I found this article written by John Linebaugh, regarding Ruger Blackhawk/Bisley strength, both cylinder and frame. The below is a small portion of the entire article. He offers a lot of min/max loads as well as his personal favorites. Lots more, too, and well worth the read.
I'm sure excerpts from this site and the link has been posted many times, but such good information from a man of such incredible knowledge on the subject bears re-posting often.
I'll be leaving my Bisley alone, unless for accuracy. There might be room but not enough.
http://www.customsixguns.com/writings/dissolving_the_myth.htmThis material is not about Colt SAA, Dakotas, or any other import. These are fine guns in their own realm, but require safe, carefully assembled handloads of much LESS PRESSURE than we are talking about in the Ruger Revolvers.
AGAIN, ALL THE INFORMATION IN THIS REPORT PERTAINS ONLY TO NEW MODEL RUGER SINGLE ACTION BISLEY OR BLACKHAWK REVOLVERS.
How strong are the Ruger Blackhawk and Bisley model revolvers? Reports from the prestigious H.P White laboratory prove to us that most American Made revolvers offer approximately 100% safety factor with current Industry standard pressure level ammunition. Example: The .44 magnum is loaded to 40,000 CUP (Copper Units of Pressure). H.P White's lab reports states that the Ruger Super Blackhawk was destroyed in a controlled test at approximately double that pressure. (80,000 CUP) The Smith and Wesson Model 29, also in .44 magnum caliber showed comparable results. Today we have stronger guns chambered for the .44 magnum (Redhawk prime example) but the Model 29 S&W and the Ruger Blackhawk gave life to the .44 magnum cartridge. The strength and design of these guns satisfied the industry at the time (1955) and the standards were set from these firearms. By careful measurement and a little simple mathematics we find that the Ruger Blackhawk in .45 Colt caliber is approximately 80 % as strong as the Blackhawk in .44 magnum caliber. Some may argue that the .45 Colts usually are fitted with fluted cylinders while the new .44 Rugers are nearly all unfluted. Exceptions to this rule are Flatop .44 magnum Rugers, THE GUN THAT WAS MADE FIRST BY RUGER FOR THE .44 MAGNUM ROUND. Lately Ruger has produced some special run of guns in .44 Magnum chambering that again have the fluted cylinder feature. Also a few early Bisleys were fitted with FLUTED cylinders in .44 caliber. However most were unfluted roll marked cylinders. But the most important factor we have found here is there is very little difference in strength between a fluted and non-fluted cylinder. The strength of the cylinder can vary more from the quality of the material and the tensile strength of the part due to different points of hardness. When steel is heat treated it can easily vary a couple of points. This is only a few thousand pounds of tensile strength but this is likely to mean more to absolute strength than the difference in the design of the part in the argument between "fluted" or NON-Fluted". The important fact is that the initial part (in this case the cylinder) was OVER ENGINEERED to account for these variables. They are amply strong to safely handle any safe load. To DEFINE SAFE: ANY LOAD THAT DOES NOT EXCEED THE INDUSTRY'S RECOMMENDED MAXIMUM OPERATIONAL PRESSURE.. In the case of the .44 magnum, this is 40,000 CUP. Not to exceed 43,500 ABSOLUTE MAXIMUM.
The Ruger Blackhawks and Bisley models chambered for .45 Colt are approximately 80% as strong as the same Ruger chambered for .44 magnum. This means we can load the .45 Colt to 80% of the pressure of the .44 Magnum round and still maintain the 100% safety level. 80% of 40,000 is 32,000.
To check our findings we again turned to H.P White Labs and their findings paralleled ours. Ruger Blackhawks in .45 Colt caliber were destroyed in controlled test conditions at approximately 60,000 CUP pressure levels.
We went further on our own here and purposely destroyed several cylinders with loads that were later pressure tested in Industry Standard Pressure barrels that proved pressures were in the area of 60,000 CUP. Now that we know just how strong the guns are we are working with perhaps you figure you can heat up the a loads a bit. Such "logical thinking" jaspers will get a REAL LOAD. Overloading often times does no visible harm, but stress and fatigue go unnoticed till something lets go. In this era when shooters and hunters are looked over very critically we need safe responsible hunters, shooters and HANDLOADERS. THIS MEANS YOU!
FRAME STRENGTH
Here at Linebaugh Custom Sixguns we build some of the most powerful handguns in the world. All of our guns at this time are built exclusively on the Ruger Blackhawk frames. (Ruger Super Blackhawk, Blackhawk and Bisley models are all identical. All frames in the new model that was introduced in 1973 are the same.) In all of my findings the first part to let go in a revolver is the cylinder. I have tested cylinders from purposely bulging them to total destruction. In all cases the frames were not damaged until the cylinder totally failed. When a firearm is fired there is pressure on the base of the bullet to propel it out the barrel. There is an equal rearward thrust against the case head and thus transferred onto the action of the firearm. This is known as CASE HEAD THRUST. Case head thrust is CHAMBER PRESSURE x THE SURFACE AREA OF THE DIAMETER OF THE REAR OF THE CHAMBER. I won't go into great detail but a 45 Colt at 32,000 CUP chamber pressure exerts just under 3 tons of pressure on the back of the frame. A .44 magnum at 40,000 CUP chamber pressure exerts just over 3 tons of pressure on the back of the frame. Basically the same.
When we fire one of our .475 or .500 caliber revolvers we hit the Ruger frame with approximately 5 tons of pressure, (thrust). This duplicates the thrust of a .458 Win Mag. In testing and building over 200 major caliber revolvers on Ruger frames we have never yet had a frame move,stretch or bend. They are very tough. The cylinder is the first part to let go.
