300 ACC Blk from 223 cases - the good, the bad & the ugly

kombayotch

kombayotch

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Since the round is getting popular, and many people will be converting .223/5.56 cases to 300 AAC Blackout, I thought I would start a thread about which cases are ok to use and which are not. Depending on the wall thickness of the .223/5.56 cases, there can be some serious issues. With some cases, the problem will be obvious as the rounds will not chamber (and may jam). However, with others, the rounds may chamber, but there will not be enough clearance for proper bullet release. This can lead to some very large pressure spikes (which may only appear when the chamber gets dirty).

SAAMI specification for the cartridge can be found here: http://www.saami.org/PubResources/CC_Drawings/Rifle/300 AAC Blackout.pdf

This drawing lists both the cartridge specification and the chamber specification. Note that the chamber is 0.335" at the top of the neck and 0.337" at the bottom. This makes the middle about 0.336" The cartridge should be no more than 0.334"' in the middle of the neck for proper clearance. Here are some neck measurements from some of the cases I have converted:

IVI 94 (military): 0.336 (VERY BAD)
PPU 5.56x45: 0.335 (BAD)
FC 223 REM: 0.335 (BAD)
PMC 223 REM: 0.333 (OK)
R.P. 223 REM: 0.333 (OK)
FC 06 (military): 0.332 (OK)
LC 03 (military): 0.331 (OK)
TW 72 (military): 0.331 (OK)
Winchester 223 REM: 0.331 (OK)
Winchester 223 REM (crimped primer): 0.331 (OK)
WCC 95 (military): 0.331 (OK)

The IVI 94 case actually chambers, but extraction requires a mallet. Firing a round made from that case could be disastrous. Resistance can be felt extracting the PPU case. These were duds, btw.

This is for the 300 AAC Blackout spec chamber. 300 Whisper, 300/221, 300 Fireball and other variations may be different.

Feel free to post measurements from other brands of brass and I will add them to the OP.
 
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I don't neck turn cases for a black rifle. Neck turning was necessary though for the 300 Whisper (TM) chamber when using .223/5.56 cases since it was designed around necked up .221 Fireball cases, which are quite thin. Other variants like 300/221 and 300 Fireball were designed to accept converted cases without neck turning.
 
Yeah, I've gotten crimped primers in Winchester White Box too. I try to avoid mil brass in general, but I had a few cases, so I decided to convert them to Blk cases.

I got a few more cases to test tonight. One is LC headstamp. I'm curious to see where that one is at... would surprise me if it didn't work since that would piss off a lot of guys down south who buy that brass for cheap. When I saw what was happening with the IVI cases, I figured I should post something since that brand isn't common south of the border, so no one down there has probably used it. But, its common here and I can easily see someone getting into trouble converting it.
 
The LC case worked fine. However, the FC 223 REM case did not. Needed the mallet to extract for it too. Pulled the bullet, resized the case and got the same result.
 
Thank so much for this thread. I'm waiting on a barrel, bought the dies 10 days ago and already have about 1100 brass sitting here.

Got lucky I guess according to your findings,did up 800 or so WCC ,240 LC and the rest mixed head stamps (only 40 being FC)
 
You should probably still check them. Measure them and load a few duds of each to try cycling through he rifle. I'm quite surprised with the FC cases causing an issue. I'm going to convert a few more of that batch just to see...
 
kombayotch said:
The LC case worked fine. However, the FC 223 REM case did not. Needed the mallet to extract for it too. Pulled the bullet, resized the case and got the same result.
Click to expand...

Weird, I am not having any problem with FC cases.


I'm waiting on a barrel, bought the dies 10 days ago and already have about 1100 brass sitting here.
Click to expand...

How are you trimming the cases to length? You must have way too much time on your hands. I just finished processing about 300 rounds and have had enough of that to last me for quite some time. I wouldn't even want to consider processing nearly 4 times as many cases.
 
Note: still have all my fingers.

I've set up a miter saw with a fixed bed and block jig.(7" Freud blade in a 10" saw) I cut 2 at a time,gets them within 10 thou of finish.( can chop 8 per min.) My final trim is 1.355,on a little Bonanza trimmer. The part that I hate is the de burring inside and out.

And yes I had some time,work was slow for a couple weeks there.That's when I found time to order the barrel and started the brass project. lol
 
Suputin said:
Weird, I am not having any problem with FC cases.
Click to expand...

And I'm not with their military cases... yes, it's very strange.

Suputin said:
How are you trimming the cases to length? You must have way too much time on your hands. I just finished processing about 300 rounds and have had enough of that to last me for quite some time. I wouldn't even want to consider processing nearly 4 times as many cases.
Click to expand...

You own a lathe, why don't you just make a pinch-trim die? Trimming with that takes as much time as sizing a case.
 
Pinch trimming is a common way of trimming material in stamping and drawing operations. The brass makers trim cases this way when they manufacture the cases. It is not done in reloading because there is no adjustability using this method. You're relying on the sharp corner of one of your die features. Here is some general info: http://mytwinchild.########.ca/2011/03/die-basic-part-13.html

I haven't created one for 300 Blk yet. But, this is how it works:

Basic Setup

et2-trm1.jpg


The case is inserted in into the sleeve from the the bottom (sleeve is that knurled part in the pic). The sleeve is either cut with your reamer or you can make it with two drills: one the diameter of the base to accommodate the body, and one of the neck diameter you have (0.334" in this case). You put the case into the shell holder and then put the sleeve over it. The sleeve rests on the shell holder. The to surface of the sleeve determines your case OAL. You then run the case up into a conical punch. The extra material gets stretched over the punch. The trimming occurs when the punch goes in deep enough that the wall of the case gets pinched between the punch and the sharp corner on the internal top edge of the sleeve.

This is a pinch-trim die someone made for trimming bullet jackets:
http://castboolits.gunloads.com/showthread.php?t=74051

It works the same way.

The top of the sleeve and the punch need to be hardened. Just use some tool steel that you can oil-harden (drill rod). To harden it: heat it red hot with an acetylene torch, then drop it into a bucket of oil. Does the job...

Better Setup

Make it like a Redding seater die, where the sleeve is mobile and trapped in the die. Then you don't have to put it over the case manually each time. The sleeve would slide up into the body of the die as the ram raises, pushing the case into a stationary punch.
 
Make something like a Sinclair expander die to hold the punch. Then, just adjust things so that it scores the material deep enough that you can just tear off the access material, but that it stays connected well enough to pull it off the punch on the way down.

I thought of a way what this could size and trim all in one stroke... but I'm not sure that a regular reloading press would be strong enough to do it.
 
I played with this tonight and discovered a little hick-up that I hadn't experienced doing this with other cases. I had previously only done this with cases that had been sized down such that the part being trimmed was of uniform diameter (.308 & .270 down to .243). However, with these cases the .223 necked portion of the cases still exist after running them into the 300 AAC Blk die and they end up causing the case to collapse at the shoulder if you just try to run them into a 60 degree punch. I solved this by adding a steep expander (20 degrees) to the end of the punch to expand the necks up to 30 cal before they get to the main punch.

Also, I occasionally got a mushroomed shoulder using a sleeve that was just drilled. Running the cases into the sizing die fixed this. But, cutting a sleeve with a with a chamber reamer would provide better support. I'm thinking the sleeve can be two parts: a body made from a barrel stub (or other soft material) with a hardened cap on top that has the cutting edge. This also give you the ability to adjust the hole for different neck diameters more easily.

This was just some proof-of-concept tooling I made with a 7/8-14 bolt for the punch and a piece of stress-proof steel for the sleeve. These aren't hard enough, so they didn't last long. But, they showed that the concept works. It just needs to be refined a little.
 
I'll post some pics of the tools and the results tonight. The other thing I found was that you could tell which chase had been fired a few times and were work hardened because they split. I was using the IVI cases for testing. These were a mixed bag of range pick-ups.

Anyone using Lee dies? Their sizing die is putting WAY too much neck tension on the cases with every brand I have. I'm pretty sure it would be too much even using thin .221 Fireball cases necked up.
 
I've got most of the bugs worked out now. Just need to play with the angles on the punch a little. Ok, some of the steps I went through to get to where I am and what I learned...

These were some cases I made with the stress proof sleeve that was drilled:

P1060527.jpg


The necks were loose in it because of that Lee die over-sizing the necks. So that flared the case mouth out a little. I originally though the mushrooming at the shoulder was due to it not being supported. But, it turns out that this happens if you set the punch too deep. It pushed down the case neck. The ideal setup is to have it just score the brass deep enough that if stays attached to the case and snaps off if you push on the excess material with your finger. The range for this is very small and the 14 TPI thread is way too coarse for the punch.

If I run the cases through the sizing die again, it got rid of most of the mushrooming. Seating a bullet expanded the necks out and got rid of that funnel effect from the neck being sized too much:

P1060531.jpg


I ended up making a sleeve for the body out of aluminum using my chamber reamer and making a bushing for the neck out of a nut. I also made a new punch with the expander at the end to open up the 223 neck before it gets to me main punch:

P1060520.jpg


This worked better since the bolt was hardened. However, I still got the funnel effect on the mouth if the hole wasn't close to the neck diameter. I had to tap them out with a rod, so this idea really is best implemented as something like a Redding Match seater die, where the press can pull the case off of the punch and out of the sleeve.

This yielded much nicer results:

P1060526.jpg


Cases on the left were just run into the punch for testing. One thing I learned is that you need to lube the inside of the case well or may tears, and it may tear past the trim point. Putting a gob of Imperial in the case mouth with your finger does the job quickly and easily. Cases on the right were put into the sleeve and nut.

P1060529.jpg


The case mouth is a bit rough, but the punch creates an internal chamfer, so it doesn't really matter:

This is what I get when everything is adjusted perfectly:

P1060530.jpg


This quick prototyping allowed me to learn a lot. Now I can design a real die for this. :D

.
 
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