SMOS Build Thread

[EO3]

Thanks, guys! Just what I needed!

[Brahmzy]

I REALLY wish SMOS made a 10.5" GFY rail.. I'm going to have to get an EraThr3 10.5, which SMOS makes, but it's overpriced and I don't want the open top.

[EO3]

I think I'm going to try out the 12" rail on a 13.7" upper. Jumping on the cool guy wagon here But really, I've wanted to go as short as possible without SBR'ing, and a 13.7" with a BE 249F or 249S pinned/welded makes that possible. Not really a fan of the KX3/5 on a 13.7 just because it's awfully heavy to have out front. Makes it kind of awkward to maneuver to me.

[fledge]

The 9" GFY rail was supposed to be delivered last Tuesday but UPS lost it. SMOS shipped out a replacement Friday and it arrived today! How's that for service!

The 9" is actually called the SMR556 9.188 SR. The actual length is engraved on the rail itself, just like on the 12". I took a measurement for those of you confused by decimals.





The weight of the rail, nut and hardware comes to 8.64oz.



Unlike the 13.6" GFY rail that shipped previously, this one came with an anti-rotation pin.



For those who complained on the loose fit of the rail over the barrel nut on the GFY rail, this one's tolerance are very snug. Same barrel nut but sans the Erath3 logo. I hope they release a lightweight nut for this.

I'm mounting to a 10.3 Ballistic Advantage barrel. Here's the gap on the end with and without muzzle device. The barrel nut is not fully torqued yet as I'm not ready to finish this upper.





And a full body shot. Screws are not inserted because nut is not timed.



I'm very pleased. I've had this part of the project on hold since last fall when Chris expected the shorter rails available by Christmas. Glad to have it all in hand now. More details on the project in the coming months.

[Brahmzy]

Ok everybody, what size crows foot wrench do I need on the 12.0?

1 3/16?

My 1 1/16s too small and my 1 5/16s too big!

And my 12.0 didn't come with the AR pin. I'm having to steal one from an NSR. How was the AR pin packaged? Ziplock somewhere in the tube?

[EO3]

Ok everybody, what size crows foot wrench do I need on the 12.0?

1 3/16?

My 1 1/16s too small and my 1 5/16s too big!

And my 12.0 didn't come with the AR pin. I'm having to steal one from an NSR. How was the AR pin packaged? Ziplock somewhere in the tube?

Yes! It is a 1 3/16 crows foot!

[fledge]

How was the AR pin packaged? Ziplock somewhere in the tube?

Small red ziplock tucked in the rail.

[JSchell1309]

Yes! It is a 1 3/16 crows foot!

A 30mm will also work as there is only a .006" difference between the two. I ordered one off amazon for ~$10 as I couldn't find any local retailer that had a 30mm or 1 3/16 by itself or in a set.

https://www.amazon.com/gp/aw/d/B002YK9QB8/ref=yo_ii_img?ie=UTF8&psc=1

Don't forget when you are running a crowd foot on a torque wrench you want it 90 degrees to the handle. If you have it in line you change the lever arm of the wrench and will not get an accurate torque value. Realistically between 30-80 ft-lbs it may not make a difference, always best to be accurate though.

[Brahmzy]

Small red ziplock tucked in the rail.

Ah, nope, didn't get one with my 12.0. Similar to how Noveske shanked us on the first few thousand NSRs that shipped. I'll call SMOS and get one on the way. Thanks.

[EO3]

A 30mm will also work as there is only a .006" difference between the two. I ordered one off amazon for ~$10 as I couldn't find any local retailer that had a 30mm or 1 3/16 by itself or in a set.

https://www.amazon.com/gp/aw/d/B002Y...?ie=UTF8&psc=1

Don't forget when you are running a crowd foot on a torque wrench you want it 90 degrees to the handle. If you have it in line you change the lever arm of the wrench and will not get an accurate torque value. Realistically between 30-80 ft-lbs it may not make a difference, always best to be accurate though.

I actually couldn't find one at my hardware store either, so I got one off Amazon as well. My 1 3/16th crows foot was $11 shipped with Amazon Prime. Good to know 30mm will also do the job!

[SINNER]

A 30mm will also work as there is only a .006" difference between the two. I ordered one off amazon for ~$10 as I couldn't find any local retailer that had a 30mm or 1 3/16 by itself or in a set.

https://www.amazon.com/gp/aw/d/B002Y...?ie=UTF8&psc=1

Don't forget when you are running a crowd foot on a torque wrench you want it 90 degrees to the handle. If you have it in line you change the lever arm of the wrench and will not get an accurate torque value. Realistically between 30-80 ft-lbs it may not make a difference, always best to be accurate though.

With a 3" extension due to the centerline length of a 30mm crows foot, actual torque with the wrench set at 50lbs is 43 ft lbs. I have a app on my phone for torque corrections. Lol It certainly makes a difference but in this application not enough to matter.

[JSchell1309]

Looks like the lower is threaded to accept a small set screw to tighten the slop between the upper and lower. Does anyone know what the thread pitch for this hole is?

Well I got the 1/4"-28 nylon tipped set screws in and they did not thread down into the hole. Diameter is correct but I believe they are 1/4"-20 Coarse thread and not the fine thread like the grip screw. Strange they would tool up another tap to thread this separate hole when it is right next to a fine threaded hole.

[Naytwan]

A 30mm will also work as there is only a .006" difference between the two. I ordered one off amazon for ~$10 as I couldn't find any local retailer that had a 30mm or 1 3/16 by itself or in a set.

https://www.amazon.com/gp/aw/d/B002Y...?ie=UTF8&psc=1

Don't forget when you are running a crowd foot on a torque wrench you want it 90 degrees to the handle. If you have it in line you change the lever arm of the wrench and will not get an accurate torque value. Realistically between 30-80 ft-lbs it may not make a difference, always best to be accurate though.

I bought this guy instead.

Powerbuilt 644134 Metric 30mm Polished Combination Wrench https://www.amazon.com/dp/B004QO9FRU..._nXj6wbW0GBK9D

Only issue is you can't really get a torque reading that I know of.

[JSchell1309]

I bought this guy instead.

Powerbuilt 644134 Metric 30mm Polished Combination Wrench https://www.amazon.com/dp/B004QO9FRU..._nXj6wbW0GBK9D

Only issue is you can't really get a torque reading that I know of.

If you want to get real fancy you can measure from the centerline of rotation of the open end lugs to the center of the closed end wrench. With the wrench parallel to the floor, fashion a crude hanger from some wire and hang a known weight from the wrench. Multiply the lbs of weight by the length you measured converted from inches to feet. Boom... ft-lbs of torque. If you don't have weights but do have a scale you can use that same length then stand on the scale. Push down on the parallel wrench until you subtract 30-80 lbs from your weight on the scale.. boom known torque.

McGuyver would be proud.

[besthaticouldo]

If you want to get real fancy you can measure from the centerline of rotation of the open end lugs to the center of the closed end wrench. With the wrench parallel to the floor, fashion a crude hanger from some wire and hang a known weight from the wrench. Multiply the lbs of weight by the length you measured converted from inches to feet. Boom... ft-lbs of torque. If you don't have weights but do have a scale you can use that same length then stand on the scale. Push down on the parallel wrench until you subtract 30-80 lbs from your weight on the scale.. boom known torque.

McGuyver would be proud.