AusVarmint

Ok I have just had 10 put though the 20prac. ( got my brother to do it for he I just haven't had time) thanks matang

So what I would like to know is the fired case neck outside size is .229 I used a .227 when I loaded. Should go down to .226 or .225 or keep loading with 227..

No group yet front bed screw came lose.

What is the neck OD of a loaded case ?

Well mate if you are happy with the neck tension and the seating depth is not changing under a compressed load or transport and you are getting good groups
hand loading is really up to your likes and dislikes and what does or doesn't work mate.
I personally like the light neck tensions less working of the brass neck the better.

Was that meant to be if the case neck after firing is .....

IF so can find out pretty close to what your chamber neck size is if you don't already know.

Also like missed said find out your loaded case OD.

This link http://www.varmintal.com/arelo.htm is great info on Neck Turning and just measuring necks etc etc

IF you click on the link for Neck Turning and Fitted Necks there is good info even if you are not turning etc.

measure your loaded cases, not your fired ones. Order the bushing below the fired diameter, I would order a 1 thou and 2 thous smaller and see which one produces best accuracy

In fact i may have a few 20 cal suitable bushings you could borrow to experiment with before you buy another

A loaded case od is .2275
The size size I got give by gun smith was .2345

.225 or for slightly less neck tension a .226

Ok Thanks missed and everyone.

Can I ask why go a loaded case and a fired case. So what's go if go to say lapua brass.

Just trying to get my head around it all.

A loaded case OD tells you what size bushing you need ie your loaded round is .227 so .226 will give you 1 thou neck tension .225 will give you 2 thou

A fired case will roughly give you the throat dimension +1-2 Thou (Harder brass will not spring back as much)of your chamber.

Not sure on Lapua 223 neck thickness but I think it will be thicker ?

Crackers are you dragging an expander ball / button back out of your case?
Ol 55

Hi crackers,
Just measured the cases I have here for you- Remington brass, once fired went .231
Resized went .227 and as I said, I had a few that had been loaded but I have pulled the bullets, these measured .228. My chamber was .233 but fired rounds came out at .231.
I would say if you are getting reasonable accuracy then keep doing what your doing.
I think we sometimes get too carried away and overthink things.

[I think we sometimes get too carried away and overthink things.[/quote]

Hard to disagree with that.
I find it better to try and not over work your brass.
Ol 55

crackers17 wrote:A loaded case od is .2275
The size size I got give by gun smith was .2345

so .2345 is the room you have in your chamber and if your cases measure .2275 loaded the clearance 7 thou. I have two thou clearance in my 17m4. Theoretically the tighter the chamber neck (amongst other things) the better the accuracy but also the greater chance of an epic fail if one of your cases is a bit thicker than the others!

If you change brass then the case thickness will vary. I asked for the JAB 20 to be a no turn chamber and set up on the winchester brass I had, it was. When I changed to IMI brass it was thicker and I had to turn those necks.

With 7 thou clearance you shouldnt have to turn any necks but you should check thickness of a loaded round if you change brass.

If you change to a thicker brand of brass then using the same bushing is going to size the internal dimension of the case neck to be tighter than the previous brass (you should remove the expander ball from your bushing neck die otherwise you defeat the point, the expander ball will be sizing the neck regardless of what bushing you use). Therefore neck tension will be higher. If you dont want that you use a bigger bushing on your thicker brass.

I have a standard factory spec chamber on my 257 wby but I couldnt get two loaded rounds to measure the same OD on the neck so I still havent ordered a bushing. No point as the neck tensin will be different for every case. The 257 expander and turner mandrel just turned up from K&M and the necks will be turned, not because the chamber needs it but so that the bushing dies can acheive the purpose they are designed for, consistent neck tension on each case because each case is the same thickness

That is a very good post Trevort

See you can do it.