I received my T81M underfolder yesterday and found that the barrel slightly points to the right.
I am fairly new to the firearm and not sure how serious this issue can be. Is there an easy way to measure the offset? Should I ask TI for an exchange or return?
Thanks.
Use this method to measure the barrel deviation:
https://youtu.be/pz11mKx9Y2k?si=GJBidOsKoStSYes4
You can also quickly gauge if your barrel is actually bent via field stripping the rifle, and looking down the muzzle for the cleaning rod hole at the rear of the reciever. If the hole is centered, your rifle's barrel is not offset or it's minimal. If the hole is noticeably to one side or the other, it's likely offset.
TI's currently stated spec for these 81Ms is no more than 4mm of deviation with the previously mentioned measuring test.
As for it causing issues, if the barrel is too severely bent, it can cause zeroing issues. If it's "within spec", iron sight zeroing should still be possible, but optic zeroing may be problematic. The rifle should otherwise still function fine. I strongly recommend you read your owners manual to familiarize yourself with the rifle, but there are two things to pay attention to:
- the gas regulator. There are 3 settings, 1 for normal, 0 for complete shutoff, and 2 for adverse. For the vast majority of your shooting, this should be set to 1. 0 was intended for rifle grenade usage on the original rifle model and 2 is only if the rifle starts having cycling issues on 1 and/or is severely fouled. You can use the base of a 7.62x39mm cartridge or casing to adjust the gas setting.
- the iron sights. The rear sight has numbers from zero to 5. Each number between one and 5 corresponds to that distance in hundreds of meters (i.e. 1 = 100m, 2 = 200m and so on). The 0 setting is only to be used to remove and replace the gas piston cover, and can be accessed via going to the 1 setting, then pulling the rear sight nob on the left side out and then rotating it to the 0 setting. On both sides of the rear sight, there is a divet that the nunber is supposed to line up with. This is designed so that the shooter from the iron sight level can see the number setting from your normal sight picture. Also, to actually zero the sights, all adjustment is done at the front sight. Windage via screwing or unscrewing the front sight post up or down, and windage via unscrewing the large screw at the back of the front sight, drifting the whole tower left or right on the dovetail, and then tightening it down again. The included tool kit should include the little wrench neccesary for this task.
Hope this helps!