223 Small Base Die Question

[AccelR8]

I've been searching and can't find the answer. What dimension does a 223 Remington small base die size the base of the case to?

edited to shorten my post just to the question. This is all I'm interested in. I do tend to talk too much...

 

[Bill K]

First, make sure your cases are trimmed to the proper setting. A SB die, should solve any issue with fitting into any of the 223 chambers. especially in AR's. Bill K

 

[243winxb]

.376" is maximun SAAMI for a loaded round.
Part of the case cant be sized. Its in the shell holder.

 

[Big Mc]

I've been searching and can't find the answer. What dimension does a 223 Remington small base die size the base of the case to?

edited to shorten my post just to the question. This is all I'm interested in. I do tend to talk too much...

Small Base dies bump the shoulder an extra .001 too .002. For use in a AR platform.

 

[Uncle Ed]

Chambers and resizing dies vary in size and nothing is written in stone. For example I have a standard Lee .223 full length die that will reduce the case body diameter .001 more than my RCBS .223 small base die.

That being said my RCBS small base die makes my Lake City 5.56 brass approximately .001 smaller in diameter than my standard RCBS .223 die.

Below a image of three types of Forster .308 dies.

For a semi-auto the resized case body should be .003 to .005 smaller in diameter than its fired diameter. This allows the case to spring back from the chamber walls and extract reliably. And a standard full length die "may" be able to reduce the case body diameter enough. Pausing at the top of the ram stroke for a few seconds will also reduce brass spring back.

And having both a standard die and a small base die will cover all your sizing needs. After sizing I check the cases in a JP Enterprise case gauge. Their case gauges are smaller in diameter and if the case passes this gauge it will chamber in any rifle. And I only use this gauge to check case body diameter.

Look at the SAAMI drawing for the .223 below and the manufacturing tolerances for the base of the case and the chamber. I know my Lake City case spring back more after sizing and they have the hardest brass.
And you asked how much smaller a small base die makes the case, and the answer is "it depends". The case diameter can vary .008 and the chamber is .002 now add brass hardness and spring back.

 

[AccelR8]

The barrel is supposed to have a Wylde chamber. Looking at a Manson diagram the diameter at the datum point is called out at .3777. I would expect my cases full length resized which measure .3571-.3572 should fit but who knows what reamer they really used and how worn and how many times resharpened and all that.

I really need to start watching my shooting dollars and I don't want to spend 50 or 60 bucks on a die if it's not going to solve the problem.

 

[Uncle Ed]

If you are not using range pickup brass or buying bulk once fired .223/5.56 brass a standard resizing die should work fine. And again pausing at the top of the ram stroke for a few seconds reduces brass spring back after sizing. Meaning the case will be smaller in diameter and more uniform in shoulder location.

Below the big difference with the Wylde chamber is (G) throat diameter and (N) freebore length. And the chamber base diameter is 0.3810 and all the base chamber (C) measurements are very close. And AR15 rifles are over gassed and forcefully eject cases and make you go look for them.

Below are just a few of the .223 dies I have and tested, I worked part-time in a sporting good store and got a good discount for my die buying OCD. And I can tell you as long as the cases are fired in your chamber a standard resizing die should work for your rifle. "BUT" resizing dies vary in size and the redding body dies below reduced the case body diameter more than any die I have.

I buy bulk once fired Lake City brass and I size them the first time with my RCBS .223 small base die. I do this because I'm also loading for my two sons AR15 rifles and I do not have their rifles to test. So smaller is better for an unknown rifle.

If you do a Google search you will find approximately 95% of reloaders get by with using a standard .223 die with brass fired in their AR15 rifles. And they hate me if I say use a small base die in a forum.

 

[Nick Caprinolo]

The small base die will return the case to SAAMI Specs.

 

[Uncle Ed]

Below FYI, a Wilson, Dillon, and JP Enterprise case gauges. The cases were placed in base first into the gauges to show how much smaller in diameter the JP Enterprise gauge is. Most case gauges like the Wilson and Dillon gauges are just for checking case shoulder location. And tell you nothing useful about case body diameter. And there are a few other case gauges like the JP Enterprise gauge that check case body diameter.

So again if the resized case and loaded cartridge fits in the JP Enterprise gauge it will fit in any chamber.

Below a "FIRED" and not resized Lake City 7.62 case in a Dillon case gauge.

Below the same "FIRED" Lake City 7.62 case in a JP Enterprise case gauge and showing its smaller diameter. Meaning closer to minimum SAAMI diameter and able to fit in any chamber.

So chambers, dies, and case gauges vary in size....AND

 

[dellet]

If you need a small base die, you’re likely over gassed,

The longer the brass stays in the chamber, the closer it will return to pre fired diameter. Unless you’re planning on shooting full auto, there is no reason to have a bolt speed capable of 700+ rounds a minute.

 

[skeeljc]

I quit using a SB die for my Wylde chambered AR-15. I use a Redding FL bushing die and bump the shoulder .003" to .004". Never had a FTF.

 

[whatsupdoc]

There is so much confusion on SB dies and when to use them.
From my experience the use of a small base die depends on the rifles chamber dimensions
that fired the round.

If you have a loose chamber and are going to use the brass in another rifle with a tight chamber
you should use a SB die. If you are shooting the brass from a tight match chamber you almost never
need to use a SB die.

I made a nogo tool to check the base of my ammo from a nut that I bored in a lathe.

A simple way to check is to get a caliper and loosely measure the base of a factory case, then lock the caliper
at that measurement. If your resized cases will slip though between your caliper jaws they do not require
SB dies if they get stuck at the base they do. This is if you wantto be able to use them in any rifle.

 

[PRR1957]

If you need a small base die, you’re likely over gassed,

The longer the brass stays in the chamber, the closer it will return to pre fired diameter. Unless you’re planning on shooting full auto, there is no reason to have a bolt speed capable of 700+ rounds a minute.

Ah yeah. 700+RPM. The Spray & Pray, Mag Dump dolts. I just love watching YuoBoob videos of mag dumps. Burn out that AR barrel in 400 rounds or less.

 

[msinc]

Small Base dies bump the shoulder an extra .001 too .002. For use in a AR platform.

I do not believe this is correct. Small base dies size THE BASE, just as the name implies, .001" smaller in diameter so they will more easily and readily fit in the chamber of a semi automatic. The base is the area just forward of the case head. That is the intended purpose. I guess I better add that the SB die full length sizes the rest of the case just like a standard FL die too, before someone bawls about that. There is a lot of bad or incorrect information on this thread. None of it so far will get anyone into trouble, but it is wrong nevertheless.

Edit: I don't understand the many posts regarding fired cases...no one is going to use them that way so who cares. You are interested in resized cases and how they will work in a rifle/chamber, to hell with one that's fired......they could have been fired in anything, once resized all that has changed to the size that particular die has made the case.

 

[Uncle Ed]

Edit: I don't understand the many posts regarding fired cases...no one is going to use them that way so who cares. You are interested in resized cases and how they will work in a rifle/chamber, to hell with one that's fired......they could have been fired in anything, once resized all that has changed to the size that particular die has made the case.

I used fired cases to show the difference in the diameter of the different case gauges.

I also stated that the resized case body diameter should be .003 to .005 smaller than its fired diameter. And Glen Zediker gave these figures in his book Handloading for Competition for the AR15 rifle.

And the OPs question was how much smaller in diameter does a small base die make the case.

And my point was if the resized case fits in the JP Enterprise gauge using a standard full length die then you do not need a small base die. And I also said chamber and dies vary in size and nothing is written in stone.

Look at the video below that also shows the difference in case gauge diameter. And why the JP Enterprise and Sheridan gauges are better for checking case body diameter.

Dillon .223 Case Gage vs JP Enterprises Case Gage​

Sheridan gauge vs Wilson Case gauge for reloading

 

[msinc]

I used fired cases to show the difference in the diameter of the different case gauges.

And answered a question the OP never asked. Which likely only confused him more. Again, who cares about several different case gauges?? The only case gauge he's interested in is his chamber. Double "again", it doesn't matter about a fired case, that is not the question or answer.....the question/answer was about resized cases and different resize dies.

 

[243winxb]

From RCBS FAQ

 

[dellet]

Part of the reason the OP’s question has gone/will go unanswered is because it’s a trick question and can’t be answered with any certainty.

A small base die, much like the dies designed to cure the guppy belly of cases fired in a Glock, is designed to size a part of the case that should not need sizing. The top of the web.

Since this is some of the thickest, toughest portion of the case, and varies considerably between manufacturers, the resized dimension also varies.

The bigger problem in using one, my opinion, is that it sizes to below, SAMMI minimum in exactly the places you don’t want to over work the brass. The shoulder and web.

RCBS description,
“The Small Base Sizer Die is for bottleneck type cases used in tight-chambering semi-automatic, pump or lever-action firearms. The sizer resizes cases below SAAMI minimums, reducing the shoulder and body by a few thousandths. It also de-primes the case. Note: Not recommended for ammunition used in bolt-action rifles.”

The whole need for a small base die is an AR built to MIL SPEC. Which has a cycling rate defined as 700-950 rounds per minute. At that rate the case is not in the chamber long enough to return to anywhere near below chamber dimension. This point was driven home when people started making AR styled semi-autos in larger calibers like 300 WM. They had a nasty habit of pulling the case heads off of anything but a reduced load due to cycling speed.

I tried a small base die when I bought a bunch of surplus once fired Lake City brass. I do not remember the finished sized dimension. What I do remember was it was still .002” larger diameter at the base than Remington 223 brass ran through the same die.

 

[6fatrat]

I have a RCBS SB die that I keep around just in case.
I will size some brass in all my 223 sizing dies and PM you the results.
Steve Bair

 

[Liven The Dream]

I've been searching and can't find the answer. What dimension does a 223 Remington small base die size the base of the case to?

edited to shorten my post just to the question. This is all I'm interested in. I do tend to talk too much...

Old Speer #8 Reloading Manual Covers this Topic 100% 20 years ago.
Bottom Line AR's Semi Auto's work best with SB Dies.
Or Why are they Sold ? Snake Oil ?

AR Barrels with a Wyle Chamber ???? Oh my goodness ? Bill Wyle is having a Night Mare ?
I have had Many AR Match Rifles and Services Rifles over the Years.
I have a White Oak Match as I post. It is a Hammer. That Chamber is in the Ball Park of Throat Size.

My Pal up the Road paid big dollars for a AR Match Rifle Barrel Fluted with a Wyle Chamber ??
I will say Not all Wyle reamers have the same Throat ?
My Chamber to His has .030 + more free bore ?

It shoots well , think of that jump for Mag length Bullets ,AR's are amazing .