Dan, boat tails are a "can of worms."
#1). If you want this in great detail you will need to find a university grade physicist. Basically, as I get it, as the bullet passes thru the fluid, air, it makes a hole. Then the fluid/air collapses behind it. As long as the bullet is above the speed of sound, approx. 1100 fps, there is a vacuum behind the bullet and the bullet is not effected by the collapse. In theory, the vacuum is dragging the base of the bullet "back..." !!
When the velocity falls below 1100 fps, then the collapsing air "drags" on the base of the bullet and any imperfections such as jacket displaced by rifling and may effect accuracy...
So the first question, when does your bullet reach the velocity of 1100 fps and below. Is it within the range you will be using the "system" (gun and ammo) and be effected. Hornady ammo with 75 grain bullets at 500 yards is still going 1750 fps per company claims... You shoot that far?
#2). Mr. Corbin, Dave (swage.com or corbins.com or
) has his book "Rediscover Swaging #" on his web site for reading, download, etc. He expresses the opinion that with calibers as small as .22 and .24 the boat tail has no appreciable effect. Wasted effort/money for civilian uses.
#3). The reduced size base does make it easier to get the bullet started in the mouth of a resized case. There was a time that boat tails were more costly. Worth it? Your call.
#4). There is an on going discussion of the effects of the "funnel shape" (reverse funnel???) of the bullet base and the insides of the barrel. If the jacket does not obdurate perfectly and seal the bore, then the funnel helps the hot gases find this avenue of leakage and escape accelerating barrel wear. Not of the greatest concern to the civilian shooter but a "big deal" to military use where full auto's spit out hundreds per minute...
Thus the concept of "rebated boat tail." The reduced size of the base causes the fluid flow over the bullet to be directed in the streamline shape. At the same time the "squared off base allows for more uniform distribution of gas pressure to push on the base of the bullet. (And, allegedly, reduced barrel wear... again, not of greatest concern to civilians.)
#5). THEN comes GENEVA. The nicer part of this argument is that the soldier on the battle field is not necessarily a "bad person." Therefore it is not "fair" to shoot this person with an expanding bullet much more sure to cause immediate death. It is more "fair" to use a FMJ that only wounds. The less nice reality is that a soldier shot with a soft point/hollow point and dies quickly, well, no further concern need be expended until graves registration picks up the remains. At the same time, a soldier that is "wounded" and needs attention will absorb the time of 4 or 6 or more attendants.
War is basically attrition. One side wears down the other side until they can fight no more. Making them take care of lots of wounded helps use up their resources...
Point: the boat tails used by the military are FMJ but designed to wobble/tumble upon striking flesh and cause a greater wound and still comply with Geneva rules... The stories are legion. The British .303 loaded with a bullet that has an aluminum plug in the tip (or wood)... you can find samples. Many 55 grain bullets, flat based have been fired successfully thru a 1 in 14 twist. Military wanted this "tumble" and 1 in 14 wasn't quite enough so they went 1 in 12 at first for the longer boat tailed bullets...
Of course we have better barrel steel today and no one likes to remember that the faster twists wear more quickly.
So, if you are going to put on a uniform and go play war, you will be issued a marginal boat tailed bullet that should enhance wounding and remain within the Geneva rules. Otherwise, you do as all civies do, you take what you can find, powder, case, primer, powder, and see how well you system (gun) likes it and how well you can use it... LUCK.
