XCR vs Sig classic green

[Koenig Tiger]

The Sig handguards cover the gas tube and piston and a portion of the barrel. They mount at the rear, to the front of the receiver, and the front of the guards mount to the rear of the gas block.
If anything the venting on the monolithic upper of the XCR should dissipate heat far faster than the Sig.

Yeah, but the SAN handguards are not in direct contact with either the gas tube or barrel and they're made of much thicker plastic than railguards grips as used on the XCR. I think the reason the XCR's grips heat up so fast is because of the way the barrel is attached to the aluminum upper as part of the quick change system. There's quite a bit of surface of contact between the base of the barrel and the upper which means the heat generated by the firing chamber will be dumped directly into the upper. Since it's made of aluminum, which is a great heat conductor, it won't take long for that heat to spread to the handguards.

So the XCR's upper does dissipate heat from the barrel faster, it just does so right under your hands if you don't give it a decent chance to cool down.

Are you sure the upper is affecting accuracy? I thought the reason they went with the monolithic design was to float the barrel assembly? If that is the case, the railed fore grip should not affect accuracy - in theory...

My guess for this is, again, the way the barrel is attached to the upper. Steel and aluminum have different thermal expansion coefficients so the barrel may become slightly loose (just enough to affect accuracy) once the upper starts to heat up.

With regard to what? Accuracy? - they can't hold a candle to an average AR that is floated.

Yeah, we all know how much you love the XCR...

But no, I was referring to it's ability withstand heat from firing multiple rounds.

 

[nickorette]

So I acquired the subject SAN classic green from Evan...had not shot or dissassembled rifle until reading this thread afterwhich I went downstairs for dissassembly and close inspection. Gas system was heavily fouled;

gas piston valve would bind between settings
min 1/16 max 1/8 thickness of carbon buildup between piston and spring retention collet
large cakes of carbon buildup in gas tube
boroscope reveals bore had significant powder and copper fouling

when I acquired rifle I was told the current owner was not the original owner. I believe the rifle has been shot alot and not cleaned properly (or at all in the case of the gas system. I spent a good hours scraping off the carbon and now believe she will run well like all the others beside her in the safe.

It's hunting season now though so I have some other shooting to do; range report will follow in a couple weeks when I get some time.

Cheers,

brobee

I bet you could have still kept on shooting it without any problems!!!

 

[Davy Crockett]

I bet you could have still kept on shooting it without any problems!!!

Check earlier in the thread. The guy he got it from was posting in this thread about having a bunch of failures with the rifle as it was.

Not that it diminishes the rifle if it doesn't run when fouled up but it's not somehow magical and can run indefinitely with out maintenance.

 

[Gundoggy]

There's something about the Swissarms that appeals to my liking for rugged dependable equipment. I have a LMT CQB/MRP piston gun, and according to reviews in US, it's supposed to be quite good, barrel is good for 20K rounds (I have spare 16" and 12" barrel too!) Still if the SHTF and I needed to lug something for survival I'd likely grab either my 14.3" or 17" LB flattop swissarms carbine....barrels are good for 35K + rounds if I recall some link to testing of these guns.

Of course if we could buy the XCR for the actual price the USA citizens get it for then it would be more than a good buy for the money it costs.

 

[beltfed]

Yeah, we all know how much you love the XCR...

But no, I was referring to it's ability withstand heat from firing multiple rounds.

I has nothing to do with my personal feelings of the system. The average floated AR is more accurate than the XCR by design and in reality. The same can be said when comparing the AR to the Sig.

With regard to heat, most (if not all?) floated handguards on ARs only contact with the barrel is indirectly through the barrel nut. Very little contact for conducted heat, however like the XCR, if they are well vented, there would/could be a significant amount of convected heat transfer.

 

[50calshooter]

 

[nickorette]

Check earlier in the thread. The guy he got it from was posting in this thread about having a bunch of failures with the rifle as it was.

Not that it diminishes the rifle if it doesn't run when fouled up but it's not somehow magical and can run indefinitely with out maintenance.

Ahh my bad. The only thing I can think of is improper gas tube installation (it can be done. I spent a half hour figuring out the proper way to do it the first time) or possibly a dry gas system. I put a light coat of grease on mine and never cleaned it since. I've got 1500 rounds through without touching the gas system and have no problems ever.

 

[Ffynn]

I haven't handled a SAN, so I have nothing to say about that, but I do own an XCR.

I've fired 400 rounds through it on setting 4 and didn't have a single malfunction. I did notice that the rifle heated up quite a bit though. In regards to accuracy... I can't say much. I was shooting at the public range outside of Calgary, and some jackass kept shooting my targets.

I have had one problem however; the detent holding the gas valve in place fell off and is now lost to me. Miraculously my gas valve wasn't shot off and I contacted Terra who got the parts to me and the rifle is now fine.