6.5x47 Lapua neck diameter

[Comrade Terry]

I’m looking at two different reamer prints for 6.5x47 Lapua. My question concerns the relative dimensions of the neck – the neck diameter at the neck-shoulder junction, and the neck diameter at the case mouth.

On the first print, the dimension at the neck-shoulder junction is 0.2933”, and the dimension at the case mouth is 0.2921”. Clearly a taper of 0.0012”.

On the second print, the dimensions are both 0.296”. No taper.

Why the taper? Why not the taper?

 

[gotcha]

I’m looking at two different reamer prints for 6.5x47 Lapua. My question concerns the relative dimensions of the neck – the neck diameter at the neck-shoulder junction, and the neck diameter at the case mouth.

On the first print, the dimension at the neck-shoulder junction is 0.2933”, and the dimension at the case mouth is 0.2921”. Clearly a taper of 0.0012”.

On the second print, the dimensions are both 0.296”. No taper.

Why the taper? Why not the taper?

Just a swag. maybe one is designed for unturned necks and the other for turned necks. My 6.5X47L uses a Criterion BBL and PT&G reamer of unknown dimension Necks are turned to .0125" fired cases measure .292" and loaded round is .289". Seems like the reamer drawing that shows .296" is way larger than necessary. FWIW

 

[Comrade Terry]

Just a swag. maybe one is designed for unturned necks and the other for turned necks. My 6.5X47L uses a Criterion BBL and PT&G reamer of unknown dimension Necks are turned to .0125" fired cases measure .292" and loaded round is .289". Seems like the reamer drawing that shows .296" is way larger than necessary. FWIW

I'm in the process of ordering a reamer, and wondered about the taper. I can't imagine turning the neck for a tapered chamber without cutting too deeply near the shoulder of a fired case. I agree that 0.296" is a bit generous as I was planning to turn to 0.0125" as well.

The taper befuddles me, and I wondered why it was that way.

 

[shoot4fun]

Wish I could tell you what you want to know but my reamer is a .290 neck so I turn them all.
If it helps, my 6.5-47 Lapua brass measured .013" before turning. My math says an unturned and loaded round should come in at .290 and I turn my brass to .012". I would think, based on the prints I've seen, that a chamber should have a .295 neck for no-turn brass. Precise numbers .2944 at mouth and .295 at neck/shoulder juncture.