New aero m4e1 upper and lower set
- Thread starter HAMBONE73
- Start date
The Aero parts should be fine.
that being said, I have started using BCM uppers for all my new builds. The bore for the barrel extension is machined a couple of thousandths smaller so you have a tight interference fit. Use a heat gun or carefully use a propane torch to expand the upper and then put the barrel in. When it cools off, it should be a light press fit.
I had to modify my receiver lapping tool to fit the BCM bore size, but it works like a champ now
that being said, I have started using BCM uppers for all my new builds. The bore for the barrel extension is machined a couple of thousandths smaller so you have a tight interference fit. Use a heat gun or carefully use a propane torch to expand the upper and then put the barrel in. When it cools off, it should be a light press fit.
I had to modify my receiver lapping tool to fit the BCM bore size, but it works like a champ now
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