[fabsroman]

Depends on the stock setup for the most part. If Leupold's website is saying that you can use lows, that means that the bell of the scope will clear the barrel of the gun.

Now, I have checked Leupold's website and ring guide on several occassions and I am surprised that they have a listing for a custom barrel. Is the barrel the same thickness as the stock barrel on the gun? If the barrel is thicker than the stock one (i.e., a target barrel/bull barrel), then the low rings might not even work from a scope bell to barrel clearance standpoint.

Does Leupold's ring guide list a clearance for the scope rings. If so, you might be able to use these numbers to see if the scope and barrel will work.