As any one who has played PG knows there are always those times when one can only muster say 29 combat value for a Direct Fire shot which rounds down to 22 being just 1 lousy point from 30. I have found a simple way to address this effect by using a die roll to interpolate between the listed combat values in the various fire effect charts.
The way it works is if the total is equal to a listed value then treat as usual. But if it falls between two listed values, say it is 25 then take the difference between the listed value that is higher from the one that is lower (e..g for 25 on the direct fire table that would be 30 - 22 = 8) and roll a die with that difference (e.g. in the case one would roll an 8 sided die) and add that value to the regular dice roll the treat that new total as normal (i.e round down). Thus say one rolled in the above example a 4 on the 8 sided die then the new total would be 25 + 4 = 29 which rounds down to 22. But if one rolled say a 6 on the 8 sided die then the total would be 25 + 6 = 31 which rounds down to 30.
If the n sided die used to get the interpolation additive value starts with zero then use the numbers printed on that die. If it starts with 1 then treat the highest number (e.g. 8 for an 8 sided die) as 0.
Thus is say one has an original total of 23 the only way to get it to bump one up to 30 (for direct fire) is to roll a 7 on the 8 sided die. But if one has a original total of 29 any roll but 8 (which is to be treated as 0) would bump one up to 30. So it always pays statistically to add a point or two to the original total using this method vs the standard method. This method works for Direct Fire, Bombing fire, Assault fire fire, but is not applicable to AT fire.
This method does require one to buy a number of n sided die. For example a have a collection n sided die that include 2, 3, 4 , 5 , 7 sided, 8, 9, 10, 11, 12, 13, and 15 sided . But say if one does not want to buy that many special n sided die one can use a larger one as a substitute for a smaller. For example one can use a 6 sided die for a 5 sided and just reroll whenever one rolls a 6 (and a five roll would be treated as a 0 as per the above rule). But I have found doing that adds mental calculations and it is much simpler to buy the full set of n sided die.
Even though one has to roll more die I find this to be pretty easy to use and eliminates that other problem (that seems pretty gamey) of having to get those extra points to make that 29 total go over the top to 30. It does make the game slightly more lethal in that on the average one will have more shots that bump up. One could address that by coming up with a method that would round both up and down. But that would add more complexity, and who wants to make the game less lethal anyway.
But it helps both sides so I don't think it would affect play balance too much other than having a 18 OB vs 17 OB artillery factor would benefit the 18 where with the normal method bot would round down to 16 and thus tend to be a wash (unless added with other arty shooters). So it could have some small effect on balance, but that might be good in that it better rewards the side with that higher factors (e.g. an 18 should be better than a 17 vs both rounding down to 16).
At nay rate I have enjoyed using this method to interpolate dice rolls and thought I would share it here in case anyone else might find this interesting or possibly enjoy it likewise..might enjoy using it themselves.
BTW, here are some sites where one can buy n sided die (and there are more ) so they are pretty easy and affordable to buy.
http://thedicelab.com/d120.html
http://www.ebay.com/itm/Purple-7-Sided-D...1290182330
https://mathartfun.com/d357.html
One more note. Once one adds the interpolation die roll and gets the adjusted combat value (rounded down to the listed values on the CRTs) the one adds shifts as normal. And the +3 and -2 limit for shits does not apply to the interpolation in that it is not a shift but is an adjusted roll. So if one bumps a 17 to a 21 by rolling say a 4 on the 5 sided die for a direct fire shot that is not treated a a shift from 16 to 21 but simply that one rounded up to 21 rather than rounded down to 16 by adding the interpolation die roll value and the rounded down to to the nearest listed value. Thus one could still get a +3 shift in this case. That way small round ups , e.g. a 29 to a 30 do not prevent one from getting a further +3 shift.