Just starting to go down the HK416 rabbit hole.  What's the most economical way to get a nearly facsimile HK416 in either a 10.5 or 14.5 inch length?  Any recommendations on which will perform better?  It looks like properly gassing needs to be addressed.  Intending to shoot suppressed.

Do you plan on using an OSS can?

Are you familiar with these 416 clones from brownells?

https://www.brownells.com/.aspx/bapid=865/ClientPage/brownells-brn-4

The vented gas block is a great add on.

MR556/416s are snappy by design.  

Short AR15s are a relatively new thing.  Back in the day when the need was identified for reliable, short AR15s, HK responded with the 416.  By today's standards its way overgassed.  Add a can and its even more overgassed.

16"/14.5 versions come with vented gas blocks.  Run fine suppressed & unsuppressed.

10.4 generally come with non-vented gas blocks.  A few years ago there was a vented 10.4 gas block (smaller vent than 14.5/16).  Despite what the internet says these ran just fine suppressed and unsuppressed for hundreds of thousands / millions of rounds.  Albeit more recoil / snap when compared to a 2023 finely tuned DI gun but again those guns and what defines "finely tuned" didnt exist until recently.

Adjustable gas blocks are becoming more popular.  For the short guns especially this is a good thing.  

Make sure to use a HK or heavier buffer.

DI guns have come a very long way in 20 years but there are benefits to the piston system.

That was almost 20 years ago and HK quickly realized their mistake when suppressed, so they added the vent. It’s much better suppressed.

I'm not sure how the Brownells BRN-4 barrels are gassed, but I chopped and threaded a 16" MR556 barrel down to 12.5" at work and only had to open up the gas port slightly from its original size.

I also run a Vltor A5 buffer setup, so my complete rig runs super smooth suppressed and unsuppressed. I think if you followed a similar formula you would be very happy. I cannot speak to a factory 10.4" HK upper and how gassy that would be.

I converted a Titan receiver set to use a 10.5" AR barrel and installed a vented 14.5 gas block over a 1.6mm gas port. It shoots great with a suppressor but is SUPER over gassed.

Which buffer and spring?

A5H0 buffer and spring. That's not even the problem though. The gas rings ate my US-made piston, and the carrier key on my Brownells bolt carrier has started to deform. No gas to the face, but the accelerated parts wear is concerning. I replaced the piston with a OEM HK one, but haven't had a chance to fire it since then.

Fuck, im getting old.  Not that old though.  Dunno, our long guns were vented with "14.5/16" gas blocks.  Short guns didnt have vents but some later did but we were told 14.5/16 vented gas blocks =/= 10.4 vented gas blocks.  10.4 guns ran either way, albeit in normal psychotic 416 cyclic rate even with the vent.

Yes, buffer amd spring matter.

An equivilent spring in strength to the HK spring is necessary. Just up buffering won't help.

Excessive bolt speeds caused by improper buffer/spring will manifest excessive wear and damage.