Case mouth swelling?

[Luky]

Have not been shooting much the last year or two and decided to clean up my brass and load what I can to keep occupied on the weekends after a few weeks of 10-14hour days working from home (my company makes ventilators and we ramping production 7x right now). Anyway I have SS tumbled and full lenth sized my brass (lapua .260, twice fired) in a redding neck bushing die on a coax. Went to trim cases in my giraud and found the case mouths do not want to fit through the die on the giraud trimmer. They fit fine in my wilson full length case gage. I can pop them through the trimmer orifice with pressure but then have to use a case holder on the bottom to pull it back out. (And considerable force).

So I started dicking around with the trimmer orifice to file/stone it out a little bigger. Even chucked up a piece of brass (that would not fit) into my drill press and put on some rubbing compound to see if i could polish the orifice a bit larger. (Worked great polishing the brass off the case end ).

I have a bin of old lapua 260 brass with loose pockets I keep for setting up the trimmer and annealer and happened to try one of those. They all fit in the trimmer orifice fine.

It seems my "recently" fired brass is all slightly bell mouthed. Not extreme as a berger 6.5 130 hybrid wont slide into the unsized neck. Both twice fired from my Surgeon with a Bartlien that has a tac-match chamber and the 7 fired lapua brass used in my Savage 10BA rebarreled with cheap eabco .260 barrel for my son (shoots great, just a really long jump to the lands). I am guessing it is something I am doing but cant figure out root cause.

I do use the TiN coated neck bushing and also the carbide bead through the neck. Do not neck trim but the lapua brass has been pretty consistent so has not seemed necessary. Brass fits and cycles through the rifles fine... this is probably only like a .001" - .002" diameter difference at the case mouth but really annoying since I cant easily use my giraud trimmer. It didnt use to be there. Any ideas what may be causing it?

 

[RegionRat]

Have you slipped a gage pin into a neck to see what size they are? If you don’t have gage pins, maybe take a crack at the OD and see what you got from your sizing process?

Do you anneal?

Any chance you used a different bushing this time?

 

[PinesAndProjectiles]

Stupid question, but did you make sure to put the bushing in your die? Or do you have the correct bushing in your die?

 

[Dthomas3523]

Make sure your seating die isn’t screwed down too far. You’ll get something like this happening:

 

[PinesAndProjectiles]

Make sure your seating die isn’t screwed down too far. You’ll get something like this happening:

View attachment 7294670

He's not seating, he's sizing.

 

[Dthomas3523]

He's not seating, he's sizing.

It’s fired brass. Could have easily happened when he seated last.

 

[PinesAndProjectiles]

Yeah but it probably wouldn't chamber like that.

 

[Dthomas3523]

Yeah but it probably wouldn't chamber like that.

Depends on the lip. It’s a savage with a cheaper rebarrel. A lot of factory or factory replacement chambers have .010 or more neck clearance.

 

[Dthomas3523]

Post a close up pic of your fired brass necks before sizing if you have any.

 

[spife7980]

You sure its the mouth belling (not uncommon) and not the bushing donut that’s causing it to stick in your giraud trimmer? All my full length type s bushing cases have a bit of a hitch when pulling out of the giraud due to the donut but they don’t require excessive force. I would sharpie the neck and shoulder and see where it’s scratching it up in the trimmer.

 

[FLIGHT762]

Stupid question, but did you make sure to put the bushing in your die? Or do you have the correct bushing in your die?

^^^^Check this^^^^. First thing I'd do is take a bullet and see if it drops through the neck of your F/L sized brass and then get a caliper out and start measuring the O/D of a fired case neck and a properly resized case neck. That will give you a starting point.

 

[Luky]

Thanks for all of the suggestions. I pulled my die apart and yes i have a .293 neck die in place, but it was a little gummy from the One Shot case lube I use. I cleaned it up with some brake cleaner and reassembled it. I lightly snug the center pin to the neck bushing then back off 1/8 turn and tighted the lock collar. Case necks are .015"-.0155" thick so this give me about .0015"-.0020" neck tension. When I check ID of mouth with calipers I get ~.262".

.

I tried measuring the mouth OD on old (fired) brass that fit the trimmer and got .2945". After FL sizing with the cleaned die it dropped to .2930"-.2935". I checked some of the cases I chamfered/deburred by hand and still would not fit and got .297" at the mouth OD. I ran a couple through the die again and now they are right at .293" after sizing and drop into the geraud, but I took too much off by hand and cases are about 2.024" long. They typically come out 2.029"-2.030" from the trimmer. My Berger manual has the case length @ 2.035" and Hodgdon data has it @2.025".

Still dont know cause other than neck bushing just being gummed up?

Old sized brass on left, newer recently size brass on right (6 firings) with flared mouth.

Love the Giraud trimmer!

 

[ken4570tc in WY]

A dull cutter during inside neck chamfering will cause the mouth to bell like that.

 

[spife7980]

A dull cutter during inside neck chamfering will cause the mouth to bell like that.

Or not properly adjusted.

 

[LAW-DOG]

I know this is an older thread but I dealt with this issue before. I full length size without the expander & then use mandrel. It seems to be worse when I used vld chamfers like my giraud or Wilson that had a deeper chamfer. It still did it with the rcbs trim mate but not quite as bad. On the 308 it only did it when I used Redding die & lapua brass or thick neck brass. Winchester 308 brass had no flare with any die. My 308 Forster die did not flare any brass. Then using alpha ocd dasher brass & Forster full length die it happened. I thought maybe it was initially pushing the necks in too far. I checked & it was pushing in too far. I got my dasher die honed & no more flare. Also honed my Redding die & problem solved. It has to be something to do with spring back tension from overworking & deep vld chamfer combo