Anyone convert an MP15 Sport to 7.62x39? I was curious if there were any caveats involved. I’ve never played Legos with my Sport, but since I have a bunch of 7.62 ammo I figured if it’s easy, why not?

Can it be done, simple answer is probably. All depends on whether the mags would fit. Best way to do it would be going with a complete upper. However, then you're getting close to the price of an AK or SKS.

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Peace was my Profession

Yes, it can be done. You need different mags and a different upper. Simple, but as Westie1 said, it's close to the price of another rifle.

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Freedom isn't free.

An online store has complete uppers for less than $400, I haven't seen an AK that cheap in years, unless I'm looking in the wrong places.

I bought a custom 7.62x39 upper off the big auction site for about $400.
Ar uppers in this cal are known to have some feeding issues due to ammo shape. Soft nosed bullets can be problematic too. After some research online, I also purchased ASC mags as they are reported to be the most reliable.

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Dave

Due to the feed issues caused by the distinct taper of the 7.62x39 case I would suggest you look into doing a 300 Blackout instead. While the 300 BLK loses between 100 and 200 fps when compared to the 7.62 x 39 it's a real sweetheart of a round to reload and you can use standard AR magazines without any issues with jamming.

BTW, I have a 16 inch 300 BLK I built myself with a Wilson Combat barrel featuring a pistol length gas system. To allow me to tune the gas system for whatever ammo I am using I installed a Syrac Ordinance adjustable gas block. Doing this allows me to dial back the gas supply to keep the rifle from being over gassed with supersonic ammo and a secondary benefit of this capability is that it's so clean shooting you have to actually see it to believe it. With 100 rounds downrange I can pull the Nickel Boron plated Bolt Carrier and it looks like no more than 5 rounds have been fired. I will also note that the most accurate powder for my rifle has been H110 and it will consistently put 5 rounds in 3/4 inch at 100 yards with either a 125 gr Nosler ballistic tip or Hornady HP.