Thread: 284 win slow speeds

Originally Posted by GWH

@Jim356

.317 neck on the reamer i see, was that the gunworks reamer?

You say a loaded round measues .314 neck dia, what is the dia if you move the calipers down closer to the neck shoulder junction? 284 is pretty fussy on neck clearance, and while it appears you have 3 thou total neck clearance, thats the bare minimum i reckon, and im picking down towards the shoulder you may not have that much.

Yes gunworks did the reaming. From what I can tell when measuring the brass it does seem to be just a fraction wider at the very base of the neck. What did you find to be the ideal neck clearance with your 284 @GWH?

Originally Posted by Jim356

Yes gunworks did the reaming. From what I can tell when measuring the brass it does seem to be just a fraction wider at the very base of the neck. What did you find to be the ideal neck clearance with your 284 @GWH?

In the early days of 284 popularity in F Class the Yanks said the 284 likes "good" clearance. I could never work out how a cartridge could have the intelligence to know it needed good clearance. Obviously with good clearance there is some safety but you are also working your brass a lot more.

In all likelihood with springback your throat is probably .315. Did you get a copy of the reamer drawing? I always request that of the Smith. That gives me information for neck turning etc.

If you are using bushing dies the neck at the neck shoulder junction will always be larger due to bushing dies generally not sizing that far down plus the chamfer present on the bush.

Originally Posted by Jim356

Yes gunworks did the reaming. From what I can tell when measuring the brass it does seem to be just a fraction wider at the very base of the neck. What did you find to be the ideal neck clearance with your 284 @GWH?

That Gunworks reamer, if the same one, does have a .317 dia on the neck, it also has different lead angles than normal i believe, I remember Robbie telling me about it at the time.

I found that 3 thou total wasnt enough. I also found the neck to be wider at the bottom of the neck, by the shoulder junction, a neck turn to increase clearance, and make sure that it cuts down into the shoulder a little prevented donuts at the neck/shoulder junction and stopped me seeing pressure signs at lower powder changes than expected.

I think im at 5-6 thou clearance, and it was much happier.

I might give neck turing a shot at some point to see in the near future to see if I get any performance increases. Thanks for the information GWH