Beretta ARX 100 accuracy with different ammo.

[briansmithwins]

I took the ARX-100 out Wednesday to try some different ammo and see if pulling the barrel resulted in group size shifting.

Some things to consider:
1) Range was 100 yards.
2) I was using a Aimpoint 2MOA optic.
3) I have astigmatism.
4) It was a cloudy day.
5) Combining 2,3,4 means I see the dot as a 'V' shape instead of a clean circle.
6) The stock ARX trigger doesn't help when trying for small groups.
7) I'm not, nor do I pretend to be, anything resembling a sniper.

All that said, here's what my groups looks like:
Ammo from left to right was Geco M193, ADI SS109, PPU 75gr HP, IMI 77gr OTM. The grid is 1" per.


Here's what happened when I pulled the barrel. The barrel was removed after shooting the above groups and left to cool while I was doing some other shooting. I pulled the barrel between each of these groups while I did some other shooting. Ammo was the same Geco M193 as the above target.


BSW

 

[barnbwt]

Hmm, seems like a tighter grouping the second time around. Are you intentionally using a 12'o clock hold, or is the gun zero'ed for like 200yds? Looks like most all shots are a good bit above the bull.

Groups 2-3 times the size of your aiming reticle doesn't seem unserviceable or anything, but I wonder if you'd get a tighter minute of angle at 50yds (just so more of the bull is visible around the dot & less washed out by eyeball artifacts)?

I'm happy to see the ARX doesn't appear to suffer from a wandering zero (sorry, had to say it after the alleged G36 'troubles' )

TCB

 

[kwguy]

I have found that the ARX does indeed return to zero quite well after barrel removal, and does not appear to suffer from a wandering zero from barrel removal. Any changing of group size or accuracy seems to come from barrel heating, just like with any other rifle.

On average, it seems to be an easy 2-3 MOA rifle, with occasional groups of around one inch when the stars are aligned (for me anyway). I wonder if that's because of the trigger?

One interesting thing I've noted is that it is easily 'combat accurate' (for lack of a better term), but is a pain in the neck to shoot for groups. In other words, at 100 yards, hitting 4 inch or so groups, or clays against the berm (using at TA11 ACOG), is really easy when shooting offhand or a simple rest at the rate of one shot every one or two seconds, but when putting the rifle in a 'lead sled' with a 3-9 power scope and going for tiny little groups, it still (mostly) yields 1.5 to 3 moa, with just about any decent ammo.

Since the barrel is not really free floated (it seems to be 'almost' free floated), I'm sure the ability to maintain tight groups falls on the ability to maintain the exact same pressures upon the barrel when shooting. The slightly inconsistent pressures on the barrel from shot to shot, combined with the relatively hard trigger pull, is probably what causes the groups to be slightly larger.

All in all, I think it's an excellent rifle. It's basically a semi-auto version of Beretta's 'off the rack' military carbine, designed for use by soldiers in the same conditions that your average military 'off the rack' M4 is used for. It certainly seems to perform about the same as the average military M4 (non-free float, non match trigger), with the added benefit of easier running and increased reliability (not trying to start anything, the M4 is reliable, if you keep it wet and / or clean and lubed). The Beretta really does require minimal to no lube, which is nice. I'd say an M4 is more durable in terms of maybe getting run over by a vehicle on a dirt road or something, since it's mostly aluminum, but the polymer Beretta is extremely light, which is a pretty good tradeoff, I guess.

Has anyone definitively determined if the ARX has a ceramic trunnion? Or a steel trunnion with a ceramic coating? I've been unable to find any real answers...

 

[briansmithwins]

The receiver around the barrel extension is plastic.

The barrel support is anodized aluminum, which some people have mistaken for ceramic. See my write up here for details: http://www.thehighroad.org/showthread.php?t=777423


BSW

 

[kwguy]

http://www.thehighroad.org/showthread.php?t=777423

That is an awesome write up!

The receiver around the barrel extension is plastic.

This is the part that I was wondering about. Is there some type of metal molded into the plastic that the barrel extension snaps into? Surely it can't be the barrel extension just snapping directly to the plastic receiver?

 

[briansmithwins]

This is the part that I was wondering about. Is there some type of metal molded into the plastic that the barrel extension snaps into? Surely it can't be the barrel extension just snapping directly to the plastic receiver?

I am serious, and don't call me Shirly...

All joking aside, the barrel extension does sit in a plastic socket. There is a spring loaded metal latch the retains the barrel extension but I can't see any metal molded in the receiver at all.

The locking pin cam is steel, but I think it's added separately after the receiver is out of the mold.

BSW

 

[barnbwt]

"The receiver around the barrel extension is plastic."

I could have sworn I saw both ad copy from Beretta touting this ceramic liner as an improvement over the G36, as well as PR releases blaming a shortage of the liners for the gun's delayed shipment to civilian hands.

Is the liner just a full-auto component? (not beyond the realm of possibility it truly isn't needed for semi-auto fire, same as the G36 not having significant issues on semi)

TCB

 

[Gtscotty]

I could have sworn I saw both ad copy from Beretta touting this ceramic liner as an improvement over the G36, as well as PR releases blaming a shortage of the liners for the gun's delayed shipment to civilian hands.

I had the same question on one of the other ARX-100 or G36 threads. The diagram here in post #21 shows the thermal barrier (part #8) and how it fits into the ARX receiver:

http://www.hkpro.com/forum/hk-long-gun-talk/202192-hk-g36-issue-solved-3.html

Also the patent application for the same part below states that there is a ceramic thermal barrier (possibly just the internal ring, part #2?) designed to be fit between the barrel and receiver.

http://worldwide.espacenet.com/publicationDetails/originalDocument?FT=D&date=20130306&DB=EPODOC&locale=en_EP&CC=EP&NR=2565576A1&KC=A1&ND=4

Is the liner just a full-auto component?

That is kind of what I'm thinking. BSW has looked on his semi auto ARX-100 and didn't see any ceramic inserts, perhaps they are only incorporated into the full auto capable ARX-160.

 

[Lord Teapot]

i looked at one of these, looked like the lower railing on the front would cut your hands.

 

[briansmithwins]

There could be a co-molded part at the barrel extension area that I can't see. I've never removed the barrel latch mechanism to get a better look at that area.

But from what I've seen the part of the receiver that's in contact with the barrel extension is the same plastic that the rest of the receiver is made out of.

And yeah, rails are tough on your hands, which is why I like rail covers.

BSW