gaileyr, since you're only shooting factory ammo, and you want the flattest shooting load, I'd try the Hornady Leverevolution ammo, it has great down range ballistics and shot equally well in mine when it was tested at the factory, as good as the 240gr Rem and 265gr Hornady factory loads.
Grafs has it on sale for $22.99 if you want the best price I've seen on it, I handload and that's an attractive price even for me!!
http://www.grafs.com/grafs/search/product/166592https://www.hornady.com/shop/?page=ballistics/popup&product_sku=82744https://www.hornady.com/shop/?ps_session=fb577ee8162f6ff887978d1774ddea4f&page=shop%2Fbrowse&category_id=1035565254fcc48f6f9ed8b329416eaepreventec47, You'd be incorrect on most counts there, most of the Garrett and all of the Buffalo Bore ammo are made for the Handi, the Garrett 500gr and 540gr are likely too long to chamber in the typical short throat of H&R 45-70s, but will work in a Handi if the throat is long enough to chamber it since it can be loaded beyond that of the 1895 levergun, the Handi is factory chambered 500S&W if you care to do a little SAAMI pressure research on it, the 1895 Marlin isn't.
Buffalo Bore uses bore rider 500gr bullets, that's how they allow the use of the bigger bullets.
http://www.garrettcartridges.com/products.asphttp://www.buffalobore.com/ammunition/default.htm#4570All .45-70 Magnum loadings are intended for use in the following firearms:
All Marlin Model 1895 variations made since 1972
Browning Model 1885 and 1886
New England Arms Handi-Rifle
Ruger #1 and #3
T/C Encore
Shiloh, Christian and Pedersoli Sharps
New Production Winchester 1886
The 500 gr. load uses a dual diameter, bonded core bullet by Alaska Bullet Works. The bullet diameter in front of the crimp groove is .449 inch, while measuring .457 inch on the shank. This dual diameter allows for reliable chambering in rifles with short or no throats. This is a non-expanding Full Metal Jacket bullet designed for the deepest penetration on the largest game animals. This load is safe for use in any firearm designed for the other BBA .45/70 MAG. LEVER GUN cartridges.
As for .458" bullet availability, Midway has about 100 listed and they're all rifle bullets, made for rifle velocities, the same can't be said for the .429-430" bullets. I don't think there are any "cheap" bullets any more, they're all getting expensive, but the plated bullets or bulk cast bullets are available for both the 444 and 45-70 and are relatively inexpensive compared to jacketed bullets.
http://www.midwayusa.com/ebrowse.exe/browse?TabID=1&Categoryid=7290&categorystring=9315***652***19785***9016***http://www.midwayusa.com/ebrowse.exe/browse?TabID=1&Categoryid=7562&categorystring=9315***652***19785***9016*** You can try those 180gr Sierras at 2500fps if you like, but you won't like the terminal performace at any range much past 150yds, the poor BC of .130-.140 isn't much better than that of a round ball, sheds velocity very fast, energy drops below the accepted 1000ft/lb level just past 150yds.
Tim
Trajectory for Sierra Bullets .4295 dia. (44 cal) 180 gr. JHC at 2500 Feet per Second At an Elevation Angle of: 0 degrees
Ballistic Coefficients of: 0.13 0.125 0.14 0.14 0.14
Velocity Boundaries (Feet per Second) of: 1300 900 900 900
Wind Direction is: 0.0 o'clock and a Wind Velocity of: 0.0 Miles per hour
Wind Components are (Miles per Hour): DownRange: 0.0 Cross Range: 0.0 Vertical: 0.0
Altitude: 500 Feet with a Standard Atmospheric Model.
Temperature: 59 F
Data Printed in English Units
Range Velocity Energy Momentum Drop Bullet Path Wind Drift Time of Flight
(Yards) (Ft/Sec) (Ft/Lbs) (Lb-Sec) (inches) (inches) (inches) (Seconds)
0 2500.0 2497.6 2.00 0.0 -1.5 0.0 0.000000000
25 2338.9 2186.1 1.87 -0.18 -0.47 0.0 0.031016533
50 2183.8 1905.8 1.75 -0.76 0.17 0.0 0.064202244
75 2034.6 1654.2 1.63 -1.8 0.35 0.0 0.099783946
100 1891.5 1429.8 1.51 -3.36 0.0 0.0 0.138016804
125 1755.1 1231.0 1.40 -5.53 -0.96 0.0 0.179182858
150 1626.1 1056.7 1.30 -8.4 -2.62 0.0 0.223584271
175 1505.6 905.8 1.20 -12.1 -5.1 0.0 0.271528398
200 1394.5 777.1 1.11 -16.76 -8.55 0.0 0.323307960
225 1294.2 669.3 1.03 -22.54 -13.11 0.0 0.379161948
250 1203.3 578.6 0.96 -29.62 -18.97 0.0 0.439309597
275 1127.5 508.0 0.90 -38.19 -26.33 0.0 0.503761432
300 1066.8 454.7 0.85 -48.48 -35.4 0.0 0.572217776