300 gr. AccuBond in 375 H&H

[crday]

I've run into an issue loading this combination that I've not seen before. Suggestions appreciated.

Load is 76 gr. of IMR 4350 under the 300 gr. AccuBond. Dies are standard RCBS. Once and twice fired cases, all full length resized and trimmed to the recommended trim-to length per Sierra's book. The same dies have been used to load other bullets without problems.

Issues are these:

The neck tension is insufficient to hold the bullet in place. Bullets will turn with finger pressure. Obviously unacceptable.

The bullet has a crimping groove, but as I seat the bullet to that depth, the bullet 'springs' back up. In some instances, the bullet is actually pulled from the case and sticks in the top of the seating die. Initially, I blamed this on compression of the powder charge, but when I switched to 67 gr. of 4064 in an effort to avoid powder compression, the same issue occurs.

This led me to believe that the bullet was sticking in the seating plug and actually being pulled out of the case. I have removed the seating stem and polished/lubed it in an effort to keep the bullet from sticking, to no avail. Although I have not done it yet, I suppose it would be possible to fill the plug slightly with AcraGlas, treat a bullet with release agent, and create something of a non-stick 'mold', but I question whether I could keep the mold straight.

I am considering using a Lee Factory Crimp die to treat the symptom, but I'm wondering what the real cause is?

 

[DrMike]

crday,

You might check the simple stuff first. I agree that it is quite possible that the bullet is sticking in the seating plug. RCBS will make a plug for you that avoids any possibility of a problem. However, it sounds as if there is insufficient neck tension to hold the bullet. The fact that you are unable to seat the bullet to hold to permit a crimp would indicate that the seating plug is pulling the bullet out. Before touching base with RCBS, measure the inside and outside diameter of the neck after sizing, and measure the bullet diameter. It only takes a moment, and it will eliminate the possibility of a flawed lot of bullets, and it will likely demonstrate that you are not getting sufficient neck tension. Armed with this information, it would be worthwhile to phone RCBS to arrange to send the die back for assessment.

 

[FOTIS]

It is probably sticking to the seating plug. Your seating plug needs a date with some emery cloth wrapped around a seated bullet or a dremel tool. Do not overdo it though. Some dies will not work with some bullet ogives. Had the same problem with my 378 WBY a while back.

 

[Guy Miner]

crday - Have those same dies & brass worked well with other bullets in the past?

 

[crday]

Yes, albeit limited. I've only loaded for this rifle one season and that with only one bullet. These dies did load 250 gr. Sierra's for last season, with no obvious neck tension problems. Admittedly, I did not attempt to crimp the 250's.

I re-read my original post and there is one factor to add:

I did attempt to crimp the 300 gr. AB with a roll crimp in the provided crimp groove on the 300 gr. AB. My idea was two-fold: First, a crimp wouldn't hurt a thing on a fairly heavy rifle and second, if I could crimp the bullet it would alleviate my neck tension issue. So, after getting a single bullet to seat to depth, I raised the seating plug a few turns, lowered the die until it contacted the case, then worked it slowly downward in roughly 1/8 turns to crimp. Crimp never happened. Instead, apparently the die began contacting the case shoulder before the mouth and set the shoulder back.

If I understand RCBS literature correctly, a standard die is set up to roll crimp, but a special die is needed for a taper crimp. These dies are standard and are not marked for taper crimp.

Right now, I'm wondering if I got a rare faulty set of dies. The neck tension issue could be explained by an oversize expander ball and the crimping issue could be explained by an out-of-place crimp ring.

Still, the odds seem against that. I don't know RCBS's production line, but the expander ball and the seating die would have to be two separate operations and the odds of one die set having two defective parts seems remote.