Any body use rcbs small base AR dies?

Dultimatpredator

Dultimatpredator

Well-known member
I just picked up a set that said new, opened...lol sure, off eBay for $30 shipped. Part number 11407 for my 243 AR. If you saw my post on AR stone stuck case you can see why I want to give it a try. I realize it was my fault for loading ammo too long and I had one case that was to large in diameter that I must have short stroked my press or I’m guessing the brass case sprung back from being over worked? Well I loaded up 20 fresh cases under max OAL and they seem to fit and feed fine. I ordered a SB die set just in case and will start using it when it arrives.

Anyone use these? If my current, corrected rounds chamber and shoot fine how much, if any will my groups open up with a looser case? Thanks for any input.
 
I use Full Length dies, and I've never had a problem. You just need to keep an eye on how much you're bumping that shoulder back. I'd recommend the Hornady Case Comparator to make sure you're setting that shoulder back accurately and consistently. When I load for an AR (or any other autoloading rifle), I bump the shoulder back as far as the FL die will let me. Basically, I set the die so that it just touches the shell plate when the ram reaches its highest point. I don't think that has any effect on accuracy - the only thing you sacrifice is a bit of case life. However, you do gain 100% confidence that the next round will chamber properly; which, to me, is the entire purpose of a semi-auto.

I don't anneal, and I haven't had any issues with significant spring back, either. One thing that might help would be to batch your brass by manufacturer and by number of times fired. Different case manufacturers will vary the mix a bit in their brass to meet their own specifications, and that can make a difference when it comes to useful life expectancy of a case.

Last, but not least - I'm a big fan of the slotted case gauges from Sheridan Engineering. You can check the case or the entire loaded round. If it passes, its a guaranteed go. If it doesn't pass, the slot lets you see exactly where the problem is, which saves you a lot of troubleshooting time.
 
Never used them in any of my AR,s and have not had any problems. Only thing I use them for is the first step to size my 20 Practical brass.
 
I use RCBS Small Base 6mm Creed for an LFAR. I wish I would have spent the extra money and bought the Redding Type S Bushing Small Base die instead. The RCBS neck is grossly undersized. It works, but it works the [beeep] out of the necks, and even with a mandrel expander, the spring back is severe.
 
i have two sets of them 223/5.56 & 7.62/308. i have them in case i get nato brass that may have some MG bulge down on the base when first processing them. some of the LC762 i got a while back were like that and needed a little extra to get them "right". they weren't awful but they wouldnt pass a Sheridan gauge after reizing in my lee 308 diees... so i wanted them fully in-spec before i started fire forming to my guns.

most of the time... they sit idle on my bench collecting dust though
smile.gif
 
My POF P415 eats anything I put through it. I just use regular 223 dies and get ridiculous accuracy. I would assume there is more of a set standard with 5.5.6/223 round so a small base die is probably not needed in most cases. But I’m guessing in a non standard “odd ball” type chambering like my 243 that’s not as common there isn’t going to be a set standard kinda like 308 AR specs being all over the place.

I did order a Lyman checker gauge as well.
 
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Never needed them with my R25 in 243. The only one that I need the SB dies for was a 17/223 that had a match chamber in. Which stinks. Where you get into trouble is if the brass was shot through a machine gun. Or the reamer was on its last leg and should have been changed.
 
I called RCBS to ask questions on the 243 AR die set. I was told the 243 AR die set is only a two thousands of an inch smaller on the inside VS the standard set. So basically two thousands of an inch is equivalent in length to the half the thickness of a piece of paper. So the AR small base die has a very minimum difference but must just be enough to help chambering issues. I would assume there is not going to be enough difference that would open up grouping. I was going to try both does to see if there was a group difference between the two but there is not enough of a difference IMO to worry about it and as long it helps feeding and chambering I’ll solely use my AR die for my AR243.
 
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I have two sets of 223 Rem. dies. One is the RCBS SB dies, set up to run in my progressive press, used to make plinking and SD ammo, where accuracy isn't a main objective. For sub-MOA accuracy, I load on a single stage press, with a set of Forster Ultra dies, which are not SB. Before I purchased the Forster dies, I used the RCBS SB dies to load my accuracy ammo, and had decent results. I bought the second set, because moving the dies between the progressive, and the single stage, became a pain. The reason I went with Forster dies for the second set, is my runout measurements say Forster dies are very good at minimizing runout, in general, and these dies did not disappoint.

Squeeze
 
Well I tried a few rounds I loaded in my standard 243 RCBS dies today. All fired and cycled fine in my rifle. My Lyman checker also shied today. I saved some of the unfired rounds to test in my checker I had a few seat firmly in the checker but they were fully seated. Most if the spent cases dud the same. I had a few spent cases stop not even a pice of paper thick above the checker base. I take it I have a tight chamber. Here's a pic of the spent cases. They were a little scratched up and you can see the high spots where the cases rubbed inside de the chamber. I would assume I need the small base die set even though the cases all fed and cycled...but they sure look like they were still right in the chamber.

2xaRnBd.jpg
 
Originally Posted By: DultimatpredatorI called RCBS to ask questions on the 243 AR die set. I was told the 243 AR die set is only a two thousands of an inch smaller on the inside VS the standard set. So basically two thousands of an inch is equivalent in length to the half the thickness of a piece of paper. So the AR small base die has a very minimum difference but must just be enough to help chambering issues. I would assume there is not going to be enough difference that would open up grouping. I was going to try both does to see if there was a group difference between the two but there is not enough of a difference IMO to worry about it and as long it helps feeding and chambering I’ll solely use my AR die for my AR243.

Unless you have a specific problem, like a really tight chamber or brass that has a lot of spring back, the Small Base Dies don't really do much for you. I really believe that 90% of the problems people run into, when sizing brass for an AR, is making sure that shoulder gets bumped back far enough and making sure it's getting bumped back consistently from one batch of brass to the next.
 
My small base die set showed up the other day. I gave my sizer die and then 1/4 turn after it was flush with my shell holder and ran some cases through and. Checked in my Lyman checker. It has way looser of a fit in my checker compared to the standard sized cases. The standard sized cases fit flush but there is literally no leeway for my case to move in the checker. When I tried some of my fired cases in the Lyman checker most fit loose and flush! Which tells me the chamber is really tight/small fro caliber...or my checker is just way out of spec? My gut tells me that eventually I’m going to get a stuck case using the standard sizer. I realize there is not really a “mil spec standard size” for 243 in an AR platform which explains why the chamber size variance I would assume? I do get a firm bolt close with my 700 bolt some times with my standard sized loads as well but I will continue to use the standard dies fro my 700 since it shoots ridiculous accurate. I believe its probably due to old, overworked brass that has never been annealed. I believe the SB die will help in my scenario.
 
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Thanks for the update.

We have run into similar problems with the .204 and the .17 Rem in the AR platform. Every now and again I would get a sticky cartridge with reloaded .223's but when we started reloading the .204's we had exactly the same problem. Bolt wouldn't fully close and we had to butt stroke the ground to get it out. Tried to bump back with a regular die with no luck. Same cartridge's loaded into a single shot rifle loaded and fired no problem. But not in the AR. Finally went to a SB .204 die and that solved the problem. Then we started seeing the same problem when I started loading the .17Rem in the AR platform.
 
Originally Posted By: DultimatpredatorMy small base die set showed up the other day. I gave my sizer die and then 1/4 turn after it was flush with my shell holder and ran some cases through and.

RCBS Rock Chuckers have a design built in to "over cam"

Most other presses do not and it makes me cringe for some reason.

Originally Posted By: Dultimatpredator I believe its probably due to old, overworked brass that has never been annealed. I believe the SB die will help in my scenario.

IMO annealing won't help that situation because you only anneal the case shoulder and neck.

You would be so much better informed if you bought a RCBS Precision Case Mic.

https://rcbs.com/Products/Case-Preparation/Measuring-Tools/Precision-Mic.aspx

and a bullet comparator from either Hornady or Sinclair.

https://www.brownells.com/reloading/meas....aspx?rrec=true

You will need 2 inserts per caliber. One for Shoulder bump and one for base to ogive.

The RCBS tool is optional really. I just like it because it tells you where zero is regarding SAMI headspace. (on your brass)



 
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