Has anyone posted a side by side comparison of the two?  If so, please link?

The ARX works and is designed and manufactured by a competent company. The 556Xi doesn't and is not.

There's your side by side comparison.

My sentiments exactly.

Here's a more useful comparison.

I have an ARX-100 and SiG 556xis in both 5.56 and 7.62x39.  The only problem I've had with any of them was the xi in 7.62 had problems I with old Norinco ammo.  With newer ammo like Red Army Standard and TulaAmmo, it runs 100%.  Some comparison comments:

Barrel:  Both have 16" barrels with 1/7 twist.  The ARX barrel is actually removable like the claim.  Just pull down a Glock-like catch on both sides of the frame and you can pull the barrel out.  It's as easy as an AUG.  The Sig barrel isn't quick change.  It has a barrel nut that requires a special wrench to remove, just like an AR.

Gas system:  Both are piston operated, with the Sig being a long stroke piston attached to the carrier similar to an AK or FN.  The ARX is a short stroke piston which is actually a fixed rear facing piston with a surrounding cylinder that moves back to push the carrier.  The ARX cylinder isn't meant to be removed for normal cleaning, so the ARX runs incredibly clean.  Basically you just wipe the powder off the exposed part of the piston shaft, and that's it.  On the Sig, you have to clean the carbon off the piston head and gas valve, like a normal piston gun.  The SiG has a 3 position gas valve (normal, adverse, and suppressed), while the ARX is only two (standard/normal and non-standard/adverse).

Construction:  The Sig has a steel upper with an aluminum lower with standard push pins like an AR.  The ARX is a polymer body with a removable lower that has the grip, fire control components, and magwell.  No pushpins or tools needed with the ARX.

Stocks:  Both have stocks that fold to the right side.  The Sig is fixed length, but the ARX can be adjusted for LOP.  Both are proprietary, so you are pretty much stuck with the factory stock.  The Sig comes with a removable cheekpiece, which works well with the iron sights, but the ARX is a straight stock that's too low and when used with standard height sights requires more of a chin weld than a cheek weld.  There is an aftermarket cheek riser available for the ARX, though.  The Sig can't be fired with the cheekpiece installed and the stock folded.  The ARX and Sig without the cheekpiece can both be fired with the stock folded.

Ejection:  the Sig is right hand ejection only.  The Beretta can be set to eject to either side and it's as simple as using a bullet tip to push a plate in the rear of the receiver to one side or the other.  This is done with the gun full assembled.  No disassembly or special left hand parts needed.  This works by having an extractor and ejector on both sides of the bolt (you end up with dual extractors, which is nice) and the position of the rear plate determines which side of the bolt performs which function.

Trigger:  The Sig has a two stage trigger with a spring loaded stop that can be adjusted for a short and crisp second stage.  It's fairly light and very nice IMHO.  The ARX trigger seems like a single stage, and it's crisp, but VERY heavy.  The Sig trigger is definitely better (if its adjusted right).

Controls:  both have ambi safety levers and swappable charging handles that are on the small side.  The ARX also has ambi mag releases and BHO/release.  However, the ergonomics on the ARX are not good.  The controls are stiff to operate, especially the safety.  Also, it can be difficult to manually actuate the BHO because there is little remaining rear bolt travel left past where the BHO is, and the last part of the bolt travel is heavier because the force of the spring used for the dual extractors/ejectors adds to the counter force for the recoil spring.  It works fine locking on an empty mag, but it takes some getting used to for manual operation.

Grips:  The 556xi has a removable grip, but some of the grips made for the regular 556 don't fit because the mounting tang on the bottom of the lower is a little wider in the xi.  The ARX grip is molded as part of the "lower", so you either like it or not because you're stuck with it.

Rails:  both have long metal top rails.  On the Sig, that's all you get in the box.  The Sig polymer handguard cooling slots can take Magpul MOE rail sections (not included), but the aluminum handguard only has screw holes for proprietary rail sections that must be bought separately.  The ARX has rail sections mounted on each side screwed to the body of the gun.  Also, the ARX has a long bottom rail, but it's misleading.  Only the front 3 slots are standard picatinny rail.  The remainder of the rail, which is normally hidden under a slide off cover, is made for an Italian grenade launcher and picatinny accessories won't fit.  Beretta is supposed to be bring out an adapter that makes the bottom rail full length picatinny, but it's not out yet.  Also, the top rail on the SiG is pretty close to the charging handle, so large overhanging optics like Eotechs may result in hitting your hand when pull the handle back.  The rail on the ARX is a lot higher and doesn't interf with the charging handle at all.

Sights:  Both come with removable flip up sights.  On the Sig, they are metal, standard AR height, and similar to Troys, although the bases are quite large and overhang the sides of the rail.  The ARX sights are polymer low profile with a rear diopter disc set for different ranges.  However, the are higher than standard, and combined with the low stock, makes looking through the iron sights uncomfortable.

Mag compatibility:  The xi in 5.56 is pretty good about taking almost any AR mag, metal or polymer.  The ARX magwell is deeper, especially at the rear, which limits mag options.  Metal mags, Lancer AWMs, and Gen 2 Pmags work OK, but Magpul M3s or other mags with overtravel stops on the rear mag spine, or protruding ribs on the lower body that start at normal AR magwell height won't work.

Sling mounts;  The Sig only has a mount at the upper rear of the receiver and a round hole in the stock, both for hook type sling.  Nothing up front, and Sig deleted the gas block mounted sling point used on the standard 556.  The ARX has a sling mount for a web sling on the gas block that can be swung from right to left, and flat sling loops molded into the polymer body, and one loop at the top rear of the stock.  They are pretty much only useable with a 1in web sling.  No QD mounts.  On the ARX, you can attach a sling mount point to one of the side rails at the front, but there really isn't anywhere to put a sling mount on the rear except for the top rail.

Accessories:  neither have good support for factory accessories.  Pretty much, there is nothing available currently from Beretta for the ARX.  No caliber conversions, bottom picatinny rail adapter, or anything else.  Sig is only marginally better.  You can get the picatinny rail sections for the aluminum handguard (if they have them in stock), and they have released the xi in 7.62x39 as a complete gun, but so far like the ARX, you can't get any caliber conversions for an existing gun.

Shooting impressions:  The Beretta seems to have more felt recoil than the SiG, and even a typical AR.  Accuracy with the Sig is better due to having a fixed barrel, and a much better trigger.

HTH.

Thanks for the thorough comparison.  It seems like the Beretta is more user friendly, but the trigger and accuracy are inferior to the SIG.

Hoping that as sales increase so will SIG support.

I had two ARX100's and three Sigxi rifles.  The ARX100 felt like such a cheesy plastic rifle,I never even fired them.  The ARX reminds me of that clunky ass FS2000. I sold both Berettas.  I still have all three XI's and they work just fine.

"feels like" is an utterly irrelevant factor in terms of measuring functionality and performance.

If that's really Tony Rumore, owner/founder of Tromix, then "feels like" is very much a relevant factor of measuring functionality and performance.

Well I am no fan of cheese so I say the hell with the ARX100

Appeal to authority fallacy.

or

That's one man's opinion.


Modern polymers have come a long way and discounting something simply because it "feels" too plasticy is absolutely idiotic. Polymers are the future of firearms, deal with it.

If the ARX has a cheesy feel, why buy one, much less two of them?  One should be able to tell that just by picking one up at the dealer.  I once owned a FS2000.  No way the ARX is as craptastic as that gun.  Do the Tavor and AUG fall in the same boat of cheap plastic feeling guns?

both the ARX and FS2000 make me exclaim when handling an M4 "wow, they don't build them like this anymore"

I never thought that would happen because in the old days, we used to say that about a Garand or M14 compared to an M4

At least the FS2000 has a lot of gee whiz features and looks like it should belong in a sci fi movie so it at least has some novelty going for it.

 

Hmmm..... Really?  Hi-Point pistols function great and accuracy is as good as the new-gen plastic pistols, but that big clunky/cheesy feel doesn't do it for me.   I guess that clunky cheesy feel of a Hi-Point pistol is "utterly irrelevant" to you.  The feel of a gun is quite relevant to me.

Tony

lol. no.