Trimmer trouble: Forster 3-in-1, 30 carbine

[16in50calNavalRifle]

Forster Original trimmer, 3-in-1 Case Mouth Cutter, 30 Carbine cases. Second trimming session (first was 6 months ago, easy, no issues).

I resized all the cases (mixed headstamp - FC, PPU, Aguilla - some once-fired, some twice-fired, plus some unfired LC - 52 pull-down brass) in my Lee turret press with the Lee 30C resizing die, and then de-lubed them in clean tumbling media. This all duplicates my process the first time.

This time, I am finding that many cases will not accept (fit) the trimmer pilot into them without forcing. AND, on those cases, when the pilot is shoved in, the resulting trim length is far below that set on the trimmer (1.287). I am getting as low as 1.255 on some of these problem cases, most of them in the 1.274 to 1.280 range.

I'm puzzled by at least two things here. First, why, after resizing, are some case mouths not big enough for trimming? (related puzzle is why the whole process was trouble-free the first time) Second, how can the resulting trim length be so far below that set? I use the setting lock screws, and have been very careful to ensure the cases are seated properly in the collet after discovering this issue (only physical way I can imagine trimming short is a case not fully seated all the way back).

I've even taken some that did not accept the pilot and resized them, again, and still the pilot did not go in easily, and still the trim length was wrong.

The LC brass seems uniformly wrong, that is so far all the case mouths are too tight for the trimmer pilot and the resulting trim length is way short.

After checking older threads, I found one that was a similar problem, but there was no real resolution. Among the recommendations/options offered were taking some metal off the pilot, or even fashioning my own. Good ideas - but not happening in this case. Also, I know many reloaders don't trim 30 Carbine brass, but I have decided to, so just abandoning the trimming is not an option.

One interesting comment in the old thread was to not just resize, but also bell the case before trimming. Seems like while it might work, if resizing and all else are in order, that would not be needed.

I plan to talk with Forster on Monday - they've been very helpful in the past - but since it's Friday evening I couldn't resist tapping into the awesome wisdom and knowledge of THR to see what people have to say.

 

[GW Staar]

I haven't loaded for 30 Carbine for 30 years....sold the gun. But, the last I knew, 30 Carbine was reloaded like straight wall pistol. You are using the expander die aren't you? And your expander is set to bell the mouth for bullet entry, right? So why do you use the 3-way cutter? Maybe things are done differently now, but I would've sized the case, expanded it short of belling.......trim the cases (if really needed) and then run them through the expander again....this time all the way in to bell the mouth.

I thought 3-way cutters were just made for bottle necked rifle? Sized but not expanded 30 Carbine cases would be too small for a pilot made for sized 30 caliber rifle with a bushing or expander pulled through.

 

[16in50calNavalRifle]

GW, the 3-in-1 cutter chamfers the case at the same time, so it's a handy time saver.

And no, I have not belled the case mouths with the expander before trimming. Obviously I am under the impression that you resize before trimming, but not expand. And I did about 300 cases that way the first time without issue.

That's why I don't understand the (apparently) under-sized case mouths this time.

 

[GLOOB]

Brass isn't made to such tight tolerances as you think. The thickness of the case mouths will vary. Your LC brass is thicker.

When you size a case, you are setting the OD to a fairly well defined range, with a little wiggle due to springback. This leaves the ID of the case mouth with that same range of variation, plus any variation in thickness.

Now after expanding, the ID of the case will be more uniform, since the extra variation due to brass thickness will now be transferred to the OD.

My guess is the pilot of your trimmer is made to fit an expanded case, since that provides a more consistent fit.

I have experienced the same dilemna with my Lee trimmer tools. I, too, wanted to trim sized but unexpanded rifle cases (don't ask). As cheap as the Lee pilots are, I sanded one down. Sanded to where my thicker necked brass just barely friction fits over the pilot, there's a suprising amount of slop on the thinner brass. The trim is still fine, but it's hella hard to find the flash hole on the thinner brass, since the pilot isn't guided straight, anymore.

I think with a 3 in one, you would need a pretty good fit, else your chamfer might get sketchy?

 

[16in50calNavalRifle]

Thanks Gloob and GW. If I have time I might try belling/expanding a case or two and see how that goes. Gloob, your comment about brass variation tracks with what I was thinking (already knew, actually) - cases of varying headstamp have varying dimensions.

Will contact Forster on Monday to see what they say. No real problem with expanding the cases first, other than that they'll get expanded again for the powder drop - don't like to work brass any more than neccessary. That, and the extra step (I got pretty fast just resizing those cases and tossing them in a container).