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Posted: 1/15/2003 6:58:30 PM EDT
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What's the easiest way to get your RAS aligned with your receiver rail once you've installed it? I'm considering an RAS and I can tell by looking at my handguards that it's not gonna be straight. Thanks, Bradd |
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Quoted: What's the easiest way to get your RAS aligned with your receiver rail once you've installed it? I'm considering an RAS and I can tell by looking at my handguards that it's not gonna be straight. Thanks, Bradd Hey Bradd, I tried something that I think is working out alright: I removed everything from the RAS upper rail and the upper receiver rail. I pressed a long, precision machinist's rule against the edges of each side of the RAS and upper receiver assemblies together and detected a slight misalignment. I found I was able to adjust it by moving the loose RAS a bit at the rear locking clamp area. I inverted my assembled rifle (keeping the upper RAS securing-screw loose) and GENTLY aligned and secured the RAS and upper receiver rail edges together in the center of the protected jaws of a 6" wide vise. LIGHT PRESSURE. I then reached up under and secured the RAS screw with a little blue loctite and NOT TOO MUCH TORQUE -- 20 INCH pounds is recommended. I then checked alignment with the machinist rule and was satisfied. I believe this is about as good as we can get in aligning the RAS and upper rail without the use of the ARMS sleeve. Hope this helps. O'DubhGhaill |
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THE KEY TO GETTING ANY M-16/AR-15 FOREND PROPERLY ALIGNED, REGARDLESS OF TYPE: KNIGHT'S M4 RIS/RAS P.R.I. SPR FOREND DANIEL DEFENSE FREE FLOATING FOREND ETC. ...IS TO HAVE THE BARREL NUT INDEXED PROPERLY. IF YOUR HANDGUARD IS NOW NOT CORRECTLY ALIGNED, YOU CAN BE CERTAIN THAT YOUR BARREL NUT IS NOT, EITHER. AND UNTIL IT IS, NOTHING WILL MOUNT CORRECTLY. WES GRANT [URL]MSTN.BIZ[/URL] |
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The barrel nut realy can't be precision indexed to the receiver flat top, as you can't expect the hole in the front of the flat top to be in alighnment to each flat top, they are not made that way in production. The sleeve approach is the only positive way. Good Shootin, Jack |
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Wes is correct, the barrel nut may be at some degree of fault. One must appreciate that the RIS & RAS Military requirement was that it install at the operator level without special tools and knowledge. Add that element to what actually "levels" the top rail...? Its those two little dowel pins that come to rest in the unused gas tube barrel nut cut-outs at about 10 & 2 o'clock. So if the barrel nut is not plumb, i.e., the gas tube does not touch either side of the barrel nut cut-out that it passes through, then the nut needs to be nudged "one RCH" in the appropriate direction. That being said, the tolerence range of the barrel nut notches, its and their concentricities, plus several other demensional factors, e.g., is it a Colt Mil-Spec part or a part some aftermarket knock-off company tried to make mil-spec but failed, and belive me, there are a whole bunch of "tried to make it to the drawing boss, but it ain't quite right and we made 500 of them, can we use em anyway, or sell em to DPMS"?. I remember buying hundreds of "mil-spec" M16 bolt catches we originally used on the SR-25. Colt's went though our QC ok, and they worked fine, held the bolt to the rear on the last round fired with a sound suppressor. However, none Colt "made to mil-spec" catches would break in-half the first time they went through the suppressor test. I also recall telephoning over 200 customers to tell them that their rifle would "not ship this week as promised", because we lacked only a serviceable bolt catch. That's when we started to make our own for the SR-25--and never has one of those failed. So back to the point. I would not worry too much about the top rail being "perfect", for one thing, the UR rail may not be quite right either. Now if you mount the front ring of a 20X target scope mid way forward on a RAS top rail, maybe its an issue for the sub-moa shooter. But you are going to most probably put a 3+ moa red dot sight out there. And being a little out of plumb will never show up as a deficiency. Try this first before pulling off your barrel nut and having it "blue-printed" at the local race engin shop. Mount your aimpoint as far back on the top rail as possible and shoot and mark a 10-round group, then reposition it one notch forward and shoot another group to the same point of aim. Keep doing this until you are all the way forward. How much did you 2nd, 3rd, 4th, etc., groups "walk off the original point of impact? Again, back to the point of the question. The RIS & RAS are not perfect solutions for all requirements. They did beat all others as originally competed more than 5 years ago. As the users re-define their requirements over time, often "pushing the bar higher & higher", that is when we come up with the FF RAS tubes, or the newest RAS II. On either of these, you can put a sub-moa scope mount (front ring) out there and still shoot sub-moa. ColdBlue sends... |
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Without a lot of hoopla, the sleeve is the only way to get perfect alignment. You don't have to leave it on if you don't want it for some reason, but you can't sure find any better way to get the old RIS/RAS to be in alignment with the receiver. The spanner wrench nothes/hubs are not designed to be endexed to the receiver flat top dovetails od the gas hole, etc. And all those otrher suggested things vary from weapon to weapon and do not corrolate or measure in expectation of reliable success. When you use a sleeve slid forward starting from the rear of the receiver, you will run into the RIS/RAS dovetails, That shows that the rails are not in alignment with the receiver dovetails. Loosten the screw holding the rails and rotate them untill the sleeve sldes forward onto them ans then re-lock the screw, now your in fair alignment, that is almost as good as one continuous rail that starts from the receiver like the SIR and sleeves already automatically do. Good Shootin, Jack |
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Forget the "vise experiment!" Wes, coldblue, you are dead on about the barrel nut and RAS barrel nut guides accounting for the RAS alignment: I incrementally and every-so-slightly adjusted my barrel nut several times until I got the alignment as perfect as my machinist's rule could handle (all well within the generous torque specs of 30-80 ft/lbs.) Thanks! O'DubhGhaill |
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To keep on moving a round spocked barrel nut ever so slightly is only guessing that you moved it into perfect alignment and not accurate and or fast as using a sleeve as a guage. Even if you get the spocked barrel nut into whare you think you want it, it does not make the RIS/RAS rail go into alignment as they are not made to those type tolerances for good indexing. There is no better (go no-go guage) than the sleeve available to the general public to get barrel mounted rails to align with the receiver. Good Shootin, Jack |
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KNIGHT'S FORENDS, ANY OF THEM, ON A QUALITY UPPER WITH A PROPERLY INSTALLED BARREL NUT WILL GIVE TOTALLY SATISFACTORY ALIGNMENT. AND I CAN DEMONSTRATE IT IN SUCH A MANNER THAT EVEN 3RDTK WILL AGREE IS ACCURATE. WITH A KNIGHT'S M4 RAS ON A COLT M4 UPPER, I CAN SLIDE ON THE ARMS #38-EX-MOD-L RAIL, WHICH ENGAGES THE ENTIRE TOP OF THE UPPER RECEIVER AND AS WELL AS THE TOP RAIL OF THE FOREND, FROM STEM TO STERN, AS PERFECTLY AS CAN CAN BE. A NO-BRAINER. THE ARMS SIR TOP RAIL BEING A ONE-PIECE DESIGN IS OBVIOUSLY GOING TO GIVE PROPER ALIGNMENT WHEN BOLTED DOWN TO THE RECEIVER, AND IS LESS SUBJECT TO PROBLEMS INDUCED BY A POORLY TIMED BARREL NUT. ANOTHER NO-BRAINER. MORAL OF THE STORY: STICK WITH GOOD GEAR. I DO NOT CARE WHO MAKES IT, SO LONG AS IT WORKS. THEN YOU'LL BE FREE TO THINK ABOUT MORE IMPORTANT THINGS. LIKE SIGHT PICTURE AND TRIGGER CONTROL. S/F- WES |
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Quoted: To keep on moving a round spocked barrel nut ever so slightly is only guessing that you moved it into perfect alignment and not accurate and or fast as using a sleeve as a guage. Even if you get the spocked barrel nut into whare you think you want it, it does not make the RIS/RAS rail go into alignment as they are not made to those type tolerances for good indexing. There is no better (go no-go guage) than the sleeve available to the general public to get barrel mounted rails to align with the receiver. Good Shootin, Jack A rather precise machinist's rule took quite a bit of guess out of the [b]fact[/b] that my RAS and upper are in far better alignment now than they were before I adjusted the barrel nut, darned near perfect, or, as I said above "as perfect as my machinist's rule can handle." I repeat what I wrote in my original response to Bradd_D, only now I refer to barrel nut adjustment as opposed to my "vise" notion: "...I believe this is about as good as we can get in aligning the RAS and upper rail without the use of the ARMS sleeve..." or KAC RAS free-float. Never doubted the benefits of the sleeve or free float, but I have no doubt that my alignment is much better now after adjusting the barrel nut and is as perfect as it's going to get without the sleeve (requiring a system change that would include ditching excellent KAC parts such as my 600m BUIS for ARMS, something I refuse to do, no matter what DoD does) or free-float. The KAC RAS rail is an outstanding piece for me and I am now dead on with my original out-of-the box Aimpoint settings. O'DubhGhaill |
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It is funny that I see this post here as I had my first problem with a KAC FF RAS last night! As I assume many here know, I have quite a few FF RAS tubes mounted on uppers. Last night, I tried to mount a Bushmaster M4 barrel to a Bushmaster Upper using a short KAC FF RAS and I had a bugger of a time getting the barrel nut to line up! At 30-ft-lb torque, the nut was just past the gas tube hole in the upper receiver. With the barrel nut off the mark, I wasn't able to get the gas tube through at all and with the two pins that lock the RAS into place, this alignment is critical for the FF RAS to align with the upper receiver (same as a standard RAS). What is the correct way to fix this? I see a few options.... 1. File down the barrel nut so that it lines up better? 2. File down the threads on the upper receiver? 3. Put the barrel in a vice and give the nut a hell of a whack and force the issue? Like I said, I have two other FF RAS tubes mounted on uppers and these mounted without any problems. This third upper has me a little frustrated and to be honest I used method #3 but I doubt that was the best way to do it! |
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Quarterbore, the manual (ARMY TM 9-1005-319-23&P) suggests using moly lube on the threads, torque the barrel nut assembly to 30 ft/lbs, loosen, re-torque, three times. Check alignment as you are doing after the third tightning sequence to 30 ft/lbs. and "[i]f necessary, tighten barrel nut assembly to next hole to allow proper alignment." The manual cautions, however: "Do not torque over 80 ft/lbs (108 N-m) while tightening the barrel nut assembly to the next hole, to allow for proper alignment of gas tube." ARMY TM p.3-39 - 3-43. Hope this helps. BTW, I found your web-site highly informative! O'DubhGhaill |
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DO NOT ATTEMP TO NUDGE WITHOUT PROPER TOOLS AND A BIG-ASS VICE. No way around this. Brownells has the Peace River Arms wrap-around vice jaws, and a barrel wrench with a half-round end option that works well in combination. The vice needs to be rock solid, as any movement of your support set-up will mask the sensitivity you need to be feeling through the wrench in order to nudge, and not bend the gas tube. ColdBlue sends... |
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Quoted: Guys, how would you suggest I nudge the barrel nut back a little? I don't have a barrel nut wrench. Thanks, Bradd Bradd, I used the Bushmaster Armorer's Action Clamp, the govt. issue Armorer's Barrel Wrench (both available at:[url]http://www.bushmaster.com/shopping/gunsmith/[/url]) with a 1/2 drive ratchet and torque wrench, and a relatively "BIG-ASS VICE." Absolutely, what coldblue wrote! O'DubhGhaill |
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Let's be really, really objective here a moment, and consider the operational consequence of a very slight amount of mis-alignment, twist, or what not. Firstly, what are you going to mount on a rail forend that is critical (to the same degree) and essential to hit your target? (a) Red dot reflex. As long as you can achieve a zero within the sight's range of adjustability, you do not have aproblem. (b) Front ring of an optical telescopic sight. Again, as long as you can achieve a zero, and the rail does not move around, no real problem. (c) Lasers. There are two conditions here: (1) M16A4 Rifle or M4A1 Carbine (either with rail forends). Using a PAQ-4 or the PEQ-2, one is using/wearing 1X NVG's to detect and engage targets. You are also shooting "from the hip" so to speak, putting the laser mark on the target and shooting. At 100 meters, a human can not hold a group within 1 m.o.a. using this method because of the subjectivity in re-aligning the laser to the previous shot's point of aim on a human shape target, and an inability to hold the weapon as tight as one does in the prone position using a rest of some sort, or sling, in the daytime. (2) 7.62mm Sniper Rifle such as Navy Mk11 Mod 0, or the same rifle in Army form: Special LW Match Rifle. Typically at night, PEQ-2's are mounted to the FF forend rail and a night sight or augmentation device is amplifing the dayscope. Because the day scope remains zeroed, most shots will be made using the scope's reticle. One side of the PEQ-2 may be used to momentarily illuminate the target for ID purposes. Since this channel has an adjustable beam width and its own very generous zeroing adjusters, it will be able to be "zeroed" with the scope. Same same with the pointer side of the PEQ-2. I have never heard of one not being "zeroable" on a rail forend. Besides that, why would a sniper "mark himself" by turning on a laser to take a shot, when he can take his shot using the zeroed scope reticle--especially now that so many are illuminated? Seems to me the pointer side of the PEQ-2 on a sniper rifle is better suited to the "hip shooting scenario" while a sniper is on a movement to contact at night, and while he is wearing his 1X NVG's. I again mention the "1X" nature of the NVG's, because until you have actually seen how bad your 100 meter groups are under stress on a E-type target using this method, it all appears too easy. So I just don't think that a little cant, or whatever, is anything to over-worry about, as long as the thing is secure and the target engagement device mounted to it allows you to hit your target. This is one of those rare "95-percent solutions" that exceeds 100% of our human abilities. ColdBlue sends... |
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Quoted: This is one of those rare "95-percent solutions" that exceeds 100% of our human abilities. Oh how true! I decided it isn't worth me taking my upper apart to see what the actual torque is but I am betting it is under the 80# max. I never needed to torque a barrel down that tight before and I normally use 30-40# without a problem. I guess I have always just been lucky! |
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