Neck Ridge Problem

[swglenn]

I am on the 13th reload of my .284 using necked up 6.5-284 Lapua brass. The necked up cases are given an initial 80% neck turn. When reloading I use a neck bushing that is backed off about an 1/8 of an inch from bottoming out and FL resize every 4th time. I annealed on the 8th reload. I am having trouble chambering loaded rounds because I have developed a outside ridge right below where my bushing die stops that extends down to the neck shoulder. The ridge is larger in diameter than my chamber neck size, i.e., 0.321 vs 0.317 neck so when I try to chamber a case it is trying to be swaged downto in the chamber neck. Loaded rounds have 0.313 in. necks above the ridge. If I run a 7mm mandrel into the neck and then neck trim I can "cut off" the ridge and chamber the cases. I can also run the neck into the 7mm mandrel and then use the neck bushing bottomed out to resize the neck. Bullets seat without a problem so I'm not pushing on a ridge inside the case. Is this the dreaded doughnut? Do I need to retire the cases and use new brass? Primer pockets are still snug, no split necks. H4831SC powder charge is on the light side with Wolf primers and Berger 180 gr Hybrids, velocity ~2825 fps.

 

[fdshuster]

swglenn: Have you tried using the bushing with it screwed down tight, held by the screw-in plug? In other words, no play in the bushing? Would this not force the bushing to size the neck closer to the shoulder junction?

I used to float my bushings just enough to hear a little rattle when shaking them. Never could prove that doing so was of any value, so now I screw them all down tight. My loaded round runouts have not changed, so the floating bushing was of no advantage there.

To test for a donut, try to drop a bullet into the case before sizing. if it falls all the way into the case, no donut. If it hangs up with the base at the neck/shoulder junction, then a donut is present. I've had them form in as little as 6 to 8 firings or as many as 12 to 15.

 

[NWnewguy]

I am having the same problem with some 6BR brass that I got with a rifle. My assumption is that it is the donut, but with the brass on the outside. This should be easier to deal with, as some light neck turning should take care of it. I don't currently have a neck turning rig, and it isn't my favorite way to spend time, but I may have to look at the 21st century turing setup, unless someone has a better idea.

 

[DOGCAPPER]

Some of the neck bushings are tapered with the small side at the bushing number..Turn the bushing over and run the case in full length it will take out the bulge but may put it inside where it will need to be reamed ...

 

[fdshuster]

patti: "Where it will need to be reamed". Only if the seated bullet makes contact with the donut.

Incidently, I've tried several of the suggested methods of removing the donuts, from the K&M dedicated carbide cutter (did not work, dia. too small & it passed over the donuts), to having custom parrallel sided reamers made by Forster thinking I could cut them out. Expensive choice & the reamers did not work either. One was too small and the other was too large & would not fit inside the case neck without removing "good" neck wall thickness material.

I've since settled on just making sure the bullets do not contact them, and do that by doing the test with the bullet(s) of intended use, taking an ogive measurement when the are making contact, recording that length, then making sure the bullets are seated in front of that location.

 

[LongRanger]

For my 1k shooting I'll keep throwing the occasional donut into the scrap box until someone can prove that they do not affect velocity that is already in the single digit ES/SD range.

Frank B.

 

[243winxb]

This 0.321" would indicate the bullet on seating is expanding the neck. You have a donut that needs to be outside neck turned off. I would use a standard die to FL size the brass. Open the neck with an expander. Outside neck turn to the shoulder. You cant use a bushing die to FL size for this. The chamber neck size of 0.317" must be a correct measurement for this to be true. Otherwise, the .321" is brass that will no longer springback after firing, and is normal. Meaning the true chamber neck diameter is larger than you think. http://www.saami.org/PubResources/CC_Drawings/Rifle/284%20Winchester.pdf