can do all-grain, but not full boil

I would consider myself an experienced beginner, as I've brewed 8 or 9 batches 18 years ago & just started back up again.

this saturday will be my 2nd Brew Day and it will be my first all-grain.

well... maybe.

I drilled holes in the bottom of a 6.5 gallon ferment bucket, which I put inside my bottling bucket and wrap insulation around and use for my MLT. so I can do all-grain

the problem is, I can't do full boil for a 5-gallon batch. only have a 16-qt kettle, so at most can only do a 3-gallon boil. recipe is 12½ lb grains and 1.040 water:grain ratio, so 13qt mash and 6qt sparge.

anyone see where this could possibly go wrong? (I understand the hit that hop utilization takes in a smaller boil)

Recipe for American IPA:
------------
Amt Name %/IBU
10 lbs 8.0 oz Pale Malt (2 Row) US (1.8 SRM) 84.0 %
1 lbs Munich Malt (5.0 SRM) 8.0 %
1 lbs Victory Malt (28.0 SRM) 8.0 %
2.00 oz Fuggles [4.10 %] - First Wort 35.0 min 12.6 IBUs
1.50 oz Cascade [6.80 %] - Boil 60.0 min 17.2 IBUs
1.00 tsp Irish Moss (Boil 15.0 mins) -
1.50 oz Cascade [6.80 %] - Boil 15.0 min 8.5 IBUs
1.25 oz Cluster [7.20 %] - Boil 15.0 min 7.5 IBUs
1.0 pkg East Coast Ale (White Labs #WLP008)

Estimated OG: 1.065 SG
Estimated Color: 6.7 SRM
Estimated IBU: 45.8 IBUs

I brew all grain using the brew in the bag method, and rarely even bother to sparge, much less get my total full kettle volume. I just mash boil and dilute to the desired volume after its all done. I usually get around 70% mash efficiency doing it this way, and have ran my homebrew through a spectrometer a few times (one of the beauties of working as a commercial brewer) and my ibu's have never been that far off from the target.

you will probably lose the slightest slightest bit of efficiency, but traditionally british brewers never sparged and most commercial breweries even today will dilute beer after the brew process is finished to get the desired og/volume. even the hop efficiency hit is relatively insignificant.

The method described above sounds equivalent to taking the sparge water, bypassing the grains, and dumping it straight into the fermenter. Hard to imagine that efficiency won't suffer...

Anyway, if the problem is the boil size, why not scrounge up a second pot, and do a split boil? That's what I do (because I brew inside on the stove), and it works fine. And you'll be able to run that dilution water through the grains!

Cheers!

Why not just do smaller batches... You could probably convert your recipe and make a 2.5 gallon batch without any problems at all

I'd be nervous about the bottling bucket being able to take the heat during a mash.

Also, not sure about your budget, but you can get a large aluminum Stock pot pretty cheap. I've seen 32 quart pots on amazon for around $30.

+1 to the split boil. You might have to dial back your volume to get it in two batches, but there's nothing wrong with splitting it.