The current tariff on UK good exported to the U.S. is 10% of the cost of the item. Hardly a deal breaker on something like a firing pin. That's less than the cost of selling an item on GunBroker or the roughly 13.6% fee to sell a firing pin on Ebay. And it is very small potatoes compared to what we all paid to import and support 15-20 million illegals. Some folks with TDS will whine and cry and act like it is the end of the world. But in the overall scheme of things, the vast majority of us are much better off than were were a year ago. My 401-K's and IRA's are all up more than 10%. I just filled my gas tank at $2.459 per gallon, and paid $3.00/lb. for bacon and $1.99 per dozen for free range eggs. There are localities here in the U.S. that have a sales tax higher than 10%.
The tariff alone obviously isn't stopping the parts sellers in the UK from shipping. That's their decision, and we haven't heard any valid reason. Fortunately, for most guns, making and heat treating a firing pin right here in the U.S. is not rocket science for any decent machinist. Real gunsmiths do it all the time.