338 Norma Improved

[Lonewolf74]

So I'm building a 338 Norma magnum and decided to go with an improved version. This is my first venture into a "wildcat" of sorts. The part I could use a little help with is the fire forming process.

The reamer I specd out for the 300 grain Berger's but did stay on the conservative side in case I wanna play with the 250's. My throat is .010 over CIP. I believe if my calculations are correct this will put the 250 .060-.070 off the lands with enough seated in the neck. The reamer and go gauge is -.004 which I believe is pretty standard for AI and should give me some crush on the neck, shoulder junction when chambering CIP spec ammo.

The real question I have, is it necessary or advised to have jam on the bullet when fire forming? I was thinking about buying some of the cheapest bullets I can find to form but that may not be possible if I need to jam the bullet because they will be too short? And along the same lines how do you shoot factory ammo if needed in a pinch since you won't have control over seating depth?

This also leads to the question if I decide to try the COW method how do you go about it with no bullet to jam? I'm not sure I understand how some people go about it when they say they create a false shoulder on the neck to head space off of?

Thank you for any help and advice
Joshua

 

[Dmagna]

I wouldn't mess with COW in a magnum like this. I would shoot full loads from a 338 Norma and let the brass expand. There is a tremendous amount of pressure in a Norma mag, I don't see any issues. Form the brass during break in and you will be all set.

 

[Lonewolf74]

Thank you for the response. My plan is possibly to get 3-4 cases formed using a standard case then send that brass to Whidden and get a custom die set as well as a hydraulic form die. However I would still go through the process of firing every case and running about 100 shots down the barrel before any serious load development. I would like to do seating depth test while forming as well as long as it's not necessary to jam the bullet on initial firing.

Debating on the form die being worth it since I'll essentially fire form every case anyway. My reasoning is with the form die it should be pretty fully formed in one firing vs two or so.

 

[Rhovee]

It takes 100 rounds to break in a barrel. Fire forming the first 50-100 rounds isn't a big deal. 50 rounds of the Lapua brass will last a longggg time. I have a 338 NMI.

 

[Lonewolf74]

I went with Peterson brass cus I got sick of waiting for the Lapua but I see it's available now and could get my hands on it.

Another question is what would be a good forming load and powder to use. I have 8 lbs of N570 and 2 lbs of N565 but I don't wanna burn up either of them to form. I also got RL26 and H1000 but again don't really wanna use that for forming. Right now I might be stuck with using what I got cus of the shortages but if I can find any what would be a decent cheaper powder to use, I'm thinking like ramshot mag or maybe 7828?

 

[Rhovee]

You'll be burning +90 grains of powder when you find a load so you should stock up or start doing some trading. If your rifle is really light, I would shoot 250's. If not then get it throated for 300's. The 260 hammer hunter and 300 Berger require same freebore. I switched to 260 hammer hunter recently and they shoot grest with H1000 or N565. .007 off. Right around 3000 FPS. My fire form loads are 285 eldm with 86 grains H1000. Make sure you jam the bullets .020. Peterson brass is short on head space. Lapua is longer but still jam. 100 pieces of Lapua will last the barrel. Just do yourself a favor and form all 100 when breaking barrel in. I have 500 rounds on mine and am still on original 50. N570 is to slow for 250's. I can't get enough in case to pressure out 300's. 94.5 grains. It does shoot great with 300's. Still might try it with 260's. Here is my last outing with 92.3 of N565 and 260'd.

 

[Tucker65]

I built a 300 Norma Improved and fire formed with surplus 50 BMG powder using some cheap bullets. But the other thing I did was chambered up cheap barrel I got from Black Hole barrels for fire forming. I purchased 100 Laupua brass and just slapped the barreled action into a tupperware stock and fire formed them all before the rifle was ever assembled.

 

[David Emerson]

So I'm building a 338 Norma magnum and decided to go with an improved version. This is my first venture into a "wildcat" of sorts. The part I could use a little help with is the fire forming process.

The reamer I specd out for the 300 grain Berger's but did stay on the conservative side in case I wanna play with the 250's. My throat is .010 over CIP. I believe if my calculations are correct this will put the 250 .060-.070 off the lands with enough seated in the neck. The reamer and go gauge is -.004 which I believe is pretty standard for AI and should give me some crush on the neck, shoulder junction when chambering CIP spec ammo.

The real question I have, is it necessary or advised to have jam on the bullet when fire forming? I was thinking about buying some of the cheapest bullets I can find to form but that may not be possible if I need to jam the bullet because they will be too short? And along the same lines how do you shoot factory ammo if needed in a pinch since you won't have control over seating depth?

This also leads to the question if I decide to try the COW method how do you go about it with no bullet to jam? I'm not sure I understand how some people go about it when they say they create a false shoulder on the neck to head space off of?

Thank you for any help and advice
Joshua

If you have .004 crush I would not worry about jamming the bullets. But use maybe not max but close to max loads for forming. I built a 338 lapua improved 30 degree. I used blem 250 hornady match bullets and unique pistol powder. If I remember right it took 35 grains to fully form the shoulder. But once it got to pressure the cases came out perfect. Some cartridges shoot just as well raw as formed. Work a load to pressure in an unformed case and try it.

 

[MagnumManiac]

I fireform my 375 Bee brass from H&H brass using Clays, 30-35gr gets the job done. I use COW, a paper wad (TP) twisted into the neck.
Never had a problem.

Cheers.

 

[cjuve]

I have fire formed both ways for my 300 Norma improved and 338-300 Norma improved. My reamers were set up off of lapua brass for a crush fit, I have not noticed any difference in outcome with either one. I check each piece of brass to make sure that I have resistance on the bolt if not I jam them and send it.

 

[horse killer]

I fired formed mine with 230 Berger's with H1000 and Norma 217. They shot great fireforming most shot under 1/2 moa. I would jest shoot them and get use to the rifle and when the barrel speeds up do your load development. In all realty you could shoot your 300 NI hunting when fireforming your brass. The 300 NI is a great round.

 

[Lonewolf74]

So it seems I'm getting sort of conflicting answers. I have no problem jamming the bullets if that's the better way to do it but what about shooting factory ammo if needed? I don't have any intention of shooting factory ammo but in times like this it could be easier to get then components to hand load and I thought if an improved is done right you can shoot factory ammo with no issues?

Thanks again for the help guy's

 

[cjuve]

So it seems I'm getting sort of conflicting answers. I have no problem jamming the bullets if that's the better way to do it but what about shooting factory ammo if needed? I don't have any intention of shooting factory ammo but in times like this it could be easier to get then components to hand load and I thought if an improved is done right you can shoot factory ammo with no issues?

Thanks again for the help guy's

It all depends on your chamber and the fit of the factory ammo that you want to shoot. There are lots of improved versions of various calibers out there that move the neck shoulder junction forward and straighten out the case tapers in which case it would be advisable to do a false shoulder and/or jam the bullets. I can fire factory ammo in my 300 Norma improved with out an issue because I made sure to shorten the length to the neck shoulder junction by .005 to make a crush fit on factory ammo.
Without knowing what specific mods you made to the reamer no one can really be sure what is the best method to use or if you can fire factory ammo. The -.004 difference of the gauge is in relation to your reamer not SAMMI dimensions

 

[Marine sniper]

Don't waste your money on a hydraulic forming die, I bought on for my 338 LAI. I measured the water grain capacity before and after- waste of time. Your best bet is to just fireform.