FL sizing belted cases; what am I missing?

[BurnOut]

I've always heard how much of a PITA it is to properly FL resize belted cases, but over the weekend, I was able to set up my 300WM (Forster) FL resizing die such that it bumped the shoulder 1.5-2 thousandths (on cases fireformed in my chamber) and went down the case to juuuust ahead of the belt (judged by looking at the contact pattern shown in the resizing wax on the case). As a novice(-ish) reloader, I was struck by how much trouble I didn't have dialing this in... which leads me to the conclusion that either I got lucky and ended up with a chamber/FL sizing die combo that closely match, or I'm missing something.

I should note that in addition to FL sizing the brass that had been through my gun, I was also working some range pickup brass that had been through someone else's gun, and I was able to note the difference in contact pattern based upon which gun the case had been run through. The brass in question was whatever Black Hills uses (my gun) and Hornady (range pickup), and I set the base-to-shoulder length on all of them based on a measurement taken from one of my fired (but not yet resized) cases. The brass from my gun showed a contact pattern in the resizing wax all the way down to @.010-.020" or so (guesstimating) ahead of the belt, while the contact pattern on the Hornady brass stopped @.080-.100" (also guesstimating) ahead of the belt.

I haven't test fit any of the brass in my chamber, but I'm guessing that there won't be any problems based upon the fact that the brass that had been through my chamber showed contact with the die closer to the belt (vs the pickup brass), thus indicating that my brass is wider just above the belt than is the pickup brass. So... did I get lucky, or am I overlooking something? Is it that .010-.020 immediately ahead of the belt that becomes a problem over multiple firings on a given case, or...?

 

[spife7980]

Is your 300wm an aftermarket or higher quality barrel and chamber job vs a factory mass produced tube? Reads to me like yours has a closer tolerance chamber and thus the dies interface the brass properly as opposed to a larger chamber reamed in a bunk barrel chambered .9 too deep like that hornady brass was shot through.

From my reading it is that .01-.02 in front of the belt thats the issue. If the brass is stretched way forward in a over sized chamber the properly sized die will push the shoulders way before the bottom of it gets near the base as you deduced. I think youre dead on with your analysis.

 

[FatBoy]

you sound like you're on the right track. I have A191 chambers in both of my 300wm and I had to have the base of my body die cut off .030 to get down to the belt when I set my shoulder setback. I run big, heavy bullets to so I run. 005" clearance at the shoulder to help bleed some of the pressure off. Maybe not the "right" way to do it but I have 6-7 firing on Winchester brass with 230 OTMs.

 

[sinister]

This is a good read on why belted magnum case clearance above the belt gets wider (due to how far the die sizes the case body above the belt): see reference the Innovative Technology Collet Die for Belted Mags:

 

[BurnOut]

Is your 300wm an aftermarket or higher quality barrel and chamber job vs a factory mass produced tube? Reads to me like yours has a closer tolerance chamber and thus the dies interface the brass properly as opposed to a larger chamber reamed in a bunk barrel chambered .9 too deep like that hornady brass was shot through.

From my reading it is that .01-.02 in front of the belt thats the issue. If the brass is stretched way forward in a over sized chamber the properly sized die will push the shoulders way before the bottom of it gets near the base as you deduced. I think youre dead on with your analysis.

My 300WM barrel is from Desert Tech, while the range pickup brass was run through a Savage, so good call on that... and after posting this (really, after completing the thought process that I went through writing it) I came to the same conclusion as you have... that it's that thin area immediately in front of the belt that seems to become problematic after a few loadings of a given case.

I then thought to myself, well, shit... that seems like an easy enough problem to solve... why not just have a belted magnum body sizing die that leaves the neck alone and simply runs down the body of the case all the way to the belt? So, standing in line at the sandwich shop, what do I come across (while browsing the Interwebz on my phone), but the same thing that sinister just mentioned... LOL

Good stuff.

Anyhow, I really like that solution, as it can be used with the entire family of cartridges (7mm RM, 300 WM, etc...). I was just getting ready to pull the trigger on a set of custom Whidden dies for a 338 WM that's getting built as we speak (where I would essentially expect that they'd do something like FatBoy did with his dies), and if that was going to be my only belted magnum case, the price would just about be a wash (between the custom dies vs. off-the-shelf dies and the body sizing die from Larry Willis); however, with even two chamberings from that cartridge family (300 WM and 338 WM), that body sizing die becomes a no-brainer.

Thanks for the help, gentlemen!

 

[MtnCreek]

Your Black Hills brass is most likely Winchester.

 

[BurnOut]

Your Black Hills brass is most likely Winchester.

It's not headstamped as being Winchester, but that doesn't necessarily mean anything.

Anyhow, as I have done more reading on this, it seems that the formation of the bulge ahead of belt can be significantly delayed by adjusting the FL sizing die "properly", which is to say to bump the shoulder back no more than .001"-.002". Based on what I'm finding, it seems that a lot of reloaders will adjust their sizing die by raising the ram on their press and threading the die down until the base of it contacts the face of the ram/shell holder; this approach would ensure that the case headspaces ONLY off the belt and essentially has to re-stretch to the chamber dimensions each time its fired, rather than headspacing off the shoulder (AND the belt) as would be the case if the shoulder were only bumped back .001"-.002".

Either way, I went ahead and ordered one of those body dies, which I am pretty sure will be able to resolve the issue if/when it crops up for me.

 

[flashhole]

Nothing wrong with head spacing on the shoulder with a belted cartridge. I do it with my 7mm RM Sauer 202. Excellent accuracy. I think you need to give a bit of credit to the dies you are using.

Did you chamber the resized cases in your gun for fit check?

 

[BurnOut]

Nothing wrong with head spacing on the shoulder with a belted cartridge. I do it with my 7mm RM Sauer 202. Excellent accuracy. I think you need to give a bit of credit to the dies you are using.

Did you chamber the resized cases in your gun for fit check?

Oh, I'll freely admit that the dies are a big part of what I'm seeing; it certainly isn't my skill as a reloader that has anything to do with it. I have been using Forster dies for all of the precision-oriented reloading that I've done and recently had cause to use some RCBS dies to make some dummy rounds... either I don't know how to use the RCBS dies correctly (which is a distinct possibility), or the Forster dies really are a step up by comparison.

In any event, I haven't test fit any of the cases in my barrel yet; however, I am pretty confident that there won't be any problems due to the smoothness with which the Black Hills cases were extracted from my barrel, and the fact that the resizing wax shows contact on those cases right ahead of the belt (thus indicating that the cases were squeezed by the die at that point).

 

[wapiti16b]

I run mine through the Willis die and then use the Forester Bushing / Bump die on my brass . Spaced on the shoulder or the belt I find this process works best with my chamber . I'm convinced that Forester products really are that much better than the RCBS . The Willis digital bump gauge is pretty nice also !