Quote:
Originally Posted by JauntyMorel
That alot easier than i thought. So just the .338 br dies, no expander mandrels? Thanks spook, that helps alot!
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Have any of you tried making 338 BR from 308 brass cut off at the shoulder and necked down to 338? That method works well for making 300/221 out of 223 cases. I'd think that might be easier than trying to make it from 6mmBR brass. You may get different neck thickness in the finished 338 BR depending on what brass you use, both from the parent case type and the brass manufacturer.
+1 on Imperial wax. Besides case length you need to check neck sizes and clearances.
Necks generally get thinner when made larger, thicker when made smaller, but not always depending on axial stretching or compression. You also need to trim the brass both to length and to make sure they're square (case trimmer) and to chamfer the case mouth both to help feeding and bullet seating.
Something which can be a problem on necking brass up or down is how to get the chamber neck diameter right. The bullet plus the brass thickness is "best" about .002 to .004 smaller than the chamber neck. How do you know what your brass neck thickness will be? You don't unless you measure it. You can:
1. Use a large chamber neck and accept reduced long range accuracy from vertical stringing . That can be acceptable if you plan to shoot offhand at modest ranges. Those chamber are found on most semi-autos. A loose neck also helps feeding reliability.
2. Select your brass and dies first, make up cartridges and measure them, then have your chamber reamer made. Most "factory" brass has reasonably well controlled brass thickness from a particular manufacturer. For some it's excellent but it costs more. Probably the best choice for you Sevens bolt action if you want it mostly to shoot up to about 200 hards. beyond that vertical stringing is the #1 accuracy problem in most subsonic firearms.
3. Plan to neck turn and use a "tight neck". . Neck turn all of your brass to have the right clearance. the neck is not tight after the urning, it just has proper clearance. It has the added advantage of having symmetrical neck thickness on all of your brass. It's a common benchrest technique with proven results, but probably not necessary for hunting/ defense/combat use. For competition or sniping it can be worth the effort but only if similar care has gone into the rifle and and other details of loading the ammo.
Janutymorel: Since you say you're new here are you also new to subsonic firearms? What are your expectations of how quiet a 338 BR might be? You didn't mention suppressors. While the bullets from the 338 BR (and any of the Whisper and Whisper clone cartridges are subsonic the propellant gases at the muzzle are not. Expect the 338 BR to sound about like a 45 ACP carbine without suppressor. The muzzle blast will still be obvious as a gunshot at 1000 yards in a reasonably quite area. You can even hear most suppressed firearms at few hundred yards in a quite area, but good ones don't sound much like gunfire. The 338 BR will will give best performance from a short barrel (16" or less) if it's suppressed. Otherwise even though it will be somewhat quieter than your 22-250 your neighbors will know you're shooting and you'll still need hearing protection.
The quietest firearms without suppressors generally have very long barrels, shoot lubricated (usually cast lead) bullets and have expansion ratios of 100:1 or more. With fast powder and high chamber pressures they can give both subsonic bullets and subsonic propellant gas at the muzzle. All a suppressor does is catch the propellant gas and release it at lower velocity but the discussion of suppressors can wait for anther thread.
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