SIG MCX: When is an AR not an AR?

[Tokarev]

http://archive.navytimes.com/VideoNe...ig-Sauer-s-MCX

A bit more from Kevin about the gun.

Sent from my GT-P3113 using Tapatalk

[Tokarev]

It was 9° here this morning so I figured I'd head to the range. I did it mostly for the novelty of shooting in the bitter cold but I also thought it might be interesting to see if the cold weather would have any obvious effects on the MCX's performance.

I let the rifle and ammo sit outside for fifteen minutes while I checked in with the range master and got my targets set up. The 100yd range was closed so I did everything from 50 and in.

I started the morning by firing a group of subsonic suppressed followed by a group of supersonic unsuppressed. Both groups were fired using the EOTech's top dot. Aiming point was center mass of the target.

Note the difference in point of impact between the two types of ammo. Now in the EOTech's defense, I have found my 300BLK AR prints about 3" lower suppressed than unsuppressed at 100yds. If I'd have used my can for both groups they'd probably have been a little closer together.



After these initial groups, I continued to experiment with accuracy testing off the bench. Ammo used was a 125gr bullet topping 17.5gr of H110 and a 220gr BTHP over 10.8gr of 5744. Both loads shot fine but I noticed the subsonic load using 5744 continually failed to lock the bolt back on the last round fired. All subsonic was suppressed.

These are fairly typical groups from both types of ammo.

Supersonic:

Subsonic:

I then tried shooting from the prone using a Troy magazine as a monopod. This didn't cause any issues. I finished off the morning with some simple movement drills and selector manipulation drills from fifteen yards. Total rounds fired was 120.

Overall, a fairly fun morning in spite of the cold. As noted the only issues were the failures to lock open with this load of subs.

While cleaning up after myself, I noticed a good bit of unburnt powder on the shooting bench. The powder appears to be 5744. I haven't used much 5744 and don't know if unburnt powder is the norm with this powder in subsonic or if this had something to do with the weather.

[KalashniKEV]

Now in the EOTech's defense, I have found my 300BLK AR prints about 3" lower suppressed than unsuppressed at 100yds.

The optic needs no defense for POI shift suppressed and unsuppressed, or between 2 different loads.

Ammo used was a 125gr bullet topping 17.5gr of H110 and a 220gr BTHP over 10.8gr of 5744. Both loads shot fine

Are these your own handloads?

Something's wrong with those subs.

[Tokarev]

The optic needs no defense for POI shift suppressed and unsuppressed, or between 2 different loads.



Are these your own handloads?

Something's wrong with those subs.

I should have been more specific in my earlier postings. The optic I'm using here is the 300BLK dedicated 2-dot model. The top dot is supposed to be regulated for supersonic ammo at 100 yards and subsonic ammo at 50. The second dot is calibrated for 150 yards with subs and 300 with supers.

I previously had the sight mounted on an AR and it has given me pretty good results at 100 on paper and 300 on steel. I've messed with it a tiny bit using subs but not really enough to make a good determination on it with that type of ammo. Obviously the dots aren't going to correspond exactly to POA/POI between the two types of ammo. Anyway, if I have a chance next weekend I'll try zeroing with 110gr supers at 100 yards.

Yes. I'm using handloads. Since I haven't seen 1680 anywhere in probably a year and am not too sure 5744 is going to work I might buy a couple boxes of factory subsonic and see how they work.

[Tokarev]

I sent an email to Western Powders asking if unburned powder is common with 5744 when used in subsonic 300BLK. The response I received said it is.

[sinlessorrow]

So, if you mount this to a M16 lower........does that make it an AR


O.O

[Tokarev]

So, if you mount this to a M16 lower........does that make it an AR


O.O

Only if a single shot 50BMG upper on an AR lower makes that combo an AR as well.

[TMS951]

Not to detract from your rifle purchase, but I am interested in the pistols you saw there.

Mainly the inclusion of the brace. Did you look at one and do you know what literature and atf letter copies came with them? It would seem with the atf latest ruling on the brace continuing it's sale is inviting some sort of litigation by the first owner who gets caught shouldering it with no idea he couldn't.

It makes me wonder if Sigs lawyers decided it is so unlikely any one would be prosecuted for shouldering it that in tern they would never get sued?

[sinlessorrow]

The one,thing I wish they would have done differently is the bolt.

I see no reason to stick to the standard AR bolt lug design in a gun like this. At least remove,the sharp corners and round the lugs. I mean why make a rifle this unique, yet keep the parts most common to break on the AR.

[Tokarev]

Not to detract from your rifle purchase, but I am interested in the pistols you saw there.

Mainly the inclusion of the brace. Did you look at one and do you know what literature and atf letter copies came with them? It would seem with the atf latest ruling on the brace continuing it's sale is inviting some sort of litigation by the first owner who gets caught shouldering it with no idea he couldn't.

It makes me wonder if Sigs lawyers decided it is so unlikely any one would be prosecuted for shouldering it that in tern they would never get sued?

There were no MCX pistols in stock at the store when I bought the rifle so can't comment on anything regarding the brace.