New member, have a M1S .300 Fireball barrel - now what?
 

Hello, my name is Dan - first post but have been lurking for some time. Been trying to register but up until lately, the "Nospam!" feature had been keeping me from completing the form.....

Anyway, I am a CNC machinist from Central Texas and I am right in the middle of putting together a .300 whisper upper for an AR-15 pattern rifle. I have built countless AR's, some exotic requiring serious machine work - and I have been reloading for many calibers and loving it!

Ok, so I ordered a 16" 1-8 twist barrel from M1S, I ordered it WITHOUT a gas port so that I could put it wherever I wanted it and make it whatever diameter I wanted it. This rifle is going to be dedicated to shooting long/heavy bullets at subsonic speeds only. Unless there is a glaring reason I shouldn't, I am planning on putting the port in the pistol position like my friend's Noveske barrel.

One thing I have yet to get a real clear idea on is the cartridge dimensions. I will be making my own brass out of .223 and want to get the lowdown on lengths for the .300/221 chamber that M1S sells.

The last thing is some good subsonic load for 200+ grain bullets. I prefer Hogdon powders, but will use something else if it's known to work well.


Cheers!

Hey Dan,

I am in Llano County, central Texas. I use the redding dies, and will be happy to give you some brass I have formed from .223 to test in your chamber. I have subsonics and lots of other goodies. I have been using 2400 for subsonics, cause I had some on hand. Start with about 9-10 grains, and adjust for speed.

This has some numbers, and loads:
.Sierra 300 PDF

Sweet, I'd love to meet up with you sometime and compare data/gear/etc.....I work in Fredericksburg, so you shouldn't be too far from me.

Thanks for the link, will check it out and get an idea on what reloading supplies I need to purchase.

Ok guys, got to test her out today.

I turned the gas block shoulder back to the pistol position and drilled a .0935 hole. With the Corbon 220g, which is the ammo type I am building this gun around, it functions FLAWLESSLY. This is with a 1/8 M1S barrel FWIW.

Next comes optics and load development, Redding dies should be here tomorrow.....

Sounds good, we got lots of experience around here. Some times it all works! We all love pics...