.50-70 Case Length

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  • Last Post 19 December 2012
RBeech posted this 07 September 2010

I'm going to give BP cartridge loading a try using a Sharps New Model 1863 - with the .50 cal liner and center-fire conversion.  A Cerrosafe casting shows the groove diameter to be 0.515, my Lee .515-450 drops them at 0.517 with 30:1 Pb-Sn - I plan to use them unsized.  The chamber length is about .150” longer than the Starline brass that I bought.  I read that BP tends to expand the bullet and I'm worried that it will expand out before hitting the throat, then shave lead going into the throat and rifling.  Is this a real concern?  Or is the case length OK at .150” less than the chamber?

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JetMech posted this 07 September 2010

I have noted 2 problems with cases too short with BP loads: The first you described, although I have yet to prove it except that when I got the right length cases, accuracy improved about 25%. The second is the BP fouling accumulates in that area.

My rifle is chambered in 38-55 with a 1.125 length chamber. Going with the standard length cases of 1.080, accuracy was mediocre. Going to the 1.125 cases was a definite improvement.

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RBeech posted this 07 September 2010

Thanks for the reply.  Do you have any thoughts on a source of “correct” length cases for the .50-70 Government?  I read in the SPG Lubricants BP primer that there is a .50 Basic available that can be cut down in length.  Do you have any knowledge of this?  Or maybe I can find  .50-90 cases and cut them down?

Russ

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JetMech posted this 07 September 2010

Either will work. The third option is to check with montana_charlie on cast boolits or the Shiloh Sharps forum. He developed a tool to stretch cases for just the reasons we've been discussing. I know he can do .45 but not sure about .50.

Good luck.

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rmrix posted this 07 September 2010

Can you give more ditails about the chamber? The old chambers vary as they do today, only more so depending on what they where intended to shoot.... as in  Paperpatch or GG bullets. Likely the chamber in your rifle was set up for the Gov. round. Not Paperpatch.

I would try what you have. Shoot a few and check for leading. And check for a bacic level of accuracy.  I shoot a lot of BPCR but not a 50-70 Sharps. I can put you in touch with my old shooting partner that owns the same Sharps rifle model you have and he would be able to provide much better advise than I can.

One thing to keep in mind is that the old chambers where simple and worked better than we would guess. That is, just a chamber with a taper down to the rifling bore is many times all that was there. Does not sound like it would work but does very well! I have an “old” chamber cut in my 45-2-4/10” Creedmoor rifle and it shoots well beyound anything you would think it could.

Again, give it a try.

All the best,

Michael Rix

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rmrix posted this 07 September 2010

If it turns out that some one has messed with the chamber and you do need something longer, Buffalo Arms Co can provide what you need.

You can find them on the net.

Michael Rix

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RBeech posted this 08 September 2010

Michael,

I didn't pour Cerrosafe right up to the rim, only about 1/3 to 1/2 of the chamber.  But from what I did get, and from looking with a bore scope, the chamber has a sharp step to the smaller diameter of the throat (I don't have the numbers or casting with me right now, but I think the throat was about .250” long from the step to where the rifling started).  I took this step to be the point where the case should end.  Using my vernier caliper, running it in until it catches on the step in the chamber, it appears that the step is about 0.150” farther in than the length of my cases.

As you suggest, I plan on giving it a try with what I have and seeing how things look.  Thanks for your input.

Russ

PS - If I load a bullet to the maximum length that will easily chamber (as I do for CBA bench-rest in the military class with smokeless loads, i.e. .30-06) I have 1 grease groove in the case and two exposed, and would need to use a bit more powder or several fiber wads to take up the extra case space.  Is this something that is normally done?  Or should I fully seat the bullet and let it take a run at the barrel?

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JetMech posted this 08 September 2010

Seat to the lands, add more powder.

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Daryl S posted this 08 September 2010

I have an original '59 Carbine barrel, re-lined and chambered by Sharps in the 1867 contract. It is, of course, .50/70 - however, the chamber is a straight taper is appears, without a step the rifling as in modern chambers.  Note these are 42” twist barrels.  Mine tipped the full length 450gr. pointed original-type bullet. I shortened the die by boring the mould out and silver brazing in a 3/8" plug.  The mould now casts a flat nosed bullet of 400gr. that shoots well for the antiquity of the barrel and the short sight radius. 

My rifle will take cass up to 1.9” in length and still easily chamber a .517” bullet in the brass. I do not size, but use a 6.5x68 seater or FL die for crimping the loaded rounds - both work.

Using short 1 3/4” cases causes no problems that I could see in hundreds of rounds and gave 3 1/4” accuracy with the orignal sights and black powder.

I also made brass out of .348's that require several firings to blow out completely & is how I got my 1.9” brass. The accuracy was about the same with the 1.9” cases.

After I grew tired of 3” groups, I re-barreled and re-chambered it to .45/60 using a GM barrel, ie: 1.9” shortened .45/70 case using my .458 2” reamer. I load 60gr. 1F or 2f and Lyman's #457125, a 525gr. bullet - it runs 1.2” to 1.5” for me now for 5 shots. The .50/70 barrel was fun for a while.  With smokeless loads and the 405gr. Remington, I shot a 10 shot gorup at 100 meters using aperture sights - 7/8” on centres @ 1,845fps - 35” bl..

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RBeech posted this 09 September 2010

I don't have any experience with chamber design/shapes modern or otherwise.  I have attached a crude drawing of the chamber casts that I get from a Model 1903 .30-06 versus the .50-70 Sharps.  The .30-06 tapers from the outside dimension of the case neck down to the bore.  The .50-70 has an abrupt step - is this unusual?  I know that it is the original barrel (serial number matches the receiver), and I can faintly see the line between the barrel and liner at the muzzle end - but that doesn't mean that someone didn't do something with the chamber before I got it.

But back to my original post, I took the step to indicate where my case should end - and if this is true then my cases are about .150” too short.  From the replies I've seen, it looks like I'll get the best results if I use longer cases, but I can probably go ahead with the cases that I have and see how it shoots.  Again, I appreciate all the feedback and comments.

Russ

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rmrix posted this 09 September 2010

RBeech,

Nice job depicting the chamber.

If I understand correctly, the standard brass (1.75” long) is 0.150” short of filling the chamber to the shoulder. And then it is about 0.250” more to the rifling. So a loaded round made with your current Starline cases, even with bullet seated out will have about 0.400” of unsupported bulllet that will expand into the void when the big red light comes on behind it.  And then it will be reduced again to bore and groove diameter as it moves forward through the throat and rifling.

Likely not good for best accuracy.

I am not the right guy to say if this is the chamber the one the contract called for when this rifles where lined for cartridge use by our goverment, but it might be. Someone knows.  And as is,  it might have given accuracy “good enough” for the troops.  However I would think you can improve upon it by giving some longer cases a try. Buffalo Arms Co has some 50 x 2” cases. You could try 20 for not too much $ and cut them to fit. I know you are going to try what you have and maybe try some longer cases and see what that gets you.

These rifles arn not known for thier accuracy as compaired to a BPCR target rifle of the times. Not even as good as what can be done with a 1884 Springfield (trapdoor with Buffington sights) They where/are just 100y man size target troop rifles for the most part.

Post War, J.P. Lower of Denver converted some to heavy barrel sporters for use on the buffalo hunts and what ever the well outfited westerner might want an accurate longrange rifle for.

 Fun project, keep me posted. Next time I call my friend I will ask him about his rifle chamber.

All the best, Michael Rix

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RBeech posted this 09 September 2010

Michael,

I think you really hit it concerning accuracy - this rifle wasn't made to be particularly accurate, especially with only a 22” barrel.  I shouldn't be worrying too much about it at this point.  I just happen to have this gun and thought it would be fun to shoot it, so I'll go with the 1.75” cases and, as time allows, try a longer case later on to see if it makes a noticeable difference.

Not sure that I'd ever go so far as to change barrels like Daryl S did, but his results indicate that this is an option if I'm determined to shoot accurately with it.

Russ

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Daryl S posted this 17 September 2010

RBeech wrote: I don't have any experience with chamber design/shapes modern or otherwise.  I have attached a crude drawing of the chamber casts that I get from a Model 1903 .30-06 versus the .50-70 Sharps.  The .30-06 tapers from the outside dimension of the case neck down to the bore.  The .50-70 has an abrupt step - is this unusual?  I know that it is the original barrel (serial number matches the receiver), and I can faintly see the line between the barrel and liner at the muzzle end - but that doesn't mean that someone didn't do something with the chamber before I got it.

But back to my original post, I took the step to indicate where my case should end - and if this is true then my cases are about .150” too short.  From the replies I've seen, it looks like I'll get the best results if I use longer cases, but I can probably go ahead with the cases that I have and see how it shoots.  Again, I appreciate all the feedback and comments.

Russ

 

 

Russ- the step you see is the end of the chamber as you surmised, and is where the end of the case should come to within .010” of touching.  It is a mean little shoulder and is usually 45 degrees in modern ctg. not square.

 My own original barrel did not have a step - the chamber was merely a cone that would accept a longer than usual case - which I've read is normal.

You do not want the bullet to scrape against this shoulder as that will peel off material.  The bullet should ride up into the throat, which will help prevent it from scraping against the shoulder.  The 450gr. bullet has a very short ful diameter section, but the 42” or 48” twist prevents longer bullets from being used.

Try seating the bullets out as far as possible, so the bullet's sides are well into the throat, rather than allowing the sides of the bullet to rub against the shoulder with shorter than desired cases an the nromal deep seating which was common in this round.

 

Note that my 22” carbine barrel shot into 3” at 100 yards.  This is not bad considering many .30/30 Winchesters won't do any better when using iron sights.

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RBeech posted this 17 September 2010

Daryl  -  On closer inspection there was a bit of a slope to the step.

I was able to load some rounds and try it this past weekend.  I loaded some rounds with 60 gr. of 2F, fully seating the bullet (2.225” COL) with a fair amount of compression (I don't have a feel yet for what is a little or a lot of compression - I don't feel like I was about to deform the bullet by using it for the compression that I ended up with, so I guess I didn't have a lot of compression).  I also loaded some rounds to the lands (2.480” COL), using 72 gr. of 2F and very little compression of the powder.  In both cases I used a 1/16” (0.0625") vegetable fiber wad.  Bullets were unsized (0.517") with SPG lube.

Both loads were hitting about 2 feet high at 100 yds - guess I need to put a taller blade in the front, or shoot at 200 yds.  I was having a lot of trouble getting a good sight picture with the small v-notch on the rear sight, so consistency was non-existent.

I'm not sure where I'll go from here.  If I decide to modify the sights (some people would say this is sacrilegious on an original Sharps), then I'll see about cutting myself some longer cases to better fit the chamber.  -  Russ

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Daryl S posted this 18 September 2010

Bear with it, Russ. It can be a blast - especialy with an original.

Compression of the powder should be a separate operation from seating the bullet. I made a post for an old pistol expander die and use that for compression of the powder - about an 1/8th inch compression is right. Please don't use phony powders. The perchlorates in their compostion are very corrosive - first and last warning. It is very hard on brass too - seems to disolve it over time no matter how it's cleaned. Stick with real black powder.

I had to remove and replace the original blade with a higher one - no big deal - just save the original blade. Mine was pinned into a slot cut in the front sight base.

The sights take some getting used to, afterall, it was a military gun.

BTW - more buffalo were shot and killed with 50/70 chambered Sharps and Rolling Blocks than any other gun or ctg. A lot of Elk also met their death's at the hands of  settlers and government hunters armed with either a rifle of carbine .50/70 Sharps. Statements from letters show the .50/70 was more effective on heavy game within it's accuracy range (under 300 yards) than was the .45/70 that replaced it.

As the .45/70 replaced the .50/70 as a military rifle ctg., the .50/70 rifles were sold off as surplus to civilians in and heading to the West. Government ammunition was easily procurred at about any fort, so this was a common rifle in the hands of West-bound people - the .30/30 of it's day.

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RBeech posted this 20 September 2010

Thanks for the powder warning.  I have not tried the fakes and don't intend to.  Right now I'm using Goex.  I've been told that Swiss 1 1/2 would be good, but the local shop was out of stock.

I'll figure something out for powder compression, I had read that it should be a separate operation but didn't have a tool for doing it (guess I could use the expander die).

I'll try changing out the blade in the front sight - I would like to shoot this thing some more, with reasonable accuracy (I have actually entertained thoughts of using it for the deer season this year - in the woods where 100 yards is a long shot - but that doesn't leave me much time to tweak things).

Russ

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Daryl S posted this 20 September 2010

An old silver coil, as in a dime, makes a fine front sight. It has lots of height, more than enough width and is easily filed down for a zero.

I'd like to try some Swiss 1 1/2 or 2F powder myself - it is somewhat hotter burning, but cleaner and developes more power per gain weight of charge. The rule of thumb is to reduce normal charges by 15%. It is supposed to be very close to Curtis and Harvey's #6, which was one on the best powders of the late 1800's.

The .50/70 should be wonderful for deer - moose/elk or buffalo for that matter.

One of my books has a picture (about 1875) some chaps starting to butcher buffalo - 5 buffalo down within 25 yards, and all shot with a .50/70 with government ammo.

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EDG posted this 18 December 2012

If you would like to try a full length case buy some of the Starline .50-90 cases and cut them off at chamber length.  When I am trying to find the lenght of a chamber I expand the case mouth until it drags on the chamber. Then attempt to push it home with your fingers. Keep trimming until it chambers. Record the chamber lenght and test 2 or 3 more to verify your work.  You can buy individual cases at both BACO and Track of the Wolf.

RBeech wrote: I'm going to give BP cartridge loading a try using a Sharps New Model 1863 - with the .50 cal liner and center-fire conversion.  A Cerrosafe casting shows the groove diameter to be 0.515, my Lee .515-450 drops them at 0.517 with 30:1 Pb-Sn - I plan to use them unsized.  The chamber length is about .150” longer than the Starline brass that I bought.  I read that BP tends to expand the bullet and I'm worried that it will expand out before hitting the throat, then shave lead going into the throat and rifling.  Is this a real concern?  Or is the case length OK at .150” less than the chamber?

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RBeech posted this 18 December 2012

I did get some .50-90 cases at Track of the Wolf, but have not done anything with them yet (so many things to try, so little time).  How do you go about trimming them?  I haven't checked yet to see if there is a case holder for my RCBS case trimmer.  Assuming there is, I think I first need to invest in a Dremel tool to take the bulk of the extra off first.

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EDG posted this 18 December 2012

A lathe is the best way if you have one. I lucked onto a 50-70 trim die and will use it to cut my cases to the right length. When I get to the point of cutting a lot of these I have access to a lathe and I will just cut them that way.

If you trim only a few cases to begin with a tubing cutter can be used for the rought work.

With a trim die I use a fine tooth hack saw blade cut off for use in my saber saw.

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RBeech posted this 18 December 2012

I would like to use my lathe, but I have not yet figured out how to do so (I'm new to the machinist hobby) - the cases are tapered and will not hold in my chuck or a collet.  I've been thinking that I could turn a tapered hole in a piece of round stock, cut a narrow slit length-wise (to allow it to squeeze down a bit) and then use it to hold the cases in the chuck.  How do you do it?

(PS - I tried a tubing cutter and it just deformed the case, and it wasn't an old worn out cutter.)

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EDG posted this 19 December 2012

I can think of several ways to do this. I normally make a holder like the case holders for a Wilson case trimmer.  Or you can just bore an extra Wilson case holder to fit if you can manage a small boring bar with your compound set at the right angle.  The case taper will lock inside the holder when you tap it in with a plastic hammer. Chuck on the holder. Put a parallel behind the case head against the chuck to provide a location. Remove the parallel and cut the case off with a sharp pointed tool bit.

You could also turn a spud/mandrel that is a light press fit in the case mouth. Press the case on the spud to a shoulder with the tailstock. Support the case with your right hand and part it off with the left hand.  Then you have to remove the band that was the case mouth from the spud. You can just turn it to chips. This method will be more difficult to control the case lenght but is easy to use for a roughing operation.

Another way is to buy a piloted 5/8' or 9/16” piloted counterbore. Make a pilot that is a snug slip fit in the case mouth. If you have a means to grip the case you can use a drill press to hog off the extra material.

The tubing cutters will work but they do roll the case mouth in a little. You advance the cutter a tiny bit and make 2 to 4 revolutions before you advance it again.  If you have a shell holder device to grip the rim and drive it with a power tool it is much less tedious.

RBeech wrote: I would like to use my lathe, but I have not yet figured out how to do so (I'm new to the machinist hobby) - the cases are tapered and will not hold in my chuck or a collet.  I've been thinking that I could turn a tapered hole in a piece of round stock, cut a narrow slit length-wise (to allow it to squeeze down a bit) and then use it to hold the cases in the chuck.  How do you do it?

(PS - I tried a tubing cutter and it just deformed the case, and it wasn't an old worn out cutter.)

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