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4296
08-12-2018, 08:44 AM
Plan to shoot reduced load lead bullets out of my Arisaka Type 99 with pristine bore and chamber. Do I need to fire my new brass first with J-word bullets and full power charges to size my brass to the rifle (subsequently only neck sizing) or will my powder charge of 16 grains of 2400 adequately form the brass to the chamber?

lightman
08-12-2018, 08:53 AM
A lot of shooters think you need a stiff load to fireform brass. I really don't know if your 2400 load produces enough pressure or not. Maybe someone else will chime in.

Larry Gibson
08-12-2018, 09:15 AM
4296

As to whether or not 16 gr 2400 will fire form (what it's called) the cases to the chamber depends on the hardness of the brass, how much they need to expand and the weight of the bullet (not mentioned?).

What cast bullet are you using?

4296
08-12-2018, 09:39 AM
Lyman 2660299

Larry Gibson
08-12-2018, 10:57 AM
Is that the number on the mould?

GregLaROCHE
08-12-2018, 12:23 PM
This is very good question I never thought about. I hope this question can be answered.

I had some light loads where fired cases had soot coming from the neck. I thought the neck wasn’t expanding enough, but maybe the whole case wasn’t fire forming.

Wayne Smith
08-12-2018, 04:33 PM
Larry, I hope not! That's a 270 mold and he's got a 7.7 - what, 315/316 typical?

Larry Gibson
08-12-2018, 04:35 PM
Larry, I hope not! That's a 270 mold and he's got a 7.7 - what, 315/316 typical?

Yup, I'm confused......

4296
08-13-2018, 10:53 AM
Looked at wrong box,will be using Lyman 2660299

Larry Gibson
08-13-2018, 12:57 PM
Looked at wrong box,will be using Lyman 2660299

Is that a product number, catalog number or mould number?

Best if you provide the mould number. I'm guessing from that number and it being for an Aisaka type 99 that the mould number is either 311299 or 314299?

Hick
08-13-2018, 06:39 PM
I don't think you need a full power load to fire form most brass-- but my experience is limited. A couple of years ago I came across some brass that had been run over by cars at the range-- major dents in the casings but no cracks. Some 223 Rem and some 30-30. I decided to experiment. I ran them through a full length size-- which didn't take out the major dents, but made them so they would chamber. I then loaded them with cast bullets at the starting load from Lyman's Cast Bullet handbook and fired them at the range. Every one came out perfect--no dents and no marks-- you couldn't even tell where the dents had been. For these cases, at least, a relatively light load of fast powder was enough.

jimb16
08-13-2018, 07:19 PM
I frequently make cases for some of my rifles. I use a lower end jacketed load as a general rule. That always seems to work for me. I never use full power loads since you need to check case length after firing and in some cases need to trim. Why stress the case unnecessarily.

Jniedbalski
08-13-2018, 07:47 PM
A light load or medium of fast powder usally is enough. If you get soot on the neck or case it isint enough pressure to seal the brass against the chamber. So up the load.

Mr_Sheesh
08-13-2018, 09:05 PM
A lot of people fire forming 5.56x45 into 7mm TCU or the other Contender fodder suggest not fire forming without a bullet, but instead just loading a typical powder charge into the case and a bullet or boolit into it then firing it - They say that the cases turn out just as well fire formed and rounds you do this with are as accurate as those rounds will be once reloaded. I'm not a full believer on that yet, but may try it this next batch of brass I need to fireform, and see. (Won't do well on a compressed load, since the case is still undersized till fire formed, usually!)

KCSO
08-13-2018, 09:10 PM
If you anneal a light cast load will do the trick. I have fire formed with Bullseye and just paper wad with no problem.

therealhitman
08-13-2018, 09:26 PM
Give the Cream of Wheat method a try. I have had great luck with .257 Roberts AI fire forming (40 degree shoulder) using it.

Tom W.
08-13-2018, 09:33 PM
I have a light load of Red Dot and a 160 gr cast to FF for my 30-06 A.I. It works great. Then again,I still have some full power J -word bullets I have loaded a long time ago that work well.... I ain't one to use COW. I want to see a hole in whatever I'm shooting at.

fast ronnie
08-14-2018, 01:34 AM
A lot of people fire forming 5.56x45 into 7mm TCU or the other Contender fodder suggest not fire forming without a bullet, but instead just loading a typical powder charge into the case and a bullet or boolit into it then firing it - They say that the cases turn out just as well fire formed and rounds you do this with are as accurate as those rounds will be once reloaded. I'm not a full believer on that yet, but may try it this next batch of brass I need to fireform, and see. (Won't do well on a compressed load, since the case is still undersized till fire formed, usually!)

My experience with the TCU has been the fireforming loads were just as accurate as the already fireformed ones were. I have also used the corn-meal method and can't say that one worked better than the other, but didn't have to go to the range to shoot the cornmeal loads. By the way, I sealed the case with wax over the end of the cornmeal. You don't have to be as careful about dropping powder or cornmeal out of the case.

Mr_Sheesh
08-14-2018, 02:38 AM
I used plastic disks cut from coffee can lids, if I did it again I'd use cardboard disks I think - more biodegradable. Used COW last time, you do have to use a non trivial powder load, too little won't force the brass to fire form fully (It will shove it part way though.)

Wayne Smith
08-15-2018, 05:23 PM
Where did you get your mold? Someone gave you a mold for the 6.5 Arisaka, not the 7.7. If the mold number starts with a 266 it is a .266 diameter boolit - your rifle barrel has a groove diameter of something like .314. No way that boolit is gonna shoot in your rifle - it is too small.

RPRNY
08-15-2018, 05:47 PM
In any event. No, full power loads are not needed to fire form. I like 14 grs of Alliant 410 topped up with cornmeal and sealed with a wax cap. Any light load of fast powder topped with cornmeal or COW will work well - the filler expands the brass effectively.

4296
08-15-2018, 06:53 PM
Lyman Item # 2660299 303 RN GC 200 gr 314299

Larry Gibson
08-15-2018, 07:43 PM
Okay, that's a good bullet. Yes 16 gr of 2400 may fire form the cases, especially if a Dacron filler is used. I suggest 18 gr with the bullet seated out so it is firmly seated against the leade when the cartridge is chambered. You may also want to slightly lube the cases so they don't stick to the chamber walls. You want the case head thrust against the bolt face so the case shoulder is blown forward to fire form.

Eddie2002
08-15-2018, 07:43 PM
Get a 32 caliber mold for your model 99, I'm using a 100 grain .312 Lee mold and loading them as dropped over 5 or 6 grains of Bullseye, I use the .7 cc Lee powder dipper. It works great to fire form trimmed 30-06, 270 and even 8x57 brass to use as 7.7x58 brass. You only need a light load to move the brass and shooting plinkers is a ball out to about 50 yds.

Wayne Smith
08-17-2018, 07:21 PM
Yup, item # and mold # are very different things. We typically use mold number here - thus the confusion. Thanks for clearing it up.

Rcmaveric
08-17-2018, 11:18 PM
To make Grendel brass from 7.62X39 I just use my cast bullets and about 13g of 2400. Makes a nice plinking round for the kiddies to pop off for me.