkering round like that. Then again it may just be a coincidence. Each to their own I say.

I always measure to the ogive, some rifles/loads/projectiles can be a bit fussy on OAL and others I’ve found aren’t.

I measure base to ojive (CBTO). But also note down COAL in my records for comparing apples with apples with someone else’s loads. Every comparator insert is different...

When I set up to reload for a new calibre I first find the maximum OAL for the chamber and keep a dummy round at this length for future reference. I then measure the length to ogive using a comparator. This gives me the length to lands, regardless of what projectile I use this measurement will be the same when using the same comparator insert. For my LR/precision rounds I measure each round length to ogive and adjust the seating die so they are all the same. I use either Redding or Forester micrometer adjust seating dies so this is a fairly quick process. As a generalisation, 15 to 20 thou off the lands seems to be a sweet spot for most projectiles and unless I happen to find a super accurate load during initial development for speed, I test varying seating depths to try tightening up the load

Originally Posted by The Claw

When I set up to reload for a new calibre I first find the maximum OAL for the chamber and keep a dummy round at this length for future reference. I then measure the length to ogive using a comparator. This gives me the length to lands, regardless of what projectile I use this measurement will be the same when using the same comparator insert. For my LR/precision rounds I measure each round length to ogive and adjust the seating die so they are all the same. I use either Redding or Forester micrometer adjust seating dies so this is a fairly quick process. As a generalisation, 15 to 20 thou off the lands seems to be a sweet spot for most projectiles and unless I happen to find a super accurate load during initial development for speed, I test varying seating depths to try tightening up the load

Glad I'm not the only one who measures every round. I use same Mic Redding dies as well, so like you said, not that slow. I wish my rifles had longer mags, but at this stage don't really want to single feed or spend the money on aftermarket mags/bottom metal etc.
I single feed one rifle but am happy enough with results at mag length with the rest of them.

Always to the bullet ogive checked with a Hornady bullet comparator and calibers. If the loaded cartridge is too long for the magazine then adjust but still always to the ogive to get the same consistent jump of the bullet to the lands. I always check loaded rounds for run out as well.

Question from future generations...
Whats a magazine?

Originally Posted by johnd

Question from future generations...
Whats a magazine?

Woman's Weekly.