Converting .45/70 to .45-60 cartridges

[Grapeshot]

This is for those Pards that have gotten or are getting the Chaparral 1876 Winchester in .45-60 WCF.

First, if you are modifying .45/70 cases, you have to shorten your .45-70 cases from 2.10 inches to 1.88 inches.  I used a Lyman case trimmer with a .45 Caliber pilot and a dial caliper to shorten one case to 1.88 inch.

I had a .45 Colt case trimming die that is used by using an RCBS press, a hacksaw and fine cut file.  Lubricating the shortened .45-70 case, I ran it into this trim die until it was flush with the top.  I then gave it a couple of passes with the file to true up the mouth.

Once that was done, I made sure that the die's locking nut was tightened down so it would not move.

The rest of the 89 cases I lubed and ran into the trim die until they protruded through the top of the die.  I then used the hacksaw to cut off the excess and the file to true up the mouth.

After I had all the cases I wanted, I champhered the case mouths.

At this point in time, the cases are a bit bottlenecked in shape.  I then ran them up through a .45/70 Sizing Die.  Then through a .45/70 case mouth belling die to set them up for a .458 bullet.

After seating Remington Large Rifle Magnum Primers, I loaded the cases with a variety of .458 bullets and a 50-grain by volume Hogdon 777.  An NEI 390 grain Gas Checked Model, a Rapine 405 grain Hollow Based bullet and a Lee 405 grain RNFP were used to fire form the cases.  To crimp them I first ran them SLOWLY up a .45 Colt Taper Crimp die.

Knowing that I was going to have to have a real crimping die and a sizing die for the .45/60 I CALLED Lee Precision using their contact number from their web site.  They had the dies on hand and I ordered a sizing die and a seating/crimping die.

This did not prove to be a practical solution, as the crimp die would not crimp.  I may have trimmed the cases to short, or their die was not as precise as they claim.  Anyway, I had a Lee .45-70 factory crimp die that I was not using, so I filed the sliding collet shorter, trying to crimp every few strokes until it would crimp the cases as slick as a whistle.

After firing the rifle with my modified cases, I reloaded with the same style bullets and new magnum rifle primers, but reduced the powder charge to 40 grains, by volume, of 777, and used the new sizing die and seating die and the modified FCD.  I took it to the range again and had a blast as I made an old frying pan dance at 100 yards with those heavy bullets.

I've reloaded a batch using some smokeless loads and some Hornady 350 grain JSP's and some Montana Swaged 300 grain RNFP's in .458 diameter.  I hope to check them out by the end of next month, if the weather cooperates around the Midatlantic eastern states.

I checked the rifling and it is faster than the originals.  It came out to 1:22 inches.

[Tommy tornado]

I was curious what to trim it back to.  My Jaimison Brass measures about 1.81 and worked fine.  I am trimming mine to about the same but haven't loaded any yet.  With a hand cranked trimmer it sure takes a while to widdle down the cases.

[Sir Charles deMouton-Black]

Use the tiny tubing cutter from your hardware store to rough-cut, then trim.  Thats how I shorten .45LC to .455 Webley.  Also use it on .348's converted to .45-75

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[quigleysharps4570]

I've been using a RCBS power case trimmer and the little power case prep machine.
Takes about 2 minutes per case...including chamfering inside and out.
Works real slick. 

[ART C GUNN]

I also had to thin the thickness of my rims when I trimmed my 45-70's down to fit my Uberti. I had a tight action which wouldn't close unless I trimmed them down. Intersting enough.my buddy who has the same rifle had no problem with his rims.

[john boy]

Gents, if you are in the business of resizing cases to shoot in your '76 ... I've found this makes the job real easy:

Forster Power Case Trimmer

Having used the Forster for a couple of years to fine tune my rifle cases - I really have come to appreciate it for zipping down the 348's to 45-75 case length.

[Snapshot]

I have measured and thought and then thinking some more. Then I have experimented with some brass and some bullets.
I have come to the temporary conclusion that the brass for my Chappy have to be 1,83".
It might be longer but then the crimp have to be in front of the crimpgrove on the bullets?
They look realy nice, but I have yet to try them out. Will try them on Thuesday.
Loaded a few with 43grns. of Vithavouri N135 and the 350grns bullet.
It is not easy to get all the powder that yaàll recomend in my neck of the woods! (Norway)
The Finland powder will have to do!
Got the RCBS 45-60 die set, and it is promising!