Barrel length has no affect on pressures. Maximum pressures in 38 Spl will run about 17,000 PSI, +P is in the area of 18,500, and .357 Mag is around 35,000 PSI. Actual pressures will be less to some extent. If your gun is chambered for .357 magnum, go ahead and shoot them without worry.
Well, first off enough dry firing can do the same thing to any revolver. Years back (5 decades), .357 magnum was regularly loaded to maximum pressures as it was commonly chambered in large framed guns. With the advent of medium framed .357 magnums, these loads did cause rapid wear of the gun. With the common use of these lighter framed guns by police departments, the ammunition manufacturers began to load .357 mag ammo at lower pressures. This is where we stand today in ammo choices except for rare exceptions such as Buffalo Bore,and some huning loads by Federal, Remngton, and Winchester. Regular use of commonly available .357 mag ammo will cause more rapid wear than .38 Spls but not enough to matter in your gun.
"Full powered" loads do have a difference in energy levels but that is not what you asked. Higher pressures within the same cartridge and bullet weight can lead to higher velocities which would give the cartridge more energy or "power". This is not a cast in stone rule, depending on powder and bullet type you can end up with a load that has high pressures and lower velocities than other loads with the same bullet. "Power" is dependent on projectile weight and velocity, not PSI though PSI may be a factor in velocity.
I think the questions you meant to ask would have been, "Would shooting .357 magnum ammunition cause undue wear in my Ruger Security Six?" and "What velocities can I expect from the various loads in my gun?" The answer to the first has been answered and the last varies depending on bullet weight, type, and use and can be found in the catalogs of the various ammo manufacturers, most of whch are online. Look for those that use a vented 4" test barrel, that info should be found somewhere on the same line as the velocity and energy listings.
Well I'm a little scared to ask this now, but how much would it take to make my Ruger go out of time or loosen up?
The ammo I use is 130 grain FMJ rounds and I've put about 150 of them through it. The gun's about as old as I am and I got it used at a gunshow. How many of those rounds would it take to make it start defecting or in need of gunsmithing attention?
If these are .38 spls, likely you will pass away or the barrel will wear out before the loads cause timing issues. If you are shooting .357 magnum, figure it will last half as long. High pressures are generally exposed by frame stretching and is seldom seen today with normal loads. The previously mentioned ammo are the exceptions. You are more likely to have general wear and tear breakages from normal use and dry firing leading to various problems long before those due to ammo. In fact, if you repeatedly snap the cylinder closed like on TV, you will do more harm to the gun than nearly any amount of shooting. I have a S&W 66 from the mid-1960s that is still original except for main spring and firing pin. It has had many 10's of thousands of rounds put through it and shows no sign of major problems. Your Ruger is very comparable in quality. Just shoot it, if you are like most of us you will sell or trade the gun off long before any problems crop up.
Yeah they're .38s, much more cost effective for practice. At 100 for $20 it beats 50 for $30 for a box of .357s.
Well then it sounds like my gun will be something I can pass down to my children if I take care of it. It doesn't see constant use so it'll be around for a long, long time from the sound of it.
Funny you mention the 66. During the first day of the gun show I wanted to get it, but I decided to wait until the second day to think it over and decided that it was the one I wanted, but when I went back it was sold. However the Security Six was still there and for the same price, so that's how I wound up with it. I haven't really regretted missing the 66, Rugers don't get enough attention from what I've seen.
If you're shooting a lot of .38 Spl ammo in a .357, you need to pay special attention to scrubbing the cylinder after each shooting session.
The .38 Spl case is about 0.10 inch shorter than the .357. After shooting, there will be a slight buildup of soot, powder residue, and priming residue at the case mouth. If it is not cleaned regularly, it will build up and "set up", making it impossible to chamber a .357.