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File 147606784655.jpg - (15.04KB , 600x600 , 6C-Ti-600x600.jpg )
99676 No. 99676 ID: 1519ac
Does anyone have an adjustable gas block they would be willing to take apart and photograph, and if possible measure with calipers or micrometers? I'm specifically interested in the part that actually cuts off gas flow, and any detent system or other system the locks the adjustment. I'm in the process of putting together a lightweight AR and don't really want to drop the money on an adjustable titanium block, so I was considering making one. Maybe I'm over thinking this and all I need is a ball detent interfacing with straight knurling on a standard socket head cap screw. Maybe I need to make a custom screw with axial slots to engage the detent. I don't know. So any advice, pictures or other insights are welcome. Comments on who makes the best adjustable gas block are also welcome.
4 posts omitted. Last 50 shown. Expand all images
>> No. 99681 ID: 19518e
>>99680
My first adjustable block used the screw that retracted and stuff, it's not great. I would definitely go with the captured pin way, and yes a straight cut is better, that's obvious now. I would just make sure that "full gas" allows for just a bit more than the regular port size, in case the adjustment system seeps a little or you have some weaker ammo to shoot, it's cold, it's dirty, or something. If your regular port is [number pulled out of ass] 0.065" in diameter, make it like 0.085" [more ass numbers] or even a little more. Doesn't matter that much now that you can throttle it with the adjustment.

I got tomorrow off, it's a bit past 1am here, not an uncommon time for me in any case as an evening shift thing. Head is a bit better, thanks.
>> No. 99684 ID: 1519ac
File 147612623215.jpg - (74.74KB , 750x562 , main.jpg )
99684
Also planning on modding a standard bolt carrier into something like pic related. Thoughts?
>> No. 99686 ID: 19518e
>>99684
Just remember, it'll be more sensitive to ammo, environment, and debris if the reciprocating mass is lower. You might have to play with spring and buffer weight to get it reliable without much maintenance.

Good thing that's all easy and relatively cheap to do on the AR, especially with the adjustable block.
>> No. 99705 ID: 1519ac
Can someone who has a commercial adjustable gas block confirm if it has a screw, a cut pin system like WPR described, or some other method of adjusting gas?
>> No. 99710 ID: 6057a8
>>99705
I can't speak for all the various adjustable blocks out there but the SVT-40 and SIG 550s use a drum with varying holes in it. They work well for preset position adjustment gas blocks.

I was thinking of suggesting a ball bearing detent that would lock in ribs or divots cut into the back of the larger .375" pin head to have an actual "setting" of sorts. Might be useful.
>> No. 99719 ID: 454a4b
File 147638096641.jpg - (206.29KB , 2376x1584 , IMG_0338-P50.jpg )
99719
Here's a dirty SG551 gas plug. :)
>> No. 101703 ID: 1519ac
So what do people like for a lightweight optic? I want to get an idea of what to be looking for during black friday sales etc. I was thinking something like an Aimpoint Micro or a Trijicon RMR but I really don't know much about that segment of the optic market. Suggestions?
>> No. 101704 ID: bd9939
File 147838680994.png - (717.70KB , 1280x801 , 1MRO_C_2200003_45__45465_1439478233_1280_1280.png )
101704
>>101703
Trijicon MRO

I bought one along with an alamo four star D-loc mount for waifu's rifle, and it blows my old aimpoint out of the water (that's not to say the aimpoints aren't perfectly useable). I like a teensy bit (3x) of magnification for target identification and use a baby ACOG, but would totes buy another MRO if I was looking for a strict home defense/up close type setup.
>> No. 101705 ID: 19518e
>>101703
I can't say enough good things of the Aimpoint Micro. If you shoot both eyes open, the Trijicon can get a little weird with the small magnification on it, it's not a true 1x red dot.

Not a big problem as it is a good optic, it's more about your preference.

Beyond that, a 1-4x, 1-6x, or another 1x-whatever optic is really nice. A lot of companies throw out pretty damn good stuff these days, they really do pretty much have the best of both worlds.
>> No. 101707 ID: 1519ac
>>101705
Not looking for a variable on this gun. Something like a strike eagle is too heavy. I have a Burris 2x-10x on my first AR and it's nice but huge and heavy.
>> No. 101708 ID: fb893e
>>101707
Take a look a Leupolds. The Mark AR is under 10 ounces before the mount and the VX-R Patrol is 11.
>> No. 101709 ID: cd5ece
File 147839574021.jpg - (188.25KB , 1200x675 , scarrrrrr.jpg )
101709
>>101704
Me and the Triji MRO just don't get along. I've tried two and I can't shoot them with both eyes open. The MRO has more fish eye effect than other red dots, and it just doesn't work for me. I've got no problems with Aimpoint Micros, PROs, COMPs, EoTechs and RMRs.

Here's my SCAR 16 with Trijicon H1 and 4x magnifier.

hehehehe
>> No. 101721 ID: b70387
File 147843452347.png - (896.61KB , 1200x1064 , LEU_LCO_Angle.png )
101721
Anybody got an opinion on Leupold LCOs?
>> No. 101736 ID: 454a4b
File 147845465954.jpg - (71.42KB , 900x600 , P1130749-900x600.jpg )
101736
>>101721

Why is it so fucking expensive?
It doesn't even include the D-EVO that they want you to pair it with. Both together costs 3200 USD (list price).
>> No. 101759 ID: 6ca38e
>>101736
I'm still just so fascinated with that D-Evo thing for some reason. Like...it's pretty gimmicky...But it also might be p. cool.

I just wish the light transmission qualities were better. But given the concept behind it, I can see why it'd be tough to brighten the image up.
>> No. 101760 ID: 9dcda2
  >>101759
The scope alone goes for $1499.

http://ads.midwayusa.com/product/355414/leupold-d-evo-rifle-scope-6x-20mm-cmr-w-reticle-matte

While my ACOG goes for $1277. (Glad I bought it when I did.)

http://ads.midwayusa.com/product/1583138947/trijicon-acog-ta31-bac-rifle-scope-4x-32mm-dual-illuminated-horseshoe-dot-223-remington-reticle-with-ta51-flattop-mount-matte

The D-EVO really sounds badass.
>> No. 102000 ID: 6057a8
So I got off my chubby butt and started making my adjustable gas block mentioned here >>99681, >>99680, and >>99679.

I'm done operation 1, 2, and I'll have a webm of some 4140 steel getting cut for you guys. I'll make the adjustment plug and set up the two last ops probably next week.

Not sure when I'll be able to actually try it out as the rifle it'll be mounted on needs some other custom parts technically not related to the gas block.

Anyone know where I can get a rifle length gas tube for an ar-15 in Canada? AR parts up here are just a pain to look for...
>> No. 102002 ID: 19518e
File CIMG0585.webm - (3.89MB )
102002
Yeah it's grandpa slow/light cut machining, but I'd rather go slow when doing a one-off than risk an extended 4 flute solid carbide that isn't mine, a CNC milling machine that isn't mine and so on.

Not to mention I don't actually have the right post-processors. Yesterday I tried this in plastic and I had CADCAM'd the toolpath to do G17/G18/G19 plane selections so that 3D movements would be G2 and G3 movements in another plane to cut down on program size. It works well when you have the right post processor for the machine you're on, but my generic post didn't agree on what the hell was going on and machine wanted to go 19 inches off into space. Luckily I was proving out the program carefully so nothing crashed.

But I digress.

Second op was done after, just the gas port (spot drill, drill, spot drill through the hole that was just drilled, then drill through all that to the gas tube hole).

Third op is going to be side features (hole for gas tube pin, threaded hole for flat spring to prevent adjustment plug from playing around) and fourth op is part cut-off and adjustment plug hole. Easy enough, all the main metal removal is done.
>> No. 102003 ID: 19518e
Hrm.

Maybe it isn't 4140 after all. There was a little burr I wanted to remove just now so I took out my knife. Normally you can knock off burrs without much trouble but the S30V knife steel just skated across. I stopped being lazy and got a file. File barely scratched it and took the burr off with some persuasion. Truth be told, not sure what kind of steel it is, it was in the cut-off bin, I assumed it was just the regular stuff because we do make some parts out of it, and it isn't stainless.

Now that I scratch at it I might've cut tool steel. Thought it was a little chattery for how modest my program was, I had just assumed the machine had some slack (it helix bored 0.002" oval, it isn't a brand new drum-tight machine) and the slack let in a bit more vibration, coupled with the long tool and part sticking out of the vise quite a bit.
>> No. 102004 ID: 19518e
File 148066542488.jpg - (590.67KB , 2389x1329 , 20161201_201558.jpg )
102004
>>102003
Oh well, tooling looked brand new after and chips looked nice.

I can't want to work on my other gas block idea, the one that doesn't need external adjustment because reasons and science.
>> No. 102006 ID: fb3bdd
>>102003
Oh well. At least your gas block will outlast the barrel its mounted on.
>> No. 102308 ID: 19518e
File 148369288446.jpg - (449.18KB , 1506x1516 , eeeeeeeeeeeeeeeeeeeeeeeee.jpg )
102308
>get home
>remember I need a 5/64ths roll pin to retain gas tube
>rummage through pins, mixed up in odds-and-ends bin
>measure
>nothing fits
>5/64th... That's 3-48 drill size
>oh neat I have a 3-48 tap!
>not set up with vise
>tap handles at work
>hold 3-48 tap in a loose jacob's drill chuck
>hold gas block in hand
>free hand 2 flute HSS plug tap
>this is not the correct way to tap this hard as fuck shit with tiny tap
>this isn't even the way to tap anything at all
>good tapping fluids at work, use what I have on hand
>tap visibly twisting
>it creaks, cracks, and makes snapping noises
>every
>quarter
>turn
>shitting bricks for a good five minutes straight
>thread almost through
>stop so that set screw can just wedge into the partial thread

Like a glove!
>> No. 102309 ID: f11f4d
File 148369636864.jpg - (311.29KB , 750x500 , olive oil.jpg )
102309
>>102308
Nice. You could up a disco with that thing.


>good tapping fluids at work, use what I have on hand
>> No. 102317 ID: 19518e
File 148373291677.gif - (2.95MB , 196x120 , 1349953292140.gif )
102317
After fiddling around with various AR things, I have a question that I've been struggling with in some way before and have not much idea how to answer.

What's the deal with bolt carrier gas vent ports?

Why two of them? I pin-gaged the three BCs I own, my Chinese AR measured .111" diameter on both holes, the Canadian NEA at .106", and the US-made LMT at .108" diameter.

Why that size (taking into account relative barrel gas port size)? Why not smaller holes (requiring less gas from the port in the barrel, therefore requiring a smaller port in the barrel)? Smaller holes on both ends would probably have less gassing when using a muffler, as there's less gas in the system in the first place. Why not larger on both sides (larger barrel port and larger carrier ports)? More gas might be less sensitive to ammunition variance or something.

I've talked about this to my engineer uncle, he said it was indeed a fairly complicated issue as the system does rely on gas pressure so you have a lot of pressure differentials that affect each other. Did Eugene and his team math it out or did they try it out in various configurations in trial-error?

tl;dr what are the design considerations of the carrier-to-gas-block port sizing?

BONUS ROUND!
In an LR-300, where the gas key doesn't separate from the gas tube, would the design considerations of carrier-to-block port size change? I remember seeing the LR-300 having more gas ports on the carrier; this makes sense if the gas block port sizes are the same as a similarly set-up AR-15.
>> No. 102319 ID: b70387
>>102317
Remember that the gas only leaves the BCG vent ports after the gas rings around the bolt have passed those ports, the bolt having been pushed out of the BCG a certain distance by that gas. Considering that, the size of the ports likely makes much less of a difference than their position lengthwise along the cylinder. The closer to the front of the BCG, the more time the gas has to act upon the piston on the back of the bolt, and, ostensibly, the smaller your barrel's gas port can be. The closer to the rear of the BCG, the less time, and the larger the barrel's gas port needs to be.

The BCG vent ports are meant to evacuate as much gas out of the BCG as possible, so they are likely sized up to the point of diminishing returns for efficacy at that purpose.
>> No. 102320 ID: 19518e
File 148374418528.jpg - (3.89MB , 2892x3258 , pshoooo.jpg )
102320
>>102319
>position of the ports along the carrier
That would also have to be matched with the cam pin channel. The bolt and cam pin travel a set distance, so up to a point the position of the gas ports would either not allow gas to escape at all, or vent gas before the carrier has fully rotated the bolt. Obviously, the latter wouldn't be as bad, but I bet it would be more sensitive to external factors as the system would not be pressurized for very long (shorter pressure impulse).

Took some closer-up pictures of the gas rings wiping past the gas ports from the Chinese AR.
>> No. 102328 ID: 1519ac
File 148383366364.jpg - (3.64MB , 5312x2988 , 20170107_185738.jpg )
102328
OP here. Here's my poor attempt at a lightweight carrier. 234 grams down from 268. Also I pussed out and bought a gas block. Too hard to find motivation after a 12 hour workday. Thanks for the ideas.
>> No. 102329 ID: 19518e
>>102328
It looks like an M16 (or FA, same thing) BCG, I think AR-15-cutting might reduce weight further if that's your goal.

Ignore if it is indeed an AR-15-cut BCG.
>> No. 102330 ID: 28e9ab
>>102328
Looks like a pretty good attempt to me. Keep it up. A couple more careful runs and you should be good to go.
>> No. 102331 ID: 1519ac
>>102330
Yeah, I was worried about compromising strength but looking at the picture of a commercial one I posted earlier, I can take way more off. Assuming they used similar steel that is.
>> No. 102333 ID: 1519ac
File 148391616723.jpg - (645.02KB , 4561x837 , 20170108_174740.jpg )
102333
Rifle so far. Waiting till the FRS-15 stock is available again(NYS). Current weight is 3.67 lbs with no mag.

>>102329
You're right, it's a FA carrier, but if I put in the AR cut now the only thing connecting the back would be the top.
>> No. 102334 ID: 19518e
>>102333
You could put a small slot on the underside like an AR-15 cut, without making it as wide.

Looking good so far, what handguard is that?
>> No. 102335 ID: 1519ac
>>102334
Handguard is a Brigand Arms Edge. Pretty pricy and I personally think it's kinda ugly especially at this shorter length, but it's extremely light at 3.9 oz, even compared to other carbon fiber handguards.
https://brigandarms.com/shop-3/brigand-edge-7/
Receiver is a TNarms polymer. Not real impressed with the quality but it'll do.
Upper is an anderson light weight.
Gas block is a SLR sentry 6 Ti.
Barrel is a Faxon Firearms 16" pencil. Would have gone with a 14.5" but no muzzle devices in NY.
>> No. 102336 ID: 19518e
>>102335
I don't mind the looks as I'm more of a practicality over most of the rest kinda person but that price is just rough for what looks like some carbon fiber stands woven together.

Do tell how well the Ti adjustable block goes. How does it function, exactly? Can it be taken apart?
>> No. 102337 ID: 1519ac
File 148394549849.jpg - (2.21MB , 5312x2988 , 20170109_015643.jpg )
102337
>>102336
It's pretty simple. A flat spring pushes on a plunger that engages three axial ballmill cuts on a screw. Basically what you warned me against in the first few posts. here's a disassembled pic that is somewhat confusing because I put the parts on the wrong side. The spring/plunger should be rotated 180 and the screw goes on the other side, not in the gas tube hole like it's lined up with. I will try to remember to update once I get it shooting but it may be a while.
>> No. 102353 ID: c47a0b
>>102337
>warned me against
To be clear, it was more my personal preference that a "it is bad". I'm sure the gas block will function perfectly, and those flats will make adjustments easy enough.

Not really sure when I'll have my gas block going, but I will watch it closely to see if it flame-cuts my adjustment pin. I don't think it would as the pin I'll use will likely be an old carbide endmill shank. Either way I do hope you'll post have a range report when you get it up and shooting.
>> No. 102859 ID: 1519ac
File 14880126528.jpg - (1.95MB , 5312x2988 , 20170225_034554.jpg )
102859
Minor progress. Made a thread protector that will get pinned and welded because NY. It's Ti because titanium fuck yeah.
>> No. 102862 ID: 19518e
>>102859
Are muzzle devices banned in NY?
>> No. 102863 ID: 1519ac
>>102862
They're banned on semi-auto rifles with detachable magazines. Part of our so-called SAFE act.
>> No. 102864 ID: 19518e
>>102863
Ah, I see, that's depressing.
>> No. 102883 ID: f5c3ed
File 148815668623.jpg - (2.70MB , 3264x2448 , 20160724_194019.jpg )
102883
>>102864
"Flash hiders" are banned, but "muzzle brakes" if "permanently attached" are legal.

But at private ranges no one asks for proof of registration so as long as no one has standard 30 round mags no one cares.
>> No. 102884 ID: 1519ac
>>102883
Sorry, but you're misinformed. It's true that the "muzzle break" clause was struck down due to misspelling, but it was later reinstated by a higher court.

http://buffalonews.com/2015/10/19/appeals-court-upholds-safe-act-but-rules-against-seven-bullet-limit/

Relevant part:
>The appeals court did overturn two Skretny rulings pertaining to vagueness in the law. The court rejected Skretny’s decisions affecting certain, limited aspects of the law pertaining to pistols that are automatic weapons and definitions of certain military-style features on a weapon, including what the law misspells as a “muzzle break” instead of a “muzzle brake.”
>> No. 102886 ID: 1519ac
>>102883
P.S. what is the purpose of that piece between your FRS-15 and lower, and why is the screw on your aimpoint mount so fucking huge?
>> No. 102887 ID: f5c3ed
File 148815874773.jpg - (11.07KB , 350x346 , Aimpoint-QRP-Comp-mount.jpg )
102887
>>102884
So it's a "compensator" then that would be legal.

>>102886
The piece is a spacer to adapt it to a .308 lower. The Aimpoint mount is just a USGI one.
>> No. 102888 ID: 1519ac
>>102887
Compensators are also verboeten.
>52 (vi) a flash suppressor, muzzle break, muzzle compensator, or threaded

>53 barrel designed to accommodate a flash suppressor, muzzle break, or

>54 muzzle compensator;
>> No. 102889 ID: f5c3ed
File 148815985334.jpg - (35.91KB , 700x173 , 10qymuu.jpg )
102889
>>102888
Oh boy! Better not let Cuomo know there are a dozen shops in WNY still selling pic related with a welded muzzle device.

It's not like it's enforced at private ranges either.
>> No. 102890 ID: 1519ac
>>102889
I know it's not enforced and no one cares, I can't even remember how many people have told me about their unregistered AWs. I'm just trying to make sure that people who are breaking the law know that they are so they can take the precautions they deem appropriate. I've sheriff's deputies tell me to just ignore the safe act, but personally I'm not taking the chance that every LEO I run across will feel the same.
>> No. 103105 ID: 1519ac
File 148980884719.jpg - (4.56MB , 5312x2988 , 20170317_234411.jpg )
103105
>>99684
>>102328
Cut some more off the carrier today. Down to 216 grams from a starting point of 268. I think I'm gonna leave it there for now.
>> No. 103119 ID: 1519ac
File 148997221097.jpg - (3.41MB , 5312x2988 , 20170319_210336.jpg )
103119
BEHOLD MY FINAL FORM!

5.07 lbs with no mag. Kinda disappointed with the weight. I feel like the NY legal stock is holding me back. Could have gone with a spur grip I guess but I feel like they wouldn't give you enough control. Oh well, it's still light. Haven't shot it yet as the thread protector isn't welded and I haven't torqued the barrel.
>> No. 103122 ID: f5c3ed
File 148997902889.jpg - (81.36KB , 620x310 , DLOC-MRO-2-copy.jpg )
103122
>>103119
You could take off the rubber buttpad to reduce the weight even further, maybe go for an ultralight mount for the MRO too.
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