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I've been having issues with the threading on my .308.

After using the moderator at the weekend the last few turns felt specifically harder. Having subsequently removed it and replaced the thread cap, this would not go one more than 5mm or so.

Thankfully I did the sensible thing and bought a 5/8 unf tap and die kit. The die worked a treat on the barrel thread, removing quite a bit of material and a quick run through of the thread cap did the trick.

The issue is obviously with the last few mm's of the moderator. I don't think I can get the tap to run through it because of the design. Has anyone had a similar experience or got any tips?

Ultimately is it a trip to a good gunsmith/send the mod back to Jackson to repair??

Is this a brand new moderator/rifle, or have you used this combination for a while?

Before using any sort of die/tap I would give the threads a good clean and put a small amount of copper slip on the threads. It's surprising how much friction a small amount of dirt and grit create for fine threads. In the case of a new rifle/moderator, the tolerances in the thread design might be at the limit such that the last bit of thread is too tight. It's amazing how much friction and force is generated in threads.

Did you have your rifle threaded by a gunsmith, or was the rifle already threaded? If you had a gunsmith do the threading I would take the rifle and moderator to them and ask if they can adjust the threading to suit.

Short of grinding down the end of the tap to cut further before it hits the baffle, I think you need a new moderator.

A tap is cheaper than a moderator, I suppose?

I would say look for a plug tap/#3 or indeed grind the existing one you have for the moderator. Do keep in mind that if you are removing a lot of material as opposed to removing excess carbon on the threads you may well be weakening the means of attachment (*) This is compounded by running a die up the barrel thread. I 'usually' thread to Class 3A however I always check the final fit against the customers moderator if supplied or in its absence a ring gauge.

(*) The indicator for this is usually when your moderator disappears off down range at some point...

I would try a plug tap.

Many thanks for all the helpful replies.

Sadly the rifle/mod are several years old - the rifle threaded by Highland (Howa) and the mod purchased later. Both parts were test fitted and properly checked for alignment before firing and no initial issues. I think the initial damage was down to me carelessly dropping the mod onto the end of the barrel rather than exercising some care. Lesson learnt.

I shall purchase a plug tap and proceed cautiously - having seen a few mods go up range at Bisley that's definitely something I'd prefer to avoid.

My tip now is make sure the moderator is inverted when you tap it and one way of doing this is clamp the tap upright in a vice, give it a good coat of tapping grease or oil and screw the moderator down onto it. a turn in, quarter turn out until it bottoms, this way the swarf from the material used will be either stuck to the tap or drop out the bottom.

Take care though, it's so easy to fire a can up range :)

Thank you David

Before you do anything, can you post a clear picture of the rifle barrel thread?