45-70 bp velocities

[littlejack]

I was just loitering on the threads this afternoon and noticed that I wasn't noticing too many velocities on the bp thread. Maybe it was because I was just not noticing them. Anyway, Seeing as how I am new at this BP shooting and reloading stuff; Would you fella's be nice and post some of your chronographed velocities with the 300 grain cast bullets up to the 400's and heavier if you like.
I clocked my Lyman 530 Postell bullets at 1100 respectively with 70 grains of Goex Ctg. powder. That was with .300 compression and a .050 opw. Alloy is 20-1 with Emmerts lube. Bullets sized to .459. I plan on buying and borrowing some more moulds and would be wondering what to expect in the fps department. I would like to settle on one of the 400-405 grain cast bullets for hunting if my rifle will like it. I have the Uberti HiWall. All replies appreciated.
Jack

[Don McDowell]

Jack here's some results I got about a year ago.

--------------------------------------------------------------------------------

Tried a handful of different loads over the chrony this morning. Not a large sample of any one load, but enough to get a general idea of what might be .
All loads were fired from my CSharps 75 in 45-70 with 30 inch barrel, RCBS 82084 bullet weighing in at 528 grs, sized .459 and lubed with Sagebrush alox, winchester cases and large rifle primers. Col of 2.98
Elevation 4800 ft, temp 45, humidity 40%, barometer 29.51 and falling.

All goex powder, and speeds averaged, none of the loads listed had over 20 fps extreme spread. 15 ft from the muzzle
3f express 72 grs 1273 fps
65 grs 1208 fps
60 grs 1163 fps
2f express 70 grs 1210
cartridge 70 grs 1141

[August]

My goal is always 1300 fps. But, I rarely get readings as fast as 1200....

[catkiller45]

I found that my most accurate load for the 45-70,with the 500 grain bullet
was only around 1060 f.p.s That is with 2F Goex black powder no doubt..
Shot from my Pedersoli Sharps...

[littlejack]

Looks like nobody else wants to play. Thanks fella's your help.
So what I am gathering from you fella's if I assume correctly, is that bp does not run a lighter bullet at a whole lot greater speed as does smokeless. I know that bp is very inefficient in its burning and pressure for the amount of powder that is used.
Is there a graph showing the psi for bp cartridges being fired?
I did clock some different loads when I first started out with the new rifle. I started out with the same 530 grain Postell bullet. I loaded 65 grains of Goex Ctg. and .300 compression. The velocity was in the low 1090's fps averge of 5.
I loaded 5 with 67 grains and got in the mid 1090's fps.
I loaded 70 grains and got to 1100 fps.
The velocity does not go up per grain of powder with bp as it does per grain with smokeless.
Being as this is the case then, one cannot expect great increases in velocity when using a max load with a lighter bullet. Maybe a couple hundred fps.
Does this mean that a max load of bp will only create a certain max pressure?
I.E.: If I load 70 grains of bp under a 530 grain bullet, will I only get a max pressure of whatever the max pressure for that load would be?
And if I load 70 grains of bp under a 400 grain bullet will the max pressure be the same as the max pressure with the heavier bullet?
So, the only reason one bullet goes faster, is that it is lighter. Correct?
I hope you all can understand what I am asking. This is very interesting stuff and a world apart from the smokless loads that I have loaded for 40 years.
Jack

[Don McDowell]

Jack there'll be some difference in pressure going from one bullet to the other, but yes I'm with you that the velocity difference between light and heavy are due to the bullet weight.Changing powder size will change this big time.
With 65 grs of 2f Goex I've clocked 505 gr bullets at 1190.
Doing some speed testing with cartridge in the 4065 , it seemed to take at least 5 grs of powder to get past the sd of the previuos load. Didn't get a whole bunch of velocity difference going from 50-60 grs.

In the Lyman 47 manual under the Ruger only 45-70 loads they posted pressure results with bp and pyrodex. Even at full throttle the 500 gr bullets were only generating about 13Kcup with 2f.

[zampilot]

I considered the amount of powder used for a marginal velocity gain when I started a year ago, so, why not just load for accuracy per bullet style per rifle ? That's what I'm doing as I dont have a chrony and dont really want to mess with one.

[montana_charlie]

Being as this is the case then, one cannot expect great increases in velocity when using a max load with a lighter bullet.

It may not mean a lot, but you can usually get considerably more powder in the case (with the same compression ratio) when the bullet is lighter (shorter).

I am convinced that 'max load' is determined by case capacity...not pressure limits...when BP is the propellant.
CM

[missionary5155]

Greetings
As with muzzleloading 5 grains of 2f is about the average break point to see any real FPS change. Also 50 grains of lead is another average break point. Not saying 1 grain of pwder or 10 grains of lead do not make a differnce... but it is so small it adds up to little change at 100 yards+.
The factories naturally knew this so when the wanted an "Express" round they dropped boolit wieght drasticly (405 to 350) and added case size 45-70 to 45-90. Walla a 45 caliber boolit now moving at 1450+ which was significant in 1880.
Realisticly you also need longer barrels to utilise all the "charcoal fed sulfur"... so the Buff hunters stuck with 32-34 inches of steel out front.
Then there is the speed of sound thing... stay above or stay below. That sound barrier turbulance is a nasty critter to fight out at 200 yards.
Have fun... I am still am and will continue until the right shoulder falls off.
God Bless you ! Mike

[littlejack]

Glad for the replies:
As per Don, I do believe that there will be SOME variation in pressure with the different weight bullets. Lower pressure for lighter bullets and higher pressure for heavier bullets.

As per zampilot, this will save powder and not have it pushed out the muzzle unburned.

CM: I agree with your statement on case capacity.

For my own knowledge, Thinking out loud:
If a person has two rifles. One is a 45-70 and say one is a 45-120. Both have 30" barrels.
If both cases are loaded to maximum case capacity and a bullet of the same seated in each. There will be a higher velocity in the 120 cartridge than the 70 cartridge correct?
But, with the 120 cartridge there will be a lot of unburned powder pushed out the barrel, correct?
Question: Will the pressures be the same in each rifle give or take or will the pressures be a lot higher in the 120 case? I realize that the powder charge does act as more weight for the pressure to push down the barrel, and this will also show up as more recoil, but is the max pressure in the 45-70 cartridge the same as the max pressure in the 45-120?

I have read that the longer bp cases were produced so a shooter could shoot a heavier bullet at the same or close to same velocities as the shorter cases do a light bullet.
Jack

[littlejack]

Mike:
You got yours posted as I was loitering on other things and writing my reply. What you said is prety much what I was pondering. The barrel length would definately need to be longer to burn the added powder. So the pressure would not go up significantly, if at all, but the bullet would be pushed for a longer peiod of time.
I need to get a good reference book and or guide to reloading bp. Any one have a good recommendation? Thanks to all. Any more expieriences or information is appreciated.
Jack

[singleshot1]

Littlejack, check out the 14th edition of the Speer manual. Bret Olin has a very good chapter on some testing they did on black powder loading. He is a R & D engineer with Speer and shoots black powder firearms. Dave

[Boerrancher]

Fellas,

No matter how much of the Holy Black you cram in a case or down a barrel, you will never exceed 36,000 psi. Which is about half of what most of your modern smokeless loads generate in the newer modern Mag cases. The main reason why longer barrels and more powder is to allow that 36,000 psi to stay in contact with the projectile longer thus increasing velocity.

Back when all anyone had was a front stuffer, they way they worked up a load for it was by slowly increasing the powder charge until they heard the distinctive crack of it breaking the sound barrier. That became the starting load and they would work up and down in 5 gr increments until the best possible accuracy was achieved. With black powder in most cases it is pointless to try and achieve much over 1,200 fps. Some rounds will hit 1400 fps, but it is not worth the effort in most cases.

Best wishes from the Boer Ranch,

Joe

[cajun shooter]

Back in the early 70's is when I first shot The "HOLY BLACK" and I did it with a 45 and 50 TC hawken rifles. Someone had printed material with pictures on how to develop a load for the BP rifle. It showed white sheets spread open on the ground in front of the shooter. It told you to fire the rifle over the sheets until you found unburned powder. You were told to back off at this point and that would be your max load for the rifle. The reasons for the long bbls of old was to give the powder time to burn and propel the lead at it's best speed.

[Scrounger]

Should we throw in a ballistic factor that we have learned in modern times that is probably relevant? That is the trans-sonic effect, that a ballistic object (bullet) will lose accuracy going through the sound barrier. A very big factor in choosing .22 LR ammo for match purposes. In black powder shooting, we should either choose a load that will remain supersonic (>~1100 FPS) all the way to the target, or one that is subsonic (<~1100 FPS) at the muzzle. Pardon this comment, I have no knowledge or interest in black powder, this is just book theory I picked up somewhere...

[Don McDowell]

Irrelevant is probably the better term.
Shooting the big long bullets that bpcr match shooters do. you're not going to keep a bullet above supersonic to 1000 yds, and a bullet that's 1100 or under at the muzzle will loose stability before it gets to 1000yds. Therefore you need to find a bullet with proper weight balance and nose shape that will withstand the transition.

[littlejack]

Very interesting topic. Black powder is a animal of different color for sure. Thanks fella's for all the information. I'm really enjoying the new rifle and the bp cartridge. Such a big piece of lead, at such a low velocity with such great knockdown power AND penetration.
Jack

[SharpsShooter]

Many BPCR loads start out at less than the speed of sound which is 1128fps in 70* air / density pressure, but the some boolits will not be stable at 100yds. They will stabilize at greater distances often grouping better at 200 than 100. The boolit goes to sleep or stabilizes for a period before deceleration and rpm drop destabilizes the boolit and it goes divergent of all axis. The key is to use a design that has a stability range across a broad spectrum of velocity / RPM. The Lyman 457125 is a reasonable example. My pet 45-70 load will punch just slightly oval holes at 100 yards, but perfectly round at 200.


SS

[chuebner]

Wow, this is most curious. From my notes of about 2 years ago when assembling loads for my trapdoor I had these results.

Rapine 460-500gr. as cast at .462 30:1 alloy
Emmert's lube
70gr. volume GOEX 2F
.550 compression below case mouth .030 card wad

M1888 Springfield, 5 rounds over friends chronograph
average velocity, 1320FPS

I was duplicating loads as noted in Steve Wolf's book on loading for the trapdoor and my velocity results mirrored his which led me to believe I was doing something right.

Charlie

[northmn]

Back when I was working up a deer load for my 45-70 with the 320 grain Gould HP bullet I used Fed Mag Rifle Primers, and Rem cases with 67 Grs GOEX 2f to get about 1390 fps. This was out of a 30" HR "Buffalo" model. I got about 1600 with 777 and about that with a duplex BP Load. I used the BP to take a nice little whitetail and it worked very well. Winchester cases can get a little over 1400 with a little more powder. From what I can tell, reading literature and some chronographing, the gains in BP are very limited using light bullets. Winchester had their "Express" loads which I think was just a marketing gimmick to permit sales of their lever guns and cartrigdes that would cycle through them due to the need for shorter over all length. The 420 Lyman 457193 gave me a little over 1200 with BP if I remember correctly.

Northmn