Super lightweight AR

rotarymike

rotarymike

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Moving this discussion from the FS/FT post.

Started with me getting a DPMS slick-side (no forward assist, no dust door) upper receiver. Got it thinking it would be lighter than a normal M4 receiver - nope. Very thick walls - would make a nicely rigid DMR/accuracy rifle, or a great upper to convert to side charging.

10.6 ounces for the DPMS, 8.3 for the (loaded) AO Precision. Not a huge difference but every ounce counts when you're trying to bump rimfire.

New data: stripped AO M4 upper 7.0 ounces.

I have a pencil weight 16" middy barrel (in 5.56), a PSA lower with Olympic LPK, and the slidefire stock.

Now I need to pare down the Hogue foretube from 8.4 ounces. This is the solid aluminum tube (not including barrel nut) so I'm thinking of milling holes like a Sterling/Sten barrel shroud. Ideally I'd like to do a spiral pattern but I'm having some dumb moments trying to work out the measurements & math to make it all look even and not retarded.

Right now, with the stuff listed above and a standard charging handle but no bcg, front sight, gas tube, or muzzle device, the whole gun weighs 5 pounds 3.4 ounces.

Compared to my 10-pound 6.8 AR, I'm liking this idea so far.

I'm thinking of using cheapo plastic sights, and cutting down an A2 FSB to just the tube and clamp. Might just keep the A2 front and use plastic rear sight on the rail.

I've got a semi-auto Rock River bolt carrier that I may mill out the rear of it some more. My one concern is that this gun needs to shoot both .22LR and 5.56 - I don't want to lighten it so much that with 5.56 it batters itself.

Thoughts? Suggestions?
 
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one thought, since a 22 conversion doesnt use the buffer or spring either a heavier spring or an H-2 buffer would dampen the 556. or H-1, whatever isnt standard.
 
Have you thought about using a polymer lower? I've had several and have had zero issues and there is a noticeable weight difference. My only suggestion would be to get the lower with the lpk already installed. It can get a bit frustrating fitting some of the parts if you are installing the lpk yourself. If you're on the fence about polymer lowers, read the reviews (link below) and remember that they come with lifetime warranties.
http://www.joeboboutfitters.com/New_Frontier_Armory_LW_15_Complete_Poly_Lower_p/nfa-lw15blk.htm
 
It's always an option (the poly lower), as long as they take normal AR grips. Many of the poly lowers I've seen have the grip built in, which won't jive with the slidefire.

Matthews in Shotgun News did a slidefire .22 AR, and went through some pretty serious modifications before he got it to run right. But I think he went overboard in some areas, and not far enough in others. For example, there exists a recoil enhancer muzzle device that helps a lot, and he ended up still with an A2 birdcage. http://www.slidefire.com/products/mp15-accessories/recoil-enhancer I doubt I'll be skeletonizing my upper or buffer tube for an additional .5 ounce, though. Rather cut the barrel back to 10" or so and braze on a titanium "extension" to hit 16".

The AR reciprocates in the slidefire stock, so you have to lighten the reciprocating parts as much as practical.

If I wanted to go the easy route, I'd make/get a dedicated .22LR upper with no gas system and integrated blowback action rather than a Ceiner kit replacing the BCG. But I would like to be able to do drum mag dumps of 5.56 too, on the off chance I might actually be able to afford quantities of 5.56 in the far future.
 
Thanks Tiger for the heavier buffer idea. I think the combo of midlength gas and a heavier buffer will certainly help. If I need to I have an M16 bolt carrier I could drop in for some extra weight too.
 
dang, that rifle with long bbl and a tube around it and the sight weighs 3.4 lbs?

imagine the 4 or 7 inch bbl.

those bbls look like a good platform for,with stamp of course, a home built suppressor. use the whole tube for volume and have baffles in the frount half. im trying to design one for my 22 like that.
 
Wait - I thought you needed the SOT stamp to make a suppressor? I thought the Form 1 was just for making SBR/SBS/AOWs.

If I can make my own suppressor (with proper paperwork etc and so forth) that will make silencing my M76 that much easier than going to Serbia and trying to piece together an issue one...
 
rotarymike said:
Wait - I thought you needed the SOT stamp to make a suppressor? I thought the Form 1 was just for making SBR/SBS/AOWs.

If I can make my own suppressor (with proper paperwork etc and so forth) that will make silencing my M76 that much easier than going to Serbia and trying to piece together an issue one...
Click to expand...


Under the 1934 NFA a "sound suppressor" counts as a "firearm" and you can use the ATF Form 1 (ATF F 5320.1) to "make and register a firearm" and put the information for the suppressor in the appropriate boxes.

The ATF NFA Branch considers sound suppressors to be "firearms" so you treat them the same way you treat a machinegun or SBR.
 
Somehow I missed that distinction. Of course I wasn't looking into the Form 1 stuff too hard... maybe I need to revisit that code.

I would much rather make the suppressor for my Mauser/DeLisle monstrosity than use a .45acp pistol silencer...
 
thats correct. and there are many you tubes about it. the dealer for FPS russia that was killed made a video on how to make a 22 can with an aluminum flashlight LIKE a maglight.

here is a cool vid of a 22 sparrow cutaway or x ray in slow mo. they call it high speed but thats the film speed.

http://youtu.be/fPqa3teOQkA

and a look at it inside.

http://youtu.be/hfshtToeoaI

here is the flashlight

http://youtu.be/oqZMzmPBMqc
 
So here's the gun as I've got it now, along with a ruler and my helper cat. Click to embiggen.



Here's me trying to puzzle out decades-old software to make an even hole pattern to drill the Hogue handguard tube.



Here's the final pattern. I decided to use .75" holes instead of .5, but the centers are all the same and that's the big reason for the pattern. According to my (admittedly limited) math, should reduce weight from 8.4 ounces to 5.6 ounces IIRC.



Not counting the barrel nut, of course.

As an aside, do you know how hard it is to find drill bits larger than 1/2 that are not spade or masonry bits? Or, of course, a $40 unibit that you'll wear out in about 15 holes.
 
Well, crap. Mill broke a gear on hole 43 of 56. Project on idle until I get that fixed.

On a good note, got the gas tube today. Just need to get the FSB and I should be good in that regard...
 
Mike: You have to see my Carbon 15 Bushmaster. You talk about light rifle...

I have only ran about 60 rounds thru it before I went to work on it..but, it is almost as light as a .22...

Steve
 
Mike let me know next time you need a large bit, I can probably help out. I have LOTS, and access to them always.
 
So to back up a minute, .22AR is on hold due to milling machine parts being on order.

I *did* pick up a carbon FFT for my 6.8 AR, though.

AP Customs carbon fiber middy handguard, with attaching nut and milspec barrel nut: 5.7 oz
Nordic Components (same company) AL middy handguard, with locknut and barrel nut: 11.9 oz.

With light and sight, have my 6.8 AR down to 7 lbs 10 oz. Don't see it going lighter unless I find a lighter light than the Surefire G2 + aluminum clamp I'm using now. Limitations, IMHO, are barrel (always going to be heavier than a 5.56 barrel) and my insistence on an A2 buttstock. I did move the light to the front of the upper receiver rail, as opposed to out there on the end of the guard, and that helps with balance & feel a LOT.
 
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