Too much HEAD! ;)

Im a rather expereinced brewer and have come accross an issue with one of my batches. About one out of every four or five beers seems to be way over carbonated. The beer tastes a little bit off too. Im not sure if that just because of the CO2 volume being so out of whack or if its something else. I have never had this issue before and my procedures were the exact same as always. Has anyone had this issue before? I find it weird that it happens only with some bottles and not all of them. How do further my investigation? Has anyone here resolved such an issue before? I really want to pu this beer in a competition but I dont want to blow anyones head off. There have been no bottle bombs. I throw the beer in the fridge one six pack at a time....

thanks for the help

from your write up I am assuming you bottle condition with a referment in the bottle.

I use 4 ounces corn sugar per 5 gallons when I bottle.
What did you use? Is there a glitch with your scales?
Those are the obvious questions.

Another question would be all about how much starch you had when you ended your mash.
Did you do a starch test?
If not and you re-fermented ANd pitched a different yeast for the bottling you might have got a yeast that can eat the starches.

Another version of new yeast is that some yeasts don't consume some of the malt based sugars very well and refermenting with a different one can get it going again. So even if you used a proper volume of sugar when you bottled you might have more sugar available that you were not aware of.

I'm out of gas, that's all I can think of.

In addition to Cliff's questions:

Do you add boiled sugar water to bottling bucket and rack on top to mix well? Or do you individually prime each bottle? (you want the same amount of sugar, exactly, in each bottle)

When bottling, are you filling to the brim of each bottle, then removing the wand so that there is the same amount of headspace in each bottle? (the amount of headspace in a bottle affects level of carbonation...)

Slightly off flavor + overcarbonation screams "infection"....if you have a mild infection in some bottles, that will produce extra CO2 and cause the "gushers" you seem to be referring to...maybe you just didn't quite sanitize well enough?

I use a little under a cup of corn sugar to prime; boil it, cool then rack beer on top of it. I have never done a starch test because I always mash for over 60 minutes. Each bottle has the same amount of beer because I am very careful when I fill them. The most likely scenario is in fact infections in the bottles....damnit! first time for everything I guess