Question about upper interchangeability

[Doc Safari]

I currently own a BCM carbine length rifle.

If I were to purchase a BCM mid-length upper, are there any interchangeability issues I can expect, or should the upper plug right in and cycle just like the one that came with the rifle?

Do I need to replace the buffer?

Do I need to tweak anything?

The reason I ask is that years ago I owned two identical Colts, and out of curiosity I swapped the complete uppers with each other. The rifles believe it or not suddenly started cycling unreliably until I swapped the uppers back to their original rifle, leaving me to believe there was some little tweak that needed to be made.

[Ilove2shoot]

The reason I ask is that years ago I owned two identical Colts, and out of curiosity I swapped the complete uppers with each other. The rifles believe it or not suddenly started cycling unreliably until I swapped the uppers back to their original rifle, leaving me to believe there was some little tweak that needed to be made.

The AR system is supposed to be plug and play. it is supposed to, and should work just fine. that being said, what happened to you before does sometimes happen. You can not say when it will happen, if it will ever happen again. heck, it can happen on a new build. just takes a little detective work to get it right if it does. if it does happen, there are a few people on this site that can help you figure it out and get it running again.

[ArmySGTPM]

Since you are changing to different gas system you may also want to test out different buffer weights to find which cycles the best for you. Since the pressures are different between the carbine and middy, a heavier buffer might be needed

[Eric D.]

Midlength = less pressure = lighter buffer

Since you are changing to different gas system you may also want to test out different buffer weights to find which cycles the best for you. Since the pressures are different between the carbine and middy, a heavier buffer might be needed

[ArmySGTPM]

Midlength = less pressure = lighter buffer

Yes but you will want to try at least a H buffer in a middy versus the carbine that probably is running in the carbine he has. Its good to try all sorts to find the one that works the best and most reliable

[carbinero]

All true as far as function, but you may want to look closely...I don't worry too much about tight or wiggle between upper and lower, but I have noticed with certain charging handle/upper/lower combinations, there is extra wear-rubbing between the bottom rear of the CH and the lower receiver...where you pull the CH back.

[Quentin]

Do you have an H buffer now? I'd suspect it will work fine with the middy or carbine gas uppers. Test with you lightest loads to be sure.

[Doc Safari]

Just in case you guys are curious, here is Daniel Defense's response to my email asking if I should change the buffer or spring when putting the middy upper on the carbine lower, and if it would void the warranty:

"Thank you for your interest in Daniel Defense and our products. You can assemble the upper onto your current lower with no issues and without needing any additional components. It does not affect your warranty in any way."

[Quentin]

Refreshing to deal with a manufacturer that knows their stuff and doesn't feed you BS. Thumbs up for Daniel Defense.

Thanks for sharing the email, Doc G.