I'm sure it'll kill deer, and probably bigger game, but its range is really limited. Think handgun ranges. Considering it is a big a step down compared to 223 for deer hunting I just keep asking WHY?. A 223 loaded with 60-75 gr bullets designed for big game will penetrate enough to kill deer and still impact with enough speed to expand out to about 400 yards. If someone wants to deer hunt with the AR platform and want to step up from 223 the 6.5 Grendel is the most logical step. Most of the lighter 30 caliber bullets are designed for varmints and don't hold together well enough for big game. The 30 caliber bullets in the 150 gr weight class just barely have enough speed to reliably expand at the muzzle, and at 100 yards are too slow to reliably expand. The heavier bullets don't have enough speed to expand at the muzzle. If you're using a large 44 or larger caliber then expansion isn't always necessary, but it is with a 30 caliber.
I suppose that someone could, develop a bullet designed to expand and still penetrate at those speeds, but as it is now most 30 caliber bullets are designed to be used at 308, 30-06, and even 300 WM speeds. A 30-30 with 150's beats 300 BA buy as much as 500 fps, the 7.62X39 with 150 gr bullets by over 200 fps. And those are considered 200 yard cartridges.
Handgun ranges? Im getting about 2200 FPS with a 125gr Hornady SST hunting bullet that is designed for medium game, definitely not a varmint bullet. Not sure what you define as handgun range, but that load will cover it, and I consider it to be a 150 yard and in load. I wouldnt consider a pistol at that range. That 125gr bullet is doing about 1800fps at 150 yards, so more than enough energy to expand and get the job done. If you want to shoot something like the Barnes bullets, you might be able to eeek out a bit more range and expansion, say 200 yards.
A 223 is a good rifle, but honestly Id only consider one bullet really viable to shoot deer with in 223, that being a 75gr Swift Scirocco. This is a bullet that is designed for hunting, and it has the weight needed to break bones if needed. It also matters what part of the country you are from. We see deer that run up to and over 300# on a regular basis here in Wisconsin. Last fall my buddies buck was a 360# 12 point buck. I dunno about you, Im not trusting a 223 to work as needed on a trophy deer. Ive seen southern whitetails and my German Shepard was bigger than most. In a perfect world, with perfect broadside shots, with perfect shot placement, yes the 223 is enough. However, when you have to take quartering and frontal shots, the 223 utterly fails. Also, 400 yards with an AR? Dont make me laugh. Ill trust my 308 at 400 yards.
I do agree with you, the 6.5 Grendel is a good next step in a small framed AR for medium game. The 224 Valk is also a contender, but jury for that is still out for me personally primarily because I havent seen great accuracy results anywhere, and the bullets at 80 to 90gr simply arent there yet.
Lastly, you need to actually post factual stats on how fast each round could potentially shoot at the muzzle not take random guesses. Below data was pulled from Hodgdon's website, and is based on max charge with the best powder that yields velocity. As you can see, you really are off.
300 BO - 125gr bullet - 2400 fps
7.62X39 - 150gr bullet - 2200 fps
7.62X39 - 125gr bullet - 2500 fps
30-30 - 150gr bullet - 2500 fps
I dont consider any of the above calibers to be consistent 200 yard guns except for the 30-30 using FTX bullets which is a special case. They are all close in, brush gun or driving type guns, which is exactly where a 300 BO in the AR platform excels. Personally I wouldnt trust a 7.62X39 150gr bullet to reliably open at 150 yards, but a 125gr bullet is another story. The 30-30 loaded with 150's is not 500 fps faster than anything. The 300 BO pushing 2400 fps looks decent now that everything is in context?
You are entitled to you opinion. However, you do need to be truthful.
