Inconsistent carbonation: what gives?

OK, so three bottled brews into this obsession and everything has turned out well except for carbonation.

The first brew, an SW1 clone, seemed to have the right amount of carbing for an English bitter. That is, on the low side. No. 2, a Blind Faith clone, seems overcarbed. I've been losing about 1/8 of the bottle to foam, but no true gushers. At first I thought infection but every bottle has been basically the same and there hasn't been any sign of infection. No. 3, a summer ale similar to Sam Summer, finally got a decent level of carbonation four weeks after being bottled.

My bottling approach has been the same throughout. I use DME for priming sugar. I'm wondering if the level of carbonation changes based on the recipe. Is there a better alternative to DME that an extreme n00b can pursue?

What exactly is your bottling procedure?

Are you boiling the DME with a bit of water, cooling that down and then pouring that in the bottom of your bottling bucket and then racking on top of that? That's the best way to get consistent carbonation. Racking on top of the priming sugar will get things fairly well mixed up, but you still will want to gently stir periodically while you're bottling.

Also, what type of bottles are you using? If you're using swing tops, you might have some gaskets that aren't sealing as well.

Give us a bit more information on your bottling procedure and we might be able to help you determine what's causing the inconsistencies.

I'm boiling 1 1/4 cups DME in two cups of water, cooling and racking on top of that into bottling bucket. Gently stir occasionally during bottling. No swing-top bottles or twist-offs. Using a wing capper.

Might be that my capper is bad. Not the actual capper, but the person wielding it. First two batches, it was my wife. Third batch it was my buddy, who has since started brewing. I might have to smack him.

Sounds like you got it right on your 1st and 3rd batches. The second batch may not have been quite done fermenting when you bottled it, leading to higher than expected carbonation. Did you use the same brand/lot of DME for each batch? Sometimes DME can take longer to carb up than dextrose. I always use dextrose. I find it is easier to work with than DME and gives more predictable results.

+1 to dextrose, I know a lot of people swear by DME but you get differing levels of fermentability from batch to batch which makes consistency a problem. Dextrose is really consistent and stable (not too mention cheaper).

In retrospect, I think maybe batch No. 2 wasn't done fermenting. I did have some activity in secondary. Fortunately, it still turned out good. Only four soldiers left standing.

If I go to dextrose, how do you do it, ie amount of dextrose to water (if any) for five gallons?

I believe the general consensus is 3/4 cup for a 5 US gallon batch. I do mine by weight to get specific carbonation levels however so I use promash to work it out.