Um.... what's thread choke? The inference is that it's something that occurs at the end of the forcing cone and beginning of the rifling. But I'd like to see that confirmed.
Yes. It is where the barrel is often choked down due to tightening in the frame where the threads are.
I have a single action that had a slight choke, and I tried the NECO kit. What a PITA!!!! Be prepared to remove a LOT OF LEADING from your UNLUBED bullets! And, it's not a 'remove the leading when you are done' bit, it is a 'remove the leading every few shots or the rest won't have any lapping effect on the barrel'! Lots and lots of cleaning in the loooong process.
And, what was my result? I was keeping track of the choke by measuring slugs after every stage of the firelapping and in the end was not able to detect any significant difference in measurement. And, I could still feel the bullets hit the choke each time I slugged the barrel. I wouldn't count on firelapping to remove a barrel choke, even a slight one, but other adventurous folks seem to report great results, so I don't know what to say about that. It did, however, make the revolver easier to clean in the end as it was more forgiving to what I fed it as far as what was known to have leaded the barrel before firelapping.
I don't know that I'll ever firelap again. Having been unimpressed (to say the least) with firelapping, I decided to try a different method to smooth the barrel on another single action that I had had reblued and which had started to lead as a result. I simply used the time tested trick of shooting a couple hundred rounds of jacketed bullets through it and this solved the leading issues. Now, jacketed bullets will do nothing to relieve a barrel choke, but neither did the firelapping in my case, and the copper was much easier to remove during the process than the leading from the lead bullets while firelapping. Now that gun is also forgiving of lead bullets, and I have no worries that I ruined any of the fine rifling by using the jacketed bullet procedure.
Just my experiences. Yours may vary.