Barrel extension on pistol upper question

[Anangrypasta]

Hey guys, know this has been discussed.... but I just got my first AR lower ever and I want my AR in an eccentric/unused cartridge. I decided on 9x39. I can only find uppers at 12.5", and no barrels, so I would need an extension on my rifle lower. Do you have to weld/pin the extension? Is that something I can do assuming I have the ability, or do I need to go somewhere to have it done for legal reasons?

 

[Raven]

Hey guys, know this has been discussed.... but I just got my first AR lower ever and I want my AR in an eccentric/unused cartridge. I decided on 9x39. I can only find uppers at 12.5", and no barrels, so I would need an extension on my rifle lower. Do you have to weld/pin the extension? Is that something I can do assuming I have the ability, or do I need to go somewhere to have it done for legal reasons?

Why 9x39? China is gearing up to issue a 9x20+ something caliber. Might be a bunch of parts, mags and surplus ammo for this new Chinese thing in the future

 

[Anangrypasta]

Why 9x39? China is gearing up to issue a 9x20+ something caliber. Might be a bunch of parts, mags and surplus ammo for this new Chinese thing in the future

Was gonna go 7.62x39, but the high cap mags look goofy in my eyes lol. No particular reason besides how unusual it is, and it isnt particularly expensive. I'm somewhat skeptical we'll be getting any new Chinese cartridges in the near future.

 

[FrankT]

I run a 10.5" side charger in X39 and better than any 300bo, love it

 

[Rebel_Rider1969]

X39!! High cap 30-30!!!

 

[chud]

16 inches is the magic number, permanent, and the definition of permanent is indeed pinned and welded.
It is very doable if you have some basic skills, the pin needs to go all the way thru the muzzle device and into the meat of the barrel enough to prevent it rotating off, then weld the pin on the muzzle device.
The muzzle device can be whatever, I dont know what youre style would be. But the basics of legality are minimim 16 inches as measured from the closed/locked boltface to the end of the muzzle or permanently (pinned/welded) attached muzzle device.

 

[Rebel_Rider1969]

In the big picture, if ya have to have 16inchs, make it a barrel.

 

[wildrider666]

New subject or issue to me or I'm really confused with what was presented as "so I would need an extention on my rifle lower." ??? Sharper folks understood this issue as a simple barrel extention IOT meet the 16 inch requirement. Pinning is less intrusive to the barrel and welding the hole only impinges the extention. Clamps and soft wood blocks will hold proper positioning and a drill press eliminates potential angle and wobble errors. The weld is a couple bucks at most shops, call first.

A plain barrel extention adds length but ZERO ballistics improvement, become the new muzzle crown but contains and circulates potentially destabilizing blast disturbing projectile stability and may adversely affect barrel harmonics. It will allow full stock use.
The Lower is NEW/virgin so it can be built as a Pistol First and there after changed to a rifle and back again as desired. A pistol brace is optional.
Sometimes the unicorn you catch becomes the albatross you can't get rid of. "If" you loose that loving feeling for the 9×39: an unmodified barreled upper may sell faster. We often see less popular and unmodified AR calibers gather dust in the for sale section.

All ammo has crazy pricing and a availability but chasing 9×39 down the rabit hole may be self defeating. I found import at $.85ppr this morning. I don't think any U.S. mfr produce it, leaving it at the mercy of import shipments and Feds "stroke of the pen" total restriction. We may recall the 5.45×39 (AK74) import restriction on 7N6. That caliber never displaced the 7.62×39 in the States. I also think the commie block folks are a have been a bit fickled over caliber selections. Some companies that planned to produce 9×39 AR uppers and barrels when it was the new flavor of the week, did not follow through. New/"Unusual"/wildcat cartridges take a long time and require significant popularity before a major U.S. ammo mfr adds them to their Line; unless its a combination firearm/cartridge introduction. Even then, "trends" rise and fall, hence; "flavor of the week" sarcasm. Some fall from grace faster than others and a few never get past introduction level (geographical or popularity), hence you "rare reference".

The former theory that odd/outdated calibers would see less demand and therefore potentially be available when other ammo wasn't failed this time around. Lss popular ammo went from normally hard to find to unavailable/market price increase like everything else. Who stocked deeply in .25/.32APC? Build a 9×39 for the fun of it, sure.