# Problem with headspace length using RCBS .223 small base die



## 97th Signalman (Apr 10, 2008)

I use an RCBS small base .223 die to reload for my Bushmaster AR rifles. When loading ammo for Military semi-autos like .223, 7.62 x 51 and .30-06, I use Lyman Rifle Case Length/Headspace Gauges to check headspace length (length from base to datum line on the shoulder) of each brass case after sizing and triming.

Lately I have encountered a problem while doing second and third reloads of some .223 cases. I use Black Hills, R-P, FC, Win, and occasionaly PPU, PMC, or LC brass. I keep them segeregated by manufacturer and number of times fired. The problem is that now I am getting a lot of rejects in that just about every sized and trimmed case measures long in the Lyman headspace/case length gauge. When the case is inserted into the gauge, the case head or base is supposed to be able to go flush or just below the base of the gauge face and above the groove that is milled across the gauge face. I am consistently getting cases that protrude from the face of the gauge by about .025" to .030". This would indicate case stretching from base to shoulder datum line that the small base resizing die has not been able to size back to spec. RCBS writes that Small base dies are suppose to push a streteched shoulder back to its proper place. The Lyman gauge is a relatively new aquisiton so I may have had this issue from early on but never spotted it until I got the gauge.

I set up the RCBS SB die in my old Pacific "O" frame press so that the shell holder just touches the die when the ram is raised all the way. With a case that sizes to proper headspace length the ram just about touches the die at the top of the ram stroke. When I get cases that gauge .025" - .030" long I notice that there is a gap of about .030" inches between the shell holder and the die at the top of the sizing stroke. No amount of force that I can generate with the press can close this gap. I even tried the die in my Lee Classic Turret Press that has a greater mechanical advantage with the same result.

By the way, If I drop loaded Back Hills match ammo or just about any other factory loaded ammo in the gauge, the case head goes flush or just below flush to the gauge face just as it should so I am thinking that the gauge is OK. I don't have a gauge to measure the gauge.

These .223 dies are the only Small Base dies that I use. I use standard FL RCBS dies for 30-06 and 7.62 x 51(.308) and I don't get any "gauge rejects" at all on bolt gun fired ammo. The Garand and CETME fired ammo will start to show stretched cases (not just OAL but base to shoulder datum line) at about the third or fourth reload which is a lot of reloads for a these guns anyway because of how the extracor rips up the base with each firing.

Has anyone else had a similar exerience? Can anyone tell me what is going on and what I should do about it? Or is it no big deal? I would be interested in any advice that you could offer.


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## xdeano (Jan 14, 2005)

If I'm reading this right your using a SB "body die", right? The body die should be able to bump your shoulder back to spec pretty easily. I use one on my 308 just for bumping shoulders .001 past spec for consistency. Have you tried to pick up a FL die just for the heck of it?

Another thing that might be happening is you have work hardened your brass and when you resize it, it is just compressing the metal and bouncing back to what it was before you resized it. In actuality doing nothing. Then you'll need to soften up your brass by annealing. Then resize to bump it to spec.

I'd pick up a sinclair bump gauge and check a before and after when your resizing just to see if you're moving any metal.

http://www.sinclairintl.com/product/5574/Bullet-Comparators

Just random thoughts.

xdeano


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## 97th Signalman (Apr 10, 2008)

xdeano said:


> If I'm reading this right your using a SB "body die", right? The body die should be able to bump your shoulder back to spec pretty easily. I use one on my 308 just for bumping shoulders .001 past spec for consistency. Have you tried to pick up a FL die just for the heck of it?
> 
> Another thing that might be happening is you have work hardened your brass and when you resize it, it is just compressing the metal and bouncing back to what it was before you resized it. In actuality doing nothing. Then you'll need to soften up your brass by annealing. Then resize to bump it to spec.
> 
> ...


I am thinking of ordering a Wilson Gauge from Dillon as a check on the Lee gauge to see if both give the came indication. I will look into a Sinclair gauge as well. I cannot check the shoulder setback prior to sizing as the case neck is expanded by firing so the case can't be fully inserted into the the gauge.


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## xdeano (Jan 14, 2005)

You're correct about being able to measure it in your gauge as a before and after due to neck dimension, that's where the wilson will shine, the gauge sets on the shoulder and attaches to a caliper so it won't matter. It's a neat little tool.

Let us know your results.

xdeano


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## 97th Signalman (Apr 10, 2008)

I tried using an RCBS shellholder with my RCBS dies at the suggestion of guess who? Yup. RCBS. Well, the Lee and RCBS shellholders measured the same in all the critical dimensions and the problem of some sized shells fitting in the headspace gage and some not was not affected by changing shellholders. I also tried an RCBS FL sizing die in place of the SB die and that made no difference as well. I bought a set of Hornady gauge bushings and measured the length from shoulder datum line to base and the difference between the gauges that gauged properly and the ones that were "long" in the headspace gauge differed by .001" or less.

I was baffled by the fact that shells which measured so close when I used calipers, fit in the headspace gauge so differently with no apparent cause. I then tried one more thing. I turned the shells around and tried inserting the rimmed portion ( Yeah, .223 is "rimless" but you know what I mean)base first into the mouth of the headspace gauge.

Viola!!!! I now know the problem. The "rims" of the sized shells that don't go all the way into the gauge are slightly oversized (at least at some points around their periphery) compared to the shells that "fit" into the gauge. It appears that 2,3, or 4 firings create a burr and/or distortion where the extractor grabs the rim. The resultant distortion is all that stops the sized case from going all the way into the headspace gauge. So all I am contending with here is extractor roughing up the rim. It probably doesn't even cause any operational issue in actual gun but it shows up as a "problem" on the gauge.

I am left with three questions:

1. Might a slight amount of extractor damage cause a feed or chambering problem? Or should I just ignore it?

2. Is there any tool or process for cleaning up the rims? I used some emery cloth and a wire wheel to clean a few that would not fit in the gauge until I did clean them up (removing burrs and smoothing nicks). However, the process is tedious and may even round off the forward edge of the rim which could cause the AR extrator to skip off.

3. Should I switch to a more aggressive tumbling media? I currently use corn cob media rather that walnut shell media. Maybe the harder media might clean up the rims enough so that I wouldn't have this rim problem

I welcome your suggestions.


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## xdeano (Jan 14, 2005)

did you notice which brass was having the majority of the problems? If you can pinpoint one brand of brass, I'd call that batch and buy some more and cut your losses.

Other than that I'm not aware of anyone who makes a cutter for the rim. The only thing I can think of is a mini lathe and cut the rims to spec. But now we're taking some money.

I'd say just pitch the ones that don't work.  If they feed through your gun it shouldn't cause any problems.

xdeano


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## People (Jan 17, 2005)

I used to have a mini-14 that had a chamber so tight the only way I could get ammo back into it was to screw the die as far into the press as it would go. Then lube the heck out of the body of the casings and give her heck. This would make the length from the bottom of the cassing to the datum line to the min spec.

I found in my press I there seemed to be some play or give at the top of the stroke.

Now that I do this you can feel the cassing press against the die then you can press it in a little more. May not be the best solution but it did solve my problem.

Chuck Norris' favourite cut of meat is the roundhouse.


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