Best dies for 300Blk in an AR

[Blowout]

I've had no issue with using a Lee dies set with the 300blk or 6.8 with my AR's. Use a different seating stem on the seating die for 300blk and modified the Lee seating stem on the 6.8 and get very little runout measuring loaded rounds when match bullets were used.

Really surprises me how good the concentricity is with such a budget priced die set. I use Forster FL sizing and ultra micrometer seating dies for 223 and 308 and get similar results.

[Dolomite_Supafly]

I have only ever used Lee dies for my 300 Blk brass and when converting .223 brass to 300 Blk, with no issues at all. I only have 1 AR I shoot it in so I am not concerned with small base die sizing.

Small base dies are not really for brass already formed and fired out of a 300 Blackout. They work the brass more than standard dies so you do not want to use them every time. Won't hurt if you do other than shorten the life of brass.

Small base dies are more for sizing brass of unknown origin or fired out of machine guns.

I use small base dies when first forming brass but after they have been fired I use standard RCBS dies to size them.

[plant.one]

I dunno, but I guess I'm just ignorant. I'm using the Lee die set and I've converted hundreds of .223 and 5.56 brass to 300BLK without any apparent problems. I'm not doing anything special with regard to shooting, just a little target practice on occasion and hunting hogs.

you're not ignorant, your sample size is just too small. one die set does not equate to large sample testing. so while your set of dies you have produces a satisfactory result, many folks have experienced the opposite. its documented all over the board here.


as noted by others - sometimes lee dies form ok, other times they dont. depends on which end of the tolerance window you're at. Lee clearly states on its website that its dies are not designed for forming, just resizing fired brass. their 'goal' is to produce a die thats around the middle of the acceptable SAAMI spec range.

http://leeprecision.net/support/index.p ... -vs-sizing
http://leeprecision.net/support/index.p ... se-forming

hth

[GunFunZS]

Add me to the sample set.

Two lee die sets that I've used in this caliber. One belonged to a friend that I was gearing up with. Eventually got my own.

Both worked just fine. I did polish the neck expander with 2000 grit sand paper, oil and a drill to make them run smoother though. IMO the lathe marks increased the felt drag, and I saw brass dust prior to the polishing. We converted several thousand brass between us.

I have loaded for guns with barrels made by faxxon, CMMG, PSA, and um, dangit can't think of the other one. (radical maybe?) So far faxxon is the pickiest. Tighter chamber, and I think the leade has a more aggressive ramp to it. CMMG is next tightest, and PSA is easily the most forgiving. The limiting factor between the barrels was not brass dimension, though you could feel it. It was how long you could seat a bullet with a fat ogive before it hit, and whether marginally bore ride bullets would hit at the leade inconsistently and cause seating issues. I get the impression from other users that ballistic advantage barrels are picky too. I can make the same bullets work with all of them, but with the tight ones, I have to seat the bullets a lot deeper.

I am not motiviated to get another die set at the moment. The lee dies are doing just fine. I do like how hornady's seating stem works though, and if I were in the market for another die, it would probably be that.

For what it's worth, each of the companies will custom fit a seating stem for you if you send them a bullet to match. Or you can order a spare stem and do it yourself with some valve grinding compound and a spare bullet. Lee's stems are cheap.

The few times I've dealt with their customer support, they were prompt, and generally either sent me the things free or nearly free, and also threw in extra stuff. They have a hidden online catalogue which is not publicly searchable. So just because you can't find what you want online doesn't mean they don't have it. Chances are good that if you email them asking for an ELD style seating stem, they will send you one free or give you a link for adding one to your shopping cart for less than $10.

[GunFunZS]

http://leeprecision.net/support/index.p ... ating-plug

[SwampDog_13]

My sb dies have made some killer ammo. I've never used anything but and miraculously never once reformed any brass to date.

[Whole Bunches]

I recommend a 300 Blackout case gauge (I use the Sheridan) so you can set whatever brand of sizing die so as to properly set the shoulder of the case in the proper position. I was having some failures to fire. It turned out that by setting the bottom of the sizing die to firmly contact the shell holder, the shoulder was being set back too much. 1/2 turn out from touching the shell holder set the cartridge headspace right between min and max...perfect functioning in those 2 rifles experiencing ignition failures...most rifles didn't care (specifically it was a Daniel Defense bbl and a Noveske barrel).

However, with that setting I found that when forming cases, the shoulder wasn't set back far enough. So for forming cases, my sizing die needed firm contact with the shell holder.

[GunFunZS]

I recommend a 300 Blackout case gauge (I use the Sheridan) so you can set whatever brand of sizing die so as to properly set the shoulder of the case in the proper position. I was having some failures to fire. It turned out that by setting the bottom of the sizing die to firmly contact the shell holder, the shoulder was being set back too much. 1/2 turn out from touching the shell holder set the cartridge headspace right between min and max...perfect functioning in those 2 rifles experiencing ignition failures...most rifles didn't care (specifically it was a Daniel Defense bbl and a Noveske barrel).

However, with that setting I found that when forming cases, the shoulder wasn't set back far enough. So for forming cases, my sizing die needed firm contact with the shell holder.

Good info.

[der Teufel]

as noted by others - sometimes lee dies form ok, other times they dont. depends on which end of the tolerance window you're at. Lee clearly states on its website that its dies are not designed for forming, just resizing fired brass. their 'goal' is to produce a die thats around the middle of the acceptable SAAMI spec range.

hth

Interesting. I did not know this.
Thanks!