300blk Brass Prep

[CGZ]

This is how I did it.

Cut brass to ~1.370 w/ mini cut off saw
Tumble brass
Lube brass
Resize with RCBS small base die. Decapping rod in place.
Trim to 1.360 (or your desired length)
Chamber and debur
Load completed round as normal.

Just make sure your using brands of brass that are not to thick. I always used military (converted blanks) and had no issues.

[Jeff213]

i resize them 300 blackout without the expander, then i cut trim and resize again with the expander decapper and it takes out the bur on the inside of the casing.

[kmr007]

Ok I successfully reformed 223/556 to 300aac. Here is what I did,

1. Tumble 223/556 brass
2. Cut using Harbor Freight Mini Saw and Zepprecision Jig to 1.370
3. Deburr case mouth - to ensure die doesnt get scratched/scuffed/damaged
4. Lube brass
5. With Decap pin installed and die properly set, formed the 223/556 brass to 300aac.
6. Checked case length, measured 1.374
7. Trim to length 1.368 - still awaiting for trimmer (undecided)
8. Case gauge check - either going with Sheridan or LE Wilson

I am using the Lyman 2 Die Set. This just arrived from Midway. BTW, Lyman die set is on sale, I believe under $40. Just like my 223 loading, as long as the case is lubed properly, I have confidence that my decap pin will not break. Also for 300aac forming, make sure to cut first otherwise the 223 case mouth is too small for the decap pin of the 300aac die to fit and will ruin it. Now I have to figure out if spending that extra for the RT1200 will be a good investment or maybe just the Lee Case Length trimmer (whatever its called).

I also measured case mouth thickness and it should be GTG at .0115. This is with LC13 brass. After reading 300blk forums, there was a list of brass that meets the requirements. Others were too thick and might not load properly. So I pulled all my LC13 brass and will use that for my 300blk loading. I have some Freedom Munitions 147gr 300blk reman loads so I will compare with that for now. I saw that Widner's Reloading has a great deal on 500 147gr bullets for sale, think it was about $70.00. I plan on using W296, Lil Gun, and H110 for supersonic loads. Only time will tell what my barrel will like.

[kmr007]

So finally got a few cases prepped. After trimming the case with the HF Saw with a 300blk Jig from Zepprecision (1.372), I used the Lyman die with attached decapping pin (lubed with RCBS lube). The OAL came to about 1.38 +-.01. I used the Lee 300blk trimmer, got it set at 1.363. It was pretty consistent. Then used a Sheridan Case Gauge. The gauge has a step, A, B, and C. Per the Sheridan manual, A = Max Chamber Dimension (No Go Gauge), B = Min Chamber Dimension (Go Gauge), and C = Min Brass Dimension (SAAMI Spec). I've checked the brass and it drops in freely and falls between B and C on the gauge. Can someone confirm if I have done this correctly?