Throating the 45-70

[kc5gxc]

I am getting the 45-70 throater from Tim. You guys who have throated these before.....how deep or how much should be cut out? Is there a nominal amount people generally go to? How did you measure the amount cut? Can you mark or tape the throater to the depth you want? Can one mount the barrel horizontally in a vise to do this?
Thanks for any suggestions.
Pete

[tacklebury]

If you have a specific bullet you want to use, make up a dummy round with it seated in the crimp groove/cannelure.  Measure from the ogive to the base, then when you run the reamer in, measure with the spike on your caliper from the edge of the lip to the back of the barrel.  When the two measurements co-inside, that'd be your minimum depth.  For most who want to shoot the 500's etc., it's probably best to go .25" to .375". 

[kc5gxc]

Thanks for the reply, Tacklebury.
Lemme ask you this.....I don't have any 500 grainers. May never shoot any...but would like to set up the rifle just in case.
If I lube up the throater , go in and mark the depth on the shaft of the throater with masking tape and then ream a total depth of .375" according to the tape marks on the shaft....can I get into trouble with too much throat with my 405 grain lead and 300 gain jacketed bullets I shoot mostly ?
Or should I make a dummy round with the 405 grainers and just throat until I can chamber those ?
Thanks for the help
Pete

[Jason F]

I would make up a dummy round at the Max length that you are gonna load it at. Then ream a little and keep chambering round till it fits without resistance. You really should have the bullets you are gonna shoot to throat it to the right depth.

[JimP.]

You mention 500 gr bullets. I cast mine using the SAECO mold 883. This is a double diameter bullet with the portion of the bullet forward from the first drive band smaller than the drive band itself. This allows me to seat this long bullet without having to change the throat. The Lyman 457125 is also a double diameter bullet. if you don't want to cast them, Montana Bullet Works has a great selection of cast bullets to buy/try, that's how I found the SAECO bullet.  Look at their selection of cast bullets, maybe you will find one to suit you and you wont have to change your throat and still shoot the jacketed bullets you like. 

[quickdtoo]

Whatever bullet you choose, just be sure to seat it in the test dummy so it's straight and has no runout, a bullet with runout may interfere with the rifling when chambering making it appear to be against the rifling when in fact it isn't and you ream deeper than needed.  Don't ask how I learned that. 

Tim

[gcrank1]

As not all bullets are profiled the same even though they may be the same weight, the correct way to do this is to be sure which bullet you are actually going to be using.
If the throater improves the leade you may fiind not a detriment to accuracy with the lighter bullets, or possibly an improvement also. My Siamese Mauser 45-70 is throated for at least 500's and shoots satisfactory with the 340 and 405 Lee's using open sights. I have not benched it nor can I scope it, but it sure throws 'em where Im pointed.
I would not do anything on the throat until I had tried some bullets/loads. I would even likely cut some brass back if needed to trial the 500's (or use some of that 'short' Federal?). Some changes cannot be reversed.

[quickdtoo]

What GC said!  The ogive shape of the bullet determines how long a cartridge can be loaded relative to the throat depth, that's the problem with the 405gr Rem and 400gr Speer and even most 350gr, their fat ogive makes a big difference compared to the smaller 300gr bullets. You can see the difference in the comparison below, L to R, 300gr Speer, 300gr Rem, 405gr Rem, 400gr Speer FN, 350gr Speer FN, 350gr Hornady RN and 350gr Hornady FP Interlock. The 350gr Speer would be a likely bigger bullet as it has a better ogive shape.

Tim

[kc5gxc]

Thank you all for the great advice.
Pete