The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

It could well be, that's about 6.7 thou"

I'd fit a bullet, measure the neck diameter, remove the bullet and re-measure, if it's the same try carefully loading the empty case with the expanded neck and see if it chambers.

What's the neck wall thickness on both old and new cases?

The new brass is .17 mm thicker( on two sides) as that is how larger diameter the neck is on a loaded round.

Yes, the difference in total is .17mm, but what is the actual wall thickness of the neck?, I think they're usually about .012".

The spec for the case gives an OD of 9.11mm so 9.33 seems rather large, if you measure then chamber and re-measure an empty case is there a difference in the neck diameter, ie. is the chamber squashing it to fit but isn't able to do so with a bullet inserted into the neck?

Started neck turning the cases to the correct dimension.

Bought a Lynn case trimmer to take .4 mm of case length. Now the problem apparently .33 pilots are out of stock in uk and the USA. Have order a .45 pilot and will have to get it machined to size.

Be very careful how far you turn down the necks, try and keep around .011" of wall thickness.

Did you measure an empty case neck O/D before and after chambering it to see if it was being compressed by the chamber?

One of the problems with neck turning to below standard brass thickness is resizing and accordingly neck tension, reducing the neck thickness to 0.011" will almost certainly mean you will need sizing dies with separate bushings such as Redding, Forster or Wilson to get the beck tension you require.

Lapua brass is usually around 0.0145" to 0.015" at the neck so using the .338 as an example:

0.338 + 0.15 + 0.15 =0.368" so your neck bushing needs to be around 0.368" - 0.002" so 0.368" or maybe 0.367" depending in the tension you require and factory dies will be built along these lines. reduce the overall diameter to .360" and you need a .358" bushing or ten thou smaller.

I usually buy my bushings in sets of three when building this sort of thing so I can get the desired neck tension and I will resort to machining my own bushings in .0005" increments if things are still not where I want them to be.

Ovenpaa wrote:0.338 + 0.15 + 0.15 =0.368" so your neck bushing needs to be around 0.368" - 0.002" so 0.368" or maybe 0.367" depending in the tension you require and factory dies will be built along these lines.

I don't want to nitpick, Ovenpaa but I just wanted to correct the statement to 0.366" to 0.367" for OP's sake.

Well spotted, that should have read .366"/.365" - Not enough coffee!

Problem solved.

Have neck turned the brass. With a bullet in place the neck diameter is now 9.1mm.

The thickness of the brass at the neck is about .3mm

The rounds now chamber perfectly.

They are still about .4mm to long but that will have to wait until i get a Lyman pilot that fits.

Good work :)