Cimarron (Uberti) 45 Colt Open Top

[beefan]

I recently, and unexpectedly, acquired a Cimarron Open Top 45 Colt revolver. It's in great shape and I'm eager to shoot it. Factory ammunition is scarce and expensive; but I discovered a die set from long ago on the shelf, and I have some used cases on the way.

I know that 45 ACP bullets will work and I have a supply of them. It would seem appropriate to load some 255 gr. RNFP bullets for this piece and this raised the question of proper diameter. Do any of you guys have know if the bore diameter is .454 (like older Colts, Rugers, etc.) or .452?

If any of you have a few of your stash to share, I'll happily compensate you and pay the shipping.

Thanks

[Soundguy]

I recently, and unexpectedly, acquired a Cimarron Open Top 45 Colt revolver. It's in great shape and I'm eager to shoot it. Factory ammunition is scarce and expensive; but I discovered a die set from long ago on the shelf, and I have some used cases on the way.

I know that 45 ACP bullets will work and I have a supply of them. It would seem appropriate to load some 255 gr. RNFP bullets for this piece and this raised the question of proper diameter. Do any of you guys have know if the bore diameter is .454 (like older Colts, Rugers, etc.) or .452?

If any of you have a few of your stash to share, I'll happily compensate you and pay the shipping.

Thanks

.452

For those open top I like light bullets.. Like 160gr lrn over tightgroup. Fun to shoot.

[jaguarxk120]

Generally you want the bullet diameter to match the cylinder throat.
I have found 8-9 grains of Unique to work best.
If you are into 45's, get a copy of John Taffins book of the 45.

[DougGuy]

I for one would not use full power 45 Colt loads in an open top revolver. Lighter boolits and much smaller powder charges. YMMV.

[rintinglen]

I would load a boolit not >200 grains and run it light. My conversion 1860's gets either 457-401 195 grainers or 452-389 190-ish boolits over 6.0 grains of Red Dot or Bullseye in the long Colt cases. I reduce the charges by 1.0 grains in the shorter S&W Schofield cases. All of these loads run~700 to 750 fps from an 8" barrel.
291637291638

[almar]

I have many percussion revolvers from uberti and pieta and one SAA from pietta (cimarron version). I slugged every bore and reamed the cylinders to +0.002. The pietas I own all have 0.450 bore and the uberties have a 0.454 bore. Slug your bore to know for sure.

[scattershot]

When in doubt,just use the .454.

[smithnframe]

Slug the barrel!

[Piedmont]

Wouldn't these also have the sights regulated for 250 grain factory loads? It seems to me the light bullet approach might cause problems.

[Soundguy]

When in doubt,just use the .454.

Cyl mouth will be the determining factor

[rintinglen]

Wouldn't these also have the sights regulated for 250 grain factory loads? It seems to me the light bullet approach might cause problems.

They were originally set up to shoot high at close range and "on" at about 100 paces, but a lighter boolit should shoot lower, making it more useful at close ranges. Now, depending on what your gun has for sights, it may or may not be an issue.

[beefan]

Thanks all. I certainly see the need for low, or modest pressures in the Open Top. I have some cast RN 200 gr. bullets, and several of the Berry copper coated 185 gr. hollow base round nose-all intended, of course, for my 1911's. Anyone see a problem with them in the Open Top? I was hoping to acquire and load a few of the 250-255 lead RNFP, in a mild load, for nostalgia, or period correctness.

I appreciate the sound, reasoned responses-just what I've come to expect from this forum.

[Baltimoreed]

Try your .452s and see how they do. Don’t know if I like the looong bbl though.

[Walks]

Lee #452-230-TC over 5.0grs Clays worked very well in My Friends Open Top. We tried unsized & pan lubed at .453 and std sizing & lubing in a Lubisizer at .452, both worked well, bbl dia was .454

[Tar Heel]

291673

[jaguarxk120]

If you have read the owners manual, it states any 45 Colt loading meeting SAAMI guide lines is OK in the
open top.
That is "standard" 45 Colt loads, SAAMI service pressure is 14,000psi with a 255 grain bullet.

If it was me I would stick to the lighter loadings, and you might want to try Trailboss powder if you have any.

[Good Cheer]

How are the chamber tolerances on the open tops?
Close on the diameters? No bulges?

[Soundguy]

None of mine are bulged...

[45 Dragoon]

Beefan, first of all, your open top revolver is perfectly fine with factory loads. The open top design is more than capable of handling these loads. Before you do a lot of shooting, I would take care of the short arbor situation. All copies of open top platform revolvers have short arbors (except Pietta's of the last decade or so) and it is a fairly easy DIY fix. Once done, you will have a revolver that can hold its own with any modern made .45C revolver with a Colt action. Don't fall prey to the "open top is a weak design" crowd. It's in fact a very robust design when done correctly.

Mike

PS. I've never shot anything lighter than a 250 gr. (usually 255 gr.) lead bullet or under 900 fps (unless it was a new box of factory loads to acquire new brass) in my open top revolvers. They are all 45C cal.