Bought an entry Core-15 M4 Scout (16", 1/9, carbine length gas sys) and it's been some of the best bang for the buck I've ever had, but... I was trolling PSA for BF deals and jumped on a 18" 1/7 rifle length gas sys complete upper which is being shipped as I post. Then I got to thinking (dangerous)... Hmmm, carbine gas tube is ~7" and it looks like the rifle gas tube is ~12". QUESTIONS: 1) Will the carbine's buffer/spring work with the new upper's rifle length gas system? I'm guessing probably, but not optimal. 2) I can feel/hear a weight inside the buffer sliding around, Can I open the buffer and change that weight out? ALL ADVICE WELCOMED!

Canadian C7A2. They don't have a problem with that set up and you won't either

Yes that is perfectly fine

A picture is worth a thousand words - Thanks for the reply!

The Army uses a heavier buffer when they convert M16A2s, I believe:



If it doesn't run right, consider a heavier buffer or an adjustable gas device.