I got a nice 556 upper but want to swap on a bcm 300. which do you recommend?

no help to your quest OP

I'm just here to say this- I've seen TOO many 5.56 uppers blown up from the 300BO round being accidentally fired in them.

300BO will feed and fire in a 5.56 gun but will blow a gun up every single time it happens

They get accidentally placed in a magazine along with 5.56 rounds then BOOOM!

Designing a caliber that would fit in 5.56 magazines and also feed and fire and blowup a 5.56 gun was dangerously stupid. A lot of people have blown up good guns and some injured because of it.

Just say no. That caliber needs to die or be legally banned outright.


https://www.google.com/search?q=300+...ut+5.56+kaboom



300BO fits and headspaces in 223/5.56 chamber:






big bullet wedges in small bore barrel when fired:







gun blows up:

repd. this was honestly good advice. do I go 308 ar10 instead

i just got a diamondback db10

308 is fairly cheap ammo

edit: also, i've never seen 308 out of stock anywhere, but .223/9mm/buckshot etc. usually is

What's your specific reason for not wanting 5.56 and that will guide your decision.

Stick with your 5.56 for a general purpose gun unless you have a really good reason to go with something else. It's what most military and law enforcement use and the most common among civilians also, and the AR-15 is called 'America's rifle,' all for many good reasons. MK262 77 grain ammo or similar 75-77 grain load if you need longer range. M193 for general purpose bulk ammo. Suppress if it want.

If you want super quiet for less than 150 yards then 9mm AR with 147 grain non +P (HST is great!) through a 4-8 inch barrel with a suppressor.

If you want long range past 500 yards then pick 6.5 Creedmoor or 308/7.62x51 and suppress it if you want to, but you can't put that on an AR-15 lower.