45-70 B.C

[brad925]

I am shooting a Buffalo Classic in 45-70. Currently i am using 300 gr. remington hollow points in it and it shoots great. I am wondering if i will have problems shooting cast bullets in it due to the shallow rifling. Also if i do go to cast if i should size to .457 dia. because thats what the remington bullets measure.

[brad925]

I either asked a really stupid ? or something that is impossible to answer...LOL!!

[Veral]

  There is no such thing as a stupid question if one doesn't know the answer, but there is such a thing is a whole bunch of stupid answers, which I just deleted a bunch of. -  Perhaps when you read anyones answer in the future, if they have a bunch of peripeheral nonsense which is supposed to make them look brilliant, ignore the whole packet.  If someone knows what they are talking about, regarding mechanical things, the answer is best just given as simply as possible.

  Your gun will shoot PROPERLY fitted cast bullets as well as it shoots those lightweight jacketed.  At worst the bore may need to be lapped.  For the cartridges which have only a taper into the rifling for a throat, like 45-70,  38-55, 30-30, etc, the bullet must be held precisely in the chamber to get a precise start down the barrel.  In other words, the first priority is to get a bullet that makes the cartridge fill the chamber.  This will almost certainly be way over groove diameter, which will not change pressure with cast bullets.  To determine what maximum bullet diameter should be, just measure the case neck of a few of the fired rounds that you are using.  The difference in diameter between new and unfired cases can be added to diameter of the bullets in the new ammo and you'll have the diameter which will shoot most accurately.  Since cases spring back a little, this will allow enough space for easy chambering.

  If you don't care for speeds over about 1500 fps, a plain base bullet will probably keep you real happy, but the barrel will almost certainly require lapping.  If you use gas checked bullets, you'll get more forgiveness for a rough barrel, but even so, lapping will deliver you a match grade barrel which gives optimum accuracy.

  If you decide to lap the barrel, get the LBT lap kit and a pack of 45 rifle push through slugs so you can measure progress and know when the barrel is perfect.  When finished, one of the push through slugs will give you an exact measurement of the barrels inner diameter.  However, barrel diameter can be ignored as long as it is smaller than the bullet that gives you a close chamber fit.

[jlchucker]

A couple of years ago I went to my club range and saw my gunsmith buddy there.  He had a BC in 45-70, and some ammo using the Lee 405 Gr FN bullet.  I had my Marlin, to try some Lee 405 Gr hollow base bullets.  We shot each other's guns, swapped rounds of ammo back and forth, and came up with a few conclusions.  1)  The BC, (at least the one my friend was using) was a real shooter with both types of bullets.  2) the hollow base bullet (I should have seen this when I bought the mold) is different than the plain-base, and although both shot very well in my Marlin, the only way to get the hollow base mold to chamber was by single-loading it.  I swapped that mold to my gunsmith.  3) AA5744 (new to both of us) shoots with little recoil but seems to send bullets out to 100 yd with tight groups, hitting to the same point of impact as the heavier-kicking RL7 loads.  4)  The BC in 45-70 is a whole different animal than the H&R 38-55 target model, which was a piece of crap that never shot well for lots of folks.

You should have a lot of fun with your BC and cast bullets. Good powders appear to be AA5744 and Unique. 

[brad925]

Veral when you are talking about measuring the cases are you talking about measuring the inside diameter or outside diameter?

[Veral]

  Inside.
  When cartridges are fired with stout loads the case swells out tightly against the chamber walls, then shrints back a little.  Normally around .003 with the larger cases, but the shrink back is relevant to chamber pressure.  If you are working up at over 60,000 psi with catridges designed for less pressure than that, there is almost no spring back.

  So, measure inside the case neck, back behind the crimp if the load was crimped.  Size your bullets to this size and they should chamber freely.  If they don't, size .001 smaller, till you get free chambering.  At that point you have the largest bullet acceptable for that particular chamber.

  If I know this diameter will be way over groove diameter when I cut a mold, I hold the forward drive band close as possible to groove diameter, and cut the base fat.  This minimizes bullet distortion upon entering the rifling.