RS Troy Industries VTAC Alpha Rail, 9"

Reviews on parts for the PTW platform.

RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Fri Jul 27, 2012 9:07 pm

Well, the rail comes in a very nice box and is well packaged. In terms of packaging, I'd put it below Daniel Defense but above Samson and Wilson Combat - who seem happy with a bit of bubble wrap (Samson) and maybe some newspaper (Wilson) before finding a box of the approximate length ;)

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Out of the box, the rail is no less impressive. Finishing is top notch in terms of both the mil spec hard anodising and the way the ribs and cooling holes have been machined. No sharp edges and it feels grippy and positive. I like it that VTAC's version lacks the sharp edges of the standard Troy Alpha (the one with the circular vents), so hats off to VTAC for working with Troy on that refinement.

Markings are beautiful. The indexing on the top rail is crisp, as is the Troy logo and on the side, the VTAC one.

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Outer diameter is 1.74" - so its a smidge narrower than something like the Samson Evolution (1.80"), but not as narrow as the Midwest Industries SS Gen 2 (1.5"). I'd put the approximate weight as somewhere between the two - so, for me, this rail is somewhat intermediate between the tubes I use.

Although The Alpha rail retains many features - inculding the anti-rotation tab - it differs from the earlier TRX in that the proprietary barrel nut and pinch bolt system have been replaced.

The Alpha rail no longer requires a proprietary barrel nut, so there's no need for a specialist tool and the existing barrel nut can be used. If your existing barrel nut is already installed and torqued to the correct spec, this alone makes life much easier - though you need to dispense with the delta ring and spring if these are still part of your barrel nut assembly. Many people choose to simply cut these off, rather than removing and dismantling the barrel nut assembly, but it's up to you.

For the purposes of fitting this rail, I have an RS DPMS barrel nut on the way from Midway UK. JetL fitted an Alpha rail to his PTW a few months back and found his Systema barrel nut was not to spec, which caused him problems in installing his rail - so I'm taking no prisoners. It also means I'll have a chance to make sure the barrel nut is properly torqued and timed.

Similar to and as a consequence of Troy's decision to utilise the standard barrel nut, the rail's mounting system has been redesigned, with three internal locking devices which secure the rail to the barrel nut, activated by hex nuts. Given that this rail is RS, these are to imperial dimensions and Troy includes the appropriate size allen key.

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As soon as I have the bits I need, I'll document the install and continue it here. The rail is a mates' (Mindz_i on the forums), so he can watch the creation of his refreshed upper unfold :)
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Wed Aug 01, 2012 7:52 pm

OK...so the parts I was waiting on from Midway UK arrived today: a PRI barrel nut torque wrench head and an RS DPMS barrel nut. I'm not that impressed with the quality of either - both items are a bit rough around the edges - but I'm hoping they'll do the job. Note to self: as with so many things in life, you get what you pay for with RS kit.

At least the tolerances will be spot on, right? Oh, wait...

Bizarrely, the wrench head doesn't fit the RS barrel nut without a fight (top), but it does fit the Systema barrel nut (bottom)...

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If you recall from my initial installment, I bought an RS barrel nut as I was concerned the Systema barrel nut was off spec.

At this stage of test fitting, both barrel nuts were inserted into the rail, both timed correctly and both allowed the rail retention devices to tighten correctly upon them. A very simple test and not conclusive evidence that both barrel nuts will work when in situ. It's early days in the install, after all. Here's one of the DPMS nut, kind of timed:

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What I did find, however, is that aside from differences in the two nuts' tooth profiles, the barrel nuts are different lenghts, as illustrated below:

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The Systema barrel nut is quite clearly longer than the DPMS one. I think this can mean one of two things: either the DPMS nut is too short for the rail to be locked into it, when the rail buts against the receiver, or, the Systema barrel nut will cause the rail to exhibit a gap between it and the receiver. Either way, the Systema barrel nut appears to be better quality than the DPMS one.

I'm going to try the DPMS barrel nut first, when I get the rest of the parts for the install.
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby biscuitdunker on Wed Aug 01, 2012 11:02 pm

Awesome write up Rich, very informative!
I'm honking on a rock of pure airsoft. For kicks.

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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Wed Aug 01, 2012 11:05 pm

Cheers Stu! The next stage is actually fitting it ;)
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby Mindz_i on Thu Aug 02, 2012 11:00 am

Looking good fella.
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Thu Aug 02, 2012 11:03 am

With any luck, the rail should be on next week :)
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Fri Aug 03, 2012 7:00 pm

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Got the rest of my bits tonight, express delivered to my door - cheers Tent :)

Here's the lineup for the rail install:

1. Clamshell upper receiver block
2. Barrel nut wrench head
3. Torque wrench
4. Grease (not shown), used sparingly on the receiver's threads
5. Cheat's vice - a cheap and cheerful Black & Decker Workmate

The first four items are absoutely essential to get the barrel nut torqued to RS spec. A decent vice is also essential, but I can just about make do with the Workmate.
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Sat Aug 04, 2012 3:54 pm

Here are the consumables I'll need for the rail install:

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1. Grease - a smear of which will be used on the receiver's barrel nut threads
2. Threadlock - recommended by Troy to secure the three rail retaining bolts
3. Duck tape - to hold the cylinder and barrel/hop in the upper while the torquing and timing goes on
4. Short flat white - optional ;)
5. Microfiber cloth...just in case

Here are the parts I'll need:

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Pretty obvious what they are, but just to note that the cylinder and barrel/hop are required to reinforce the upper when it's tightened down in the clamshell receiver block

The Install

First thing to do, is smear the receiver's barrel nut threads with grease, then insert the barrel into the receiver and get the barrel nut hand tight. I always read on RS forums to tighten and untighten the barrel nut three times, so that's what I'll do - though there is no resistance and the nut fits fine. Any excess grease is wiped off with the microfiber cloth.

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Next, insert the cylinder and barrel/hop into the receiver and use a swatch of Duck tape to make sure it all remains in situ. I can't use the charging handle to retain the internals, because it will interfere with the jaws of the Workmate. You shouldn't have this problem with a proper vice:

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The upper then goes into the clamshell receiver block and into the 'vice'...this is the easiest way to arrange it with what I have at my disposal. I then slip the wrench head over the barrel and onto the barrel nut:

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At this point I realise that because the wrench head has no cutout, I won't be able to see the gas tube hole as I time the barrel nut. Still, at this point I just need to crank the torque wrench to 30 ft lbs and tighten the barrel nut until I hear the click.

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Next, I whack the torque wrench up to 60 ft lbs and time the barrel nut's teeth to the gas tube hole. This is trial and error, because I can't see what I'm doing, but eventually I get there - testing the timing with the gas tube and gas block assembly. I then tighten this on:

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I now test fit the rail on the torqued and timed barrel nut. The rail goes on, timed to about 1 O'clock and is then twisted anticlockwise, so the rail's antirotation tab butts up against the receiver. The barrel nut is thus held in a groove inside the rail, which holds it on.

Fit is good, so I prep the rail retention bolts with threadlock and tighten them equally. The bolts draw the rail into the receiver and make it plumb. Care needs to be taken that the top rails of the receiver and rail line up. Some people use a carry handle for this, but this install was easy enough to do without one.

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The upper mocked up, looking very dirty with a pair of Diamond Head sights ;)

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It's not over yet, however. As is common with this kind of rail, there's not quite enough clearance between the rail and the front receiver takedown pin tab on the lower, which means a tiny bit needs to be filed off the lower bottom edge of the rail.

You can see how little clearance there is, here:

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Doing this kind of modification tidily is beyond me and since this isn't my upper and I want a good result for the owner, I need to phone a friend....

To be continued!
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby Happidave73 on Sat Aug 04, 2012 4:32 pm

Looks great Rich & thanks for the guide makes me think I might have ago at doing mine!!

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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Sat Aug 04, 2012 4:44 pm

Cheers Dave :)

I'm just annoyed I've got this far and the rail needs to be modded. Still, I had to fit it to know.
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby lUcIfEr on Sat Aug 04, 2012 6:34 pm

Nice review TRH, great pictures and description. I was thinking of getting one of these rails for a while... ;)

The Troy/Vtac rails seems like a bargain for their quality, and I've seen a couple mil. pics where operators use these rails, so it might be an alternative if I want to take the "non-common" route, rather than using a KAC RIS or DD MK18 rail. :D
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Re: RS Troy Industries VTAC Alpha Rail, 9"

Postby The Reptile House on Sat Aug 04, 2012 6:53 pm

Cheers Luc - most kind :)

It's a good looking rail and it feels great in the hand. Ideally I'd expect it to work without being modded, but it could just be a tolerance thing with the upper, or my lowers.

Interestingly, I think if I tried the Systema barrel nut - which is longer than the RS one I've used here - the clearance would be OK. It would mean there was a bigger gap between the receiver and the rail, however.
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