I am looking into the Marlin 45-70 to add to the collection. I know it is up to the shooter, but what is normal accuracy range on that cartridge for the average shooter with open sights? any thoughts on the rifle itself?

if you are the average shooter and you have open sights i would say it's range is about 75 yards. i've heard good thing about the guide gun.

You have any idea how available rounds are, by any chance? I guess if you are putting a hole in something that big, it doesn't matter where I hitting it..........

My eyes are bad and could use the sights for out to 100 yds lots farther if my eyes would focus properly.

Yes it dose matter where you hit a deer even with a 45/70 , a gut shot deer is a gut shot deer.

Put a scope on it and it is good for 200+ yds .
The standard 300 gr load is loaded by Rem ,Win. and Fed at least
Rem has a 405gr load
But where the 45/70 shines is using Garret or Buffalo big bore loads or hand loads .

I use a Marlin 1895 with a scope and my handloads .
With the right bullet and load it is a great close range elk and moose gun also

I have a stainless Guide gun and have found with the ghost rign sights its easy to keep my shots in the 2-3" range with ghost rign sights out to 100 yeards, usually closer to 2" than 3. With my 2.5x scout scope it is easy to keep shots in the 1 1/4-1 1/2" range. IT is definately minute of whitetail even with ghost rign sights out to 150 yards and 200 yard shots with the 2.5x scope are fairly easy. I shoot mainly reloads with 405gr Rem JSP and H322 @ 1800fps and for the mean stuff 405gr Kodiak bullets @ 1800fps. Plenty stout for anything that walks on this continant out to 150 yards, and good on moose/bou/deer out to 200.

This gun is like any other high powered centerfire rifle, given the appropriate amount of practice, it will kill a deer as far away as you can see one.

Most people typically limit their open sighted shots to 100yrds with ANY rifle. With a scope and factory loads and a lot of practice, this gun is capable of about 300-400yrds with easy kills on deer, there's quite a bit of power there, but the rainbow trajectory becomes a problem. With handloaded ammo, a bit of practice, and a high powered scope, as far as you want.

I've got two Marlin 45-70's (and three other .45-70's currently), one in their Stainless Guide Gun and the other in the Cowboy rifle...literally the long and short of it (ok, bad joke). I shoot the Cowboy for cowboy action long range events at deer vital sized targets out to 600 and 800yrds on occasion...and this is with limited velocity ammo...I've got a 1200yrd range that I shoot on, with handloads that approach the maximum pressure of the Marlin, I can typically make hits on a 2MOA target (24") about 85% of the time from a prone position.

The trick to the .45-70 is practice. For the average shooter, it will kill a deer as far away as basically anything else. For the dedicated shooter and reloader, it's capable of taking deer a LONG way away...or a cape buffalo, whichever you choose.

45/70 is a great cartridge, as is the Marlin 1895. I'd suggest the regular/full size 1895 vs. the guide guns.
"Normal accuracy range"? Well, what's your definition of "normal". Back when my eyes
were younger I could shoot a Marlin 30-30 to 200+ yards with a peep sight, and keep 'em inside 4-5". Today, I'd use a scope.
For a scope I'd look at the Weaver 1-3x. It's a 20mm, 1" tube, matte finish. Should be
able to handle anything your 45/70 will, maybe 200yds., but given the trajectory I'd try
to keep shots within 150yds.
If you want to go with "open" sights I'd take a look at Williams. Either put one of their rear sights on it with a U notch or shallow V blade, and then a white bead for replacement of the front sight. Other option would be their Williams FoolProof peep sight. Get it with the large twightlight aparture. Again, go with the white bead front.
Ammo for the 45/70 is readily available from all the major makers. I'm listing a couple
links for you here, including one custom ammo maker.
Links:
http://www.cheaperthandirt.com/ctd/default.asp

http://www.midwayusa.com/

http://www.cpcartridge.com/index.htm

Scopes/sights:
http://www.riflescopes.com/store/default.asp

http://www.williamsgunsight.com/