Trimming the Base of Seating Dies

[Jeff82]

I've been having trouble getting a crimp on my 38-special handloads when using my RCBS cowboy seating die on my RCBS Pro-2000 press. I been thinking that a potential fix to the problem would be to trim off a few thousands of an inch from the base of the seating die in order to allow me to screw it down a little lower in the press. Is this a reasonable thing to do, or am I on the road to ruining a good seating die?

--Jeff

[troyboy]

Before modifying the die, I would speak with RCBS. The die should work without modification.

[wallenba]

First, if you have one, or if you can scrounge one, try taking a Lee die lock ring and after removing the 'o' ring, install it upside down. This can buy you more than the few thousandth's you need.

Is the Cowboy die set specific to .357, or both 38 SPL too?

[RickinTN]

If you end up trimming something trim a shellholder. Always cut the least expensive part!
Rick

[Jeff82]

The die is for both 357 and 38-special. I think the problem is that the shell plate on the progressive press rises a little bit higher on the casing than a normal shell holder on a single stage press does. Trimming the shell holder would be worth looking into, but it would be more complicated to do.

[Forgetful]

If you end up trimming something trim a shellholder. Always cut the least expensive part!
Rick

beat me to it. +1

[5Shot]

A shell plate is a bit tougher to trim....

[country gent]

I have had to trim sizing dies to get shoulders pushed back far enough for custom chambers occasionally. Trimming the shel plate formost progressives would mean facing the top down as all would have to be modified as it rotates each "station changes. Is it the die wont go thru the tool head farenough or is it hitting shell plate and not low enough? If there is gap between shell plate and die bottom and it will not go lower then try moving the die ring to bottom side of tool head ( make sure there is clearence for it when operating the press). If the die is snug on the shell plate slip a case into the die by habd and measure from case head to die bottom it should be .125 or more. If less then the die needs faced down. I "adjust" the die as I dont want dedicated shell holder to have to keep track of.

[shooter93]

I've trimmed crimp dies and still have one trimmed so it will crimp 44 special with the 44 mag die. They are quite hard but you can trim them. Won't hurt anything as it will still crimp the longer round. I didn't have trouble with seating but rather crimp but it would work the same.

[prs]

Its blessing in disguise. Use that die as a seat only and crimp in last stage of your progressive. Result, better ammo.


prs

[Motor]

This may be a dumb question but I noticed you said the die set is for .38spl & .357 :

Are you using it without the spacer ring? I'm not even sure the cowboy set has the spacer ring but if it does and you have it on the seat die a .38spl will not be able to reach the crimp bore.

[Jeff82]

The Cowboy dies do not come with spacer rings. What it comes down to is that I can get a good crimp when using a single stage press. On my progressive press the shell plate is thicker, so I can't feed that cartridges deep enough into the seating die to get a good crimp. I could use a separate crimping die, but then I can't use my powder check die.

[Motor]

Jeff82,
There are a few ways to shorten your die. It depends on how much you need to remove. The mouth of a standard seat/crimp die does not have much effect on the job it does.

If you only need to take off 1/32"-1/16" (.030-.060") and don't have access to a lathe with carbide tool you could use a belt sander. You could also chuck it in a drill press and use a dremel tool with sanding drum.

If you do use a sanding method make sure you keep the die from over-heating. You can quench it with a wet rag or even dip it in water.

Motor

[bedbugbilly]

Or - to trim a touch off, could you not thread the die body in to a single stage press in reverse - from the bottom up through the top. Put a layer of duct tape on top of your single stage to prevent any damage to the press, screw the die in from the bottom and lock it in place with a lock ring with the about you want to trim off extending above the top of your single stage - carefully file off what you need to? The top of your single stage should help you to keep the "trim" square with the die body and the tape prevents you from filing any of the press.

[Forgetful]

I'd just use a 6" grinding wheel chucked in a drill press, and a block of wood clamped down with a small hole to retain the shell plate, and take off 0.005". Doesn't matter how hard it is. $2 part. And it'll still be flush and square.

[Three44s]

Are you sure you need to shorten your die?

Perhaps you just need to be able to screw it down closer to your shell plate.

I have a LNL press and my Lee dies are a bit short and I have to turn some of my Lee lock rings upside down to get the die set deep enough in the press head.

My best fix has been to favor Hornady dies as they seem to have a longer body than many of the manufacturers.

In you case, a separate crimping die might be another option.

Best of luck and good shooting!

Three 44s

[1hole]

Jeff, you have diagnosed your crimping problem AND solution correctly; shorten the seater a tad. The only functional part of a standard seater is the top, not the bottom, so you won't harm a thing even if you don't get it perfectly square or take off a quarter inch but you needn't be that drastic.

The most practical way to remove a few thousanths from a deeply hard cased reloading die is to grind or (belt) sand it down. Lightly hold the die's bottom against your available abrasive and - for appearances sake - try to grind it evenly. Disassemble the die before you start and clean out any bits of metal or grinding grit afterwards, then reassemble and use it normally.

[bbqncigars]

I 'trimmed' a couple of dies back in high school with nothing else but a Dremel and steady hands, guided by the near blinding light of ignorance. They did (and still do) the job. :-)

[upnorthwis]

I had the same problem when switching dies to the Dillon 550B. Have shortened several off them on grinding wheel and they work just fine. Never had to go past .020 removal so there was plenty of chamfer still there to guide brass.