Fire forming vs neck sizing dies


October 5, 2010, 06:52 AM
I am going to have the need to increase from a .243 neck to .308. Which is the best method, and is easier on the brass. Neck sizing will be done in stages, with annealing between sizings.Will fire forming produce better results , this will be a drastic increase of neck size in one step. Can this be done?

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October 5, 2010, 07:23 AM
You will be expanding the neck, so I am not sure what you mean about neck sizing in steps. Anyway, I haven't tried it. I assume you have a metric butload of .243, since .308 is fairly inexpensive and readily available.

Phoenix 6.0
October 5, 2010, 08:30 AM
id bet u can trade somebody 243 for 308. seems like a easier process besides a bit of shipping possibly

October 5, 2010, 01:55 PM
That's a lot of resizing. I don't think you can fire form the neck to expand it. I could be wrong but don't see how you could possibly get consistent forming firing a 243 projo through a 308 hole

October 5, 2010, 02:01 PM
If you do have a metric buttload of .243 I may be interested in trading you for some .308. PM me if you are interested.

October 5, 2010, 02:25 PM
You will not get good, consistent results by fireforming without first necking up to .308. The gas will escape around the case mouth and prevent the brass from forming.

This is false economy. .308 brass is pretty inexpensive; just buy it and save yourself all that necking up and fireforming. Sell your .243 brass to someone who needs it and recoup some of the money spent on the .308 brass.


October 5, 2010, 03:54 PM
This is not a standard .308 brass case, and is not readily availiable. If it were , I would just buy it...and save hours at the bench.

October 5, 2010, 04:59 PM
May we ask what "it" is then?

Jimmy K

October 5, 2010, 05:55 PM
CAUTION: The following post includes loading data beyond currently published practices . USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information Go here, this might give you an idea how to fire form. Using cream of wheat. Also check the 30BR link on the page. Seems they neck up 6mm to 308 in 1 step using expanders. Or just load a 243 diameter bullet and shoot it. :uhoh: :eek: I have necked up 224 to 7mm in 1 step using an expander, some necks will split. It will form to your chamber if the gun stays together. :uhoh: :D

October 5, 2010, 07:53 PM
I fire form with a small amount of Bullseye, Cream of Wheat filler and a toilet paper wad. You have to set a secondary shoulder before fire forming, of course. What .308 chambering are you fire forming for?

October 5, 2010, 10:42 PM
Sorry for being so vauge... it is the new round from Hornady the .300 ossm. Which would be a 300 wssm.The brass is being made from 243 wssm via HSM. It looks like the easiest on the brass will be with neck expansion dies.

October 6, 2010, 06:50 AM From Lee Forming vs. Sizing

Case forming dies are usually cut to size the case slightly smaller than the minimum SAAMI (Small Arms Ammunition Manufacturers Institute) dimensions, to account for the brass case's tendency to spring back after sizing.

Our full length sizing dies are cut to size the case closer to the middle of the SAAMI dimension, because that is where most rifle's chambers are made, and to size to the minimum would shorten case life. Whether or not our full length sizing die will work as a case forming die depends upon the chamber dimensions of your rifle, and how much spring back there will be when sizing the case.
When i was forming 223rem to 7mm TCU, the FL die could not be adjusted to contact the shell holder. If it made contact, the shoulder was pushed back way to much. The brass was sized just enough so the brass would chamber by controling die adjustment. Have fun with your new calliber. :)

October 6, 2010, 06:57 AM
Yes I have discussed this round before, but I heard about fire forming and was weighing the pros and cons. Now how is cream of wheat used? So you went from .223 to 7mm in one step with fire forming, what method did you use?

October 6, 2010, 07:02 AM Thread on Cream of Wheat. Fire forming using an auto is not a good idea IMO. Bolt actions only. IMO

October 6, 2010, 07:37 AM
True the ar platform is an auto type weapon, however it is gas operated the recoil does not cycle the weapon. Would be the same as fireing a blank without a blank adapter.

October 6, 2010, 07:41 AM
So you went from .223 to 7mm in one step with fire forming, what method did you use?
No Fire forming. The brass was annealed, then run into the FL die. Neck opened in 1 operation. Then loaded and fired with normal powder charge to finish the fire forming. I read that your brass is thicker walled, might not be as easy. Can't you follow Hornady instructions? If they have some?

October 7, 2010, 11:59 AM
Some good info thanks guys just got a .284 chambered and wanted to use some laupua 6.5x284 brass. The barrel is for an AR type so it looks like I wont be "fire forming" too much with the heads up from some. Anyone have an old .284 bolt action they want to let me borrow for fire forming purposes? :D

October 7, 2010, 12:48 PM
Here's a discussion with some info;

I'm sure there's other info out there, that was enough to satisfy my curiosity.

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