284 Win bushing.

[barnesuser28]

Can anyone tell me what size redding neck bushing i need to order when using necked up Lapua 6.5x284 to have .003 neck tension? I dont have any brass yet and i am planning on ordering all my supplies at the same time.

Riley

[barnesuser28]

anyone?

[SBruce]

I dont shoot a 7mm so I cant expand a neck and give you an exact number, but I can get you close, assuming you're using brass that is similar neck thickness as mine.

My 6.5-284 Lapua brass is averaging about .015" thick. Necking up will probably thin them by about .0005, I say this because when downsizing from 308 to 277, I gain .001 and when downsizing from 6.5 to 6mm I gain about 1/2 thou.

Lets just assume for a minute that your expanded necks will average ~.0145"
That's .029" of neck, plus the bullet of .284 should give a loaded round of .313" on the neck diameter....................I would order a .312, .311, .310, and .309 to start with. Use whichever one gives the best measurements and least runout once you've got everything in hand. But still tight enough that bullets don't move under recoil or when chambering the round.

Also remember, that not all bullets will be exactly .2840" diameter. Some brands may be .0005 bigger or smaller. I've seen this in many other calibers, don't have any reason to think 7mm would be any different. That's just one more reason to order more bushings then you think you'll need, just in case.
Also, if someday you decide to use Norma brass, it may or may not be the same neck thickness as Lapua. Or if you decide down the road to turn the high spots off the necks, the .309 will be tight enough to still give good tension.

Hope this helps.

[Outlaw6.0]

Well stated Shane. I am using a .312 in my 7saum, in your case, I would also recommend the .310 & .309. Without having the brass on hand, it's a crap shoot at this point.


t

[barnesuser28]

i think i will go with the 309 bushing, should give me enough tension evenif my lot of brass is a little off, this will be a repeater so enough tension is important.

Thanks, Riley

[SBruce]

Originally Posted by barnesuser28

i think i will go with the 309 bushing, should give me enough tension evenif my lot of brass is a little off, this will be a repeater so enough tension is important.

Thanks, Riley

You should certainly have enough tension with the 309.

There is however a downside to too much tension. Or too much working of the brass perhaps is the better wording. With a no-turn saami max. chamber, your brass will expand .004 or .005 upon firing and then necked down possibly . 008 or .010 with the 309, and then "necked up" by the bullet seating into it again by another .004 or .005. This doesn't really hurt anything, except it will eventually work harden your case necks prematurely, causing the need to anneal or replace cases for best precision and accuracy. Lapua cases arent cheap, I wouldn't want to replace them prematurely.

Too much tension often also leads to excessive and unnecessary runout on loaded rounds, which can then induce less accuracy...........Goods and Bads in all decisions unfortunately.

[barnesuser28]

I will be annealing the necks probably every 3rd firing, i will contact my gunsmith and ask what the neck diameter of his reamer is. I didnt know that excess neck tension can cause runout problems so i think i will go with the 310, not that it will make a huge difference.