The Perfect Rifle Cartridge to Reload Cast Bullets For…. IMO The 300AAC Blackout

Casting for a rifle cartridge can be frustrating…

One of the many obstacles us Casters and Reloaders face when casting for a rifle cartridge is of course the dreaded “Leading” issue. What limits us from functionality and accuracy when casting for rifle cartridges is our lead alloy and bullet coating. To sum it up briefly, one of the most important factors to know about your alloy is its hardness. The Lee Hardness Tester (Buy the Lee Hardness Tester Here) makes quick work of finding out our BHN value. More importantly, it includes a reference chart to Tensile strength. So far, in my experience, what has worked for me is shooting cast boolits at pressures near or at this min to max tensile strength value. The key is to obturate (expand and and deform) your CB (cast boolit) to seal your chamber temporarily. Once the CB exits the muzzle and breaks through the pressures turbulence you want the CB to return back to near its original dimensions. CBs shot above your alloy’s tensile strength may permanently deform the boolit while in flight. This usually leads to poor accuracy, and most likely leading of your barrel…. Say hello to an easy cartridge to reload your cast bullets for: 300AAC Blackout


My complete Guide to reloading cast boolits for 300AAC Blackout


Sourcing headstamp’s…

The Perfect Rifle Cartridge to Reload Cast Bullets For.... IMO The 300AAC Blackout 3As you may already know, the 300AAC cartridge utilizes the same headstamp as .223 and 5.56mm. To avoid chambering issues and having to neck turn converted brass, I stick with only using NATO brass. The headstamps you see here are LC 5.56 and Federal Cartridge with Year. In my experience, these two headstamps had no issues in converting to 300AAC. I usually order by 1k batches HERE and periodically Everglades has them on sale. They do a great job with giving you quality, once fired NATO brass.


Converting Brass to 300AAC Blackout…The Perfect Rifle Cartridge to Reload Cast Bullets For.... IMO The 300AAC Blackout 5

To convert 5.56 brass I found the easiest and cheapest way is to source a 2 inch Chop Saw from Harbor Freight and a 300AAC cutting jig. There’s other jigs out there with detentes for a little more value. I personally find this one to be more than adequate for its price. It takes a little bit of patience to setup. I set it so the saw cuts the necks and leaves the cartridge to an OAL of around 1.368”


Forming the 300AAC Blackout Brass…

The Perfect Rifle Cartridge to Reload Cast Bullets For.... IMO The 300AAC Blackout 7

For this I prefer a good compound pressure single stage press, such as a Lee Breech Lock Pro or RCBS Rock Chucker, and Lube…..Lots of lube... If doing a large batch, I use non-latex gloves and grab a glob of Hornady Unique Case Lube and lather the gloves thoroughly.  Grab a hand full and rub your hands together with the cases. You’ll find that this really goes a long way and makes lubing cases fast. (A method I learned from Full.Lead.Taco).
The resizing die I found to work the best is the RCBS Small Base Die 300AAC. This resizes and swedges 5.56 cases at SAAMI spec compared to some of the others. I found this die was the fix for those who had chambering issues with their AR uppers. Since using this die I’ve run my 300AAC’s through 13 different friend’s and family barrels without issue, from bolt action to a fully semi auto lol. Again, I can’t stress the importance of Lube here. Getting a stuck case out of this die would be its only negative as it is very difficult and time consuming.  The Perfect Rifle Cartridge to Reload Cast Bullets For.... IMO The 300AAC Blackout 9







Trimming Brass a Faster, More Precise Way…

The Perfect Rifle Cartridge to Reload Cast Bullets For.... IMO The 300AAC Blackout 11With all the options of case trimming, my personal preference is the Forster Original Case Trimmer. You can find them at a decent used price on ebay with pilots for roughly $45, and the cutters are extremely sharp. If you ever need a new cutter, replacements are just over $20. I like this cutter because it’s always within .001″ and setting the depth is quite easy. If you’re a perfectionist like me, this cutter will suit you if you ever decide to reload for long range. Also, Forster sells a 3-way cutter to chamfer and debur your cases very uniformly. Many do swear by this. To speed things up I make use of a cordless power drill. Though Forster does sell a power adapter, I found no need to purchase it. If you screw off the handle, the end will chuck up fine in your drill. Now you have a speedy, precise lathe. One awesome thing about 300AAC Blackout is that once you set the trim length to 1.358″ you wont have to trim again.


Chamfer and Deburing, Removing the Military Crimp…

The Perfect Rifle Cartridge to Reload Cast Bullets For.... IMO The 300AAC Blackout 13

As mentioned above, Forster does sell a 3-way carbide cutter. The downside is it’s set to use on one caliber. I prefer the RCBS Chamfer Debur Tool . It serves two purposes for me; not only does it chamfer and debur great, but you can again make use of your drill and remove that military crimp! There’s a bunch of options on debur tools, To each their own I say. This is just an option which serves two purposes for me


Getting Your Brass to Bling. Avoid Exposure to Lead

So as you probably know, there’s a few ways to clean your brass (Ultra sonic, media tumble, wet tumble, etc.). Now that you have some prepped brass, it’s time to remove the excess case lube, grime and get it load ready. For those who do not know, there is a major risk of lead dust inhalation if you chose to dry tumble your brass. Corn cob media tumbling does the job in getting brass clean… but can cost you more in the long run. The dirt and grime from fired cases have lots of lead remnants. The agitation from using a vibration tumbler does release this into the air and poses a high lead inhalation hazard. I was not aware of this until recently. After having my blood levels tested a year ago my levels did increase from this exposure, though not high enough to have the EPA visit my home. This is a serious concern for us Casters and Reloaders and I strongly recommend if you do use media, tumble outside and use a 3M mask, else I strongly recommend investing on some sort of “wet” cleaning.
I absolutley LOVE how well the Frankford Arsenal Wet Tumbler works. It absolutely makes it shine, sometimes better than factory new, and even cleans the primer pockets! Combine that with the Frankford Arsenal Media Seperator and Frankford Arsenal Transfer Magnet and you’ve got your self a great SAFE setup to clean and polish your brass without having to pick the media out of the flash hole. A teaspoon of Lemi Shine and two squirts of Dawn dish soap does the trick and the lemon scent is quite refreshing IMO. After separating your brass, a quick bake in the oven @ 200*F for 15-20 minutes can dry out these cases and make ready for reloading. Also, for those who are concerned about stainless pins being trapped inside cases, thus risking breaking your decapping pin, stick with getting stainless pins from Frankford and spend a few minutes on the separator if more than 300 cases were cleaned. I’ve lost count of how many times I’ve cleaned… though I’ve used three bottles of lemishine so far. That’s a lot of tumbling!

Flaring the case neck…

Lee makes a great tool called the Lee Universal Neck Expanding Die. This is a must have tool if you choose to load cast lead bullets in rifle cartridges. What this does is exactly what the name implies. To take it to the next level I pair this die with a NOE Expander Plug. This plug works by replacing one of the Lee plugs and expands the case neck while flaring the mouth to a specified value. You can choose multiple sizes to fit your exact CB. When choosing the correct expander plug, NOE list the sizes in two diameters.  For example: “.310 x .306 EXP Plug”. The first diameter will indicate the flare of the mouth. The second diameter is what the plug will expand your case neck to. NOE’s rule of thumb is 0.001″ ABOVE final sized CB diameter. This rule works IF the CB you plan on seating is Gas Checked. Else, if you use a plain base bullet you risk having the CB swedge to a smaller diameter. For me, personally, as an example I use a .311 x .307 Expander Plug when loading a Gas Checked final sized CB that’s .309 diameter.
Short video explanation here on my YT channel:


Choosing Your Cast Boolit and Powder…

The Perfect Rifle Cartridge to Reload Cast Bullets For.... IMO The 300AAC Blackout 15

IMO what makes the 300AAC an awesome cartridge to cast and reload for is the selection of bullets available. The cartridge shoots nearly any .309 caliber boolit, even .310 Round Ball!! (See: Full.Lead.Taco The True Pea Shooter! 300blk Round Ball Loads Suppressed! (Pew Pew Loads!)). For me, I personally like shooting supersonic. I’ve even shot 75gr cast Zinc bullets at 5.56 velocity; (that will be another article). IMO if you want to shoot a cast lead bullet fast, Gas Check them. The bases of our cast boolits can really determine it’s accuracy. CBs with non-uniform bases sprue cuts allow gases to expel unevenly and can deviate the CB’s course. Gas Checking the base fixes the problem and allows a more uniform gas dispersion, increasing the CB accuracy potential. As I mentioned in my first paragraph, you want to ride the border line of tensile strength of your alloy. You can utilize programs like Quickload to get you in the ballpark. From my testing, Gas Checks help raise this number slightly while keeping lead alloys simple (Water Quenched Wheel Weights). The three powders I found to work great in a few AR15 rifles, including mine, are: Hodgdon CFE BLK, Hodgdon H110 / Winchester 296, and Hodgdon H4198. I have been able to push a 135gr HTC boolit from NOE (Picture of mold above) to just above listed max charge using CFE BLK and H110.
CFE BLK @ 20.5gr’s (Compressed load). Average velocity is at 2010 FPS with a standard dev of 7.92!. No pressure signs were observed in my rifle so I could have loaded more if the case had more room LoL! H110 gave the best velocities; @ 18gr’s velocity  was 2200 fps and a SD 11.67 **Warning above listed Max**. This round I have shot at 400 yards with little bullet drop using a Red Dot. This load does give me flattened primers, but no ejector marks. Can’t complain with groups like this! 10.6gr’s of H4198 makes for a great 230gr Lee Cast boolit

CFE BLK and H110’s secret in 300AAC…

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From what I’ve observed load developing a few rifles, both these powders start to really tighten up groups and SD numbers when they are 95-110% case capacity. The loads listed above also gave the best group and chrono numbers. This powder also shows a 99% burn rate when at full or compressed case capacity according to Quickload. I stress caution on using what was mentioned above. ALWAYS WORK UP YOUR LOADS. This mold from NOE HTC310-135-RN-GC has given me the best groups out of my budget 300AAC build.





Final thoughts…

In summary, The 300AAC Blackout is just an absolute blast to cast and reload for. I wouldn’t say this cartridge is a 1K yard shooter. It will adequately handle the average shooter and reloader’s needs in both hunting and target shooting to 500 yards depending on bullet. I find it to also be extremely reliable to reload on progressive presses since the cases are shorter than most rifle cartridges. A huge plus is the availability of converting common brass, and also the total cost of a completed round. It uses less powder than .223 and cost can continue to lower when you source lead cheaper.

I hope I shed some insight on reloading cast boolits (CB) for the 300AAC Blackout.




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Tail Gunner
Tail Gunner

Good article. Detail level is great.

GunFun ZS
GunFun ZS

Great article. I can’t give input re: gas checks or SD, but what you’ve said exactly tracks with my experience and what the knowledgeable guys from 300Blktalk have been saying.

I’ve come up with an idea for improving 300 Blackout loading on the loadmaster, but I haven’t had time to implement and film it yet. Primarily, the powder measure can be a nuisance. I am sure the same issue happens on your presses, but in short, the case slightly misaligned with the powder through measure and this results in a munched case neck every so often.


Lessons learned in my first foray into reloading 300BLK: – even if the cases are sold as “ready to load”, run them through a proper resizing die anyway (RCBS SB). – 300BLK is not like loading for .223 – the inside of the neck MUST, as well as the outside of the case, be lubed and lubed well. – If a shell is feeling difficult when it is going into the resizing die, stop and back it out immediately – apply more lube to the inside of the neck, and try again. If it is still acting difficult, toss it,… Read more »

The Reloading Press
The Reloading Press

Great article Eagle, I was confused about your recommendation for neck expanders, are you going.002 under or over bullet diameter when choosing your expander? I love the article. It seems a little amazing that Bacon has created this place for us to hone our article writing skills and get our knowledge on page. Thanks manno.


I play around with the expander die until my coated bullets can more or less sit in the neck of the case without finger support. If the case looks like a trumpet, then it’s probably flared too much…


I agree, the 300 blk just tends to be a great cast bullet cartridge! It seems like it can handle the widest variety of bullet weights.


That was an interesting read Eagle!