Speed Check, Fellas?

[Guy La Pourqe]

I've been at it a couple years now, with cast boolits… and I am still learning things.

I am currently playing with smokeless loads in 45-70 in a Rem roller repro, and am sitting down to do some serious work with it. Question - in your opinion, how fast should a 510 grain round nose be moving in this calibre to approximate black powder velocities? I have heard 1100~1200 FPS... but I notice that the velocities really start to level out in the high 1300's... the extreme spreads and standard deviations drop to respectable values around those speeds. I ask, because I am getting some leading.

How fast is too fast for these guns? At what velocities do the gas checks come out?

Hope you all are having a good one, and that the 2019 hunting season is good to ya!

Cheers!

[pworley1]

You are getting into Ruger No. 1 velocities with those loads. You might try a bullet in the 400g range to see if you get better results.

[1Hawkeye]

The old government black powder load was a 500gr round nose at 1180 fps and winchester's old smokeless load was about the same. Lyman's 457125 is a close duplicate to the gov't bullet. If you want speed try the Lyman Gould hollow point 457122 it weighs 330grs.

[country gent]

My BP loads are running in the 1150-1200 fps range with a 550 grn bullet. This carries well and really takes rams down. at 500yds. These big bullets carry velocity very good.

One other reason for the sub sonic start is it helps to avoid the transition from super sonic to sub sonic. Alloy lubes and fouling all contribute to leading. My bullets are 20-1 and I heave very little leading in the bore. I believe at the lower pressures and velocities a hard bullet may lead worse since it dosnt get bumped up to that perfect fit. Another is where is the leading occurring at Breech mid or muzzle? These rifles have longer barrels ( some out to 34") some bullets may not carry enough lube for these longer barrels.

[koger]

I have several 45/70's and shoot the 350gr Lyman/Goulds listed above with 15 grs of Unique with no leading and a 20-1 alloy as state above. I have not seen what they are running, but they shoot great and no leading. I recently tried some of these bullets without sizing them, and sprayed them with Lyman moly. Shot great, and no fouling, about 3 or 4 patches with Hoppes #9 and you are good to go.

[bigted]

1150 to 1200 for those boolits. As above, express loads do better with 300 to 350 grain boolits.

First I would check your fired case mouth. Remove gently any crimp from the unsized case, measure the mouth and see what diameter YOUR rifle is asking for. This above anything else will cure leading.

Next (as above) , recheck the lead/tin mix. Your rifle will desire a 20 to 1 mix or softer.

Black powder will bump em up if soft enough but if smokeless is employed , then getting the throat filled with your boolit diameter will do wonders for leading.

[Larry Gibson]

Guy La Pourqe

"........I am currently playing with smokeless loads in 45-70 in a Rem roller repro, and am sitting down to do some serious work with it. Question - in your opinion, how fast should a 510 grain round nose be moving in this calibre to approximate black powder velocities? I have heard 1100~1200 FPS... but I notice that the velocities really start to level out in the high 1300's... the extreme spreads and standard deviations drop to respectable values around those speeds. I ask, because I am getting some leading."

1100 - 1200 fps is about right with 28 - 32" barrels for BP loads.

Leading is usually caused by a poor alloy, poor fit and/or a lube that isn't working. What are you using for an alloy, a lube and what are you sizing at?

"How fast is too fast for these guns? At what velocities do the gas checks come out?"

Not a matter of "how fast" with smokeless powder for these guns.....it's a matter of pressure. Ergo that depends on the powder and it's burning rate you are using. You want to basically keep the pressure under 28,000 psi (modern transducer measurement) or 18,000 C.U.P. Lyman's #4 CBH has some loads using RL7, 3031, N135 and Varget that keep you under those pressures and get into the 1300+ fps range. Quite safe loads for TDs and RBs.

I use a 500 gr Rapine 460500 in my TD. It is cast of 16-1 alloy, sized at .4615 to fit the .461 groove diameter and lubed with a beeswax/olive oil lube. It is loaded over 36 gr IMR4895 with a Dacron filler. The measured psi (Oehler M43 PBL) runs 25 - 26,000 psi. The velocity is 1325 fps out of my 29.5" TD barrel with SD of 15 fps and an ES of 40 fps (10 shots). It has proven to be an excellent load.

GCs are not really needed at those velocity levels with PB bullets and proper alloys. If you're using a GC'd bullet sans the GC then I suggest using a GC for better accuracy and perhaps it will cure the leading problem(?).

[Guy La Pourqe]

Well thanks, boys. My loads came out of the cast lead handbook, and the loads and velocities are for the old trapdoor guns. It doesn’t bother me one bit to slow them down... once I learn my way around the gun with smokeless... I will switch to a more manly propellant.