I'm using a BC Rich 7 String Warbeast MK3 (25.5" Scale), and I'm recently starting to tune down to A standard to play some Bolt Thrower and write my own riffs, but the 10-62 Ernie Ball strings I currently use feel far too light. I've seen some sets that go 11-70, which sounds nice but I'm worried it may damage my guitar? What gauge would you advice/are my fears unfounded/is there anything I can do to reduce the possibility of damage? Thanks in advance

The myth that heavy strings damage the guitar probably originates from the fact that, all else being equal, heavier strings will generate more string tension than lighter strings. When using heavier strings, the tension has to be adjusted for in the guitar setup. Neglecting to do that might cause too much tension on the neck. When downtuning, you're reducing the string tension. Downtuning guitarists tend to use heavier strings to adjust for that lower tension. Because of that, there's not actually that much set-up needed.

Using a 11-set for A standard for a 7-string sounds like a good idea. Even with that scale length, 10 is fairly light. 70 might be quite heavy for the low strings, so I'd recommend trying out a set like 11-64 first, unless you feel like the bottom 62 is just incredibly slinky somehow. Keep in mind that a really good set-up for the guitar can completely change the way even the same strings feel.

I'd recommend taking the guitar to a tech to set it up for a slightly heavier gauge. They will be able to set it up to last and to play really well, and if you simply take care of the guitar, you can just maintain those settings yourself.

I tend to go with the 70-13 for A standard though I normally use that with 6 strings. for 7 strings I'll go a bit heaiver and the lightest i will go is 11 for the high. I have two 7's in C standard and one in G standard. I have a 8 string that I usually go f standard. and another 6 string that is basically back to D standard like 8 steps below normal E standard. some I like a bit of that lose play cause of what I'm writing with them. some I want that regular solid string tension. I do make sure I have it set up close enough so I don't have to do some weird tuning so it sounds right. but with some lose tension but i get the bwang i want I like that slightly fucked sound you get like early bolt thrower. all my basses are done in proper so they all will sound correct regardless. I want to buy another to keep in more normal tuning. since I have everything dedicated to lower tuning but occasionally I like going some speed metal.