.17 HMR is the ticket as long as you keep the shots under 643 yards.

OK 223 is weak for coyotes but every one running off? how many did you shoot? don't get me wrong I do need some finishing shots on coyotes too. but I normally only outright loose maybe 1 or 2 a year and that is because I am more hesitant to put finishers in them. a facing solid chest hit aught to dump them. I mean sure go 308, but there are other options if you can go 243 in AR 10 that would also be an upgun situation.

20" to short, I have killed a fair number with 12" and 14" Contender using a 50 grain BK, any where from 50-300 yards.

I avoided shoulders,guts and legs though. A wild critters will to live and or escape should never be under estimated, no matter the size.

Shot placement, shot placement, shot placement...end of discussion.

Get yourself a quality box of ammo then report back, remington 55gr umc is a joke. Thats for punching paper, inaccurately.

A quality box of 223 is still less than cheap 308 ammo. Doesnt sound like you reload.

Using quality ammunition.

Nice job. Keep stackin em

Was recently watching PA outdoors and was surprised at the # of youth hunters that shot deer with a .223. If a .223 can kill a deer it certainly can kill a coyote, shot placement and bullet type are where to start. If you want to go bigger I would go to a .243, and if that doesn't work my next choice would be a .35 Whelen loaded with .357 240gr Hornady XTP jacketed hollow points, they shouldn't go anywhere then!

If I was going AR 10 I would go 22" 243.
It would be like a meat saw. As a matter of fact I have an upper on backorder.
22 Nosler and 50s at 3600 is doing the trick for me though. 223 is a little weak for marginal hits. I like an edge when I can get it.

Bad shots and it is a caliber problem??? Bigger caliber isn’t going to help if you can’t make good shots

I don't know about that, 243 slinging 75s at max speed will pick a up a bit of the slack lol.

It's surprising a shot to the shoulder with softpoints isn't going through and hitting the important stuff. I've always had really good luck with SP's in my .223's. Then again I don't believe I've shot any of that particular brand.

I don't know what would remedy the shots to the guts and legs without the same result. I've seen them run away after taking a hit from the .308,243,22-250 and some others with hits to the gut. Anything from rib cage to the head have always had the best results for me. If you're shooting them walking or running straight away from you and want them dead on the spot I'd go with a .243 or .308 but that's just me.

I agree with your assessment that you'd be better off with a properly placed 17HMR than with poorly placed UMC softpoints in the stomach and legs.

If you don't reload and want to go to something bigger but stay in the AR15 instead of go to the AR10 take look at the 6.5grendel. But use quality ammo. Heck the they also make a nice raccoon round also.

I've gone as light as 45 grain Sierra Varminters, and still haven't had any problems with .223 getting the job done. Even if my shot placement is off, coyotes I've hit tend to do that thing where they run in a circle and try to bite whatever bit them - and that usually gives me enough time to send a couple more. I can honestly say I've never tagged a raccoon with a .223, but the last time I hit a possum, it left a .22 entry wound and a pile of entrails on the other side. I gotta agree with everyone else here. You might need to try different ammo. Sure, I've had some rifles that shoot Remington UMC OK, but I've always had doubts about the terminal performance of those really cheap bullets.

A little side note

Rem 308 150gr SP's

I was still hunting deer in northern WI and spotted a nice buck working his way down a ridge toward me so hunkered down and waited as he passed me I shot him at 8 feet in the chest right behind the elbow, perfect hear/lung shot. He took off like a scalded cat, I couldn't believe he didn't drop or at least show signs of being hit, I didn't even take a second shot expecting him to drop. Good snow I thought I'd track him and get a second chance. About 40 yards away I started seeing flecks of blood on the snow at 60 some large patches that looked like he was coughing it up and another 40 yards and he was laying in the snow with a wound on his side the size of a dinner plate at first thought it was an exit wound and I actually stood there looking for another hunter after thinking about that I hadn't heard a shot examined the deer a little further and found the bullet had splashed on a rib and just a few pieces of jacket has sliced through the lungs. I wrote it up to being way to close. I drug him back to the truck and headed out with a couple more doe tags in my pocket.

I picked up a nice set of tracks and started to work them. A couple hours into it I could see the doe and yearling were going into thick black spruce thickets and circling to the downwind side and circling back behind me as I followed them through. I finally got to one of the thickets and started in then backed out and circled to the down wind side and waited and sure enough here they come walking straight to me watching the thicket at 20 yards I held on her neck in a straight line to the top of the heart, she went down but when I got to her it looked like someone had taped an M-80 to her throat and blew out a chunk of meat and wind pipe the size of a large softball. When gutting her there was zero penetration another bullet had exploded with out penetrating.

After I got her to the truck I tossed the rest of the ammo in the creek and went to town and found a box of my beloved 180gr RN's. Everything was just fine after that, never could get myself to use 150gr SP out of a 308 after that. They were Remington 308 150gr SP's, their 180gr RN's worked fine.

So even a bullet that sounds like it should be perfect for the job sometimes fails, maybe you just had a bad batch.