This is the inside neck reaming system I use - made by L.E. Wilson.
I installed several T-Nuts in the top of my workbench. Those T-Nuts provide steel threads for positioning
2 different shotgun presses and a variety of different reloading tools, when needed. This setup helps maintain an
orderly reloading bench . . . . well, most of the time.
I like the L.E. Wilson Neck Trimmer (shown above), because it also does a great job of "inside" neck reaming. It is available from their nationwide network of dealers. I made the orange mounting plate from 1/2" aluminum plate. The 2.5" round, white nylon "Hockey Puck" is used as a stationary anvil to keep from always reaching for a mallet to tap cases in and out of the Wilson case holders. Please note, I DO NOT MANUFACTURE (OR SELL) THE ORANGE PLATE SHOWN ABOVE.
I prefer to turn the "outside" of case necks from any rifle with a "true" benchrest (tight neck) chamber; because those cases require neck turning, and BR rounds are always loaded single shot. However, for rifles with a non-BR chamber, inside neck reaming removes the donut from inside the rear of the case necks; and it does a great job of making neck tension more uniform.
I almost never crimp the neck for rifle handloads, because crimping can deform the bullet. I prefer to use "tight" bullet tension - especially for AR rifles. The AR-15 and AR-10 rifles chamber rounds with so much force, the inertia can pull bullets completely out of the case if a round gets rechambered a few times. Try it sometime . . . . but, be prepared to clean up a messy powder spill.
I use pin gauges to detect and help eliminate the donut in case necks
I use different size pin gauges to ensure
tight, uniform bullet tension. For .224 caliber bullets (in an AR-15 rifle), I use a .220" pin gauge
and a .220" reamer. For .224 caliber bullets (in a bolt rifle), I use a .221" pin
gauge and a .221" reamer. For any non-BR .308 caliber, I use a .305" pin gauge and .305"
The first step is to determine how much to resize the outside of the case neck to allow your pin gauge to barely fit "part way" into the case neck. Then use the same size inside neck reamer to smooth and uniform the entire length inside your case neck.
Before adding powder, verify the inside diameter of your entire case neck is correct by slipping your pin gauge "all the way" into the neck. When you withdraw it . . . . you will hear a fairly loud "POP". That shows the inside diameter of your case neck is exactly the same size as your pin gauge. This technique accurately measures neck tension. You just need to know (in thousandths of an inch) how much smaller your case ID is than your bullet diameter.
Be sure to use a VLD chamfer reamer on the case mouths, especially when using tight neck tension. This minimizes downward pressure when seating bullets. It avoids shaving bullets, and it also reduces case run-out.
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