50-70 Barrel bore measurements

[Texan1650]

SO, have been looking for a 50-70 Barrel for a new rifle. Used mostly for hunting. One well known barrel company quoted their barrel as being .500 in Bore and .508 in grooves. 50-70 barrels harder to find that I figured. But having said that, from everything I have read, the .508 is a little scary to me. Molds cast bullets of .513 to .515. I know a bullet can be sized to almost what ever you want, but I dont think I want to try and put a jacketed bullet or a commercial factory load that uses a .512 cast bullet through a .508 barrel. Thoughts?

[JMtoolman]

I had a guy make me a barrel for a Sharps carbine. Mine had a .514 bore, so that was what he made me. It shoots the .514 sized and lubed Lyman mold #515139 just great. Works for me!

[HumptyDumpty]

SO, have been looking for a 50-70 Barrel for a new rifle. Used mostly for hunting. One well known barrel company quoted their barrel as being .500 in Bore and .508 in grooves. 50-70 barrels harder to find that I figured. But having said that, from everything I have read, the .508 is a little scary to me. Molds cast bullets of .513 to .515. I know a bullet can be sized to almost what ever you want, but I don't think I want to try and put a jacketed bullet or a commercial factory load that uses a .512 cast bullet through a .508 barrel. Thoughts?
Personally, I'd go with the original bore diameter. However, with lead projectiles, I doubt it's going to harm anything. Heck, I put plenty of .311"-.313" projectiles down barrels with .308"-.309" grooves. Now, a few of those have been jacketed, but at reduced powder charges. I don't think I'd be comfortable using a full charge with such heavy projectiles as the 50-70 uses. Are your planning to push the 50-70 beyond it's original limits, in a strong modern action? If so that sounds awesome, but it would definitely be best not to use oversized jacketed bullets. If not, I'd just stick with lead.

[Chill Wills]

If it should end up that you buy a .500 - .508" replacement barrel, there are enough correct molds around to choose from. Start by looking at Buffalo Arms to see what they have and a number of the current mold makers will make what ever you need. Lastly, you can size down to an in between size, a few thou over and still shoot with good accuracy.

Given you also want to shoot jacketed bullets, I agree with your concerns about using too large a bullet in the smaller 0.508" barrel.

[Bad Ass Wallace]

I have a Swedish RB in 12.7x44R with a bore that slugs 0.496/0.508". I load cast boolits that are sized to 0.510" and they don't seem to cause problems.

https://i.imgur.com/XyVVmgdl.jpg

[HumptyDumpty]

I have a Swedish RB in 12.7x44R with a bore that slugs 0.496/0.508". I load cast boolits that are sized to 0.510" and they don't seem to cause problems.

https://i.imgur.com/XyVVmgdl.jpg

Is that the original barrel? A friend of mine has one, which we went out shooting the other day. All the ammo was made by me, using .515" projectiles; it shot very well. I wonder if it also has such a tight bore:???:

[Bad Ass Wallace]

Yep! all original with a pristine mirror bore. Has the deepest rifling that I have ever seen on a BPCR.

[John in PA]

Springfield Armory, the originator of the .50-70 cartridge, made barrels nominal .515. groove diameter. Shiloh and C. Sharps use .512 for groove diameters. The original Sharps Rifle Company in the 1870's had a nominal groove diameter of .509. I would choose your barrel specs based on the most commonly available bullet mold diameters and reloading die dimensions (expander die, mainly) Because more repros than originals are being shot these days, I would suspect that the .512 diameter is most likely the one with the greatest variety of molds and other components.

[varsity07840]

Accurate Molds will make you any size you want in a variety of styles suited for a .50-70. I have there originals, one with a .510 groove and two at .515. I use the government style 450 gr in 20:1 lead. I have a single cavity Lee that drops at .512 and a 2 cavity that drops at .517. I use them both as cast, lubed and then cleaned up in a .512 and .517 sizer respectively. All three have 1 in 42 twists. Modern .50-70 barrels are usually faster and may need a longer, heavier bullet than the government style. Shiloh's standard twist is 1in 22, but they will make a 1 in 36.