Consistent seating off lands?

[dbooksta]

How do you get consistent OAL to the ogive without putting every loaded round in a gauge and hand-adjusting it, or else pre-sorting the bullets by length to ogive and adjusting for each set?

As far as I can tell no seating die seats exactly to the ogive. Didn't think this mattered much before but: I just did a batch of .338LM using an RCBS Gold Medal seater and 250gr Lapua Scenars. I had benchmarked my lands by pushing a long dummy round into the chamber and measuring its COAL, then loaded .05" shorter. When I fired the loads the accuracy was fantastic, except that one of the rounds wouldn't chamber because the ogive hit the lands! Its COAL was the same as all the others. So obviously even with these high-grade bullets there's at least .05" variation in ogive vs. bullet length.

I've heard Redding Competition seaters bear closer to the ogive. Does it result in significantly closer ogive lengths than the RCBS GM seater? Or are there other seating dies or methods I should be looking at?

 

[jcampbellsmith]

I work on my neck prep. Secondly, if I feel a bullet has seated deep into the neck (just slipped into the neck) or is hard to seat, I measure the loaded round. If my suspicion is correct, I mark the round up as a fouler. At 100yds +-3 thou is making no odds with my 260 Rem, but if I'm shooting further out at paper, then I'm looking to use the most consistent rounds.

The only time I tweak the seating is on my first off rounds where I have seated the bullet too deep and want to get back to my preferred OAL measurement. I use Redding Competition seaters, but I can't claim scientifically that they are better or worse than any others. German Salazar has written a good article on the performance of a number of seaters.

I hope that helps. I try to put my effort into the brass prep (80%) then load up the rounds with the minimum of fuss and go shoot them.

Regards

JCS

 

[dbooksta]

Thanks, I assume you mean this article by Salazar on runout?

Don't quite understand the rest of what you wrote: Are you saying you seat a batch and then measure to the ogive of each finished round and mark/redo outliers? Or are you saying you keep the necks loose enough that you load to press on the lands as the round is chambered (which is fine if you want to shoot on the lands, but wouldn't work if you want a setback)?

 

[jcampbellsmith]

Thanks, I assume you mean this article by Salazar on runout? Yes.

Don't quite understand the rest of what you wrote: Are you saying you seat a batch and then measure to the ogive of each finished round and mark/redo outliers? - No, I try to measure as few loaded rounds as possible.

Or are you saying you keep the necks loose enough that you load to press on the lands as the round is chambered (which is fine if you want to shoot on the lands, but wouldn't work if you want a setback)? No, I don't soft seat.

Key word is 'feel'. As I seat the bullet I 'feel' how much or how little resistance I am getting to the bullet seating in the case neck. It's a very crude assessment, but I've a fairly good idea when I have less than normal resistance on seating or more than normal resistance. I measure to confirm my crude assessment and mark the rounds up for foulers. I don't reseat any of them.

Regards

JCS

 

[Dogtown]

If you want to see the amount of seating force you're using, then you need one of these:
https://www.kmshooting.com/catalog/arbor-press/arbor-press-with-force-measurement-option.html

 

[dbooksta]

Seems to me seating force is more of a case issue and the problem you're having is a way out of spec bullet. I don't know about .338" bullets, but 30 cal and down a 0.050" variance in bullet length to ogive is way out of spec and I'd send the manufacturer a note expressing my disappointment.

Right, given the previous responses I may not have explained the problem correctly. It may be moot if the ogive length to overall length on match-grade bullets is supposed to be very tight. These are 1.55" bullets, so a .05" spread does seem large. Since they're Lapua Scenars from a single lot I'll ask if this variation is within their tolerances.

The original question assumes that we can expect significant (i.e., > 1%) spread between bullet OAL and length-to-ogive. If that's true, and we aren't soft-seating to the lands, presumably we want to hold cartridge length-to-ogive (CLOG) constant for maximum precision, not COAL, which is what we usually quote. So the original question was how can we achieve consistent CLOG since no seating die seems to seat off the ogive?

 

[J-ROD]

I use a redding seater with micrometer. It doesn't seat off the ogive but gives me consistent results. Loading bergers, typically my rounds are +/- .001" when i check with my hornady comparator to the ogive, yes i check everyone. The only time this varies more is with high/low neck tension or compressed loads.
If you seated off the ogive, the bullets would probably stick in the stem if that makes sense .


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[nuclear_shooter]

I use a redding seater with micrometer. It doesn't seat off the ogive but gives me consistent results. Loading bergers, typically my rounds are +/- .001" when i check with my hornady comparator to the ogive, yes i check everyone. The only time this varies more is with high/low neck tension or compressed loads.
If you seated off the ogive, the bullets would probably stick in the stem if that makes sense .


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My experience mirrors this. I use the standard Redding dies. My bullets were seated to a very consistent head to ogive with once fired brass. I checked my seating stem to make sure that it indexed off the bullet surface (not quite the ogive, but close) and not the meplat. If that does happen, you might want to get one of the VLD stems. Seating off the meplat can cause inconsistent head to ogive and can deform the ballistic tip.

 

[8nbait]

compressed loads?

 

[dbooksta]

For reference, here's an old thread on this same problem at ARFcom. Between that and other reading I'm gathering that:
A. Most seating dies bear on the ogive "close" to the base. Some so closely that compresed loads can crack the seater stem (Redding explicitly warns against this, and I saw some reports of Forster stems cracking).
B. Not all seater stems are hollowed out to accommodate the most streamlined bullets on the market, so one should check to make sure there is no contact further up the ogive towards the tip.
C. You can machine, or pay the die companies to machine, a stem to a specific bullet so that it bears over a wider area towards the ogive base and definitely doesn't contact higher up.

 

[dbooksta]

Just took apart the die and confirmed the problem: The seating stem, at least on my RCBS GM .338LM seater, is nowhere close to the ogive base. I twisted a bullet in it to see it marking about a third of the way down the ogive from the tip! Then I spent 15 minutes with my Dremel trying to open it up, but couldn't get it to bear further than about halfway down the ogive. For anyone who cares about distance to lands this is no good!

The stem opening would have to be extremely thin and strong to reach near the ogive base. So kudos to Forster, Redding, and every other company who pulls that off.

But that's true only if the seater uses a stem of the same diameter as the caliber. I can't see any reason for this to be the case: A good seating die should have a substantial "seating plug" with an opening barely tighter than the minor diameter of the caliber's rifling. In order to avoid marking the bullet it should have a short secant ogive no sharper than the longest possible bullet for the caliber, followed by a long open cylinder to accommodate tangent ogives or any meplat imaginable. Anyone aware of such a die?

 

[jcampbellsmith]

...... I can't see any reason for this to be the case: A good seating die should have a substantial "seating plug" with an opening barely tighter than the minor diameter of the caliber's rifling. In order to avoid marking the bullet it should have a short secant ogive no sharper than the longest possible bullet for the caliber, followed by a long open cylinder to accommodate tangent ogives or any meplat imaginable. Anyone aware of such a die?

Maybe you should manufacture and sell seating die stems to your design? Just a thought. Regards JCS

 

[dbooksta]

Maybe you should manufacture and sell seating die stems to your design? Just a thought. Regards JCS

Yep: I talked to RCBS about why they don't do this, and it turns out a simple design like I describe here has been tried and doesn't work because it will compress bullets under seating pressure, deforming them and/or getting them stuck.

However I have come up with a more complicated design that will avoid those problems, as well as the problems Redding and Forster have with stems cracking. I'm trying to see if I can get any of the die companies to bite....