sig mcx virtus barrel (weird?) hole

[Pyrocat]

Hi all,

I bought a SIG MCX Virtus 11.5" (223) in 2019 and had accuracy issues since then. The gun shoots >5 MOA at 100m with all the ammo I tried (cheap, match, 55gr, 62gr, 69gr, 77gr). According to some people on the Internet, that could come from either an improperly set barrel or flash hider. After all these years I finally decided to give it a try and remove/reinstall the flash hider and the barrel. (I know it has been a long time to take action but you know how it is...)

After getting the barrel out, I noticed that there is a hole near the barrel lugs:

is that normal? why machine a hole if it's not to be used ? :-/ It doesn't look like a venting hole since it's obstructed by the receiver once the barrel is installed.

And I obviously have no idea if that thing has been there from the start or if I just dropped a pin when removing the barrel. I checked on the ground and didn't find anything... but now I don't even know if I can shoot that thing safely.

Any help from other SIG owners will be greatly appreciated!

 

[xxflyingturtlexx]

nothing weird; that is for extractor support pin; thats how they install it in the factory

Most accuracy issues on the mcx were addressed by virtus and usually are related to shooter and ammo.

Make sure your barrel bolts are torqued in required sequence and torque.

They seem to like 77grain.

 

[xxflyingturtlexx]

Mine has the same port

 

[Pyrocat]

Mine has the same port

Thanks for the check!

On all the virtus sold by my gunsmith it's the only one that seems to have a defect but once you put the gun on a solid rest with a 10x scope and can't do better than 5' with 6 different types of ammo... I even thought it was the scope that was broken but I shoot 5" groups at 650 yards with it on my rem 700 (223 also). I also get better results with my other rifle just using the iron sight (prone, 100m).

I tried with a scope, reddot and ironsight - always the same group sizes no matter what I do.

I'll check again now that I have reinstalled all parts that are known to produce bad results!

 

[ToddM]

It's worse with the Legacy pencil barrels, but MCX's are known to have some barrels that won't shoot at all, especially if you are shooting the lighter grain bullets. I had a Legacy 16" that the best groups I saw it shoot were with FGMM 77gr with a 10x optic and that was ~4", with various 55gr ammo it was 8-12". Other heavy 223 match ammo would be ~6" at 100. Meanwhile I have JP light 5.56 barrel on an old S&W M&P (when they first came out) that will shoot match .223 ammo very well and even good quality 55gr in the 2" range. Funny part is the JP barrel is cheaper than Sig's ridiculous prices. So make sure you try some heavier match ammo if you haven't, some guys have horrible groups with the lighter stuff but great accuracy with the heavy stuff.

They blame it on the 1:7 barrel but I have other barrels in 1:7 that shoot very well with lighter bullets so I don't buy it. Personally the idea that a .223 "battle rifle" can't shoot better than 8" groups with 55/62 grain ammo is basically worthless unless it's a precision rig you only plan to shoot match ammo out of.

 

[Constructor]

Sig uses a recessed crown with a 45* chamfer and they are not concentric, the chamfer on one side was twice as long as the other side. Mine was shooting 2-3 MOA with IMI and S&B 77gr ammo but 4+ with other.
I cut the barrel down to 14" and recrowned it with a single point cutter, 11* and no chamfer. Those one piece crown cutters with a pilot and chamfer never cut concentric.
14" + a Surefire Warcomp(enclosed) ends up 16.1"

 

[Constructor]

One more thing to check, make sure the barrel clamp cross bolts are torqued correctly at every cleaning. After cutting and crowning the barrel I went to test today and the groups were 3-6. I tightened to 50in lb the other day from memory. Manual says 60 in lb, I went to 65 today, groups went from 3"+ to 1.25" with handloads(62gr gold dots).

 

[Pyrocat]

One more thing to check, make sure the barrel clamp cross bolts are torqued correctly at every cleaning. After cutting and crowning the barrel I went to test today and the groups were 3-6. I tightened to 50in lb the other day from memory. Manual says 60 in lb, I went to 65 today, groups went from 3"+ to 1.25" with handloads(62gr gold dots).

That I already checked

 

[metroplex]

One more thing to check, make sure the barrel clamp cross bolts are torqued correctly at every cleaning. After cutting and crowning the barrel I went to test today and the groups were 3-6. I tightened to 50in lb the other day from memory. Manual says 60 in lb, I went to 65 today, groups went from 3"+ to 1.25" with handloads(62gr gold dots).

Thanks for trying this.

I have a 62 in-lb (FN SCAR) and 65 in-lb (Ruger PCC) limiters from Fix it Sticks. I was wondering if I had to buy another 60 in-lb for the barrel clamp of the MCX Spear LT.

Have you noticed anything with the screws torqued to 65 in-lb, signs of stripping, stretching, etc?