Threading the Howa Lightweight Barrel

[Frontier Gear]

This came up in a "for sale" posting on a Howa lightweight 20" barrel. I didn't want to derail that sale post to discuss it, but I also wanted to share this information.

I just cut down my 20" Howa Lightweight barrel to 16.25" and decided to have it threaded while I was at it. There isn't enough wall thickness to use the common 5/8"-24 threads that you see on most .30 cal and 6.5mm muzzle devices. There is enough wall thickness to go with 1/2"-28 thread pitch which is common for the .223/5.56 muzzle devices.

The caution point is that you do NOT want to use a .223/5.56 muzzle device on your 6.5 Grendel. So you have two options. Buy a 5.56 muzzle device and have it bored out by a machinist/gunsmith, or find a muzzle device with 1/2"-28 threads but with a larger bore size.

For my rifle, I wanted a flash hider and I just happened to have a new spare Brownell's A1 style of flash hider in my parts bag. Even though it says it is 22 caliber, it has a huge bore through the middle of it (at least mine did). I could almost put a 3/8" drill bit through it.

It works fine and I have probably put two or three boxes through the gun with it on.

[grayfox]

Good info. Especially since I asked the question!! Thanks for sharing.

What I did with another caliber was that I cut back to 20", then put a 9/16-24 thread on it. The minimum diameter IIRC was ~0.620". I had my GS do the threading, then took a 9/16-5/8 (both 24 pitch) thread adapter (all of these were the precision style threads) and put the MB on it. I was careful to not fall into any tolerance stacking that could negatively impact the rifle. It shot pretty well actually. Just fell out of love with the caliber and sold it. But since it worked, maybe this light Grrr could wind up the same? As I recall there needed to be some shoulder left on the barrel behind the threads, that's why I think it was a 0.620 min. 9/16-24 thread is 0.5625 in the OD. This is all from memory... but you get the idea.

edit: might have been a min of 0.590...

[Frontier Gear]

I don't know if you could get 9/16" out of it or not. Mine did have a shoulder at the end of the threads. If you look close at the photo, you can see a crush washer behind the flash hider, so there was enough of a shoulder for that to work.

[flyrod]

My standard barrel was thick enough for 5/8" threads:



Also, most of the "223" brakes I've seen have huge thru holes. I put one, unmodified, on a 338. I suspect that a lot of AR barrels are threaded in a haphazard way.