7PRC ADG Bushing Size

[IdahoJoe29]

Sure
But how do you get the first loaded round if you only start with components?

I’m not starting with ammo then reloading it.
I’ve tried measuring neck thickness and doing the math, but last time I tied that I was off.

So I figured I’d ask the clan, just to get me close and started.

Gotcha. I guess I am asking from my perspective of having fresh brass and press and seating dies but haven’t sized anything yet so I haven’t bought bushings yet. Was just gonna take my measurements off of virgin brass loaded


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[wapitibob]

I was planning on measuring a loaded neck and going .001 less than that measurement for my bushing? Is that not the correct way to go? And if not why? Thanks

It's one way to determine bushing size but with a .001 under bushing you'll get close to .001 spring back from the neck brass and end up with no neck tension. Also, when using a neck bushing, it sizes the OD, so wall thickness variance will change the neck ID size, which facilitates the use of an expander ball/mandrel to uniform the neck ID if wall thickness varies very much.

 

[BRTreedogs]

Gotcha. I guess I am asking from my perspective of having fresh brass and press and seating dies but haven’t sized anything yet so I haven’t bought bushings yet. Was just gonna take my measurements off of virgin brass loaded


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Maybe it’s an old habit. And not required with better brass.

But i size virgin brass to uniform and much as possible.

 

[IdahoJoe29]

It's one way to determine bushing size but with a .001 under bushing you'll get close to .001 spring back from the neck brass and end up with no neck tension. Also, when using a neck bushing, it sizes the OD, so wall thickness variance will change the neck ID size, which facilitates the use of an expander ball/mandrel to uniform the neck ID if wall thickness varies very much.

Ok so what do you guys recommend for a measurement under OD? Maybe .002-.003 and then run an expander die to get uniformity on inside diameter?


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[wapitibob]

Ok so what do you guys recommend for a measurement under OD? Maybe .002-.003 and then run an expander die to get uniformity on inside diameter?


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I think most are in the .003 range. I'm at .005 and run .004 neck tension.

 

[MTBlazer89]

Sure
But how do you get the first loaded round if you only start with components?

I’m not starting with ammo then reloading it.
I’ve tried measuring neck thickness and doing the math, but last time I tied that I was off.

So I figured I’d ask the clan, just to get me close and started.

I am new to this, but the process we used was, We took one piece of virgin brass, primmed it, loaded a light load, seated a projectile (we used a factory round for length). We used this to determine neck size. We also fired this round so we could loosely fit a bullet and find the lands in my rifle.

I may have worded this in the wrong order, but I know we sacrificed one piece of brass and a couple bullets to determine neck tension and OAL of my chamber/lands.

With new ADG brass, 7mm Berger 195s we came to .315 for bushing size. My buddy had a .314 so we have been using that.