In order to guarantee reliability and proper function of your GEN12 upper you will need to follow these following steps to beef up your 308 lower so it will manage the abuse of shelling 12 gauge munitions!
All of the items except the thread locker and tools needed will be included with the purchase of each upper kit and standard on any full firearm purchase.
You will need to install these items into your lower in order to guarantee reliable function of your GEN12. We found consistency in the 308 market is not standard and the tolerance are not consistent. So we have included parts to our standard required to increase reliability with your GEN12 and there is no issues when switching back to the 308 upper.
The Kit you receive with every upper will include 5 items:
- anti walk tiger pin (x2) with screws (thread lock the screws with a medium strength product)
- bolt catch
- increased power bolt catch spring
- magazine latch
- increased power magazine latch spring
Why the changes? The changes were made to increase function. The magazine spring need to be modified to increase the "bite" in to the notch of the magazine, and a bevel needed to be added to aid in feeding magazine. The bolt catch on a standard 308 will maintain contact with the GEN12 BCG so we had to grind off approximately .04" to maintain proper cycling of the BCG. For similar reasons we needed to increase the spring power of the bolt catch, to keep the bolt catch from bouncing from the recoil produced from the 12 gauge.
IMPORTANT NOTE: You must install the antiwalk pins. The standard trigger pins are inconsistent between manufactures, and that means the quality of the pins could vary. To ensure your pins do not break under the 12ga recoil, you have to install the antiwalk pin kit.
If you don't know how to install these parts, then you will need to find a video on Youtube or similar on how to install an AR15 lower parts kit. Here are a couple links we found that are good reference:
1. Magazine Catch Install
2. Bolt Catch Install
The last recommendation we have is to use a thread locker to secure some points on your lower receiver. We use Loctite 243 (blue- medium strength). We offer these as a recommendation because after extensive shooting and abuse from firing 12gauge shells, these areas have proven to work loose.
The areas to add thread locker are as follows.
1. Bolt Catch screw (that is if your lower does not use a roll pin)
2. Castle Nut: we have seen stacked/ punched end plates and castle nuts loosen after extensive use.
3. The screws on the anti-walk trigger pins
There is nothing here that most would not be able to do. However, if you don't have the necessary tools or you are not confident you will complete these tasks successfully then we recommend you have a qualified gunsmith or shop perform the work.