Find a different gunsmith. Leave the first setup alone and get the second barrel done properly. Dont use the Bolt from the first barrel in the second barrel. The barrel to barrel extension must be redone to exact specs. That means taken apart and metal removed then reassembled and checked again till it is right. If not repeat the process over until its right. The headspace is checked with the go-gauge installed in the bcg in the upper receiver.
There is a headspace issue. It won't blow up. It would be best to have it done right.