Thread: Converting .223 brass to 300blk

Looking at advice on how to convert adi 223 brass into 300blk. I've watched videos on YouTube etc. However they all seem to have pre-made jigs and miniature cut off saws.

Anybody have any experience of converting brass here in nz?

Yeah . . . I made up a wooden clamp that held several cases and then cut them off with the table saw (using a blade with plenty of teeth) . Final tim to length done in a normal case length trimmer.

It was as dangerous as all he'll, I don't recommend it at all. Next time I'd just scrounge once fired.

I bought a mini pipe cutter. Slow but quiet and very little mess.

Hiya ; i got two small lengths of wood ( 300mm long x 47mm deep x 15mm thick ); hinged them at one end. Got an 9mm drill bit ( snug fit for 223 cases ) and drilled 10 holes with the wood clamped tight with hinge at one end and vise grips/ wood clamp at other end. Drilled the holes 1-2mm deeper than the 1.358" trim length about 25mm between centres ( sorry to keep jumping from metric to imperial ) Open up drilled block. put 10 223 cases in ; close & clamp in vice . Get normal 100-115mm grinder with the cheap super fine cutting discs from bunnings/ Mitre 10 and cut off all the tops protruding.. Take out of vice , dump out 10 cut cases & go again. Hav done 600-800 cases like this no problem. Remove grinder burr off cut case with chamfer tool & case form with 1-2 mm "long neck". Trim to length but if you careful on drill depth / grinder control that takes bout one minute/case. Ive reloaded those modified cases 8-10 x each without a worry. Gunsmith that ive talked to suggests running supersonic loads 1st in those modified cases before going subsonic in them to make sure the tiny shoulder fully blown out . Good luck , have fun .

Damn those are some good ideas. Cheers avopik. That seems like the least likely way to trim my fingers as well as the brass!

When making 351WIN brass or 35 self loader brass from 223 brass I used a 357 trim die to cut down to size. It is quick and easy and the necks end up square.I suspect it would work as well for 300BLK.

I did a very crude method of cutting the neck and shoulders off deprimed 223 cases with an angle grinder.
Sized the case to 300blk without internal size button in the die. (The first one got stuck so I pulled it out after that)
Trimmed to 300blk length with a lee trimmer in a drill.
Chamfered the top
Sized the case again with expander button in the die.

With running super loads pushing a 125gr projectile they have been holding up well so far.

Iv got a heap of cut but not formed cases I got a while back that I havent run thru the die yet
send me a pm to remind me and ill have a dig around later

Easiest way there is: Hand large bag of 223 brass to mate. He tips it into feed hopper of Dillon 650 with all the fancy trim dies etc. Bzzz click plonk zing! 300blk brass goes into bag. Better living everyone

I made up a wooden jig in a vice and use a dremel with cutting disc, also use a Worlds Finest Trimmer for quick easy trimming. Have done over 2k of 556 cases over the last several years. Cheap but time consuming, lucky I’ve got plenty of spare time in the man cave.