Efficiency improvements from Marris Otter?

I've done 10 all grain batches so far. My efficiency really increased on the last two brews, from low 70's to mid 80s. such that I overshot my target gravity by nearly 10 points.

Some background leading to a question:
- I am making 11 gallon batches, batch sparging in a 10 gallon cylindrical c
cooler.
- I grind with Barley Crusher at factory setting

- The only obvious factors present for the last two batches are that they used Marris Otter, at 90% and 44% of the grist for batches 9 and 10 respectively.

Any ideas as to why I should see such higher efficiency using MO, vs 2-row and Vienna combinations? Or am I just getting better at this whole brewing thing?

Have you considered it may be your calculations that have a variance.
Different batches of malt may have different potential.

Where has increase efficiency is good consistency is probably more desirable.

I using Beer Tools Pro, and let it generate/calculate the sugar potential for the MO grain vs 2-row, Vienna, etc.

Perhaps you refer to batches in the sense of the 'as built' potential of the specific bag of grain, vs the average for the type? I wonder how much variance there is within a given brand and type of grain.

Certainly I'm not chasing high efficiency - I'd be totally content with a consistent 75%.

The other poster was referring to the fact that the extract potential of every malt varies with each lot sold. For instance, when you buy bulk grains from a malt house, you get a spec sheet that tells you exactly what the extract potential is of that malt in your sack... as it will differ from lot to lot when it is malted.

You arent only looking at extract potentials between types of malt, but differences in different lots of the same malt.

This being said, I dont think that would contribute to a 10% increase in eff. numbers.

Now that you mention it, I made a Mild Brown last weekend and overshot my OG by about 5 points. I used MO as well instead of my 2-row for a base. Before that I was dead on with my calculations. I made 10 er so beers on this system too and only changed the base malt.

I noticed this as well. I use Beersmith to do calculations, so it should be consistent. Whenever I use MO, I get above 80%, typical is 75 - 78%. My worst is generic US 2-Row, I got from one of the online retailers. I think I got 68 - 70 on everything I used that grain on. I have had better luck with Rahr (~75%). I have never bought a bulk bag, so I never get the spec sheet. If I overshoot by 10 points, thats a bonus!

English malts (like Maris Otter) should have a slightly higher extract potential than most other malts, but brewing software should account for that difference.
According to Promash, English 2 row yields 38 pppg, while US 2 row only yields 36, and Vienna yields 35.
Also, according to Noonan (New Brewing Lager Beer), the English malts are not affected so much by a coarse crush.

-a.

For the US brewers this may help.(gets more relevant half way down.)

http://brewingtechniques.com/bmg/schwarz.html

You can buy two sacks of Weyerman Pils, and have two different extract ratios. Not only does it differ from malt to malt, but lot to lot. The generic value in your brewing software is just that, generic and more times than not... not accurate to the malt that you are using.

Well then MO's got a hot batch out there right now.