Re: suppressor purchase
You'll want to match your intended purchase to two things.
First, the caliber of the weapon. If you've got a 7mm, then a 7.62 can should fit and work.
Second, the attachment method. If you're looking at a screw-on can, then you'll just want to match the threads between your barrel and the can. If it's a QD mount can, then you'll still need to match the QD adaptor threads to the threads on your barrel. Generally, your thread options on a 30 caliber can are 5/8 x 24 and 3/4 x 16. You'll need to match your threads to your intended mounting system. After that, it's not rocket science to mount it up.