So I have been pumping out OFB LC like a madman.

Got the 1050 set up with the trim head. Dillon decap in 2, swage in 3, trim/size in 6, Lyman M die in 8.

Ran about 3000 rounds with the M die set to where the bullets just sat into the case mouth. I pulled a case every so often and check it in the case gauge, check the pocket, overall length, and set a bullet in the case mouth to gauge the M die expansion of the case mouth.

At one point, gradually I started to feel more resistance on the downstroke, thought maybe I didn't lube enough, or some SAW brass or something.

I stopped and checked everything over, and found that the M die had come loose, and screwed itself down. I flared the brass alittle bit. Prior to this I had not been expanding to the point of "flaring", only expanding the case mouth. I was able to pull that whole bin aside and separate it.

I took the calipers to that brass, and on the outside of the case mouth, it is .252-.253.

I readjusted and found the spot where I could move the M die stem up or down, with no effect on the case mouth expansion, about .247. so I reset it at that setting.

Dug out some of My first brass, and it was reading .247. That seems to be the sweet spot of the die where the bullet set in nicely.

Has Anybody ever checked this measurement? if so, what was Your measurement?

Also, do You think that the Dillon taper crimp die will crimp this back into tolerance?

Half tempted to just toss it into the Blackout bin as it is OFB LC, but I got enough rejects in there as it is.

Thanks, Dave

See, this is the "goofy" part of your question.  You have the brass,... try it.


What cartridge are you loading and what are these terms - M die, OFB LC?


ETA - I used the tool I had available to me (Google) to look up Lyman's Neck expanding mandrel die (the M die).

Okay as luck would have it I just finish trimming 800 or so .223 brass on the XL650.

I am a Lyman "M" die user and it can be your best friend or worst enemy.

I wouldn't use anything else it seems to work out just fine for me.

I measured a few of the cases and the flare is .245 thousands of an inch.

The necks come in at .243 thousands of an inch.

With Hornady 55 grain full metal jacket boattail bullet the necks come in at .246 thousands of an inch.

I use a Lee FCD for a slight crimp.

It all works out pretty good for me.

OFB LC = Once Fired Brass Lake City.

I will try to see if the taper crimp die will fix it, just as soon as I am ready to switch the 1050 over to the loading toolhead.

Flashbang, Thank You, it would seem Your measurements are pretty close to Mine.

Get better lock rings.

I really can't think of a reason why the taper crimp die would not take the mouth flair out.

Motor

Well, I guess this solves part of My problem.

Guys who ask goofy questions usually have a loose screw somewhere.  

To keep this post on topic, let me ask this - what benefit do you derive from using the M die?



P.S. - I didn't know there was such a die until your post.  I sometimes use a Sinclair neck expander, but only when neck turning my cases.

The Dillon case trimmer sizing die, does not have a neck expander. So after trimming/sizing, You need to open up the neck of the case.

Mr Bulletfeeder recommends the use of the M die to help with the seating of the bullet while reloading.

I cleaned it really well, and used some blue Loctite on it this time.

And trust Me, I got more then one screw loose.

I always use the M-Die after the trimmer and put a small step in the brass that allows for easy seating of FB bullets, I use Dillon and CH4D tapper crimp dies to just remove that slight step

"M" dies are used mostly by people who load cast bullets. Neck expanders usually just expand the neck then flair the case mouth to prevent bullet shaving.

The "M" die expands the neck but it also steps it up in diameter at the case mouth so a flat base bullet or a flat base cast bullet has a small step that it can drop into. This allows the bullet to sit directly in line with the case before the seating starts. This in turn results in straighter seating.

You can get different size expanders to suit your needs.

OP: You are not the only one to have your expander come loose in the last week. No it wasn't me but I read about it.

Motor

things like this I like to tap the threads with a ball peen just enough that they wont back out with use

Oops!  I posted this in the wrong thread.  How goofy is that?

I don't know that I would call it "Social Media". I like to think of it as a "Club", a group of People concentrated in one area by the same ADDICTION.....I mean Hobby.