Modern Sporter - Build Discussions

^I agree! The selfish me just wants to fit the RIS II on it, as well as another set for the Geissele SMK anti rotational tabs at the bottom. Is mil spec front portion a good place to start? I'm by no means an expert though, but chances are if you mimic the Vltor front portion, compatibility might jump from 50%(just a guess) now to 95%, which I'm sure will make most if not all of us very happy ;)
 
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DILLIGAF said:
I rather have to fit the anti rotation tabs on the handgaurd to ensure a perfect fit.
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Only problem that might happen is if ATRS uses a specs that require the complete removal of tabs for some handguards, that might be quite undesirable since there won’t be any anti rotational ability for some handguards

My understanding is that the anti rotation tabs are a “back up” just in case the barrel nut loosens, and still allowing the rifle to go into battery and fire just fine and won’t disassemble itself, despite front sight loses zero slightly. But by no means was it for making sure the barrel nut stays tight. I might be wrong though, and your suggested use of anti rotational tabs doesn’t sound bad either. I’m just not big in modifying equipments.
 
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The tabs on the most of the handguards listed here have plenty of meat on them. We are talking about a few thou of material that will take just a couple of passes with a fine file.

Fitting handguards that have these types of anti rotation built in is common practice on billet receivers and is more fun then just bolting crap together.

Once the uppers make it out to the public im sure their will be a list made up of witch ones work and witch ones require fitting. Buying cool new rifles out of the gate is always a fun trial and error experiment.
 
DILLIGAF said:
I rather have to fit the anti rotation tabs on the handgaurd to ensure a perfect fit.
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This has been our thinking hence not messing with what we know works. In the thousands of AR style rifles we have done over the years only 1 comes to mind where the hand guard backed off causing any sort of issue. This was easily remedied.
 
Maybe it would be good to sticky a post with the parts that we know for sure will be compatible? To avoid having people buy things that won't be usable. Just a thought.

Do we know handguards that will fit 100% without fiddling around?
 
xdmer said:
Why are there even anti-rotation tabs .. they have to be a style thing ...
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Some say it’s so the rail doesn’t rotate even if your barrel but comes loose, meaning your barrel nut can’t move. Others see it as just an alignment piece. I’m sure a few see it as a gimmick. If you take your time and build the rifle properly it isn’t needed. The rails I use have it as part of the design, the Aero Quantum MLOK.
 
Anti rotation tabs are important as the tension on the barrel nut is not usually enough to ensure no movement. Geisssele had to redesign the MK8 rail by adding tabs because customers complained about rails rotating.

The whole point of the Modern Sporter is to have compatibility with standard mil spec parts. I measured the Geissele MK13 rail and it is going to need like 7 thousands removed on each anti rotation tab to fit across the lower. That's not exactly a minor adjustment. I also don't want to have to take it in to a gunsmith to get it milled down and fit and pay for the service etc.

Not sure why you guys can't test fit a few of the most popular handguards from Geissele, Midwest, SLR, and Frotis etc to ensure a seamless fit and save the customer from the hassle of having to custom fit handguards...
 
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xdmer said:
Why are there even anti-rotation tabs .. they have to be a style thing ...
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Its the new " Kool " right now. Thats how it goes in the ever changing gun community... lol... Now it's the retro rifles making a comeback as well. A fix to a problem that didnt really exist.

Just buy a rail without them if you dont want them. easy peasy solution !
 
GUNNZ said:
Anti rotation tabs are important as the tension on the barrel nut is not usually enough to ensure no movement. Geisssele had to redesign the MK8 rail by adding tabs because customers complained about rails rotating.

The whole point of the Modern Sporter is to have compatibility with standard mil spec parts. I measured the Geissele MK13 rail and it is going to need like 7 thousands removed on each anti rotation tab to fit across the lower. That's not exactly a minor adjustment. I also don't want to have to take it in to a gunsmith to get it milled down and fit and pay for the service etc.

Not sure why you guys can't test fit a few of the most popular handguards from Geissele, Midwest, SLR, and Frotis etc to ensure a seamless fit and save the customer from the hassle of having to custom fit handguards...
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If you can measure 7 thou then you can figure out how to operate a file.
 
0.007" with a file on aluminum isn't exactly a lot of work.... You're literally talking a couple minutes max...
Why would atrs spend their valuable time worrying about what handguards fit and which don't. There are literally thousands of different handguards available, so what you consider popular, might seem obscure to others.
There are so many options that don't require customizing, so why bother with one that does?
 
purplezuk said:
0.007" with a file on aluminum isn't exactly a lot of work.... You're literally talking a couple minutes max...
Why would atrs spend their valuable time worrying about what handguards fit and which don't. There are literally thousands of different handguards available, so what you consider popular, might seem obscure to others.
There are so many options that don't require customizing, so why bother with one that does?
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Yeah I get that but why not make the receiver close to AR mil specs so you can ensure a good proportion of different manufacturer handguards fit without adjustment?

If it's not a huge issue to change the CNC program on the upper and the changes don't alter function/form of the set I don't see why this would not be done.

Also, this forces me to cut up an expensive handguard to fit the ATRS receiver set. What if I want to put it on something else down the line...
 
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