Reamer question (cylinder vs barrel)

[Benevolence]

I purchased a Clymer .45 ACP reamer with the intent to ream a barrel out to fit a 460 Rowland (I have the compensator and stiffer recoil spring, and this is in a fnx45T). Unfortunately, in my naivety I got a cylinder and not a barrel reamer so the solid pilot is larger and doesn’t fit (.455 vs .445 I believe). It also appears that the cylinder reamers have a constant diameter throat whereas the barrel reamers have a taper ‘lead-in’? I was thinking of turning down the solid pilot to fit in the  rifling and use to ream the extra 0.063” required for the 460Rowland.

 

My question was if the difference in throat (if there truly is) will increase pressures or decrease accuracy drastically. The bullets used for this are hard cast, powder coated lead going at a healthy speed (I suspect gas checked). If I understand it correctly, the jump should be good for lead bullets and perhaps even help decrease pressure relative to tapered?

Edited January 1, 2021 by Benevolence

[jcc7x7]

Send the reamer back and get the correct one.

[Toolguy]

It depends on whether it's a rimmed or rimless case. Rimmed headspace on the rim, rimless headspace on the case mouth. For rimless in a barrel chamber, you want a sharp shoulder for the case mouth to run up against, then a taper in the rifling just ahead of the case mouth. In both, the case diameter is larger than the bullet diameter. In the revolver cylinder, the first part is case diam.+, taper, then bullet diameter for the throat. In the barrel, there is case diam.+, then rifling, with a taper in the rifling from groove diam. to land diam.

You need a reamer with a land diam.- for the pilot.

[Benevolence]

Okay, thanks for the information, I appreciate it. I am returning the cylinder reamer and decided to rent a 460 Rowland reamer and do it right especially with how high pressure of a cartridge this is.