Headspace check absolutely necessary? AR10 build

[buffdriver]

Thanks to threads and input here, I'm assembling my first .308 AR. BCG is a Lantac NiB eBCG going into a Aero Precision upper. Both are reputable manufacturers.

The upper was complete as purchased. Is paying for a 'smith to check headspacing a must?

[223to45]

Since you are using 2 different manufacturers, I would say yes.

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[Bret]

I agree. When it comes to 5.56x45, there is an industry standard that everyone goes by which is why most parts interchange. 308 is another animal because there are so many different versions that are not compatible. That said, perhaps call both manufacturers. If they both say you're good to go, then perhaps I'm over thinking it.

[veeref]

I would, especially since your BCG is coated. I built a Mega 308 AR with a NiB BCG, and it would not headspace with both a Rainier Arms and Mega 308 barrel. When I swapped the bolt with a non-coated one, it spaced fine. I attributed it to the additional coating. I guess the tolerances were so tight the NiB coating wouldn’t allow my bolt to go into battery.

[Bret]

I would, especially since your BCG is coated. I built a Mega 308 AR with a NiB BCG, and it would not headspace with both a Rainier Arms and Mega 308 barrel. When I swapped the bolt with a non-coated one, it spaced fine. I attributed it to the additional coating. I guess the tolerances were so tight the NiB coating wouldn’t allow my bolt to go into battery.

The same thing happened to me, but with a 5.56x45 build.

[alrick18]

Always check, especially when you have multiple manufactures. Then you added into the mix a coated BCG, slow down and get it checked, I will hate to see you ruin your rifle.

[Firefly]

Heavenly God yes you always check