7 RUM Neck Bushings

[Sparky1950]

Setting up for 7RUM loads, rifle not yet finished. Anyone loading 7 RUM, Rem Cases, Redding Comp Dies. I need the correct bushing sizes . Berger 180's. No luck in search

Thanks Guys

 

[Brain]

Re: 7 RUM Neck Bushings

By "rifle not done yet" I'm guessing it's a custom bbl. SAMMI spec chamber?

Bushing size is determined by desired neck tension. Way too many variables to say that a single size bushing is the one <span style="font-weight: bold">you</span> need. Redding lists .313-.321 as the range for the 7RUM.

For whatever it's worth, I use a .314 for my 7RUM with 168 and 180 Bergers.

 

[Sparky1950]

Re: 7 RUM Neck Bushings

Thanks Brain.

Correct on SAMMI 'Minimums' chamber, but I don't know how to define it yet. I loaded assembled dummy rounds for throating, and have measurements for assembled rounds, but don't know how to equate it to bushings.

Should I just wait and measure fired cases, or is there a method to closely guesstimate the size. I don't mind buying more than one bushing if necessary. I guess I'm short on experience in that area.....

 

[Brain]

Re: 7 RUM Neck Bushings

You're going to need more than one bushing to get it perfect.

Typically, subtract .001 from the average outside neck dimension of loaded rounds to determine bushing size.

Get bushings +.001 and -.001 in addition to the measured "optimum". You might find that the rifle shoots better with more or less neck tension than the measured "optimum".

I would wait until you have determined whether or not neck turning is needed for the minimum chamber before ordering bushings. Neck thickness variances in a minimum chamber might warrant light turning. Also, if you're going to the trouble of a minimum chamber, why wouldn't you neck turn for concentricity anyway?

ETA: PM sent