Reloading for AR15 ( .223 )

[Ronin6]

Why Small Base Size?

[kcstott]

Because eventually your brass will stop chambering because the case head near the web will swell and not be resized small enough to overcome the spring back.
It's been proven in the benchrest circles, small base full length size everything, bushing neck size, and follow up with a mandrel expander. Redding type S is a full length small base bushing die designed by Thomas "Speedy" Gonzales for this very reason. and he came up with that 20 years ago.

[bohoki]

i use lee rgb dies and have had no problems of course you know trimming is required

[jimmykan]

I used to buy fired 223/556 brass from a commercial wholesaler, and they would state in their product information that most of the brass was collected from military firing ranges, and a good portion of that brass was fired out of M249 SAWs.

Why was that last bit relevant? Apparently machine guns have generous (loose and sometimes fluted too) chambers because their open-bolt design means the bolt's return stroke has so many jobs to do:

1. Strip the cartridge from the magazine or belt or link
2. Feed the cartridge up the ramp and into the breach
3. Chamber the cartridge and strike the primer just as the bolt closes to fire it

Any drag encountered in that process will slow down the bolt's momentum, and if there's not enough momentum left when the bolt closes then the round doesn't fire. So the chamber has to be loose.

As a result, the fired brass comes out of the machine gun chamber very "bloated", from the neck all the way up to the case head. Some may even have split necks from the over-expansion.

Machine gun brass is tougher to size than brass fired from a rifle, and still might not fit in a standard chamber even after regular sizing.

Regular sizing dies can only size a case down to about 3/16" above the bottom. The bottom 1/8" is blocked by the shell holder, and then there is usually a 1/16" radius on the opening of the sizing die that does no sizing either.

A small base sizing die has minimal radius at the opening, so it sizes as far down the case as possible, but there is still that last 1/8" that it can't reach.

If you still really need to size down that last 1/8" then you need to run the case through a roll-sizer.

[sl0re10]

I think I read it will be easier to use brass first fired in a different rifle in yours the second time.


I use a small base size die for 223

[Sailormilan2]

As was stated, brass fired in a machine gun is often really over sized. Due to excessive headspace. Brass also has some spring back. Once you size it down, it will often "spring back" a bit. Especially oversized brass. Machine gun brass often takes two sizings, or the use of a small base, or ultra small bass(really works the brass).
My solution has been to size with a standard die(RCBS in .308 and Redding in .223), and since I use a multistage Hornady, mount my Dillon case trimmer, which also sizes the brass at the same time. So, I get my brass trimmed, and any spring back is taken care of in one step. Position 1, size and deprime, position 3, size and trim. Works for me.

[TomReloaded]

I reload 223 until the neck splits or primer pocket goes loose, using a normal Lee die set. I've never had a problem requiring a small base die.

AR's have loose chambers as is.

[baih777]

If you are use your own once fired brass.
You wont need it.
If you pick up range brass or buy online.
Then i would have a small base die handy.
Remember when Covid started. Everything was hard to find.
Otherwise a regular 223 rem die will work.

The Lee ultimate 4.pc die set comes with a collet.die. it works pretty good at.removing the case mouth crimp from once fired brass.

[trailblazer87]

I have to do the same for my 308 brass, one of my rifles has a much larger chamber than the other, Criterion uses a tight chamber so I have to squeeze any previously fired brass back down to spec to get it to fit, now anything that comes out of that chamber will fit any if my other 308s.

[ar15robert]

I started with small base dues went to regular line 15 years ago no issues. Shut mini 14. Armalite m15 and my latest at pistol. Brass is mostly once fired out of friends guns.

Have so much brass that’s once fired for now and a crapton of second fired too.

[Itsrockysmodernlife]

If you’re using brass that was shot out of your ar or in most cases any ar built to 5.56 spec it’s unlikely you’ll need them. It will be form fired or near form fired. Now if you’re buying brass that may have been fired out of bolt action, machine gun (especially) then it’s nice to have them. I personally found small base dies to be annoying because of the tighter tolerance. Especially on brass I shot out of my rifle. I switched to hornady custom dies and I’m quite fond of them. Small base dies definitely have a purpose for some but most people will never have a need or notice a difference. Personally I load my 5.56 rounds to 5.56 specs so If I get 4 uses I’m happy and I keep it moving.

[TKCastle]

Why not have one less worry. I use SB 223 dies for decades and my 223 loads are way more accurate the any Factory offerings.

Just do it and be done with it.

[kcstott]

Why not have one less worry. I use SB 223 dies for decades and my 223 loads are way more accurate the any Factory offerings.

Just do it and be done with it.

[Itsrockysmodernlife]