reelfisher10, sorry if I misunderstood your initial question, I thought you were thinking of re-loading with steel shot. Your question seems to be: Why do 12 ga 3-1/2" shells seem to be more powerful than than the 10 ga (3-1/2") loads? You've observed that with similar maximum loads, the 12s are at a higher velocity. An interesting observation and question.
By outward appearance, the average shooter will assume the larger diameter 10 ga is obviously more powerful that the smaller 3-1/2" 12 ga. But, what is meant by
powerful? Obviously, the easiest way to make a comparison is using the muzzle energy of the maximum load from each shell. Given the same load weight, the faster one will have a greater muzzle energy and thus is more
powerful.
[SIZE=-1]I have looked at the heaviest 12 gauge manufactured and it was 2 3/8 oz at 1210 fps. And the heaviest 10 gauge was 2 1/4 oz at 1210 fps. I am not understanding how the 10 gauge is more POWERFUL. So I assume by manufactured shells the 12 gauge is more powerful but for whatever reason if you wanted to you could SAFELY make the 10 gauge more powerful through reloading?[/SIZE]
It all has to do with the allowable pressures. The 12 ga 3-1/2" Super-mag is a much newer shell than the 10 ga. So, the newer guns chambered for the new shell are capable of higher working pressures than old 10 ga guns. Typically the bigger the bore, the lower the alllowable working pressure of a shotgun -- the new 12 ga 3-1/2" is an exception.
Here are the SAAMI specs for Shotshell Maximum Average Pressure (MAP) in PSI.
[SIZE=-1]10 gauge 11,000
12 gauge 11,500 (except 3-1/2")
12 gauge 3-1/2" 14,000
16 gauge 11,500
20 gauge 12,000
28 gauge 12,500
.410 bore 2-1/2" 12,500
.410 bore 3" 13,500[/SIZE]
The loads you'll find in reloading manuals take the MAP specs as Gospel. Since the 12 ga 3-1/2" Super-mag can be safely loaded (or re-loaded) to higher pressures than the 10 ga, it's quite understandable that it can accommodate more powerful loads. (It's a similar situation with the new compact 7mm mag rifle cartridges being more powerful than the larger, but ancient, 7mm Mauser -- the newer rounds are safely loaded to much higher pressures.)
Back to your specific questions:
[SIZE=-1]So if it says 1 1/4 oz shot that just simply means that the weight of the shot (pellets) weighs 1 1/4 ounces?[/SIZE]
Exactly. But, for "equal" loads you have to be talking of an ounce of lead to an ounce of lead. Once the load clears the muzzle, lead, steel, and the non-toxics will behave differently.
[SIZE=-1]Do they both have the same amount of powder?[/SIZE]
Not necessarily. Different powders release there energy at different rates. For
Steel Powder, in some loads, the 12 ga takes more powder than a similar 10 ga load. With
Blue Dot, it may be the opposite.
[SIZE=-1]If you were to reload these shells how would they be different?[/SIZE]
It's basically the same process. Since the 10 ga are a little larger in diameter they may be easier to handle and go a little faster. However, popular high-volume re-loaders like the MEC 9000 and Grabber are not available in 10 ga.
As you intimated, don't base you selection by "power" alone. How the gun fits, handles and performs on the patterning board are important factors to be considered. Shooting 12 ga 3-1/2" Super-mag high pressure loads is an experience many choose to avoid.
[SIZE=-1]I hope this answers your questions satisfactorily.[/SIZE]
