I'm trying to squeeze a little more accuracy out of my reloads and I think increasing the COAL will help. I had been loading everything to 2.800" and calling it good. Today I tried something that was suggested to me for finding a good COAL. I took a fired shell and squished the end a little so a bullet would be too tight to fall in but loose enough that closing the bolt would push it into the brass as it hit the rifling. I came up with a COAL of 2.900". I seated 10 bullets at 2.875" and none of them were tight to close or showed any signs of rifling marks. I loaded the rounds a little light at 40gr. of Varget and I'm using LC Match brass which has less volume anyway. Am I on the right track?
- Thread starter oneshot onekill
- Start date
Re: Finding proper COAL
Almost. That COAL will vary a bit and it will be different for various bullets. You can get a bullet comparator to clamp on a caliper which will give you the base to ogive distance. Bullets have different distance from ogive to tip, so if you were to seat another bullet at 2.90 the ogive may be pushed further towards or away from the lands. Get that base to ogive measurement and seat based on it. Seating dies seat the bullet on the ogive and it gives more consistent results.
Josh
Almost. That COAL will vary a bit and it will be different for various bullets. You can get a bullet comparator to clamp on a caliper which will give you the base to ogive distance. Bullets have different distance from ogive to tip, so if you were to seat another bullet at 2.90 the ogive may be pushed further towards or away from the lands. Get that base to ogive measurement and seat based on it. Seating dies seat the bullet on the ogive and it gives more consistent results.
Josh
Re: Finding proper COAL
That makes perfect sense. At this point I'm only using one type of bullet but I'll be sure to find the right COAL for everything I use.
That makes perfect sense. At this point I'm only using one type of bullet but I'll be sure to find the right COAL for everything I use.
Re: Finding proper COAL
When you've found the max OAL as you did you really won't gain much, if anything, from a comparitor.
You are now seated about 25 thou off the lands and that's typically a good place. You will still need to experiment by seating a bit further in AND out (5 thou steps are good) until you find what your rifle likes best for that bullet and load.
All seaters work off the ogive.
When you've found the max OAL as you did you really won't gain much, if anything, from a comparitor.
You are now seated about 25 thou off the lands and that's typically a good place. You will still need to experiment by seating a bit further in AND out (5 thou steps are good) until you find what your rifle likes best for that bullet and load.
All seaters work off the ogive.
Re: Finding proper COAL
You can also do it this way: http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1705470#Post1705470
I use this method to make a dummy round that is just kissing the lands. I then set that into my seating die and tighten down the adjustment when ever I change between different bullets. I then have a very close starting point. If I want to go shorter, I run one through and measure. If it's still long I adjust it down, run it again till I get it right. Then I just lock it down and run them all through, checking every so often with the comparator to make sure they're coming out right.
You can also do it this way: http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1705470#Post1705470
I use this method to make a dummy round that is just kissing the lands. I then set that into my seating die and tighten down the adjustment when ever I change between different bullets. I then have a very close starting point. If I want to go shorter, I run one through and measure. If it's still long I adjust it down, run it again till I get it right. Then I just lock it down and run them all through, checking every so often with the comparator to make sure they're coming out right.
Re: Finding proper COAL
doesn't horanady make a tool for this?
once COAL has been established isn't there a test similar to an OCW test that can be run to find that "sweet spot"?
doesn't horanady make a tool for this?
once COAL has been established isn't there a test similar to an OCW test that can be run to find that "sweet spot"?
Re: Finding proper COAL
Bullet length will vary enough within the same box to screw up your COAL measurements if you're measuring to the bullet tip. I commonly find a maximum variance as high as 0.015" in boxes of "premium" bullets.
That won't matter if you're measuring to find a COAL that's just "good enough" because, as Fuzzball noted, bullet seaters seat to the ogive, not to the nose.
If you're adjusting seating depth to tweak accuracy, you really need a bullet comparator, such as the Stoney Point device (now sold by Hornady) because the taper of the ogive is much more consistent than bullet overall length. But even with a comparator, the COAL you've measured for one bullet isn't necessarily the right length to use with another bullet.
The diameter of the bore measured to the lands is about 0.008" less than the caliber. The ID of most comparators, however, is 0.011" smaller than the caliber. That means the comparator is measuring to a point on the ogive that will be slightly closer to the bullet's tip than where the ogive contacts the grooves. The distance between those points will vary between two bullets if their ogives do not have an identical taper.
OCW was created to address variability in MV/POI even when charge weight is identical (or nearly so). If you already have determined the OCW, all you need for tweaking jump/seating depth is a simple ladder test.
Bullet length will vary enough within the same box to screw up your COAL measurements if you're measuring to the bullet tip. I commonly find a maximum variance as high as 0.015" in boxes of "premium" bullets.
That won't matter if you're measuring to find a COAL that's just "good enough" because, as Fuzzball noted, bullet seaters seat to the ogive, not to the nose.
If you're adjusting seating depth to tweak accuracy, you really need a bullet comparator, such as the Stoney Point device (now sold by Hornady) because the taper of the ogive is much more consistent than bullet overall length. But even with a comparator, the COAL you've measured for one bullet isn't necessarily the right length to use with another bullet.
The diameter of the bore measured to the lands is about 0.008" less than the caliber. The ID of most comparators, however, is 0.011" smaller than the caliber. That means the comparator is measuring to a point on the ogive that will be slightly closer to the bullet's tip than where the ogive contacts the grooves. The distance between those points will vary between two bullets if their ogives do not have an identical taper.
OCW was created to address variability in MV/POI even when charge weight is identical (or nearly so). If you already have determined the OCW, all you need for tweaking jump/seating depth is a simple ladder test.
