243 ai neck turning

[drumgool]

I am in the process of building a 243 ai . My barrel is a Shilen with a .270 neck so I will have to turn my necks. I have a couple hundred 243 brass so I turned a couplenecks for practice .
I notice some pictures on the web of 243 ai formed brass the the neck looks a little shorter than a regular 243. I was wondering should I neck turn my brass all the way to the shoulder before
I fire form my brass.

[Blue Avenger]

will they chamber if you do not?

[drumgool]

I don't know yet. I do not have the rifle assembled still waiting on a few items.
I have been reloading for years but never had a wildcat I thought if they would chamber without
a bullet I would fire form with the cream of wheat and then then resize with my bushing die run through
expander mandrel then neck turn.

I have a Redding bushing die set with .267 bushing can you adjust the die to neck size a reg 243 . If so I can run the brass through that and it will chamber . It will be sizing down the O.D. by .008 that seems like alot I don,t know . Just trying to get a starting point.

[pa_wdchuckhuntr]

I've been turning my necks lately just to get a more uniform neck tension. None of my rifles "need" the necks turned but I've noticed the Federal, Remington and Winchester brass have signifigantly thicker spots than the Lapua brass which can't benefit accuracy. I figure it's a one time deal and if it helps my accuracy any it's a bonus.

[twarren]

Fire form first then turn the necks.

[bobcat30]

Am considering a 243 ai build do i have to turn necks on all ai barrels or just the 270?

[82boy]

Good question drumgool.

I would say that yes the neck length is changing, because you are changing the shoulder area of the case. There is several ways to skin the cat on brass making. I have used and prefer the pistol powder and COW method. I would do neck trimming after they are fire formed, there is a few reason why. One is like you have found out about the different neck length. Another reason is when going up or down in caliber it removes the donut. Third it is just a more uniformed way of doing things.

Not to nit pick on equipment but I am not a big fan of Readings competition neck sizing die, In fact I just sold the last one I had about a week ago and could not be happier. If you are going to use it I would not get fancy with it, just do as the instructions say raise the ram to the top position, screw the adjustment down until it stops and back it off .002. I would leave it there and never touch it again.

The problem you are finding is something similar to forming the 6PPC. When you take a 220 Russian brass and blow it out to a 6PPC you do all kinds of things to it, to simplify things lets just say you change about every dimension of the brass besides the head. With the 6PPC the neck length changes, like your experiencing with the 243AI. When neck trimming prior to fire forming you need to stop cutting short of the shoulder where the end of the neck would stop. (Without formed brass it is kind of a crap shoot.) Now I have cut down too low before and when the brass fire formed the cut was now into the shoulder, but surprisingly it did not cause me any trouble thus far. I have fired this brass around 5 to 6 times. From reading I have found that the experts say that cutting the necks too long in a PPC will shorten the brass life, and what they describe I have not experienced, nor would I want to, but I have see it happen with other shooters; What happens is the neck breaks clean off of the brass, the rest of the brass is ejected, and the neck stays in the chamber. Now have fun getting that neck out of the chamber. The shooters I have seen this happen to have been able to remove the neck with a cleaning brush, but it did not look like fun.

Hopefully I have answered your questions.

Am considering a 243 ai build do i have to turn necks on all ai barrels or just the 270?

It depend on who chambers the barrel and what reamer they have. There are no turn dimensioned reamers, and some are "Tight Neck" reamers like is mentioned by the poster that needs turned for a 270 chamber. The tight neck is suppose to give a bit more accuracy and brass life over the no neck turn units, but you don't have to have it.

[82boy]

Thought I would clarify my post , the reason why the necks break off is because of the thin spot cut in the what is now the shoulder area of the cartridge. When they break they break right at that line. This doesn't happen until several firings.

[dcloco]

Then you are turning too much of the neck.

Might fireform (unless you have a tight neck chamber) and then turn the necks.

Or, measure a fired case neck length, and neckturn to that length.

[BillPa]

Ya know I preach and preach learning how to make a chamber cast. Its easy to do, cheap and most importantly eliminates any doubts, questions, guessing or the dart board approach what the chamber dimensions are. All you need is Cerrosafe, a heat gun or torch ,some cheap incidentals and a mic.

Not that I don't trust anyone, I just don't trust anyone! ;D Before installing the barrel or even chambering a piece of brass I'll make a cast so I KNOW what things are from the start. Heck,I even cast FL dies so I know if and how much they overwork the brass. You would be (un)surprised what you discover!

http://www.brownells.com/.aspx/lid=1..._Secret_Weapon

Bill