Indexing a three-prong flash hider?

[Doc Safari]

I'm waiting for the post office to deliver this AAC Blackout flash hider, three-prong, not for use with a suppressor.

https://www.aimsurplus.com/product.aspx?item=ZX64177&name=AAC+BLACKOUT+FLASH+HIDER+5.56MM+1%2F2-28+NON-SILENCER&groupid=9427

I'm the first to admit I'm not an expert on this stuff, but it seems to me that it should be indexed with one of the slots at top dead center.

Am I correct?

Supposedly the suppressor version does not use a crush washer, but requires Rocksett instead.

This version seems more appropriate with a crush washer?

I confess I looked for installation instructions online and only found instructions for the suppressor version.

What do you think?

[markm]

I installed mine one of two ways. No index, for can use. And centered prong at bottom dead center like an A2. There's no wrong way.

[Doc Safari]

I installed mine one of two ways. No index, for can use. And centered prong at bottom dead center like an A2. There's no wrong way.

I guess my reasoning is that you want a prong on the 6 o'clock position for the same reason the A2 Birdcage flash hider is closed on the bottom. Without really good technical info to the contrary that's how I'll have it installed. If you look at a Valmet M76 flash hider it appears they followed this pattern.

[voiceofreason]

I've always figured a 3 prong flash hider is going to be equal on all sides. I understand the concept that you want the two prongs on top to act as a muzzle brake to counteract muzzle rise... but the amount of force helping one from a flash hider is minimal compared to a true brake.

Have run A2 birdcages no indexed correctly in a pinch, didn't notice a difference in recoil characteristics, but that is not a scientific study, just experience from one day's shooting

[26 Inf]

I'm waiting for the post office to deliver this AAC Blackout flash hider, three-prong, not for use with a suppressor.

https://www.aimsurplus.com/product.aspx?item=ZX64177&name=AAC+BLACKOUT+FLASH+HIDER+5.56MM+1%2F2-28+NON-SILENCER&groupid=9427

I'm the first to admit I'm not an expert on this stuff, but it seems to me that it should be indexed with one of the slots at top dead center.

Am I correct?

Supposedly the suppressor version does not use a crush washer, but requires Rocksett instead.

This version seems more appropriate with a crush washer?

I confess I looked for installation instructions online and only found instructions for the suppressor version.

What do you think?

Not that you'd want a suggestion from me, but.....

You don't want to torque it too much or too little to get it indexed correctly.

I use crush washers on A2's, for everything else I either peel washers (if supplied with the device) or these:

https://www.brownells.com/rifle-parts/barrel-parts/rifle-barrel-hardware/washers/ar-15-1-2-28-accu-washer-system-prod54363.aspx

I try to stay at low torque value and use Rocksett.

[Doc Safari]

Not that you'd want a suggestion from me, but.....

You don't want to torque it too much or too little to get it indexed correctly.

I use crush washers on A2's, for everything else I either peel washers (if supplied with the device) or these:

https://www.brownells.com/rifle-parts/barrel-parts/rifle-barrel-hardware/washers/ar-15-1-2-28-accu-washer-system-prod54363.aspx

I try to stay at low torque value and use Rocksett.

Really? Why the difference? (Just because I took issue with you on one thread doesn't mean I don't value your input). :)

EDITED TO ADD: Okay, I ordered a set based on your recommendation due to the bore alignment issue. Is there any other reason not to just use a crush washer?

[26 Inf]

For a non-suppressor device I wouldn't think so, it is the mil-spec.

I have a little note with them in my parts bin 'convex portion toward barrel shoulder' to keep me from getting mixed up about which way they go.

Those accu-washers are nice, unless you need the exact same index on every device, the kit will last for several installations.

ETA: Brownells video on the install using crush washer - https://www.brownells.com/aspx/learn/learndetail.aspx?lid=11441

[Iraqgunz]

Crush washers are fine for this and it doesn't need indexing.

[MegademiC]

Mine is indexed opening up top. With a prong up too, i wonder if the gas in line of site is diminished(or worse?).

[Doc Safari]

Mine is indexed opening up top. With a prong up too, i wonder if the gas in line of site is diminished(or worse?).

It's a flash hider...and one of the best. The whole point is that you don't get gas in line of sight. Right?

[LDB]

So it's prongs at 2, 6 and 10 which gives slight protection from stuff coming up into the barrel especially when prone and possibly very slightly reduces muzzle climb due to the opening at 12.

Or it's prongs at 4, 8, and 12 which stops any gasses from coming straight up into line of sight.

Or?

[Doc Safari]

So it's prongs at 2, 6 and 10 which gives slight protection from stuff coming up into the barrel especially when prone and possibly very slightly reduces muzzle climb due to the opening at 12.

Or it's prongs at 4, 8, and 12 which stops any gasses from coming straight up into line of sight.

Or?

I was only thinking that having the opening at top dead center would stop dust from being kicked up in the prone. Even without flash, there would still be concussion exiting the muzzle and if it's directed down it would kick up dust.

I could be wrong: it's NOT a muzzle brake so the blast cone might be contained enough that debris is not kicked up even in the prone with a slot on the bottom.

Apparently the orientation doesn't matter.

[RVTMaverick]

Hey Doc.

My .02, I have been under the impression these should always be timed with a solid at the bottom\6:00 position, just for the simply reason of, when one is shooting prone, to help with
NOT kicking up dust/sand....

Peace Jeff


I was only thinking that having the opening at top dead center would stop dust from being kicked up in the prone. Even without flash, there would still be concussion exiting the muzzle and if it's directed down it would kick up dust.

I could be wrong: it's NOT a muzzle brake so the blast cone might be contained enough that debris is not kicked up even in the prone with a slot on the bottom.

[Mike Miller]

You're overthinking this. Just tighten it a bit and leave it alone, whatever orientation the prongs end up

[26 Inf]

The way the flats line up you'll have one prong dead center, either top or bottom. You can time it however you choose. I can't find that there is a 'right' way. Myself, I've indexed mine prong to the top (SilencerCo not AAC).

[jackblack73]

FWIW, the Dead Air flash hider is designed to be timed with an open spot at 12:00/tine at 6:00. I base that on the fact that there's a pin hole at 6:00, which allows the suppressor to be attached with index mark at 12:00. I don't know if there's a pin hole on the AAC.

Like others said, without a suppressor it doesn't really matter. But I would probably still time it correctly to satisfy my OCD.

[RVTMaverick]

Like others said, without a suppressor it doesn't really matter. But I would probably still time it correctly to satisfy my OCD.

LOL Plus 1

[bergners]

I'm waiting for the post office to deliver this AAC Blackout flash hider, three-prong, not for use with a suppressor.


This version seems more appropriate with a crush washer?

I confess I looked for installation instructions online and only found instructions for the suppressor version.

What do you think?

I found the instructions here http://www.advanced-armament.com/assets/images/pdf/manuals/Blackout_Flash_Hider_Installation_Instructions.pdf
In step four it says Do not use a washer with the Blackout flash hider. The design of the Blackout flash hider requires no timing.

Steve

[rustyx]

Use timing washers not a crush washer.

[Renegade04]

Given that 3-prong FHs do not need to be indexed in any certain way, I did choose to index mine with a single prong on top for aesthetics.

https://i.imgur.com/VLLVCwa.jpg

[LDB]

I think if I ever got one I'd go with a prong at 6 to reduce kicking up dust if/when I was prone.

[Doc Safari]

I just had my gunsmith install the flash hider with the supplied Rocksett and an Accu-Washer ( https://www.brownells.com/rifle-parts/barrel-parts/rifle-barrel-hardware/washers/ar-15-1-2-28-accu-washer-system-prod54363.aspx ). Since orientation isn't an issue I had him install it with one of the prongs top-dead-center for aesthetics.

He raved highly about the Accu-Washer system.