Nottingham low attenuation ? (66% AA)

[MXDXD]

I just bottled a Lapsang Souchong-infused Porter that has been fermenting since 3 weeks with Nottingham.

To make a long story short, I kept it between 60F and 62F in the first week, then raised it to 66/68F in the two following weeks.

I was bottling today and for some reason I thought my OG was 1.068. Thus I didn't really react when the Hydrometer was showing 1.019 (adjusted). That would've given me an AA slightly above 70%, which I figured was a bit low for Notty, but could otherwise be explained by the somewhat low fermentation temp and a not very fermentable grainbill (see below). But my OG was actually 1.058, which brings the AA to 66%, and that seems... quite low.

The grainbill was the following :

68,2% Maris Otter
11,5 Brown Malt
6,8% Dark Crystal 85L
6,8% Carapils (Dumb move in retrospect)
6,8% Chocolate Malt

Is there a reason to be concerned? I never take samples on 1-gallon batches and I mostly let it run 3 weeks regardless of the OG, unless I'm doing a real-high OG one OR a Saison.

 

[hottpeper13]

I just had a Notty finish at 1.018, the batch was split with Wyeast 1217 and that also finished at 1.018. mash was 152* and ferm temp was same as yours. I like 3 week primary's.

 

[MXDXD]

I just had a Notty finish at 1.018, the batch was split with Wyeast 1217 and that also finished at 1.018. mash was 152* and ferm temp was same as yours. I like 3 week primary's.

Did you had an important amount of non-fermentables like I did?
I mean, in the end, I'm not THAT mad if it was indeed done, because it would otherwise have been a very, very bitter beer, and the low attenuation actually helped attenuate (!) somewhat the bitterness imparted by the tea.

But.... yeah, that's a very high number for what's normally a good attenuator.

 

[Gnomebrewer]

What was your mash temp?

 

[MXDXD]

what was your mash temp?

153.