Reloading questions re: grains vs. pressure, .451.

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460_Smith

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I hope I'm not duplicating a thread or posting in the wrong spot here, but I searched the site and didn't find the answers to my questions, so here goes:

I just bought my reloading equipment (had to-I'm mostly interested in Smith and Wesson 460 magnum:$$$). I got the RCBS Rockchucker (I believe the term for the equipment is "single stage"). I looked through the manual that came with it and there's only 3 "recipe's" for this round. Each recipe Lists bullet weight, powder type, and amount of powder, among other things. My concern about bullet selection is that there are limited options available to me right now and I don't know what to expect from using a bullet of different weights in the same diameter if I can't find the one's in the manual. I'm familiar to precision work, but I'm not familiar with the reloading process yet. In short, the biggest question I have is: Can I substitute a bullet of a different grain than the manual specifies and achieve the same results? My concern is that I don't want to use a different bullet than the one's in the manual and find that either the dimensions of the bullet itself or the weight of the bullet are going to create an excessive/dangerous pressure. Does the weight of a bullet significantly change the max operating pressure? Do bullet's of different grains in the same calibre come in different lengths? If so, does that affect pressure?

As a side note, I was at the range the other day and fired a few rounds. The first went off fine, the second had some disturbing results. The case was forced back against the back of the gun and prevented the cylinder from rotating when I tried to #### the hammer. I immediately opened the cylinder and made a visual inspection. After removing the rounds and spent casings, I saw that there was a visible amount of gun oil in the chambers, so I decided to discontinue firing. When I got home, I also noticed a small brass shaving had been sheared from the case and remained in the gun, stuck to the gun behind the cylinder. Does excessive oil in the chambers create an excess pressure in high powered (or any, for that matter) revolvers? Is there something else that might lead to this situation? The ammunition used was a few months old, but was certainly never violently treated in any manner.

Any insight you fellow firearm enthusiasts can offer is greatly appreciated.
 
If all other variables remain constant, an increase in bullet weight increases pressure. That is, same case, same gun, same powder, same powder charge weight, bullet weight increases, pressure increases. As well, differing bullet designs and shapes increase or decrease pressure with the bullet weight remaining constant. Differing bullet shapes and designs change the amount of surface bearing on the throat and rifling. This changes the resistance of the bullet to passage down the bore.

Bullet material or jacket material changes pressures as well. Some jackets engrave more readily, some bullets upset sooner, some materials - especially the monolithic "non-toxic" materials don't swage as readily, thereby boosting pressures. Most bullet manufacturers who put out manuals will list their other bullets of caliber for which you can use that data. For obvious reasons, they choose not to list their competitors' bullets! Powder and tool manufacturers tend to be more generic, and with experience, one can judiciously "interpolate" and "extrapolate" non-maximum loads with some degree of confidence. But if you wanna play with max loads, exact, relaible data, following the "reduce by ten percent and work up" rule is mandatory. (I'm thinking anyone buying a .460 is likely interesting in 'maximum'!
 
Thanks, ykkid. That's a lot of good information. Being new to this stuff (and considering the pressure's I'm going to be operating at), I think I'm going to err on the side of caution here. I guess I'll wait 'til I find exactly what the book calls for instead of trying to find safe substitutes.

And yeah, I bought a 460 because I'm interested in max pressures, along with max everything else. What can I say, some might think I'm compensating for something, but setting that thing off is one heckuva fun kaboom!
 
460_Smith said:
Thanks, ykkid. That's a lot of good information. Being new to this stuff (and considering the pressure's I'm going to be operating at), I think I'm going to err on the side of caution here. I guess I'll wait 'til I find exactly what the book calls for instead of trying to find safe substitutes.
Click to expand...

Actually what was said is VERY condensed. Internal ballistics (what happens inside the gun) is extremely complicated. Why? because it is not linear. Meaning if you change one thing by 10%, then other things DON'T change by 10%.

There are dozens of variables going on at the same time, and some have almost no effect if changed, and some have drastic effects if changed.

There is no "rule of thumb" that can be applied.
 
I would make sure no matter which load you use, to wipe out all excess oil from the cylinder. I'm under the impression that it makes it hard for the casing to grip the chamber wall while firing so it slips back and creates back thrust and pressure where it's not wanted.
 
Buy a loading manual that has info for the 460. Read all the articles at the front of the book. You will find it interesting.

Start with the START Load, and then work up, looking for the load that groups best.
 
So I guess if I were to try to simplify what you guys are saying, would I be right in saying that you think I just plain shouldn't try to substitute one element of a particular cartridge for another under any conditions with my obvious lack of experience? It's looking like there's no simple formula for substituting one bullet of a given weight with one of the same weight but a different design, or one of a specific design and weight with another of the same design in a different weight. I just wanna do everything safe.

Thanks for the replies so far, guys...
 
Buy a copy of the ABC's of Reloading. You're on the right track but obviously need a great deal more info before you proceed further. Having said that, as a generalization, in a revolver, substitutions of different brands and designs of bullets of the same weight doesn't make that much of a difference. The only real caution in this scenario is jacketed vs. lead bullets. Anyway, read the book, there is a wealth of information in it. - dan
 
Not only would the weight of the bullet be a critical difference in your load, the depth of seating is even more critical in a straight wall case like yours. A small increase is seating depth could result in a very large pressure increase.
All of which reiterates the above points, you cannot simply change a major component without some prior knowledge, and hopefully a proven recipe.
 
Not having followed the .460 saga very closely - I tried the hot magmun road years ago and found it too bumpy - I don't know if there are shorter cases compatible with the cylinder, such as the 38/357, 44 spc/44mag, 45colt/454 Casull combinations, but if not, I would advise loading a few hundred rounds using something less than the maximum load shown in manuals. There are numerous little, rather minor insignificant errors of die adjustment, interpretation of manuals, (crimp, for instance, is one of those 'relative' terms) and the like. Insignificant, but if you make two or three wee boo boos in one run, AND you are pushing top loads, things can get sticky. Now, I doubt one could blow up a .460 without really trying, but still, a few practice laps before opening up full throttle is just good sense.

And, yup, SandRoad, what I said first was VERY condensed. I didn't mean to write a loading manual. ABC's, a few real manuals like Hornady's, Lymans', Sierra's to name a few, and a few thousand articles in Reloader, Rifle, Rifleman, and the popular mags can't be condensed into a web post. But he gotta start somewhere.
 
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