.45-70 for Coyotes? That is a tad bit expensive. I personally use my Remington 700 VS in .308 for coyotes. I load up Speer 125 gr. TNT HPs that are going about 2900 FPS. Every coyote I have shot in the body with that load and that gun has never escaped. I did blow a shot once and hit one in the leg and it escaped, but that is coyotes for you.
Actually I have a story I haven't really told anyone yet for some reason (am I really humble?). Dad and I were calling and he is close to the call with a 12 gauge and I am above and behind with the Remington 700 VS in .308. I don't see anything, but I hear him start shooting. I immediately get on my knees and by that time he has shot three times. I see a coyote running about 30 yards away to the right where I couldn't see before (it wasn't really a good rifle call as we were on the flat part of a sloping ridge). My dad had a far shot with the shotgun, but managed to get some good hits with the first three rounds and even put out a 4th shot. I stand up and sight in on the coyote that is now about 60-75 yards away running, but hurt. Keep in mind the
Remington 700 VS in .308 with a HS Precision PRT25 stock, IOR 20 MOA mount and rings, 30mm Leupold 6.5-20x50mm scope, and Harris Model 25(s) bipod weighs quite a bit. I squeeze the trigger and shoot and the coyote goes down! I didn't hear the definitive "thump" of a solid hit, but the coyote was hauling butt and is suddenly stopped. He wasn't dead, but he was done. I ran over to a rock to shoot one more time, but didn't have a good rest and he wasn't going anywhere so I didn't shoot. I went down to inspect the coyote and it was dead by that time. I saw that the coyotes rear right leg was snapped in two and hanging on by skin. I figured out that my dad must have got some good hits in and the coyote was bound to die eventually as often coyotes will run about 100 yards and fall over dead. Before it could get away, I actually hit it in the leg and it gave up with a nearly severed leg. I was rather amazed at the whole bit that I could even get close while standing with that rifle and the scope zoomed up to about 10-12 power (I had no time to adjust anything).
Is there a lesson to all of this? Sure. For coyote calling, do you really need a heavy full barreled gun? Probably not. How many shots are you going to take in a call? With a rifle? Max 5. Is the barrel going to heat enough in that time to make a difference? No. So in hind sight, I wouldn't trade in my Remington 700 VS in .308. I shoot that gun at coyotes, deer, and for Palma matches (800, 900, & 1000 yards). However, if you are wanting to get an economical rifle for calling coyotes, I would seriously consider a regular barreled .22-250 or even a .243 that is light and easy to carry back and forth from the truck to the call and is easy to shoot standing or from a kneeling position with. Why a .243? Still a varmint round with more versatility for deciding to shoot a pig or deer if you just happen to be calling (this is my father's current want, he has shot two pigs with one shot each with his .22-250 while out hunting coyotes, but the sporter barreled .243 would be more appropriate).
As far as Southern Sharks comment, I don't think he read you were shooting coyotes and I think his recommendations are near overkill. The other thing you have to keep in mind is that large caliber rifles with SP ammo are going to have projectiles that travel a long ways. I know in some places while shooting coyotes, you want that bullet to break up and slow down as soon as possible. Rule #4 always applies, but the safer the better.
Good luck and good calling.
(Whooo Hoooooo. My 1100th post!)