HM Defense 300blk FTF

[FUPA-0]

Hey guys I'm pretty new to ARs especially troubleshooting them. I bought a HM Defense 300Blk with 16" barrel second hand. It doesn't look like the original owner altered anything with the gas system or BCG.

Here's the problem:
I am shooting 123gr Magtech and 110gr Hornady Black soft tip ammo so no subs.
The first couple times to the range I was shooting just the Magtechs in a Hex mag and would get one failure to feed out of every 30rds. It was random so it wasn't happening at the beginning of the mag or end. This happened after a couple of range trips so I decided I needed to try a weaker buffer spring. I bought a Nemo 300blk spring that is a little bit shorter then the stock spring.
Last night night at the range I used the Nemo spring and was shooting the 110gr Hornady Black ammo in a Pmag gen2 magazine. This time I had two failure to feeds with the hornady ammo. One FTF about five rounds in and another about two rounds from empty.
The crazy thing is, this trip, I didn't have any FTF with the Magtech ammo and I used both the Hex mag and Pmag.
I shot about 100rds of the Hornady Black and 60rds of the Magtech. The BCG does lock back on an empty mag sometimes. The rifle has no problem ejecting empty brass. I clean the AR after every trip to the range and lube it well but not over lube it. From what I gather online if the weaker buffer spring doesn't work then I probably need to open up the gas port to 1/8th. I know the factory gas port isn't that big now.

Thank you for your time.
Below are pictures of the two FTFs from last night and pictures of the rifle with the rail off.

[FUPA-0]

[rebel]

Looks like the gas block is leaking pretty bad.
Not saying that's your problem but could cause issues.

[FUPA-0]

Looks like the gas block is leaking pretty bad.
Not saying that's your problem but could cause issues.

Thanks Rebel, I was thinking that didn't look right and could explain the intermittent FTC.

[dellet]

Fix the gas leak, go back to the original spring, probably ad an adjustable gas block. Looking at that port it looks huge, you might measure it while it’s apart.

Pistol gas, a large port and supers are a recipe for disaster. Add in a reduced power spring and it might just be cycling too fast.

[Mike7.62]

Fix the gas leak, go back to the original spring, probably ad an adjustable gas block. Looking at that port it looks huge, you might measure it while it’s apart.

Pistol gas, a large port and supers are a recipe for disaster. Add in a reduced power spring and it might just be cycling too fast.

That was my first thought, but there are too many variables in semi auto malfunctions, and I am by no means an expert.

[FUPA-0]

Fix the gas leak, go back to the original spring, probably ad an adjustable gas block. Looking at that port it looks huge, you might measure it while it’s apart.

Pistol gas, a large port and supers are a recipe for disaster. Add in a reduced power spring and it might just be cycling too fast.

That was my first thought, but there are too many variables in semi auto malfunctions, and I am by no means an expert.

I'm with you there. This is my first AR and there are so many different things that can cause this issue. I'm going to call a couple of gunsmiths and get their take on it too.