Which AR cal, noob Reloader

[Caveman Jim]

Nice! IIRC you made your brass from 5.56. What did you find to be the easiest way to cut it down to 300 BO?

A harbor freight chop saw, With a cut off jig and a vacuum attachment.
I cut them at the preferred length (1.35+/-) the resizing stretches it just a bit and not so much left to trim off.

 

[Caveman Jim]

This process makes many uniformed soldiers.

 

[Hueco]

What do y'all know about 375AR?

The idea of a casing that would allow me to use both pistol bullets and rifle bullets either sub/super is incredibly snazzy.

 

[Sweep1308]

I don't see this as a huge bonus IMHO. The biggest consideration I make of a caliber in both super and subsonic loads, is if my projectiles will perform as desired at the different velocities. From FMJ to expanding bullets of various types

 

[P7M13]

300BO is my vote:

• Designed for your application
• Uses the same bolt as 5.56
• Can be made from common brass - "so easy even an @Caveman Jim can do it"
• Uses the same magazines as 5.56

IMO the only drawback is that 300 BO will chamber in 5.56 followed immediately by disaster and since it uses 5.56 mags you need to be very careful not to get them mixed up. I strongly suggest you find a way to keep them straight like one or more of these among others:

• A different color mag used only by 300BO. Example: Black for 5.56 and FDE/Coyote for 300 BO
• Use plastic for one and metal for the other
• One distinctive brand used only for 300 BO. Example: Magpul for 5.56 and Lancer for 300 BO

Looking in my safe, it's hard to see which AR is which, so I have toe-tags at the end of the hand guard or on the muzzle device. Additionally, I have the caliber written in white paint on the bottom of the hand guard.
I do the same with mags so there's no confusion, paint marker (white) or Sharpie in gold or silver.

Making brass isn't the hardest thing in the word. It just requires more dies and time/process.

I can't imagine recoil on 338 specter would be any different than shooting a pistol caliber of similar bullet weight through a rifle as the speeds should be about the same. Just like subsonic 300 blackout is basically 45 acp with a better bullet coefficient, 338sp might be similar to say 44 mag with a better coefficient.

@wired has one and I never get tired of him showing it off.

I love that cartridge.

Gee @Reno, thanks. Was set on avoiding the rabbit hole of any more wildcat calibers, but this one has me intrigued. I certainly have hundreds of 30 Remington brass variants to use....

 

[Member 34319]

Looking in my safe, it's hard to see which AR is which, so I have toe-tags at the end of the hand guard or on the muzzle device. Additionally, I have the caliber written in white paint on the bottom of the hand guard.
I do the same with mags so there's no confusion, paint marker (white) or Sharpie in gold or silver.




Gee @Reno, thanks. Was set on avoiding the rabbit hole of any more wildcat calibers, but this one has me intrigued. I certainly have hundreds of 30 Remington brass variants to use....

Join the waitlist for a barrel. They are hard to come by.

 

[brucekr]

I'd recommend the 300 blackout too with a couple of notes

If you are going to cut down your own brass, do a little research on which ones to avoid. Maybe mine is an unusual experience. I originally cut down a few hundred cases that were originally from some Turkish ammunition factory. The wall thickness on the case portion that would eventually become the 300 neck was thicker than others, so when I sized it and put a projectile in, the stackup was too thick and I had feeding issues. So I bought a case gauge and so far only about 3 or so of 200 cartridges will pass the test. I've since said the heck with making my own brass and have amassed a few hundred factory 300 cases.

The other thing is that if your magazine of choice is magpul, buy the 300 blackout pmags. This caused me some feeding headaches at first. There are some youtube videos that explain why this happens, and I can tell you firsthand that my feeding problems are all but gone now. For steel mags, you likely won't run into the same issue.

Someone else mentioned the rubber bands you can buy, that's what I did as well. I have a 5.56 and 300 pistol build that are very similar, but different enough to not mess up.

 

[Sweep1308]

I'd recommend the 300 blackout too with a couple of notes

If you are going to cut down your own brass, do a little research on which ones to avoid. Maybe mine is an unusual experience. I originally cut down a few hundred cases that were originally from some Turkish ammunition factory. The wall thickness on the case portion that would eventually become the 300 neck was thicker than others, so when I sized it and put a projectile in, the stackup was too thick and I had feeding issues. So I bought a case gauge and so far only about 3 or so of 200 cartridges will pass the test. I've since said the heck with making my own brass and have amassed a few hundred factory 300 cases.

The other thing is that if your magazine of choice is magpul, buy the 300 blackout pmags. This caused me some feeding headaches at first. There are some youtube videos that explain why this happens, and I can tell you firsthand that my feeding problems are all but gone now. For steel mags, you likely won't run into the same issue.

Someone else mentioned the rubber bands you can buy, that's what I did as well. I have a 5.56 and 300 pistol build that are very similar, but different enough to not mess up.

Good reminder to ALWAYS buy a case gauge for the calibers you load. Might not use it too frequently when loading brass you've done a few times, but for new combos, which are becoming more frequent, it's a must!

 

[brucekr]

Oh yeah, one more thing about cutting down your own brass. Trimming it the first time sucks. I have the frankford arsenal case prep station and I was having issues getting uniform case lengths. So, I decided to try a lil crow case trimmer. Nothing fancy about it, but it works like a charm every time. Use some grippy gloves to hold the base of the shell. It will save your fingers a ton of fatigue in the long run.

 

[Caveman Jim]

Oh yeah, one more thing about cutting down your own brass. Trimming it the first time sucks. I have the frankford arsenal case prep station and I was having issues getting uniform case lengths. So, I decided to try a lil crow case trimmer. Nothing fancy about it, but it works like a charm every time. Use some grippy gloves to hold the base of the shell. It will save your fingers a ton of fatigue in the long run.

Here's a tip if one has weakened hands like I do.
A simple pair of needle nose pliers is perfect for the task.

 

[Member 53328]

5.56 in a 11.5 barrel would be my choice.