Large Frame AR build issues

[kentuckyMarksman]

I'm finishing up my first large frame AR build. Pretty much everything went together just fine, except for 1 issue I'm having.

I went with a ZEV receiver set, and the ZEV Wedgelock handgaurd. I also went with the JP 6.5CM Barrel Kit, that comes with their gas block.

After I installed the barrel on the receiver, I tried sliding the handgaurd onto the upper receiver. I noticed that I had to remove the gas screw in order to get the handgaurd in place. I removed the gas screw from the gas block and installed the handgaurd. Now I notice that the hole for the gas screw is partially blocked, so I can't get the gas screw reinstalled.

I also noticed that the gas block is extremely close to the inside of the handgaurd. It's not touching anything, but I can press against the handgaurd and make it touch the gas block.

Is it a concern that the gas block is so close to the handgaurd?

Should I enlarge the closest M-Lok slot on my handgaurd to allow me to reinstall my gas screw, or should I look for a different gas block, or a different handgaurd?

 

[CrabsandFootball]

Its one of those things you hope you caught before you bought the components.

The Barrel flexes under fire and you may see some weird pattering due to it. I would not feel comfotable machining away the inside of that rail, which may also create structual issues with it.

Your good options are replace the handguard with something that has more internal clearance or Replace the gas block with something low profile.

This is one of the reasons you want to stick with the same manufacture if you can with Large Frame AR's. There is so much variance and no real spec that you often time run into fitment and function issues.

Those types of gas blocks are notorious for failure as well.

Not sure if that hand guard is mated to that upper but you may have to choose which you want more, a ZEV receiver set or a JP barrel.

 

[kentuckyMarksman]

The barrel is .875" at the gas block. Is there a lower profile gas block with the adjustment screw farther forward?

My barrel has the +2" gas system, is there a larger diameter handguard long enough to cover the gas block?

Guess another option is to find a shorter ZEV handguard that doesn't cover the gas block (I'd prefer it covered).

Is it the JP gas blocks that are notorious for failure? What type of failures are common with them?

 

[Mute]

A possible solution is to find a new gas block that will fit under the handguard, perhaps one that fits with a set screw rather than clamp on style that is usually bulkier.

 

[bigjake83]

A SLR or SA set screw AGB will fix this problem.

 

[bigjake83]

Also does the handguard make contact with the left and right when flexed or just when flexed down??? Because it is common to have to relocate the bipod attachment because of the relationship to the GB and crews or fasteners from the pic rail attachment.

 

[kentuckyMarksman]

It makes contact left and right when flexed. It does not make contact up or down when flexed.

 

[MNhunter1]

Should be no contact, if there is, it will likely impact your accuracy, essentially defeating the "free float" of the barrel. Either way, I always favor an adjustable block on any larger frame/large caliber AR. They are much more selective than their smaller AR15 platforms and greatly benefit from the adjustable gas. All my free floated barrels with low profile blocks tucked under the handguard use a .750 gas block journal. Sounds like you are trying to squeeze a barrel and block combination underneath a handguard with an ID that is not sufficient to accommodate it. If your block cannot be secured to the barrel and clear the handguard for installation, that is a problem.

 

[kentuckyMarksman]

My handguard mas in inside diameter of 1.325".

It looks like the Superlative Arms is only 1.044" wide. That might be my answer. Current gas block is 1.320" wide.

 

[MNhunter1]

My handguard mas in inside diameter of 1.325".

It looks like the Superlative Arms is only 1.044" wide. That might be my answer. Current gas block is 1.320" wide.

I have no experience with the Superlative Arms blocks. I've been very happy with the SLR Sentry blocks.

 

[kentuckyMarksman]

The SLR Sentry 8 says it needs 1.35" inside diameter, which I don't have. SLA looks like it will work though.

 

[celltech]

Superlative Arms blocks are good to go. Have one on my 6.5 Creed and it works great. Odin Works adjustable is also good, but I would not recommend it for anything hotter than a .308

 

[kentuckyMarksman]

I installed the Superlative Arms gas block. I probably have close to .25" clearance to the top of the rail now, and about .125" on the sides. Much better than before.