I want to make some light loads and thought Id try some sr4759 per a couple of loading manuals, But I found that the suggested loads only fill the case about half way. Ive found the same recepie in a couple manuals so It must be safe, but Im still a bit wary of hangfires.

Anyone had any experience with sr4759 and reduced 45-70 loads?? Maybe I should have just tried some black powder..

I will be using 340 and 405 gn cast bullets. Any help appreciated.

I don't shoot the 45/70 but have been known to tinker with reduced loads in other cartridges.

Some powders are sensitive to loading density and some aren't. For example, 2400, 4227, and Unique are often used for reduced loads in rifle cartridges, with very low loading density, yet they generally work just great.

I suspect you'll be fine with 4759.

Some people prefer to fill up the empty space with dacron or other fillers, but I've never had any luck with fillers, and there are reports of barrels being damaged by fillers. Proceed with fillers at your own risk.

I don't shoot a 45/70 either, but have you thought of trying Trail Boss powder? They have loads for 45/70. I use it in my 44 mag with cast bullets and it makes a very light load while filling the case nicely. The powder is designed to be very bulky to fill up large-capacity cases, but it shoots very mild. I've found it to be very accurate as well.

Several years back I shot 27 grains of AA 5744 and a florist foam wad behind the RCBS 45-500 BPS bullet. I used a dowel rod to push the foam down over the powder . Out of a Remington #3 Rolling Block and aperture sights, the unsized and pan lubed bullets would cloverleaf at 100 yards...

For my money, AA 5744 is the best smokeless powder for cast bullets that money can buy.

Try 10 grains of Unique with any 300 to 405 gr cast bullet.

That load was recommended to me in a letter from Lyman many years ago.

I shoot the Lyman #457122, a nominally 330 gr. hollow point bullet using 16.0 gr. of SR-4759 through an 1895 new Model Marlin and a Ruger #1S. I use a piece of dacron batting 1/2" square and 1/2" thick pressed lightly over the powder. Velocity was a bit over 1600 FPS, accuracy from the Marlin averaged 1.5" and 1.0 to 1.25" from the Ruger.
I was using Cream of Wheat (COW) for a filler putting in enough to come within 1/8" of the case neck, then compressing the COW when seating the bullet. Accuracy was a bit better and velocity was about 100 FPS faster. However, one day at the range, I had a misfire. When i got home and pulled the bulelt, the COW was caked about as hard as a rock and I had to dig it out with a screwdriver. While it apparently did no harm, it did make me a bit nervous about the deal so I switched to the dacron batting. I found that by using either the COW or the batting, the extreme spread was reduced substantially, from 50 FPS to 20 FPS.
Back in the 1970s when I was reloadinf commercially, a fellow came up and asked if I could make a light kicking load for his 1873 Springfield carbine replica so that his girl friend could shoot the gun in comfort. I loaded up 10.0 gr. of Unique under the Lyman #457191, a 292 gr. nominally bullet designed for the 45-60 and 45-90. Velocity was estimated to be about 1200 FPS (No chrony back then) and recoil was very mild. IIRC, I used a wadded up square of toilet paper as a filler. Both he and his GF were happy with the load, but I don't like using Unique in the 45-70 as a rule. It's too damned easy to get a double charge i that case and not see it in time. At least with 4759, a double charge will either fill the case so full that you can't miss it or overflow all pver the place and make a mess.
Paul B.

You might start with 20.0 grains 2400 and work up. Years ago that worked well for me with a 300 gr Hornady HP.

I'm one of those who uses Unique in the .45-70, 12 grains of it under Lee's 459-405-HB. I use two loading blocks, empties are upside down and charged cases are rightside. A glance in the charged block will reveal any difference in powder level. Never found any double charges, but I have found a few dead bugs that take up a lot less space than 12 grains of Unique.

I've used two that I like a lot. NEI 425.458 cast from wheelweights powered by 20 grains of 5744 and SAECO 015 cast from linotype powered by 13 grains of Unique. Both have mild recoil and are very accurate.

I'm another 12gr unique guy in my trapdoors. It just works and doesn't seem to be very position sensitive. Cast from 340-405.

Nuther vote for Unique, 12 to 14grains with a 400gr commercial cast bullet. I believe I chrono'd the 14grain load at @ 1,400 fps from my GuideGun.

Accuracy at 50 yards is good with no recoil and just a "POP!" for muzzle blast.

The 4759 is an excellent powder for the 45-70. The air space with it is of little concern. Many 4759 charges give close to full power ballistics and do not really qualify as light loads.
The guys here recommending Unique are offering good advice if you can develop the right technique for verifying that you do not have a double charge.
Always charge all of your cases and triple check the charge level in all cases before you seat a bullet when using Unique. I have shot up 2 lbs of Unique with 14 grains of Unique in this manner. I am working on the 3 lb now.

4759 is without a doubt, the very best powder. I use it in a lot of calibers and there are never any surprises, no pressure excursions, no fliers and extremely good accuracy. I will not use anything else in my 45-70 BFR revolver. I just tested some 300 gr XTP bullets and with 32.5 gr's and a Fed LP mag primer, I shot a 9/16" group at 50 yd's.
In a rifle, I found 3031 is the next best, much better then 4198. Recoil is mild and accuracy is top notch. 2400 and 4227 do not even compare.

5744 would work in a rifle but every load in my revolver with it sucks. No velocity and when I turn up a fired case, a pile of unburned powder falls out. Every primer and dacron wad tried, no luck at all.

I strongly suspect that 5744 was developed as a powder for the 7.62x39. It first came on the market as a surplus powder from Accurate that no one knew what to do with. I bought a case of four eight pound jugs from Accurate, c. 1980, for roughly the current price of a single pound.

I and other bargain hunters around the country rapidly found out that it was not worth a whoop in most pistol cartridges, but was great for small rifle cartridges and cast bullet loads. I shot mine up in an Siamese Mauser .45-70 conversion and an H&R in .357 Max. Lesser quantities went down the barrels of a .25-20, an M-1 Carbine, and a series of SKS.

My understanding is that there are at least two powders that are good when you are using cast bullets and you have a large case, Unique and 5744. Apparently consistent ignition and consistent pressure can be a problem with a small volume of powder in a very large case. Unique works well in this situation. 5744 also powers such bullet nicely but it also fills up a lot more of the case. Not quite the same thing.

So if you want to power a cast bullet and there is a large case volume, Unique and 5744 both do nicely. BUT all other things being equal you'll need a lot more of 5744 than Unique. If you shoot a lot, Unique works every bit as well as 5744 but, because you use a lot less of it, Unique costs substantially less.

I've used both powers in both my 45-70 and my 50-70 with equally good results. Currently I'm using 5744 in both BUT I'm going to be switching back to Unique. The charge required is much lower and hence the cost will be less.

I shoot 340gr Lee bullets with 30gr of IMR 4227 and get accuracy that will take charchol and golf balls at 50-65 yards. One of my best groups (off hand) was 1 1/4" using a 2.5X scope at 100 yards.

Lots of great load data at www.gmdr.com for reduced loads in several calibers.

I've experimented with a few of the loads in my 45-70's the best so far is 11 gr of Red Dot under a 405g cast bullet. Chugs over the chronograph at 1040fps (30 fps slower in my guide gun) and will group <1-1/2" at 50 yards with open sights and under 3" at 100 yards in my 22" barreled Marlin 1895. Fun, mild recoil and low(er)report load. Burns very clean too.