284 win expanded neck runout

[Tod Hendricks]

Has anyone forgone the 284 expander mandrel and instead pushed a 7mm bullet in the 6.5-284 lapua brass and fire form in 284 chamber? Pros Cons? I am asking due to excessive neck run out after expanding.

 

[lrgoodger]

I have made a special chamber for fireform expanding 30BR brass from 6mmBR. I just load the 6BR normally and fire the 6mm bullet down a scrap 30 cal barrel. The case forms perfectly in the chamber to perfect 30BR brass. The 30BR bullets seat straight and so shallow that there is no concern with the donut formed by the part of the shoulder that became thick neck.

I have been wanting to do this with the 6.5-284 cases to get 284 Shehane brass. I also find that expanding them with a mandrel induces excessive runout. It takes a firing or two to get them straightened back out. If you don't spec a reamer with a long freebore, you will have problems with the pressure ring on the bullet getting into the donut area. The donut will be there whether you expand by mandrel or by fireforming. If your freebore is long enough to keep the bullet base well above the donut, it will not be a problem.

 

[Steve Blair]

I have a bunch of 6.5 FMJ bullets for my AG-42B and a .284 Shehane fire forming barrel. I'll give your approach a try. Sounds better than wasting 7mm bullets.

 

[AlanPF]

Tod,

Maybe I'm not understanding your method, but why would pushing in a bullet cause less runout than a mandrel? My mandrel in the K&M type and doesn't cause excessive runout.

Alan

 

[dkhunt14]

I don't think you can get a 7mm bullet in a 6.5 case without trouble. The bullets would really fit tight and tale a lot of pressure to seat. I use a K&M mandrel and don't get a lot of runout. When I shot the 308 Baer at 1000 Br. I Sometimes would get one that the expander caught and really made them crooked. When I got a really crooked one I would put it in as a sighter. I had one that was so crooked I wasn't going to shoot it. My buddy said why didn't you shoot that one. I said look at it and he said it won't hurt a thing. I said it is your gun and I don't want to hurt it and he said shoot it. I shot it and it went in the patch with the other ones. Now I had to pound the bolt shut, because it was that crooked. I then went on to shoot a 4.01 inch 10 shot group and 99 score fireforming. Now this was with Sierra 240 grain and the bullets were about 15 thous. into the rifling. I believe when you put the bullets into the rifling it tends to straighten things out. Matt

 

[Tod Hendricks]

LRGoodger, I hadn't thought of throwing a 6.5mm down the 7mm tube. I will try it, thank you.

Alan, I have the K&M and a Sinclair and both seem to bend the necks, using either Sinclair benchrest press or Co-Ax press, both presses operate perfect in other operations. Use lots of wax and have mirror polish on the mandrels, went as far as doing 3 steps, 6.5, 277, and 284 mandrels, no better and maybe worse, I think that gives me 3 opportunities to bend em.

dkhunt, actually the 7mm 180 hybrid went in the 6.5 case a lot easier than I thought it would. You can sure see where the shank ends in the neck. I only did a couple cases and they both put a couple thou of run out in the neck, less than the average mandrel bend. Some of the cases are taking two or more firings (even jammed) to straighten out and I am not satisfied with the performance of the chambering yet.

Thanks all for the input

Tod

 

[lrgoodger]

LRGoodger, I hadn't thought of throwing a 6.5mm down the 7mm tube. I will try it, thank you.

Tod

Don't 'throw' a 6.5mm bullet down your GOOD 7mm barrel. Have a fireforming barrel done with the same reamer as your good barrel.

 

[Henryp]

I use a K&M 270 then 284 expander with imperial wax
Henry

 

[BT1]

Another vote for the 2 step expansion. I used the exact same procedure, K&M 270 then 284 expander with imperial wax, then turned necks, before shooting. Produced 600 cases in the past year, without a single failure.

Steve

 

[Alex Wheeler]

Are you guys talking about thickness run out of the necks or the concentricity of the necks? I use a sinclair expander with imperial die wax to expand my 6.5-284 brass. I get a max thickness run out of .0025'', which is pretty bad, which is why i have a .313 neck and turn my brass. I don't care about concentricity as that will fix it self once the cases are fired.

 

[Miketherock]

It's odd that you would be getting excessive runout with a K&M mandrel.

I use the raised window attachment and find if I don't screw the mandrel housing in tight it lets everything float nicely and I do not have any runout issues expanding Lapua brass up to 7mm in one pass.