Interesting 45/70 chrono results

[jonk]

Just thought I'd pass this on.... I did this experiment this weekend with my 1873 trapdoor. All bullets were cast in a Lee 405 HB mould and lubed with Felix lube. Some were hard, some soft lead. They were sized to .459. Charges were as dropped (not individually weighed). Interestingly the loads WITH filler in all cases showed lower velocity.

There was really no difference in accuracy among them and it was lackluster at best- about 7" at 50 yards. The gun just doesn't like this bullet/powder combo. I'm going to try another powder next time out, perhaps 4198.

1027
1006
1012
1023
1006
1014.8 Av V
9.731392501 SDev
Trapdoor Soft Lead
12.5 gr Trail boss no
filler- no great accuracy

991.8
975.1
981.9
982.8
976.8
981.68 Av V
6.535059296 SDev
Trapdoor Soft Lead
12.5 gr Trail boss
Pufflon filler- no increase
in accuracy

1069
1053
1044

1055.333333 Av V
12.66227994 St Dev
Trapdoor Hard Lead
12.5 gr Trail boss
no filler, no great accuracy

992.5
1009
1017
985.4

1000.975 Av V
14.55572625 St Dev
Trapdoor Hard Lead
12.5 gr Trail boss
filler, no great accuracy

[DonH]

What is your bore/groove dia? I would be surprised if it is as small as .459 in the TD. As for bullet metals, at this velocity level softer is better. This is the collective oopinion of a large percentage of shooters of BP era rifles (and repros).

I am a BP guy myself but for smokeless you would probablt get better accuracy with 5744 or 4759. 4198 can work well also but may need a filler. For BP pressure equivalent loads I use the 40% rule with 4198 (40% of 70 gr = 28gr). 1150-1200 fps is a good velocity range for pleasant shooting with the old rifles. 40%/4198 is somewhat faster than this.

[jonk]

I haven't slugged it but it doesn't really matter as the mould drops bullets at 460=461 and those are very hard to chamber- 459 is the fattest that will comfortably chamber in the gun. Unless someone has a heel-based bullet.

[Larry Gibson]

Jonk

That would have to be about the tightest chambered M1873 that I ever heard of. Most m1873s have very little Leade in the throat if any. So if the bullet is not seated far enough the breech block can be hard to close, especially with hard cast bullets. I've shot many as cast (.464+) Lee 405HBs in numerous TDs and the only chambering problem came from the bullet not being seated deap enough. Also a TD with .459 groove depth is a rare item most are .460-.465. Thus your bullets are probably undersize and not obturating at the low pressures of your load which is causing the poor accuracy.

Larry Gibson

[jonk]

Well it could be; all I know is a 460-461 bullet badly bulges the case even using an M die and/or a Lee universal flare die (tried both) and won't chamber.

[KCSO]

I don't think I will ever use T/B in a trapdoor. They list the 13.0 max charge as producing 24,000 psi and that is max for a trapdoor. I have not gotten really good accuracy from T/B unless I push it a little harder, 15.0 shoots fine groups and shoots to poa with my b/p loads in my Sharps carbine. The b/p loads are a lot less pressure and do a better job slugging up the bullets.

[jonk]

I've done blackpowder. It also wasn't remarkable.

[Larry Gibson]

Jonk

Cast the lee 405 HB out of 1-20 tin-lead alloy. Size the bullets to .459 if necessary and lube with SPG or I can tell you a simple homade lube formula for BP. Just partial size the case (W-W, R-Ps, Feds, PMCs or Star Lines) so the inside diameter is .457 where the bullet base is. Flair the case mouth. Prime with a standard primer like WLRs. Load 7 gr of 4759 over the primer and then put 54 gr of Goex Cartridge on top of that. Seat the bullet so the case mouth is over the front of the driving band. Put a roll crimp on the case mouth. That will pretty much duplicate a M1873 service load. The duplexing will ensure ignition and will blow most of the BP fouling out. A blow tube will not be necessary. I've not found any original TD in reasonable condition with a strong bore that would not shoot 5 shots of that load into 3-5" at 100 yards.

Larry Gibson

[jonk]

The duplex load sounds like an idea... otherwise that's pretty much what I did with the black powder already.

I did use FFG though as it is hard to find CG Goex locally.

[35remington]

I have had the same experience using dacron with Trailboss in the .25-20. Fillered loads were nearly 100 f/s slower than loads without. May be something about how the primer flash penetrates the charge. Satisfied my curiosity about doing so, but I prefer other powders for low velocity use in the .25-20.

You could argue Trailboss doesn't need filler, but I was curious about any beneficial effect and gave it a try.

[Vern]

The 405 hollow base is a good bullet but it needs to be 1-10 so it will expand to fit the barrel. I shoot only black in my trapdoor and have had very good results winning the first match that I shot it in. We shot out to 600 yards. The load I was using was 60 grains of FFG. a .030 card wad, and on top of that I put a 500 grain Lyman round nose bullet. This rifle is and 1884 with the Buffington sight. The bullets need to be soft for this rifle so that it can expand to fill the bore.

[Larry Gibson]

Vern

1-20 is softer than 1-10. Also Frankford arsenal found in 1880 or so that the 405 gr HB bullet did not obturate to fill the bore. It took a 500 gr bullet at .459 to obturate into the .460-.465 bores of the TDs. It's an inertia thing. That resulted in the M1881 (500 gr ) bullet. Also FA settled on 1-16 alloy to be the best for the 500 gr bullet. The HB of the M1973 (405 gr) bullet was only there to control the weight given fixed external dimensions. The skirt is way to thick to obturate ala minie stye. They also quit using the wad in the 45-55 carbine load as it was found the wad stuck kittywampus in the HB and adversly effected accuracy. FA ended up seating the carbine load bullets deeper to sit on the powder which gives very good results. This, of course, gave quick identification to a 45-55 round because it was shorter vs the rifle service load with 70 gr BP. FA then quit headstamping the carbine loads with a "C" (first known use of headstamp). The Lee 405 HB will shoot much better if shot as cast, particularly if that is .461+.

Larry Gibson