Since they're an in between size, what spring do they take? Thanks.

Doesn't Bridger sell replacement springs for that size?

Check out F&T website,they have them listed .

So they do. Unfortunately.

Do they interchange with any other size, or are they completely proprietary? Wondering if I can swap with 1.75's.

I would go with #2 music wire and base plate them. That is what I use on all of my 1.5s.

What does “ unfortunately “ mean in your response?

No idea about your first question. I would use different springs other than Bridger ...junk IMO!

That would be what ever spring fits a 1 3/4s trap in my opinion. The springs on my 165s are plenty strong the way they are, junk or not.

Decreases my odds of finding a crossover. Have some 3 coiled that I'd like to put the odd spring to use on a different trap but don't know what.

I got some good springs that were sleepy Creek close out parts. I got 2 dozen 1.75 to beef up my 1 1/2 victors. The springs are (to me) as big as #2 springs. MTP and F&T have them on close out sale.

x2 on the #2 music wire

X3 #2 music wire

A Bridger 1.65 is a 1-3/4 sized trap. So any spring made for a 1.5-#2 sized trap will fit just fine. But like mentioned above, 1.65s have more then enough power. I’ve held everything from fox to mountian lions with them.