Does anyone have details on forming 8x52R (T66) to a Siamese Mauser. The 45/70 case is too large across the rim; is there another base case that could be used.

I would think that general information on other calibres could be aired here also.

Years ago Geo. Nonte wrote a book on cartridge conversions. There's a lot of stuff in that book and it should be available from a used book source.

From what little experience I have, rim modifications are not all that unusual, nor are they particularly difficult.

From Nonte:

.45-70. Trim to 2.04"; turn rim to .560" dia; run all the way in .33 Winchester die; reduce neck and set shoulder back in Lyman 8mm neck die till bolt closes; fire form. Use .323" bullets.

The following is from John Donnelly's manual of cartridge conversions:

\Designed for Siamese Mil. T66 bolt rifle.
180 fr. spire 40.o Gr. IMR 4320 @2000 Ft/sec.

Make from 45.70 Gov.
Anneal case and run in F/L .40.65 WCF and .33 WCF dies {a form set will do the same job}. Turn rim to .556 dia. and back chamfer. F/L size in 8x52R die. Case may {usually} need I.D. neck reaming. F/L size again.

Case length 2.02 in. Loaded 2.95
Head Diam. .500 Belt n/a
Neck Diam. .347 Rim Thickness .065
Rim Diam. .556 Shoulder Diam .426
Neck Length .297 Length to Shoulder 1.63
Shoulder Length .093 Primer LR
Shoulder Angle Deg. 23.01 Body angle 1.48
Case capacity (cc's) 3.81 Case Capacity (GR) 58.80

Good Luck

Thanks for the info.
I have one of these rifles in mint condition and would like to shoot it in original calibre. From what I can gather this short stubbie case should be a good cast bullet cartridge.