Avoid This Common Mistake! Easy Receiver Screw Size Tests.

Use these quick measurements and tests to check which screws your receiver is drilled and tapped for. This video is applicable to MOST firearms available in the U.S. There are some manufacturers who drill and tap their receivers with metric thread pitches, but that is not extremely common.

If your firearm's manufacturer has a website, be sure to check there first to see if they have the screw sizes listed for your particular model. If they don't you can always give them a call so they can run your serial number. We are asked quite often if we can check by the serial number and unfortunately, we don't have access to manufacturer's databases.

If you have a set of precision calipers, you can use the following information to measure any screws that came with your firearm.
#6-48 screws outside diameter measures .138"
#8-40 screws outside diameter measures .164"

If you don't have a set of calipers, you can use a 1/8" Allen key or hex wrench. If the hex key fits snugly in the hole in your receiver, then it is drilled for #8 screws. Do not force the wrench in to the receiver, you do not want to damage the threads! If it does not fit in the holes, your receiver is drilled for #6 screws.

Replacement screws are available here:
https://www.egwguns.com/scope-mounts-rings-replacement-torx-mount-screws-w-bit

#8 Drill Out Kit is available here:
https://www.egwguns.com/8-drill-out-kit

Modification of your firearm may nullify the manufacturer's warranty.
Our products should be installed and checked by a qualified gunsmith.
No liability is expressed or implied for damage or injury which may result from improper installation or use of our products.