Case prep - 300wm

[Deleted member 107666]

I talked to my gunsmith. The reamer is set up for a no neck turn req'd, however he mentioned for proper/even neck tension, I would be benefited by a very light/cleanup neck turning to ensure uniformity.

 

[dok7mm]

What is the exact chamber neck dimension? And what clearance will your loaded round give you in that chamber?

My best rifles have .003- .005 clearance, with .004" being ideal for my hunting rifles. Most are tight necks or minimal and I turn my necks to get the proper clearance. In my no turn necks, I always use the FL die and mandrels to get consistent neck tension. Even with my tight necked rifles and brass turned to .0001 consistency, I have found the FL sizing/mandrel method to provide better SD/ES than the bushings, testing one against the other.

If your chamber neck exceeds your loaded neck diameter by more than .004", Redding cautions that using one bushing can interfere with neck tension and recommends using an intermediate bushing. There is also the fact that the bushing # is often +/- of what is stamped.

If you have bought your brass, seat some bullets in a few cases and measure the loaded neck. Compare it to actual chamber neck, to see what your clearance is, in the unturned state. Then you'll know how much clearance you'll have to work with when you skim turn.

It's your rifle and your decision, just trying to help.

 

[catamountsierra]

I talked to my gunsmith. The reamer is set up for a no neck turn req'd, however he mentioned for proper/even neck tension, I would be benefited by a very light/cleanup neck turning to ensure uniformity.

This has been my approach to neck turning. I try to take off the bare minimum to clean up the necks to an even thickness. I want my necks as thick and even as I can get, mostly because it seems to help with concentricity and consistent neck tension.

 

[backcountrymeats]

OP, that ADG Brass is pretty consistent straight from the factory.

I'm not sure what you are hoping to gain over that, when it doesn't seem you know the steps to take to get you there? I would calm down and back away until your chamber is cut and you have a chance to at least shoot your rifle.

^^^^ great advice ^^^^

I run ADG brass in my custom .300wm also. Very consistent brass. Belted brass already has a disadvantage right off the gate with its short shoulder lengths and needing to grow excessively which can create many many issues if not done and maintained correctly. ADG brass is SOLID. My recommendation which is what I do as well as MANY MANY other .300wm shooters is:
- Run brass through expander Mandrel to open up necks to .306"-.307".
- Take ALL measurements of your brass and log them into your reloading book (trust me you will refer back to these measurements all the time)
- chamfer and debur necks
- charge and seat bullet
Go have fun fireforming all brass!

I neck size only for the first 3 firings allowing the brass to fully fill the chamber. After the 3rd firing I FL size at every firing from then on bumping the shoulders back .002". My ADG brass grew .019" on first firing, .003" on the second firing, and third .0005"-.001" on the 3rd firing.

Don't start load development until you have 1x Brass! Your velocities, nodes, and groups will be WAY off from one another from new brass to once fired due to the case growing so much initially.

Good luck with your new rifle
Backcountrymeats