(On my ... lost part of this post the first time)

Am working on a AR15 in 300/221 Fireball (which is pretty close to 300 Whisper). Bought a very nice stainless steel barrel with a three position gas block from a well respected smith. Had him make a chamber gauge at the same time. Bought a Redding Deluxe die set in 300/221. Is probably NOS as they looked new but are marked 91.

The LC 97 brass is FL sized using a Dillon carbide die, sized in the FL die of the Redding set, and trimmed to 1.350" ... the case don't go all of the way into the chamber gauge and do not allow the bolt on the AR to close. (The headspace of the BCG was checked on an M4 that is known to work with military gauges and it closes only on the GO gauge just as did the M4's bolt.)

The cheapest piece in the reloading system is the shell holder I took 0.020" off of it as the case is obviously too long. Now cases can go deeper into the die. Now the brass is pretty close ... will chamber with a little help from the forward assist.

The hook on the shell holder started at 0.090" thick. Means there is 0.070" left to work with. Obviously a little more needs to come off, or the bottom flat of the die needs to be ground off.

Anyone have any feeling as whether or not I can get by with a 0.050" to 0.060" thick hook on the shell holder?

What a PITA! Thanks for listening

I had the same problem with a setup and had success cutting a shim to fit under the case that pushed it up in the shellholder. I think it gained me about 10 thou which was enough. Remember to drill a hole for the primer and decap pin.

I put the shell holder in the lathe with a 6 jaw set-tru chuck and cut the top down until I got cases that would fit the gauge and chamber in the rifle.

Asked someone to measure the height from the deck of a Redding #10 shell holder to the top. They got 0.125". Mine now measures 0.104".

Where the heck did the other 0.021" go?

(Makes me wonder if the rifle is short chambered by 0.020" Guess I need to get a few cases that work in other rifles to see if they fit mine!)