Drilling out a LaRue Quad Rail handguard..

[jlow]

I have an old LaRue Stealth upper with a 20” barrel and rifle length gas system. I would like to replace the barrel with a JP16” JP Supermatch barrel with a mid-length gas system together with a Seeking Precision Low Profile Adjustable gas block adjustable gas block.

The problem I am facing is although the gas block will fit into the quad rail, there is no opening in the bottom of the rail to tighten the 2 hold down screws for the gas block. I think both the adjustment and lock down screw can be taken out first to get the gas block in and the gas adjustment screw can be reinserted later through one of the side ports, but the only way I can think I can reinsert the two lock down screws is to drill out the rail so that the two gas block lock down screws can be inserted and tighten down.

My question is has anyone done this before? Is there any problem with doing this that I am missing? I know I have to measure the location of the screws carefully and drill the handguard with a drill press, but anything else?

 

[RyanScott]

I’m missing something. Why don’t you take the rail off of the barrel nut, attach the block and then put the rail back on?

 

[jlow]

A good question. Unfortunately at the back of the rail, there is a locking system and a hole (see image). The hole is not large enough for you to pass through the gas block mounted on the barrel. So the gas block can only be mounted after the rail is in place. With the 20" previous barrel, this was not a problem since the gas block sits outside the handguard, but with the shorter barrel, the gas block now sits inside the rail so...

 

[chongoMT]

Before you drill access holes, try this longer multi step process. Identify where exactly the gas block needs to be and where those set screws are gonna live. Install the gas tube into the gas block and then start that onto the barrel with a loose handguard, attempt to get the gas tube and gas block all screwed on while the handguard is loose. Be gentle and twist only enough to attempt access to the set screws through one of the other holes, but be careful not to crank the gas tube and bend it.

 

[jlow]

chongMT - It's a good idea except with the quad rail handguard, it is really tight in there. For example, just holding the gas block by the gas tube and inserting into the handguard, it is impossible to rotate the gas block inside the handguard.

RyanScott - your question is actually very good. If you look at the picture of the handguard I posted, you will notice the hole is not round but it has an area on the top to allow passage of a regular gas block. My problem as it turns out is because I am using a Seeking adjustable gas block. If you look at this photo, you can see it does not taper up the same way on both sides. With the right side much "fatter". When I try to push it through the handguard hole, this is where it jams.

I am now wondering if I can grind out this area inside the handguard - it won't be real easy as it is about 1" deep and all solid aluminum but I am thinking a grinding bit on a drill press may work?

 

[Molon]

A good question. Unfortunately at the back of the rail, there is a locking system and a hole (see image). The hole is not large enough for you to pass through the gas block mounted on the barrel. So the gas block can only be mounted after the rail is in place. With the 20" previous barrel, this was not a problem since the gas block sits outside the handguard, but with the shorter barrel, the gas block now sits inside the rail so..

Maybe I'm missing something in your description of the problem, but the "locking ring" is a separate piece from the hand-guard. Remove the locking ring from the aft section of the hand-guard. Will your gas block now pass through the entire length of the hand-guard? If so, attach the locking ring to the installed barrel nut and make sure that it is properly aligned. Next, install your gas system on the barrel. Now, slide the hand-guard on, making sure that the index pins on the hand-guard are properly aligned with the corresponding holes on the locking ring and then tighten-down the collar.

The pic below shows on of my builds with a Larue hand-guard that has an intermediate gas system underneath the hand-guard.

....

 

[jlow]

Molon - good to hear from you. It's been a long time.

The problem here is the adjustable gas block. A few photos:

Photo one shows the locking ring which you are right can come off.
Photo two shows the partition which a regular gas block can pass through.
Photo three shows the profile of the Seeking adjustable gas block which does not fit the hole in the partition. Notice the bulge on the left as pointed out by the red arrow.
Photo four shows me trying to get the gas block through. Notice the interference due to the fat side of the gas block (red arrow).

 

[Molon]

Molon - good to hear from you. It's been a long time.

The problem here is the adjustable gas block. A few photos:

Photo one shows the locking ring which you are right can come off.
Photo two shows the partition which a regular gas block can pass through.
Photo three shows the profile of the Seeking adjustable gas block which does not fit the hole in the partition. Notice the bulge on the left as pointed out by the red arrow.
Photo four shows me trying to get the gas block through. Notice the interference due to the fat side of the gas block (red arrow).

Well that just sucks.

 

[jlow]

Yea... I also looked at a number of other adjustable gas blocks but it seems none of them retain that "slim" profile. I am apparently not the first person to find this out as I saw a similar post on "6.5 Grendel Forum" last year with the same issue... See link.

http://www.65grendel.com/forum/showthread.php?19818-Larue-LAT-disassemble-what-am-I-missing

I am now wondering if that part at the rear of the handguard can be removed? It seems that is a separate piece that is joined to the actual handguard which is CNCed . If I can remove it, I can put it on after I put the gas block on the barrel and then re-attach the handguard to the rear piece - don't know, it's a long shot but I will talk to LaRue tomorrow to find out.

 

[oldfatguy]

I am now wondering if that part at the rear of the handguard can be removed? It seems that is a separate piece that is joined to the actual handguard which is CNCed . If I can remove it, I can put it on after I put the gas block on the barrel and then re-attach the handguard to the rear piece - don't know, it's a long shot but I will talk to LaRue tomorrow to find out.
[/QUOTE]

Would not be too difficult to file (or Dremel) the interfering portion of the ring to make clearance for the bulging side of the gas block.

OFG

 

[jlow]

LOL! Guess what I have been doing with a Dremel and an aluminum oxide grinding bit? It's working and the gas block can now go in about 1/3 of the way. Will do the rest tomorrow.

 

[oldfatguy]

LOL! Guess what I have been doing with a Dremel and an aluminum oxide grinding bit? It's working and the gas block can now go in about 1/3 of the way. Will do the rest tomorrow.

While you are working on it might be a good idea to grind a bit of extra clearance so removal will be easy.

OFG

 

[Scotts556]

I would of just sold that hunk of shit hand guard from 2003 and gotten a more modern one.

Scott

 

[jlow]

Annnd the trolls have finally showed their ugly head. Much slower than I thought! Must be getting weak in their young age...

 

[jlow]

A little grinding there a little grinding there, and it all fits like a charm.... All together and gas block is not touching the handguard but gas adjustment screw is in one of the openings on the top to allow easy gas adjustment - sooo sweet!

 

[oldfatguy]

Love it when a plan comes together.

OFG

 

[jlow]

Just a little eye candy to thank everyone for helping me think/work through this. "Adjusted" barrel opening, and gun setup for SD. Weight BTW dropped from a whopping 11 lb 3 oz to 9 lb 5 oz a drop of 30 oz or about 2 lbs.

 

[Wolfhound76]

A little late but there is an adjustable that fits under the handguard. The SLR sentry 7 set screw version fits with no modification. The adjustment screw is towards the muzzle end so you just need a long Allen wrench to adjust it. If you use a LaRue barrel the .450 setscrew version lines up with the front and rear dimples in the barrel.

No help to you, but maybe it'll help someone else with the same problem. I use their non adjustable as it saves a little weight over the LaRue block.

 

[jlow]

Thanks! It's an interesting option. The SLR Sentry does indeed seem slimmer, but if someone is thinking of using one for this specific application i.e. with a LaRue Quad Handguard, please keep in mind that it might still need some adjusting due to the adjustment screws that sits on its side. The handrail is a tight fit out of the box and so you might not know until you either try it or get exact dimensions from the company.

I of course was glad that I did not have to throw away a $70 gas block and then have to buy one that cost $126.

FWIW, adjustable gas blocks are super to fine tune the gas so that you get less mangled case rims. Important to me as I use Lapua brass.

 

[Wolfhound76]

Thanks! It's an interesting option. The SLR Sentry does indeed seem slimmer, but if someone is thinking of using one for this specific application i.e. with a LaRue Quad Handguard, please keep in mind that it might still need some adjusting due to the adjustment screws that sits on its side. The handrail is a tight fit out of the box and so you might not know until you either try it or get exact dimensions from the company.

I of course was glad that I did not have to throw away a $70 gas block and then have to buy one that cost $126.

FWIW, adjustable gas blocks are super to fine tune the gas so that you get less mangled case rims. Important to me as I use Lapua brass.

There's a set screw version as well. The clamp on won't fit.

 

[jlow]

It's been a couple of months since I last posted, and this build is now finished and here passed it's final test.

Took the new build out for the final real test at 600 yards - Larue Stealth upper/handguard, JP Supermatch 16" barrel, Afcom billet lower, Trijicon Accupoint 1-6x, and AccuTeck bipod. Shooting Berger 73 grain BT target/Lapua brass/Wolf SRP/Varget at 2,655 fps.

My Applied Ballistics app got me on target on first shot at 17.5 MOA elevation and only have to take two shots to adjust for the wind which was a little squirrely today ~10mph from south at 3 O'clock.

As expected, with only a 6x scope, it's not exactly my 55 power NF and I could only hold approximately center on target. Still very happy that after the first two initial shots, the next 12 rounds managed to stay in the 9 and 10 ring of an F-class target for a group size of 1.5 MOA (9.3"). Now I just need to clean and load up the brass for this SD gun.

 

[Farmerman55]

Sorry for digging up an older thread, this has been very useful for me. I’m researching trying to use an adjustable gas block & a 12” Larue upper now, running suppressed mid-length gas system. Still trying to find a gas block that will fit!

 

[jlow]

Use the Seeking adjustable that I used and follow my steps to change the Larue, it worked perfect for me.

 

[Txhoghunter35]

I am having the same issue with a 350 legend I'm changing. Except I use .875 Gas Block LaRue should really change this its frustrating. I have tried a adjustable and non adjustable neither will fit.

 

[Txhoghunter35]

I have an old LaRue Stealth upper with a 20” barrel and rifle length gas system. I would like to replace the barrel with a JP16” JP Supermatch barrel with a mid-length gas system together with a Seeking Precision Low Profile Adjustable gas block adjustable gas block.

The problem I am facing is although the gas block will fit into the quad rail, there is no opening in the bottom of the rail to tighten the 2 hold down screws for the gas block. I think both the adjustment and lock down screw can be taken out first to get the gas block in and the gas adjustment screw can be reinserted later through one of the side ports, but the only way I can think I can reinsert the two lock down screws is to drill out the rail so that the two gas block lock down screws can be inserted and tighten down.

My question is has anyone done this before? Is there any problem with doing this that I am missing? I know I have to measure the location of the screws carefully and drill the handguard with a drill press, but anything else?

I Did the exact same thing on mine. I called LaRue they are zero help on anything except how to process your card. I actually bought a milling bit put it on my router and shaved the sides down so I could use my JP adjustable works fine can't see it at all from the outside.

 

[JohnCarter17]

And this is an answer to this problem also

https://rubbercityarmory.com/product/rca-adjustable-gas-key/