AR-15 Rifle Handguard question

[socalbeachbum]

I am ordering up parts to build my son an AR-15 upper. The barrel has the gas port at the 'rifle' position.

My question is, in choosing a free float handguard length, what size do I choose to have the handguard terminate right at the rear of the gas block? I'm building it in such a way that it could accept later, any gas block, or iron sight gas block, so the handguard must end at the rear of the gas block.

 

[MTMilitiaman]

The rifle length gas system is 11 inches, I believe.

 

[Ifishsum]

My rifle length handguards are 12"

 

[Varminterror]

Rifle float tubes are 12".

 

[Hummer70]

On my 16" AR I have a Daniel Defense that goes right up to the just short of the end of the barrel (low profile gas block). With the bird cage suppressor only about 2 1/2" extend beyond the hardguard. They make two lengths and I have the long one.
I wanted their long handguard so I could mount a folding bipod at the very front (like the BAR 1919A2).
It is a "car gun" I carry in the very back in the little tool box under the deck in our Honda Pilot. It is zeroed for 100 yard POA/POI.
Also has a collapsible stock. It is a heavy barrel so you know you have something different soon as you pick it up.

I also have a modified case deflector that directs ejected brass to between 1:00 and 2:00 and not in the danger zone the A2 developed. I molded epoxy putty to make it and degreased the bump first. I thought it would fall off eventually and has been on it about 8 years now I guess.

I also have a Hard Blue barrel on it so it should never wear out.

 

[FL-NC]

Rifle size.

 

[Everready73]

Leaving the gas block exposed might not be the best idea. Especially if it is not pinned. That is one of the advantages of having the handguard cover the gas block... Protection. Its not hard to remove the rail if you would ever want to replace the gas block and they make front sites that mount to the rail, so you wouldn't need to mount one to the gas block

 

[socalbeachbum]

Does anyone know the length I need to stop just behind the gas block stepdown?

 

[boom boom]

Does anyone know the length I need to stop just behind the gas block stepdown?

Free float tubes are generally designed to go over a low profile gas block while traditional handguards use the gas block as a forward stop for the handguard front cap. My guess it either you go with a non-free float design, use a mid length free float tube, or you modify a rifle length free float tube by cutting the end.

Offhand, I have never seen a free float specifically designed to allow access to the gas block so you can change them. Gas port length is 7 inches for carbines, 9 inches for mid length, and 12 for rifle. I do know that some mid length free float tubes run at least 10.5 inches long so that might be your best bet aside from cutting a rifle free float tube (just noticed that Troy makes an 11 inch mid length special order at Midway so that might be the way you want to go).

Given the diversity of AR rifle handguards, it is possible that someone, somewhere, makes what you want. I would suggest calling somewhere like Brownells or Midwayusa and asking that specific question.

 

[Varminterror]

Does anyone know the length I need to stop just behind the gas block stepdown?

You've been given the answer multiple times above, although there's been a few derailments of non-related or nonrelevant (or incorrect) info. "Rifle length," aka 12", will stop right at the barrel shoulder, not making contact with the gas block. "Extended rifle," 13.5", and 15" models are designed to cover low profile gas blocks, which is NOT what you want.

I've used exposed gas blocks without pins for many years, and I see no advantage in "protection" by covering the gas blocks. If you're banging into a gas block hard enough to cause it to come loose, then you either did a piss poor job installing the block, or you've hit it hard enough you'd have broken most free float handguards on the market anyway, maybe even hard enough to fracture the upper at the barrel extension mortise, or fracture the lower at the extension bridge. That one sounds like a Red Herring to me.

If you want a free float handguard with an exposed gas block, leaving room to use a fixed A2 sight base/gas block if you so desired, then you're looking for a 12" handguard, aka "Rifle Length."

An example - for @boom boom - of a free float rifle length hand guard which ends behind the gas block is the Bushmaster Varminter Special or Remington R15 VTR Predator, pictured below. The vast majority of free float handguards are made in the same dimensions to give this same look - "rifle" ends behind a rifle length gas block, leaving it exposed, carbine end behind a carbine length gas port... Unless a guy seeks an "extended" handguard, over length (i.e. 15" or 18") or uses a size up compared to their gas length (i.e. a rifle length forend on a mid-length barrel), most forends are NOT designed to cover the gas block.

 

[socalbeachbum]

Varminterror, clear, thanks, 12" got it. If I had more patience, I'd just get the barrel in my hands then measure. But I don't. Thanks!

 

[Doc7]

This is a rifle system with a Samson Evolution 12.37" rail.

 

[socalbeachbum]

doc7, exactly what I want thanks

 

[boom boom]

You've been given the answer multiple times above, although there's been a few derailments of non-related or nonrelevant (or incorrect) info. "Rifle length," aka 12", will stop right at the barrel shoulder, not making contact with the gas block. "Extended rifle," 13.5", and 15" models are designed to cover low profile gas blocks, which is NOT what you want.

I've used exposed gas blocks without pins for many years, and I see no advantage in "protection" by covering the gas blocks. If you're banging into a gas block hard enough to cause it to come loose, then you either did a piss poor job installing the block, or you've hit it hard enough you'd have broken most free float handguards on the market anyway, maybe even hard enough to fracture the upper at the barrel extension mortise, or fracture the lower at the extension bridge. That one sounds like a Red Herring to me.

If you want a free float handguard with an exposed gas block, leaving room to use a fixed A2 sight base/gas block if you so desired, then you're looking for a 12" handguard, aka "Rifle Length."

An example - for @boom boom - of a free float rifle length hand guard which ends behind the gas block is the Bushmaster Varminter Special or Remington R15 VTR Predator, pictured below. The vast majority of free float handguards are made in the same dimensions to give this same look - "rifle" ends behind a rifle length gas block, leaving it exposed, carbine end behind a carbine length gas port... Unless a guy seeks an "extended" handguard, over length (i.e. 15" or 18") or uses a size up compared to their gas length (i.e. a rifle length forend on a mid-length barrel), most forends are NOT designed to cover the gas block.

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