So... I'm building / restoring a Remington Rolling Block rifle this coming winter, that was customized in in the early 60's as a bench rest gun...

I'll be rebarreling the rifle with an uncontoured shilen 8mm match barrel, that we'll be chambering in 32-40 ( using .323 jacketed bullets, & .325 cast 8 mm bullets )... my goal is to build a rifle that shoots sub MOA out to 300 yards with both jacketed, & cast bullets... because the action is a #1 Black powder action, we are also concerned about chamber pressures ( the gun was converted to 225 Winchester in the 60's, & several of the action parts have likely been changed out with smokeless parts to help the old action deal with the higher pressures of the 225 Wincester ) we also built & refitted new pins, even though the action was still reasonably tight... so we are planning on starting with the jacketed cartridge, & chambering the gun, with maybe 1/8" - 1/4" freebore in the throat ( chambering for a 180 grain jacketed spire point flat base bullet seated out as far as practical at least to start with... then once chambered, either casting the chamber for a custom bullet mold, or finding an existing 200-220 grain 8 mm mold that should put the cast bullet engaging the rifling... just enough to get the breech to close...

I'm not fully understanding freebore & accuracy... I assume guns chambered for Weatherby were freebored for lower chamber pressures, & at least some jacketed bullets are capable of good accuracy with a space between the bullets nose & the rifling, while from what I understand, cast bullets shoot better ( maybe less deformation ??? ) if they engage the rifling when the cartridge is inserted...

1st... is my logic flawed,

2nd... any suggestions ???

You are just in the wrong place.
Go to a Schuetzen forum where they labor over 32-40s all year long. Maybe plan on a custom reamer and a custom mold.
Standard 32-40 operating pressures should be no problem for a RRB but high pressure is not the norm with the 32-40.
Personally I would start with an action that is more suited for the extreme accuracy you seek but it is your fun....

I have started one of these but in a different order. I have a set of 32-40 dies and 500 new Win cases.
Now I need to decide on a rifle to rebarrel and a gunsmith.....
I have the Ruger #1 with a beautiful stock and a crummy 7 Mag barrel....
But I really prefer something I can put a tang sight on...

I suspect youl be using a scope.. At that low of velocity wind variances would ruin alot of groups, and a sub moa group would take a extreemly experienced shooter to accomplish that, and that would be occasionally. After youve shot it for several years trying, 1000 yard shooting with modern guns/ammo would seem easy.. shoot during the predominating wind, not the calm, and fire fast enough to get the shots off in that same wind.. I used 45/70 sharps with black powder and open sites at first and then good target iron sites..6 inches at 1000 yards was a decent group with that setup, but eyes are alot to do with that.. Weigh All your bullets very accuratly, weigh the cases, weight the powder, Trim your cases each time you relaod.. Its easist and most accurat to leave a trimmer set up just for that case.. you will be using cast bullets and with that size case you may be under the speed of sound, your target distance the should be over or under the speed of sound. As the bullet looses velocity the twist must be able to stabilie the bullet at the muzzle and 300 yards.. A tall order to get a barrel built and done right unless your buider can do the math and you dont make a big change in bullets after the build.. When all done its not going to be a couple trips to the range to do this, it will probably take some time and many, many,many trips to the range to get the loads to achive this, then have a good day.. my opinion only.. Have long plug ezpanders made in several diameters around your barrel size, the brass cases tend to size the lead bullets and can hurt accuracy.. crimp or not, or amount of crimp must be repeatable and precise.. ADDED my oppinion again,, buy a sharps from one of the montana companies, they are extreemly accurate, and barrels lapped, twist right,rifling spacing depth right, on and on,, proven guns, and you will save alot of money jut in gas in the long run.. dave

Sorry... yes, a 15 X Unertl scope will be added. & this is just a "fun" gun, not a specific competition gun... I also have my own rifle / pistol range, so twaeking of loads is as easy as walking out door, to the Mule ( Kawasaki, not 4 legged ), & a quick 75 yards to the shooting bench... the Mule makes 300 yard target changes less tiring, & much quicker...

I'm more curious about the specifics of differences needed in throating between cast bullets & jacketed bullets, & I have no intention of breech seating bullets, only shooting fixed ammo... I also have started collecting bags of new Bulk Winchester 32-40 brass

the "shoots'en" guys won't likely have anything to add, since typical 32-40 barrels are 1 in 14 or 1 in 16" twist, & my barrel is a 1 in 10" twist barrel, & they rarely shoot fixed ammo...

quote:

Originally posted by Magnum Wheel Man:
Sorry... yes, a 15 X Unertl scope will be added. & this is just a "fun" gun, not a specific competition gun... I also have my own rifle / pistol range, so twaeking of loads is as easy as walking out door, to the Mule ( Kawasaki, not 4 legged ), & a quick 75 yards to the shooting bench... the Mule makes 300 yard target changes less tiring, & much quicker...

I'm more curious about the specifics of differences needed in throating between cast bullets & jacketed bullets, & I have no intention of breech seating bullets, only shooting fixed ammo... I also have started collecting bags of new Bulk Winchester 32-40 brass

the "shoots'en" guys won't likely have anything to add, since typical 32-40 barrels are 1 in 14 or 1 in 16" twist, & my barrel is a 1 in 10" twist barrel, & they rarely shoot fixed ammo...

Think you will find the shootsen guys to not be as monolithic as you assume. The same guys that shootsen often shoot a lot of other cast bullet rifles.
A guy that shoots a 30-30 with both types of bullets might have the sort of info you are looking for.
But if you really have interest in accuracy with cast bullets pay very very close attention to the twists they use.....
A 10" twist may totally negate all your concern about the throating.
The slow twists in the 32-40 and 38-55 are used for a reason....until the ranges are stretched so long that a heavy bullet is must for resisting wind drift.

Get this verified or go to a cast bullet forum for the specific info as noted above.. Im giving you some thoughts, trying to help, maybe some willnot help, or worse.. here goes ...

lead wont have as much grab on the case im thinking, could be wrong, youll probably want to seat the lead bullet into the lands to get pressures up.... I wouldnt want a jump with that fast of twist becouse you could get into stripping problems, dont know about the 32-40, power could be low enogh that it wouldnt be a problem.. The biggest problem with jacketed bullets and lead bullets is if there is any copper at all in the bore when you shoot lead it will raise havoc.. I would throat it for jacketed if you want to do both, and if you want a longer bullet you can have a postel (rides on the lands) mold made to your bullet weight, that will not matter if your throat is shorter than what you need for lead.. Lead bullets can be heavier (than jacketed) to help make up for the less pressure to drive them out the bore.. dave

quote:

youll probably want to seat the lead bullet into the lands to get pressures up.... I wouldnt want a jump with that fast of twist becouse you could get into stripping problems, dont know about the 32-40, power could be low enogh that it wouldnt be a problem.. The biggest problem with jacketed bullets and lead bullets is if there is any copper at all in the bore when you shoot lead it will raise havoc.. I would throat it for jacketed if you want to do both, and if you want a longer bullet you can have a postel (rides on the lands) mold made to your bullet weight, that will not matter if your throat is shorter than what you need for lead.. Lead bullets can be heavier (than jacketed) to help make up for the less pressure to drive them out the bore..

thats kind of what I was thinking... & had heard that about copper fouling & shooting cast bullets, so it wasn't something I intended to shoot the same day, I'd just like the option to develope 2 loads that shot good in the gun, one a jacketed bullet, one a cast... but wanted to discus or confirm before I get too far into chambering & throating of the new barrel...

thanks for the replys so far...

I have always felt it was better for any bullet to fit the throat well but it is of greater importance with cast bullets. A throat for a jacketed bullet should be no more than .001" larger than the bullet diameter (I'm speaking of the diameter of the parallel section of the throat assuming it is configured this way). A cast bullet throat should be bullet diameter.
In the case of your 32/40, a throat diameter of .324 would be fine with cast bullets sized to fit that diameter. Throat length should be such that the cast bullet will have it's front band definitely engraved by the rifling when seated to the desired depth. The jacketed bullet will be seated as required to fit. A cast bullet match rifle can have more of the driving bands exposed. In a hunting rifle, one would want all but the front band to be seated within the case. Regards, Bill.