According to the 2015 style guidelines an Irish Stout should be 25-45 IBU's. So it really is not that far off. Sounds like maybe you need to keep an eye out for how bitter a beer you want. Maybe you would like a breakfast stout or maybe a lighter pale ale. Hit the grocery store beer isle and try a few different beers to see exactly what you enjoy. Most craft beers have the IBU's and ABV listed on the bottle. Then find a kit of the beer you like. If Irish Stout is what you like then get the same kit and don't add all the hops. Cross it off as a learning experience and brew on!

 

I would not laugh at a Brewers Best kit. And shame on those who would. I’ve made a lot of good beer with those kits. If you followed the instructions and kept everything clean, you’ll get good beer. Don’t worry about it.

 

I’ve never experienced a BB kit being too bitter. But as I’m sure you’ve already considered, don’t make a universal change to all of their kits. I’d only consider a change to that specific kit. As suggested before, if you brew it again, only use half of the boiling (60 minute) hops. That’ll work, unless there was a problem with the hops in your first kit like too much hops or too bitter hops.

 

jkrags, I have brewed an IPA that was over 100 IBU. It did not get bitter. It smelled over-hopped when I was bottling but after two weeks I tasted it and it was really good. The bitterness might be due to the grains that you steeped. Give it some time and it should mellow out.

 

I use magnum all the time and I've never used an ounce at 60 for anything. If you don't know the AA value for the actual hops you used, it could be higher than the calculator is showing. My current bag of Magnum is 13.3 and if I plug an ounce into my Guinness Clone recipe, I get over 50 IBUs instead of the 39 that East Kent Golding gives me. I also don't use any late hops and if I plug in a half ounce of Eldorado at 5 minutes, it jumps to 0ver 56. Eldorado is a really odd choice for an Irish stout, as well as tending toward a dank, harsh bittering quality, IMO. That being said, it'll probably mellow a little.
Next time, do a little research and dial in the IBUs based on your actual hop batch. And water profile can boost or tame bitterness, too so you could look how to change your water to accomodate different beers.

 

I brewed several Northern Brewer kits and I believe they are quite a step up in quality as they are fresh kits. Yeast, hops and grains fresh ground. And if your buying an extract kit, fresh DME/LME as well.

 

My guess is, is if you felt something was truly wrong with the kit, you would probably get your money back. And I'm not saying that's the right or wrong approach. I do know Brewers Best are generally good kits. I've used them. I've even purchased them at clearance prices knowing they were old and still produced decent beer.
Brewing comes with a learning curve and it's been said by some much wiser than me, that to brew good beer, you gotta be willing to dump beer to get there sometimes. Lord knows it's tough, and I've punished myself consuming some pretty not very tasty brews. Most of us have...
There could be many reasons why your beer is to bitter, that are no fault of the kit. One being how long it took you to cool your wort.

 

You won't need a kit next time. You'll be able to ask for recipe help beforehand and procure the exact ingredients you need. For a Guinness clone you'll want UK hops to start with. That's a particularly easy to brew and it always turns out well almost any way you do it.

 

If the kit and recipe called for those hop additions, there aren't too many ways that it could be in the right IBU range. The Magnum would have to be in the 9% AA range and I've never run across that. And who puts El Dorado hops in an Irish Dry Stout?

 

Lol. El Dorado? I thought that kit used Northern Brewer? 10 AA isn't out of range of Magnum and we don't know so it's all a guess. That's why I said COULD be many reasons that aren't the kits fault. It very well could be a kit issue and if the brewer feels so inclined, he should complain. That's a decision he must make. If the kit was purchased from a reputable brew shop, I'm sure they would make it right to keep a future costumer. But I agree, adding an oz of Mags for 60 min boil does sound pretty steep.
One good thing. Sounds like the brewer has found BF and can now enter recipes beforehand!

 

Even at 10AA, it pushes high with the El Dorado addition. Again...why would they ever think El Dorado is a hop for Irish Stout?
And I just checked the recipe for the Brewer's Best Kit online and that calls for an ounce of El Dorado at 55 as well as a half-ounce at 5. Even at it's lower range, that goes almost 60 IBUs and they state that the IBUs are 35-38. Seems like someone isn't keeping up with QC.
Too bad new brewers might buy that thinking they're going to get a Guinness-like beer, but a lot of their kits get good reviews.

 

So the calculator that we've all been using with great success is giving values that are twice what their calculations say it should be? I don't buy it. Based specifically on their El Dorado additions found online, I don't see how they can be holding to 37.5. Also I find El Dorado to be a particulary harsh hop when used for anything other than flame out or dry hopping and I don't doubt that that's part of what you're experiencing.
Just let everything ride and you'll have a drinkable beer at the end of the process. Chalk it up to experience and build a recipe that's more to your liking.

 

I Have been away from extract batches for a while so CORRECT me if I'm wrong but part of the equation they would use would include volume of boil. There is the possibility of their calculation being for a partial boil, which would lower the IBU`s from a full boil. Are you boiling a full 5 gal JKrags or boiling a smaller volume and adding cool water at flame out to get your full volume and do the kit directions call for a full 5gal?

 

Were there specialty grains that you steeped? If so, did you stick to the right temp range for the water? Too high of a temp can force tannins into the wort. It can create a bitter harsh taste. Some people say that squeezing the specialty grains after steeping can force tannins too. Some debate over that though.

Like someone else said, stouts need some time in the bottle to mellow out and allow the harshness to fade. Give it a bit more time.