Thread: OAL - gauge and comparator

Hi team,
I’ve been reasonably successful reloading just using oal with digital callipers but have just got myself a Hornady oal gauge and comparator.

Problem is the old oal and new oal are quite wide spread ( yes I know the comparator makes a huge difference in oal ) but I put my old load and new load into the comparator and they are quite different. I’ll measure when I’m home later and give oal in the comments.

Question is should I go with the new oal from the gauge or stick with my old oal. The reason I ask is I’ve been missing a few animals lately which makes me wonder if my ammo isn’t made properly. When looking at the difference in oal I’m starting to wonder if maybe it’s too far into the lands? Which is weird as I’ve practically been key holing at 100m so not sure what the heck’s going on this why the gauge experiment. Any help is much appreciate.

What's your es like? What distance are you missing?

The comparator measures from close to the point where bullet shank changes to ogive (tapered front section) so is not the same as ullet length or coal. Most bullets have an ogive to point length somewhere between 0.4" to 0.7" as an exampe. So you comparator reading will always be that much shorter than c.o.a.l (unless you use secondary zeroing facility on your vernier calipers.

consistency in the measurement is what matters. It matters now how you do it as long as you always do it the same way.

and Bearing surface to Ogive length can also vary a little bit. Some anal people sort their projectiles by bearing length

I've got the old Stoney Point (now Hornady) comparators, Sinclair comparators and one 30 cal Whidden comparator. They all give a slightly different reading ie they are measuring at a slightly different point near the ogive.
I'd change over to your new one. Otherwise it was a waste of time purchasing it. Just note your old measurement and your new measurement in your reloading book and use the new measurement for future reloading.

I found a difference in COAL (to tip) between batches of the same bullet, loaded to the same length to ogive with the comparator. Difference was a couple of thou IIRC. Hornady must have changed the bullet shape slightly.
I think @Flyblown had a similar experience.

There's always a slight difference for projectiles oal. Lead tipped are the worst followed by hollow point. Plastic tips less so.
As you are doing Base to Ogive that is the correct and only way to measure. Cartridge OAL only comes into play to ensure your loaded cartridge fits your magazine.

Just to muddy the water a bit sometimes the Base to Ogive measurement can differ from lot to lot. Sierra used to be very bad for this.

I always check.

Originally Posted by Cigar

I found a difference in COAL (to tip) between batches of the same bullet, loaded to the same length to ogive with the comparator. Difference was a couple of thou IIRC. Hornady must have changed the bullet shape slightly.
I think @Flyblown had a similar experience.

Correct.

There was a big change in bullet shape between batches of 108gr ELD-M (6mm). I could see the COAL difference with the rounds standing in the tray with bullets from an earlier batch. The bullets were the same length, but the ogive shape was different. Because I measure using the comparator, I ended up with longer COAL than I wanted. Luckily it wasn't the other way round.

So just home -
Old rounds are measuring 2.281 (inches) in the comparator grouping we’ll at 100m but miss a bit too much at distances, could just be my shooting though.

New rounds ( haven’t subtracted any give for lands ) is at 2.235
These are with the Barnes TTSX 30 cal 130s

Should I just load and develop new loads at the “new” length and go from there?

Just wondering if my old loads although shooting extremely well at 100m could just be too far into the lands to begin with?

To find oal I was just putting a projectile into a case and closing the bolt down on it, removing case and projectile and measuring that.

Just to be clear the comparator you are using for OAL looks like this.
Lets call this A

https://www.gunworks.co.nz/shop/item...oal-gauge-copy

Or are you using an insert on a caliper by itself
Lets call it B

Originally Posted by Flyblown

Correct.

There was a big change in bullet shape between batches of 108gr ELD-M (6mm). I could see the COAL difference with the rounds standing in the tray with bullets from an earlier batch. The bullets were the same length, but the ogive shape was different. Because I measure using the comparator, I ended up with longer COAL than I wanted. Luckily it wasn't the other way round.

Greetings All,
Have found some significant differences in batches of three different Hornady projectiles. The ogive seems to have become sharper and I can tell the difference by sight. All needed to be seated deeper to maintain the same jump. Some showed measurable differences in velocity as well as impact on the target.
Grandpamac.

Originally Posted by G.I_Joel

So just home -
Old rounds are measuring 2.281 (inches) in the comparator grouping we’ll at 100m but miss a bit too much at distances, could just be my shooting though.

New rounds ( haven’t subtracted any give for lands ) is at 2.235
These are with the Barnes TTSX 30 cal 130s

Should I just load and develop new loads at the “new” length and go from there?

Just wondering if my old loads although shooting extremely well at 100m could just be too far into the lands to begin with?

To find oal I was just putting a projectile into a case and closing the bolt down on it, removing case and projectile and measuring that.

Greetings G.I_Joel,
You mention "miss a bit too much at distance" and I wonder if you are doing any testing at 200 and 300m to check accuracy and trajectory at distance. Some loads can shoot quite well at short range but turn to custard further out. Only testing at longer range will tell.
Regards GPM.