Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!aplcen!boingo.med.jhu.edu!haven.umd.edu!mimsy!uunet.UU.NET From: bcstec!iftccu!bressler@uunet.UU.NET (Rick Bressler) Newsgroups: rec.guns Subject: Re: Reloading questions: 40 S&W and 45 ACP Message-ID: <35647@mimsy.umd.edu> Date: 14 Jun 91 20:05:23 GMT Sender: magnum@mimsy.umd.edu Organization: Boeing Commercial Airplane Group Lines: 78 Approved: gun-control@cs.umd.edu James D. Del Vecchio writes: # I have this issue and last of Handgun Quarterly/ Shooting Times. # # A few items: # # Per mag maximum chamber pressure is about 35,700 cup for 38 super, 40 S&W, # and 10mm Auto, vs about 19,900 max for 45 ACP. # # Why is this and what significance of it? Are the 45 cases weaker for some # reason, or is it the construction of the pistols? Is it possible to make # a 45 withstand the higher pressures? Thicker cases maybe? While I'm not positive, (I haven't examined anything but the .45 action in this list) I suspect that the cases of these newer rounds are fully supported by the actions, while the .45 is NOT. This translates into part of the case not being reinforced by the action and is therefore unable to take the pressures that a fully supported case can. I think the problem is similar to that of the .44 special. The .44 special can be loaded nearly to Magnum velocities. However, this round was designed in the late 1800's and there are still many non-magnum guns out there. Therefore, the ammunition manufacturers have to load the .44 special to the least common denominator. The eventual solution to this problem was the creation of the .44 magnum. The case was made a tiny bit longer so that it wouldn't fit into the older .44 special guns. It was then loaded up to magnum pressures. If you have a NEW .44 special (there aren't many made any more) or a .44 magnum, you have great flexibility on how you load the .44 special case. The .45 ACP is also an 'old' round. The original designs for this gun didn't fully support the case, so all ammunition has to be loaded to these specifications. I have a friend with a semi auto Uzi in .45. This particular action fully supports the case, and he has slowly been working up to much higher pressure loads. So far, he is approximately 50% or more over a 'standard' .45 load with none of the classic signs of high pressure. Don't remember his exact chronograph readings, but these loads are really zipping along. He figures (I don't know how) that his loads are approaching 28-30,000 cup. As the usual, the disclaimer 'don't try this at home' applies!!!! # # I've been told the 38 super and 10mm are both louder than the 45, is this # entirely due to the higher muzzle pressure? In general, higher pressure loads will have more muzzle blast, all other things being equal. (Barrel length etc). # # Is the .40 also louder than the .45, say with the subsonic loads? Can't say on this one. # # According to their charts you can get more velocity using the same powder # charges and bullet weights in a 4" 40 S&W than you can with a 5" 45. # Why would this gun be more efficient? As you said, these loadings yield higher pressure in the .40. In general, higher pressure = higher velocity. (Sorry if I'm stating the obvious). The reasons that you get higher pressure from the same load are many. It depends on how much empty space there is in the case, bore diameter, bullet weight, powder burning rates and a whole bunch of other things. In this case, remember that while the bullet weight is the same, the diameter is smaller by a fair margin, and the case capacities are quite different. These are probably the primary differences. Also, powders can burn quite differently under different conditions. There are whole books written on the subject. That's why most of us hand loaders rely on others to work up new loads! It doesn't pay to try guess about what any particular new load might do. Even the very experienced tend to leave this to the 'experts'. # # Jim Del Vecchio # ---------- Rick.