Cases with a neck wobble
- Thread starter propliner
- Start date
If fired from your own gun, its a wonky chamber
Chamber is out of alignment with bore. I assume cases are from same gun. If it's not to bad and rifle shoots I wouldn't worry. Possibly of case life being reduced due to sizing die straightening the case. Measure them with a case concentricty gage and see how far out they are.
The biggest cause of case neck runout happens when the expander is locked down off center.
Below the Forster benchrest sizing dies have a high mounted floating expander. The expander enters the case neck while it is still held and centered in the neck of the die. Meaning these dies can not pull the case neck off center and induce runout.
Below a Lee sizing die that has the expander held and centered in a locking collet.
A trick used to center the expander in RCBS dies is to place a small o-ring under the expanders lock nut. This lets the expander float and self center in the case neck. The only problem with this method is if the case has a ding in its rim the case will tilt in the shell holder inducing neck runout.
Another method is to remove the dies expander and use a expander die that expands the neck on the upstroke of the ram with the case resting on its base.
Expander Mandrels — Not Just for Neck-Turning
http://bulletin.accurateshooter.com/2009/06/expander-mandrels-not-just-for-neck-turning/
Below is a factory loaded cartridge with a "slight"
amount of neck runout.
Below the Forster benchrest sizing dies have a high mounted floating expander. The expander enters the case neck while it is still held and centered in the neck of the die. Meaning these dies can not pull the case neck off center and induce runout.
Below a Lee sizing die that has the expander held and centered in a locking collet.
A trick used to center the expander in RCBS dies is to place a small o-ring under the expanders lock nut. This lets the expander float and self center in the case neck. The only problem with this method is if the case has a ding in its rim the case will tilt in the shell holder inducing neck runout.
Another method is to remove the dies expander and use a expander die that expands the neck on the upstroke of the ram with the case resting on its base.
Expander Mandrels — Not Just for Neck-Turning
http://bulletin.accurateshooter.com/2009/06/expander-mandrels-not-just-for-neck-turning/
Below is a factory loaded cartridge with a "slight"
amount of neck runout.
Awesome, thanks guys. I'm going to try a new die and then if they aren't up to spec I'll order an expander die and do it as a separate step. I'm in the process of outside neck turning all my brass as well.
I've also noticed that some of my brass has a base that's not perpendicular to the case wall. When I put it in a Lee chuck and spin it the whole case wobbles off-centre. I know this also contributes to poor accuracy. I'm wondering if one side of the rim might be bending down as I pull it out of the expander ball. I'm lubing inside the case neck so the tension isn't that high but .223 brass has a thin rim at its base. I might just get away from expander balls altogether.
Edit: I'm now thinking the uneven rims are being caused by semi-auto ejection. This would also cause the case to sometimes pull sideways when coming down through the expander ball. It might be the cause of both problems here.
I've also noticed that some of my brass has a base that's not perpendicular to the case wall. When I put it in a Lee chuck and spin it the whole case wobbles off-centre. I know this also contributes to poor accuracy. I'm wondering if one side of the rim might be bending down as I pull it out of the expander ball. I'm lubing inside the case neck so the tension isn't that high but .223 brass has a thin rim at its base. I might just get away from expander balls altogether.
Edit: I'm now thinking the uneven rims are being caused by semi-auto ejection. This would also cause the case to sometimes pull sideways when coming down through the expander ball. It might be the cause of both problems here.
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The case wall of almost all bottleneck cartridges is tapered slightly so it is not exactly perpendicular to the head of the case. Either your Lee chuck has dirt in it and the case is held canted, or the case is pretty much toast if it noticeably wobbles from the web area up. Something is definitely wrong if it is bending the case that much and that case is essentially junk brass and probably should be crushed and discarded/recycled. If it is just the neck area wobbling, it is still not good, but it probably can be corrected a few times. The lifetime of such cases is low.
If you are reloading for an AR type platform do yourself a big favour. Full length resize with a die set to give you about 3-4 thou of shoulder bump. You want that case to get squeezed to size the body properly for a semi-auto action, smaller than would be required in a bolt gun. Since dies are tapered to match the taper of the cases getting resized, getting it in there a couple of thou further than is required for a bolt gun ensures they are properly body sized. I prefer Redding Competition body die which does NOT touch the neck. THEN follow up with a Lee neck collet die to set the neck inner diameter. If you want to do it in one step with a die that does both the body and the neck, as per Ed's reply using a Forster or Lee full length die.
I have seen this with brass from semi auto. The case rim is deformed from the extractor and causes the brass to enter the die at an angle???
For me it is 8mm mauser from a hakim
I know that the base-to-wall angle is not exactly perpendicular but my point is that it isn't consistent all the way around and the body and has a wobble with reference to the base. Im thinking if the base has a bend in it from ejection it won't sit flush in the chuck. I'll run some across a file to see if there are high spots.
I'm currently full-length resizing with a Lee die but I'll fire this brass and move onto some new stuff.
