Anyone having issues w/ RCBS AR series SB dies?


April 20, 2013, 12:46 AM
I have installed the RCBS .223/5.56 AR series small base sizing die(#11107) into my Hornady LNL AP w/ LNL bushing. The problem I am having is just as the base of the die contacts the shell plate it is completely sunken into the bushing to the point that the set screw in the lock ring is actually tightening against the turned down portion of the die body below the knurling.

Even at this setting AND making the slightest contact with the shell plate it comes up short on headspace by .010". I have been over the SAMMI specs and checked measurement gear(which is slightly off as compared to a known chamber). Measurements aside I am sizing via the stripped bolt test on match chamber.

If I install the same die in my LNL Classic single stage and adjust it for slight cam-over it sizes right on with no problems. The die is also higher in its bushing to achieve this dimension.

Has anyone else encountered this? I size/deprime as a seperate operation but I would really like to be able to utilize the progressive/case feeder for this operation. I have also had this issue with resizing .308 fired in my M1A.

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April 20, 2013, 09:11 AM
Some ides have that problem on the LNL. So far I have been able to use all brands I have on it, but I had to get inventive on a couple. The Hornady and Bonanza (Forster) split bolt lock ring will screw up farther on the die and still lock down. That may give you the depth you need. I had to screw the lock ring up off the threads and against the top of the die, with a spacer on one die, to get the depth I needed.

April 21, 2013, 03:38 PM
I have an LnL AP with the RCBS AR Series SB die. I am almost out of threads on the sizing die. At the top of the stroke, the bottom of the die is just touching the shell plate.

I could be having the same situation as you are and don't have enough sense to know it. I'll be happy to help with comparing any measurements if it will help but I'm staying tuned hoping to learn something.

April 21, 2013, 03:45 PM

Don't know if I loaned them out or I just can't find them.

If loaned, it could only have been to Big Bob and he's been dead for several years.
I may look for them later on. I like them, didn't see that they cured any problem/s I may have had. Using other non small base dies now with no problems.

April 22, 2013, 12:08 AM
Thanks, I will try the split rings to get a little more depth out of it.

SC_Dave: Try to check your headspace with a stripped bolt to check for a tight fit. My DPMS would chamber the ammunition but another AR with a match barrel wouldn't make it into battery. None of the ammunition was ever fired. I did take before and after measurements from one round that I pulled down and chambered in the DPMS and the chamber pushed the shoulder back .003"!

The lessons learned here:

I allowed assumptions to enter my practices despite knowing better.

Do not assume that setting the die to the instructions is good enough for all situations. This was loaded with fired brass from an internet dealer and origin was not specified.

I did measure the headspace while setting up the die but my mistake was not taking a prior headspace measurement. Once I resized the case and the headspace measurement read what it needed to be i assumed that the die was set correctly and began loading without another check on headspace for other cases. The one I happened to measure was likely already at the correct headspace before entering the die.

I now have the opportunity to apply the lesson as I fix this mistake 300 times.

Dynamite Rabbit
April 22, 2013, 12:23 AM
My die is down so low the lock ring isn't on many threads at the top.

I had to grind a small amount off the bottom of the die to be able to adjust it low enough to push the shoulder back far enough on Lake City brass to fit a case gauge without pushing too hard on the shellplate.

April 22, 2013, 12:47 AM
I will probably try to chuck the die in a lathe and knock about .010" off of it. Might just sell them and use Reddings. RCBS makes good products but I have had issues with the two sets I own. Part of mixing manufacturers I guess.

April 22, 2013, 02:10 PM
119er, I checked mine and it seems acceptable. I have a Stag Arms which has a 1-9 twist and NATO chamber.

On my press, I have the RCBS die adjusted snug against the shell plate. This barely leaves enough threads to lock the set screw against.

I don't know if any of this helps you or not I am trying to absorb this headspace info as much as possible but sometimes for me it's more than I can wrap my head around. But, I'm that special kind of dumb you read about in books. :o

April 22, 2013, 02:47 PM
I now have the opportunity to apply the lesson as I fix this mistake 300 times.Don't feel bad. Even though I know better, I was so wrapped up in measuring something else, I forgot to check shoulder position on some new to me cases (Different, harder, thicker brass. *sigh*) when sizing them. I had to size 600 cases again. At least I did check before loading them. :o

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