Have any luck with these? 45-70 in particular.

No problem at all, they will shoot great.
The Ranchdogs shoot well and if you want something with more stopping power check out Beartooth.

I have a Marlin 45/70 in Microgroove. I have had very good result both in velocity (no or negligible leading) and accuracy. I have used several commercial offerings and have settled on, for elk hunting, the Beartooth 425 gr gascheck sized .460.

Reason I ask is I bought some 405 gr casts and my groups have been terrible, some going through side ways at 100 yds. This gun shoots 1 1/2 " groups at 100yds with jacketed bullets and 6-8" groups with casts. Need gas checks?

I found out early that my 45/70 with microgroove bbl. didn't like cast at .458. But when used as cast at .460 things took a turn for the better.And with out gaschecks too.

the cast bullets, do your bullets have a flat base or are they "boat tailed"?

A buddy's unit does very will with cast/gas checked slugs. Like near 1 moa. If one is running smokeless, he should be using checked slugs.

I've had good luck with cast bullets in the micro groove barrel, provided the bullet is slightly oversize. With groove diameter cast bullets they shoot well with low velocity plinkers. For full power loads, they work best when a couple of thousandths over groove diameter.

My Lyman and RCBS molds cast a flat base, but I also shoot a local commercial cast beveled base 350 gr. as cast at .460 (unsized) which does well out of the micro-groove bbl.

With out gas checks?

My 1895G shoots far beter with plain base bullets (no gas checks) than with gas checeked lead. The load you use can affect accuracy a lot too. Groupc could easily vary by a few inches at 100 yards depending on how many grains of powder you are using and which powder you choose....

.

Micro-groove will not shoot cast bullets. That is purely a myth. As with any barrel the cast bullet must fit or it will not shoot well. Micro-groove is a button rifling process and will make the groove dia. slightly larger than a cut rifle barrel. That means that a MC barrel will usually require a cast bullet .001 or so larger the a Ballard or cut rifling barrel.

Jacketed bullets seldom require an accurate fit to shoot well but the cast bullet needs a perfect fit to shoot it's best otherwise the powder flame can escape past the bullet as it moves down the barrel. The flame cutting of the bullet will destroy accuracy.

My rifles like a LaserCast 405 bevel base bullet over 13 grains of Unique at about 1300 fps. No filler. That closely matches the original Black Powder loading. It is also a killer on any game animal in North America. And, it doesn't kick the snot out of the shooter.

.

my 95 microgroove was terrible with 405's . tried 325's and brought it in to 1.25 inch groups consistently . never got to check the twist before someone borrowed it forever f-ing thieves!