The small base dies see increasingly common use because of all the AR shooters buying surplus once-fired military brass that a full auto weapon has left too big to be resized small enough to feed reliably into a tighter chamber. If the brass was fired new in your gun, though, a standard sizing die will usually work without paying for the narrower diameter of the SB die (which also works the brass more, shortening case life). If it came out of your gun, length should be the only issue, and there are a couple of tricks you can use to shorten it.
One that I've used when the cases were very close is simply to run the case into the sizing die and count to five, back it out, rotate it 180° and run it back in for another count of five. I can sometimes see up to two thousandths additional shortening from doing that.
The other is board member F. Guffey's favorite trick, and that is, after the case has been deprimed, removing the decapping pin from the sizing die and sliding an automotive feeler gauge between the case head and the shell holder, then running it up into the sizing die. There is generally room in a standard shell holder to get quite a bit of additional sizing that way, though, again, a few thousandths are usually plenty. I've done up to five thousandths trying that method out.
I suppose there is a clever way to drill a clean hole in a feeler gauge so you can decap through one, but other than abrasives and carbide end cutting end mills, I don't know what it is.
I never knew this about the Garand. I have shot thousands of military surplus rounds through mine without a hitch. Also shot a lot of factory ammo too, Without a problem. Have look into this more. Where did you get info? Thanks Steve
There are two issues. First, and foremost, it's about protecting the operating rods. They are increasingly scarce, which is why match rules now allow NM op-rods in guns for as-issued matches. The Garand was designed to shoot ammo loaded with medium speed powders like IMR4895. H380 is about as slow as you want to go. Military ammo is loaded within a pressure envelope safe for the Garand, so that's not a problem, but many commercial loads use slower powders to squeeze more velocity out of a bullet for the peak pressure generated. When you fire one of these you get higher port pressure, and this can batter and actually bend an op-rod. If that happens, you have to find a replacement. Hornady's load manual addresses this by now having a whole separate second section of .30-06 loads just for the Garand. They are pretty mild, but if your op-rod has some mileage on it, they are a good place to start.
The Garand's action itself is plenty strong. If you need to fire those slow powder loads in your Garand, go to Brownells and buy a vented gas cylinder plug. These replace the plug you have, but bleed off a portion of the pressure in the gas cylinder. They are either adjustable or come with a series of different size vents in screws that you can swap into it. The neat thing is, you can adjust them to bleed enough gas that the gun no longer throws the brass a mile away, but drops it close enough to find. The downsides are you may need to adjust them
The second issue is out-of-battery slamfires. Most commercial ammo won't cause you a problem because this kind of slamfire is usually due to high primers, which are rare in commercial ammo. However, more recently there have been some reports of out-of-battery slamfires that occurred just because the primer used is more sensitive than a military primer. An incident of an out-of-battery slamfire using Federal White box ammo was reported, for example (I don't have a link at hand, but can find one if you want it). Winchester has made their primers more sensitive, too, in recent years, so avoiding those two brands in the Garand may be advisable.
I used Federal 210M for a long time in both the Garand and M1A with no problem before I learned of this issue, but have now changed to the CCI #34's. They offer some added insurance, as they are made to military sensitivity (hardness) specifications, and the military has fired many millions of rounds of their ammo in these guns without out-of-battery slamfires being a major issue. But getting the primers below flush with the case head is still the most critical thing to do with any primer.
I'd like to think the high primers are the only slamfire issue if the gun is in good shape and if the case is properly resized to fit in a Wilson case gauge at inspection. Unfortunately, once an out-of-battery slamfire occurs, there is enough metal damage that you can't be sure of being able to learn what the tolerances were when the incident occurred.
You can find more about these issues at the ODCMP forum