Yes you absolutely can. It is the same process as the original purchase. Paperwork might be a little different but you effectively have to sell the suppressor to the trust and pay another transfer tax even if you already own it.
I asked this question when I bought my nfa item. The simple answer is yes. The long answer is that you can although it is unnecessary since federal laws allow the nfa item to pass one time without a trust protecting it. If you want to take the time and pay to add it to the trust feel free to do so.
I do believe so. Not 100% sure but I would call or email someone at silencer shop. There customer service is top notch.
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