I'm the proud owner of my first AR. I am still learning about this rifle so please, excuse the ignorance. I would like to be able to hunt whitetail deer with this rifle but I don't think the 5.56 will cut it. I have shot opportunities to 600 yds in the area that I hunt but my average shot has been 80-100 yds. I am interested in the 6.8mm or possibly the .260 but I want a bull barrel contour, if available. I would like this rifle to shoot .75 moa or better and from what I have read on this site, this is not out of the question. What are your thoughts? Should I proceed or just buck up and buy an AR-10? Any help would be appreciated.
Past 300 yards, the 308 has significant advantages that would be hard to pass up, not the least of which is the increased energy. A minimum of 3 times the animals weight in ft. lbs. of energy at impact with a frangible bullet well placed will leave plenty of margin for efficient killing. Two times the weight of the animal in ft. lbs, should be considered the bare minimum for deer, provided your tracking skills are firmly established. The AR-10 platform is quite effective for anything from a 22-250, 243 win., 6.5 WSM, up to and including the 338 SAUM. I prefer the DPMS AP4 platform over the Armalite or Stoner, because it is STOUT.
As soon as I get caught up on machine work, I will build myself a 6mm WSM on an old SR-25, just got the Broughton barrel in last week. .75 MOA is typically attainable with a stock barrel and a little blueprinting. A custom barrel will often shoot sub 1/4 MOA. We kind of enjoy taking money from bolt gun guys at the matches....very .....satisfying.
I'm very confident that 5.56 will put the animal down. I just need it done on the spot, if not, darn close. The 400 acre farm that I hunt has a patch of timber on the SE corner where the big boys (2 B&C and 1 P&Y in the last 2 yrs) hang out , that is thick and nasty. Unfortunately all of the neighbors know and they sit close to the fence row. These people are not locals (lease) and will claim a deer that is not theirs if it crosses the property lines. My brother shot a buck last year with a 22-250 and obliterated the heart; it still ran 90 yds. Short of a head shot, I don't know where else I would feel comfortable shooting a deer and getting an immediate kill with a 5.56 (average mature whitetail buck is well over 200 lbs, some over 300). I have had good luck with a 7MM SM, but had a spill on a hunt and that was the end of that rifle. I just didn't want to have to buy an entire AR-10 or anything else if I could modify my AR-15.
I think an AP4 or other AR10 type platform, shooting 110 VMAX bullets would solve your problem quite well. Handloads with 48 to 49 grains of Benchmark powder and a neck shot will drop the deer like a ton of bricks, and put a smile on your face.
