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Expanding vs Turning Mandrels
- Thread starter Polaris_Doc
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ntsqd
Well-Known Member
Something mentioned above in this thread triggered a thought. The idea stated was that a mandrel will push any thick neck sections to the outside. Logical and reasonable that this is true.
The thought that I had is, is that good? Not that having an inconsistency on the neck ID is good, just that having an inconsistency on the neck OD means that the bullet may not be centered in the throat of the barrel. That would be bad, too. I know that is part of what neck turning is all about. to make the neck as uniform in thickness as possible.. It was just that the statement didn't seem to account for, or acknowledge that.
The thought that I had is, is that good? Not that having an inconsistency on the neck ID is good, just that having an inconsistency on the neck OD means that the bullet may not be centered in the throat of the barrel. That would be bad, too. I know that is part of what neck turning is all about. to make the neck as uniform in thickness as possible.. It was just that the statement didn't seem to account for, or acknowledge that.
WildRose
Well-Known Member
For purposes of getting a clean release from the shell it's probably better, but for purposes of precise neck tension I would say if you don't have a generous neck it could be problematic.
The ideal would be to use a mandrel when uniforming necks on your new brass then turn your necks to a consistent thickness for the best of all worlds.
Mikecr
Well-Known Member
The mandrel is driving thickness variance outward -away from seating bullet bearing.
I you don't expand then bullets won't seat as centered.
Either way, you can forget centering with bore from neck thickness variances.
But you can pretty much forget the centering part anyway. It doesn't happen.
I you don't expand then bullets won't seat as centered.
Either way, you can forget centering with bore from neck thickness variances.
But you can pretty much forget the centering part anyway. It doesn't happen.
Look at it like this.....if you have plenty of neck clearance then the only thing that matters is whats touching the bullet. If you use an expander mandrel or button your are pushing the inconsistencies to the outside. On a smaller scale you are doing the same with the bullet during the seating operation.
BrentM
Well-Known Member
I use .002 mandrels and undersize .001-.002. . I tend to see similar SD and accuracy with a little more tension, .002-.004, so I'd tend to just stick with it. I've played with .001 tension and struggle to get consistency there without turning necks.
ntsqd
Well-Known Member
I think that I can see MikeCR's point. Assuming a generous but not excessive neck clearance, one that removes any influence that the case neck might have on the axial position of the bullet, the next thing that influences bullet alignment with the bore is the fit between the OD of the bullet's bearing surface and the ID of the throat. If you have any clearance there, the bullet can easily be eccentric by that radial clearance dimension, and if you have the absolute minimum clearance there then you risk pulling the bullet in live extractions even if you have not engraved the bullet in the rifling and it will still be slightly eccentric. If you don't have any clearance there then you can't chamber a round.
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QuietTexan
Well-Known Member
What caliber? I've started really buying into initially running smaller calibers tighter and larger ones looser.
After going over a lot of info from Mike and Mark and other smart guys something I messed with is shortening the length of neck sized on my .338 while using the same sizing mandrel to open back up has shifted the groups some. Not turning the necks and using a full caliber mandrel (LE Wilson "new", I think it's actually .338 - to try to target .0015 spring back on new brass), so pretty loose.
Hornady factory loaded brass, not very well matched, could be case volume causing differences also.
sheephearder
Well-Known Member
I have had similar problems with reloading Hornady factory brass. In my opinion, all these necks need neck turning.
WildRose
Well-Known Member
I've learned after a lot of trial and error and generally being headed that neck turning should simply be a part of our normal bras prep with new brass or once fired brass from factory ammo.
Nothing has helped my loading and shooting as much as starting to pay serious attention to uniformity of the brass and neck tension.
Polaris_Doc
Well-Known Member
I can see how there are so many things that work for everyone in a different way, but man it is frustrating!!
So if I anneal every firing with an AMP mark2, then I would assume the spring back is very little compared to brass that's been fired/sized a few times. At least that's my experience in a few different cartridges when using standard FL sizing dies. So that said, I'm assuming. 003-.004 down with the sac bushings and up to .002 under bullet diameter with mandrels? Would assume if I was .001 under I'd not have enough tension with annealed brass?
I appreciate all the info guys.
So if I anneal every firing with an AMP mark2, then I would assume the spring back is very little compared to brass that's been fired/sized a few times. At least that's my experience in a few different cartridges when using standard FL sizing dies. So that said, I'm assuming. 003-.004 down with the sac bushings and up to .002 under bullet diameter with mandrels? Would assume if I was .001 under I'd not have enough tension with annealed brass?
I appreciate all the info guys.
WildRose
Well-Known Member
I'm not comfortably myself with so little neck tension especially one that is magazine fed.
If all you're doing is single feeding straight into the chamber you can get away with a whole lot less that if you are loading them into and from a magazine.
QuietTexan
Well-Known Member
Ultimately you have to shoot it and see, but you're on the right path to move forward and try it. -0.004" bushing /-0.002" mandrel is a perfectly good place to start. The next logical step to me after that would be -0.003/-0.001". Same +0.002 mandrel movement, less ending tension.
My 6.5mm I'm currently using -0.003/-0.001" after annealing with my AMP. Was using -0.002/-0.0015" for the first two firings on the brass, the shoulders weren't being bumped yet and the mandrel was barely doing anything to the necks because they were popping back open pretty well (I moved up the half-thou because the -.001 wasn't even touching seemed like) but the bullets sat fine. Annealed at 3F when the shoulder started bumping, definitely felt the mandrel moving the necks at that point.
I've done -0.002/-0.000" after annealing in my .338 cal single shot action because bullet set back isn't a worry there, and it has more surface area to grip. So everything here is somewhat relative.
My 6.5mm I'm currently using -0.003/-0.001" after annealing with my AMP. Was using -0.002/-0.0015" for the first two firings on the brass, the shoulders weren't being bumped yet and the mandrel was barely doing anything to the necks because they were popping back open pretty well (I moved up the half-thou because the -.001 wasn't even touching seemed like) but the bullets sat fine. Annealed at 3F when the shoulder started bumping, definitely felt the mandrel moving the necks at that point.
I've done -0.002/-0.000" after annealing in my .338 cal single shot action because bullet set back isn't a worry there, and it has more surface area to grip. So everything here is somewhat relative.
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BrentM
Well-Known Member
204, 224, 6mm, 6.5. Haven't tested much on the 30's. Don't really shoot them anymore. I never felt the 30's were that sensitive tho. I just run a .002 mandrel on everything now and it seems to work fine. I'm not a bench shooter tho so maybe my acceptable accuracy is less than others. If I can get .5moa consistency with low sd I'm happy. I don't intentionally chase bugholes AT ALL COST anymore. I look for it but I'll stop once I get a solid performer.
