I (nearly) always ask
And she (nearly) always says ok. There have only been a couple of exceptions in over 30 years. One time about 20 some odd years ago I put a gun on lay-away whithout asking her. She got ticked because, at the time, we were saving for a cross country trip. So she considered the expense unjustified. The other time was a couple of years ago, at a gun show. I was looking at a particular Remington, the purchase of which would have depleted our available funds drastically (for the next week), and she looked at it and said,
"Don't you have one of those?"
Honesty compelled me to answer,
"Ummm, three." (actually 5, but only 3 in that caliber)
Her response;
"Uh-huh", and walked away.
Knowing it would be trouble in the long run, I passed on the gun.
Other than that, she has been most reasonable. At least as far as guns are concerned.