Inconsistent shots

[level3ninja]

There's a few things that could be contributing such as how warmed up the machine is etc, but my guess is it's the age of the beans. They're probably still off-gassing. How light/dark are they roasted?

[worthy1]

Hi all,

First post although i have been reading coffeesnobs for a while getting all the info i can. I recently made the jump up from a 12 year old breville machine with a built in grinder to a Diadema Unico Splendor and a Macap M2M Grinder (got them both as a package). The Breville served me well to make Latte's but then I had to get off milk for a while and its shortcomings where obvious when needing to make espressos.

It has been both fun and frustrating at times trying to get a decent shot that is not sour or bitter. I have learnt a lot and have wasted a lot of coffee trying. I upgraded a few parts such as a IMS shower screen and got a VST 18g and 15g basket. I didn't do too bad on the 18g basket but wanted to switch to the 15 to lower the caffeine dose I was getting. The 15 was too finicky for me in my early stages. I know the VST's require you to have everything else down pat to get that nice shot so I figured I would switch to a more forgiving basket until I got there. My 14g Espresso Parts Basket arrived and it only took me a couple of shots to get what I think was the best shot I have had so far. It was 2.05 on my grinder, 14.1g in and 29.5g out in 25sec.

I do find it hard to cut the machine off right on the target I am aiming for as it can easily go over in that time. I WDT and believe I am pretty consistent with my tamping from shot to shot. Excited first thing this morning to taste the shot again I went through everything the same only to find the flow rate way slower and I only got out 19g for the same recipe. Confused I tried again but dropped the dose back .1g to 14g and tried to tamp slightly lighter. Still slow and it took me 40sec to get 29g which was very bitter.

What could be causing this inconsistency? I keep probably 2 days worth of beans in the hopper. The house would have dropped a couple of degrease overnight if that matters. I am wondering if whatever causes this has been the problem so far but because I have been tweaking each shot each time to make it better I haven't noticed until trying to use the exact same recipe.

Any help would be great, I am expecting new grinder burrs in the next day or two although I didn't really notice a difference in the grind. I roast my own beans (popcorn maker) and they are about 5 days old.