Model 1 300 Fireball thread pitch
 

Just got off the phone with a lady from M1, and she specified that the thread pitch on their Fireball barrels is 1/2-36. The option to have it changed is $50. I don't understand why they don't use 5/8-24.

Kevin

I think it's because they don't really want to do 300-221 barrels. Look up tp555 and get a real barrel. You can have your 5/8-24. It's no more difficult to machine that from a Douglas barrel blank then any other thread. Also you get the port in the pistol position.

tp555? Is this a username here? Company? The blank is a Douglas? What are the benefits of having the port in the pistol position? I would assume this would allow the use of pistol powders to cycle the action, yes? Higher port pressure closer to the action as opposed to the placement down the barrel.

I love this place,

Kevin

tp555 makes barrels for ARs. His business is Paladin Machine service:

The pistol gas position should allow for more flexibility with subsonic loads. Other users have barrels with the gas port in the pistol position and have had fairly good results, I am sure they will chime in with input.

Paladin Machine Service
3832 gates ford rd.
Kershaw,Sc 29067
(803) 475-7542

(He is just now finishing my barrel in .30/221) :grin:

Do you mind me asking how much you paid for your barrel at Paladin?

Sent you a private message

M1S WILL thread 5/8 24 AND port in the pistol position. All you have to do is ask. The reason they charge extra for the 5/8 24 threading is that they order the barrels from an outside source and assemble your upper from a "box of parts". If you want 5/8 24, they order a non threaded barrel and then thread it in their shop. Just costs extra to "have it your way". If money is no object then a fully custom barrel is the way to go.

Thanks for the correction.

As far as money goes... Barrel blanks are not all that expensive. Although you certainly won't be getting a $500 upper going the custom route unless you already have spare parts lying around that you don't count into the cost. But you can "have it your way" for a reasonable price.

In my area, ARs and everything related to them are super expensive. I did not pay more building my own than going with an off the shelf rifle. I didn't save money either of course.

I bought a M1S 300 fireball upper this month and 5/8 24 is now the standard thread pitch on them. They are also sending them out with a .123 gas port hole size standard.

I do manufacture an adapter to go from 1/2 X 36 to 5/8 X 24 for those that have a M1 Sales barrel with that thread.

PM for details, it costs less than the $50 that they want to charge......


When I ordered my M1S barrel, I asked them to leave the threads and the gas port off completely and I would take care of that stuff. They did leave the gas port undrilled, but still sent me a 1/2 X 36 barrel. Wasn't worth trying to mess with an exchange so I setup of the CNC lathes and made a pile of adapters.