.257AI Re-sizing Issue

[SSTX]

I've run across a case re-sizing issue that I'd like to hear some opinions on. The rifle is a Remington M700 with Shilen barrel chambered in .257AI, and I'm using an off-the-shelf RCBS 2 die set. Fired cases readily rechamber in the rifle with little effort, but full-length sizing seems to be moving the shoulders forward and causing significant effort to chamber.

Case diameter behind the shoulder remains consistent between fired and sized cases, so it doesn't appear to be a collapsed shoulder (which I've done before). Progressively moving the sizing die from a full turn off the shellholder to 1/4 turn tighter after contacting the shellholder has not helped, and I don't have the right tool to measure shoulder set-back with calipers. I suspect that the expander ball on the decapper is the culprit, along with maybe the resizing die being a bit "loose" in the shoulder area. I've resorted to using a Redding neck-sizing die, which seems to have a less aggressive expander ball and does not produce the same issue as the full-length die. Eventually, though, the cases will need to be full-length sized. I had a similar issue on another .257AI built on a Ruger 77 with a Douglas barrel, using a different set of the same RCBS dies. I eventually sold that rifle before solving the re-sizing problem.

Any thoughts on this issue would be most welcome.

 

[gohring3006]

My guess is that your right, expanderball. Take it off the die and try it see if it still does it I bet it won't...

 

[dkhunt14]

You really need a Hornady headspace gauge for your reloading. You need to know if you are bumping them and how much. The gun could be on the minimum headspace and you are not running the die down enough. A .002 to .003 bump is what you need. I have a bunch of custom guns and all of mine are minimum headspaced and most of them need the die against the shellholder or close to get the bump needed. Headspace gauge and the busing set is cheap. I use a bushing that goes to the middle of the shoulder and that will measure your bump accurately. Matt

 

[Ol'Gator]

A silly question but are you using standard .257 caliber dies?

 

[SSTX]

A silly question but are you using standard .257 caliber dies?

No sir, I'm using RCBS .257 Roberts Improved 40 dies (part #32201), but they're standard production rather than being made from a fired case or chamber casting for my specific rifle.

Matt, I agree that I need the proper bushing, I only have one for my 7mm Rem Mag right now. I've tried the die from 1/4 turn past contacting the shellholder for "cam over" to 1 turn above the shellplate with no effect. Guess another visit from the Big Brown Truck is in the making......

 

[dkhunt14]

Without the compariter bushung it is hard to tell if you are bumping the shoulder or not. Once I know that I may be able to help you. Matt

 

[MagnumManiac]

The fix is simple. Get yourself a set of cheap automotive feeler guages, put a .005" guage under the case AFTER you have adjusted the die so that there is no gap between the shell holder and the die bottom when a case IS in the die during sizing. If there is a gap, then FL sizing is NOT taking place.
Use the guages until you get one case to chamber freely, take note of how much it was, then get that much turned off the TOP of the shellholder.
Or, I have turned .010" off and .015" off some shellholders and then adjust the same as per the instructions furnished with the die set with good results.
I have never needed to remove more than .015" to get correct head clearance on any shell holder I have used. I only use RCBS products, so your product may differ some if not RCBS.

Cheers.
gun)