Achieving OAL Consistency

Chris623

Chris623

New member
I'm running some tests on Sierra's .224" 63 gr Varmint bullet. I'm using a Dillon 550B for the priming and bullet seating steps. As anal as I've been, I still get a .010" difference in OAL while loading 50 rounds. I've checked my procedure and can find nothing indicating it's something I'm doing wrong. I'm using a Lyman .223 seating die. The OAL just vacillates back and forth. Any thoughts?
 
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Measure the length of those bullets, right out of the box, and you will see the difference before you load them.

Cartridge base to the tip of the bullet is a good thing to measure if you are trying to fit a magazine but it is going to fluctuate due to the forming of that tip at the factory (some more than others, plastic tip/hp/sp etc.). You are not doing anything wrong. Cartridge base to ogive is a more accurate way to measure.
 
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I grabbed a new box of Sierra 1365 off the shelf. Out of first 6 random pull, had less .001 difference in two different bullet comparators. Pull out 4 more and found one .002 short of the shortest of first 6. So small sample, I would think you would see .004-.005 minimum of variation bullet base to ogive.
 
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I just opened a new box of the #1370 63 grain SMP's 10 at random varied 0.006 in OAL of the bullets. The ogive measurement is the only way to properly seat bullets if you are going for the gusto.

Greg
 
I guess what I didn't realize was the fact the exposed lead tips made for a variation in length of the bullet. I'll go measure some and observe that.

Greg, you know precision is my goal. I'm trying to learn how to load as close to perfect rounds as I can for target purposes. Typically, perfect isn't attainable, but the harder I try, the closer I'll get, I hope. I've a lot to learn and the only way I'll do that is to expose my ignorance with questions.

Does the ogive change from bullet to bullet? If so, how can a bullet seater compensate for that?
 
I just measured 10 more. Spread was 0.006 OAL. Base to ogive measured only a variant of 0.002. The one that was 758 vs the one that was 752 OAL had ogive measures of base to ogive of 0.428 vs. 0.0426.

That proves it to me pretty well.

Greg
 
Disconcerting, to say the least. So to seat the bullet .005" from the lands, I need to use the ogive to seat the bullet and not the tip...........is that right? I presently have a tiny circle the seating tool prints where it touches the ogive. I thought, basically, that's what I was doing. ????
 
Crud in the seater stem can give you OAL's all over the map. Also, if the bullet is tipped going into the seater stem can make a difference, slow down on your seating, try and feel the bullet engage the case mouth.
 
Took the die out of the press and blew it out with an air compressor and wiped it with a long-stick q-tip. No gunk. I always try and feel the bullet engage the case mouth. Try to start it by hand so it doesn't tip.
 
Chris yes to seat a certain jump to the lands it is measured from the ogive of the bullet. For me oal only matters because there are mag length limits. If the bullets you are using have a low ogive to tip variation, you can use aol the lock your seating die,if the variance greater than what is acceptable. You will have to measure(ogive to cartridge base,this would need to be done anyway) and seat individually to maintain a tight control of jump to the lands.
 
Originally Posted By: GLShooterI just opened a new box of the #1370 63 grain SMP's 10 at random varied 0.006 in OAL of the bullets. The ogive measurement is the only way to properly seat bullets if you are going for the gusto.

Greg

I happened to load 50 rounds this evening using 20 cal 40 grain Berger hp bullets. My measurements with these bullets mirror your findings. Bullet length and therefore OAL varied by 0.005 while the base to ogive measurements only varied by 0.0015.

Base to ogive measurements are where I focus my attention when loading.
 
I'm no expert, and it may not be a big difference, but primer seating depth may also play a role. I uniform all my primer pockets, but still notice variation even with CBTO.
 
This is all fascinating to me. With this rifle, I'm loading my first jacketed bullets. 99.9% of the bullets I've loaded in my life were lead.......with flat meplats. No problem setting things to a fixed OAL. But registering that measurement off the ogive is totally new to me. I've a lot to learn, guys.

I'm trying to load my rounds to an OAL of 2.314". Trying to get my rounds as close to the lands as possible............at least for my first tests. Then I'll drop back .005" at a time until I find an OAL that gives good results. The only magazine on the market that will hold that round is an ASC magazine. The longest round they will hold is a 2.316".............but Gred told me to load my rounds to 3.214" because trying to make them closer would be a nightmare. Now I see what he meant.
 
Same brand of brass? Same number of loadings on them? Same case prep? What's your methods of cleaning brass? Are you using the same speed and pressure when you raise the ram to seat a bullet? The last one is the biggest. To fast and you can seat a bullet deeper without even knowing it.
 
Originally Posted By: Sniper66I'm no expert, and it may not be a big difference, but primer seating depth may also play a role. I uniform all my primer pockets, but still notice variation even with CBTO.

This was an issue i had. Drove me nuts for a hour until I figured it out.
 
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Originally Posted By: FirehandOriginally Posted By: Sniper66I'm no expert, and it may not be a big difference, but primer seating depth may also play a role. I uniform all my primer pockets, but still notice variation even with CBTO.

This was an issue i had. Drove me nuts for a hour until I figured it out.

How does primer seating depth affect the length of a round?
 
Originally Posted By: spotstalkshootI was wondering how seating primers properly would change the length at ogive.

me too!!!
 
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