HowTo: Reforming 221 Brass to 300 Blackout for Reloading

| December 8, 2013 | 2 Comments

Within the pass couple of years since the ratification of the 300 Blackout by SAAMI in 2011 it has continued to gain and enormous amount of popularity. Initially I did not see all the rage behind the new cartridge until firing 220gr subsonic rounds down range through Darrell’s Micro 7 with Yankee Hill Suppressor, the thump on the back stop down range was louder than the initial firing of the weapon.



But I digress and need to stay on track, though stay tuned for the range review of the Remington Micro 7.

Right away I started collecting everything needed to start reloading for this cartridge, yes that is correct I actually had my reloading gear before actually having a firearm chambered in 300 Blackout, the firearm piece could be figured out later (Hi I am Mr. Revolverguy and yes I am a reload aholic and may need an intervention). I was not totally new to this cartridge I knew it was introduced by AAC and was based on the 300 Whisper. AAC created this cartridge with a few things in mind, create a reliable 30 caliber solution while utilizing the existing M4 carbine platform with only the need to change the barrel. This idea would create a number of advantages over the 5.56 and 223 Remington, greater barrier penetration, create ballistics very similar to that of the 7.62x39mm round fired by the AK47, along with easily being suppressed creates a deadly combo.

When it came to collecting brass for the 300blk I quickly figured out there was a number of ways to do so. You could make your own brass out of 223 brass by cutting the length of it down and necking it out to 30 caliber. You could also neck out 221 brass which is a lot quicker than the previous routine of cutting and sizing or you could just simply purchase brass as there are many manufacturers making factory brass as well as reforming old 223 brass. Darrell and I decided to utilize the last two methods for collecting our brass. Darrell purchased brass from West Desert Tactical and it turned out to be great brass reformed from 223 brass.

300Micro (1)This brass is advertised as ready to load out of the packaging with primer pockets swaged. All of the brass was of the right dimensions but I chose to debur all of the cases first as the edge of the brass was a little sharp, this is more personal preference than anything. This brass most likely would have fired fine without the deburring step.

I on the other hand collected all of Darrells 221 brass. With my Redding National Match Competition Dies on hand I immediatly started the resizing process only to figure out I did not have the right tools for the job. The case was requiring tremendous force and to keep from ruining such great dies or crushing the case I stopped the process, one thing I learned over 17 years ago when I started reloading was to never force your press. One quick call to Redding solved my problem. The dies I have do not have the tapered buttons required for this process, bummer not to fear Redding would have these parts in my hand within a few days.

300Blk-220grSMK (8)

The part numbers needed are 16276 tapered 270cal button and 16301 tapered 30cal button. These buttons would screw right into my resizing die with no issues and they were of very good quality. One thing I notice was the smoothness of the buttons, it was almost as if they had some sort of grease on them already but they hadn’t. If you were to buy the Redding 300-221 die both of these buttons come with the die and aren’t needed. By now you have probably figure out that resizing the 221 brass to 300blk is a two step process,?from 270 to 30cal.

?Die with the original button on it and the two new buttons


Here is what the original 221 cases (two on the left) ?look like next to a 300blk case.


You start with the original 270 button and very little lube so you don?t dent the cases, it doesn’t take much and I experimented with both RCBS pad lube as well as the Hornady case wax lube and ended up using the Hornady case wax it seemed to require less force.


Here is what the 221 brass (two on the left) look like after being necked out to 270cal next to the 300blk brass.

resize2214After batch neck sizing all of the brass to 270cal I then installed the 30cal button.


On my first 30cal neck sizing I noticed more force was needed and felt again something was not right. I did not have the expander button/rod deep enough into the seating die once correcting this slight flaw I was back in business though on this first case I did dent the shoulder a little due to adding more case wax, to much lube. There is no need to add any additional lube/wax to the 30cal neck sizing step there will be plenty left on the cases from the first step to get the job done.

Here is the finished product of 221 brass (two on the left) after being necked out to 270cal then 30cal sitting next to a preformed 300blk case from West Desert Tactical.


After the necking out process the 221 brass was a little long and out of SAAMI spec for 300blk so it will need to be trimmed. Once trimmed it can be primed loaded and fired.

The tools used for this job are

RCBS Rock Chucker, Redding Competition Die Set, 270cal tapered button part#16276, 30cal tapered button part#16301 and Hornady Case Wax.


221 is still a great cartridge but since Darrell sold off his 221 rifle years ago what better way to utilize these cases instead of just throwing them away.?I hope this brief tutorial assist someone on forming their own brass from 221 to 300blk.

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2 Comments on "HowTo: Reforming 221 Brass to 300 Blackout for Reloading"

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  1. Carl S says:

    I would think it would be cheaper to buy ready made .300 BO than forming it from .221 FB. I just bought 200 Norma .221FB for $80.00 a 100.

  2. Yes in this day I would agree. At the very beginning prior to the cutting of 223 and availability of brass this was a was to accomplish.

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