There has been much talk lately on the internet about the Sig556 vs. the Robarms XCR,  well I thought I would muddy the waters further by tossing a 3rd weapon into the mix.  The LeitnerWise SRT conversion.  I am not a professional gun writer, just a fireman by trade.  I compared these weapons as I would any tool used for serious work.  


The Tools, Sig556, LW SRT conversion, XCR



The Tools with a friend (wifes carbine)



The Range



The range faces East, with targets set @ 25, 50, 100, 200, and 300 yds.
Weather conditions:
Day 1, 55 degrees, sunny with light variable winds, 5-15 kts from the North.
Day 2, 60 degrees, same as Day 1.

The course of fire for the range test:
25 yds. off hand with 1x optic
50 yds. off hand with 1x optic
50 yds. from bench with 1x optic
100 yds. from bench with 4-16x42 riflescope

The Ammunition



Federal Premium 55 BTHP Match (used for 100 yd. groups)
Federal American Eagle 55 FMJ
Norinco .223
Malayasian M193 55 FMJ
Winchester white box 55 FMJ (wally world)
PMC 55 FMJ
My Reloads, 55 grain spitzer over 27.5 of Hodgdons BLC-2

320 rounds were fired through each weapon, a mix of all types listed above.


Optics used:

Sig556-Trijicon Tripower in a ARMS mount.
LW SRT-Eotech 552
XCR-Aimpoint M3 in a MI mount.

A Weaver V16 (4-16x42) with A.O. was used on all weapons to shoot 100 yd. groups.



SigArms 556

The 556 was ordered @ Shot '07.  When it arrived I was pleased to get it, but slightly disappointed with the fit and finish.  The plastic is ugly as a mud fence IMHO, and the finish on the upper receiver was thin and light in color.  So I made changes:
-MolyResin SoCom Black on the upper receiver and barrel
-Magpul CTR stock and trigger guard
-Old style SE Vortex FS
-B&T handguard rail system


ACCURACY
25 yds offhand  2-4"
50 yds offhand  3-6"
50 yds bench     2-4"
100 yds bench   1.25" best group, 2" overall average
Barrel-1/7" twist rate, hammer forged.

3rd in test group.










ERGONOMICS/CONTROLS
Trigger-Smooth, easy to maintain a "surprise break".  Best in group.
Safety/Selector-Ambi, positive feel, good positioning. 2nd. in group
Charging Handle-Right side, firm in feel, good shape and gripping surface, requires   righties to remove hand from firing controls to manipulate.  Best in group.
Bolt catch/Release-Non-Ambi, left side, small, always functioned.  2nd in group.
Magazine Release-Poorly placed with a long reach to activate.  3rd in group.
Cheek Weld-Good with the proper optics and mounts.  AR mounts and BUIS are to high, limiting the weapon in this area at this time.  3rd in group
Adjustable Gas System- 2 position, clean and dirty, does not require tool to adjust.  2nd in group tied with the XCR.    

2nd overall in group.


OVERALL FUNCTION
The 556 leaves me with the impression of a smooth, solid shooter. Recoil was the lowest of the group, making accurate follow up shots easy.  The 556 is the heaviest weapon of
three, with a muzzle heavy feel.  Shell ejection was at 2 o'clock about 15'.  The spent cases had a slight crease about 1" from the case head, not enough to ruin the cases for reloading.  My main complaint is with the mag release making tactical reloads difficult as you have to shift your grip.  0 malfunctions of any kind.  I have shot the 55X series and find the overall feel of the 556 not that different.  

2nd in group tied with XCR.


APPEARANCE
New from the box was weak, at best.  I was expecting better quality from SigArms.  The cheap Israeli plastic and substandard receiver finish were disappointing.  I think I have remedied that but it was costly.

3rd in group.


CLEANING/MAINTENANCE
The 556 is the most difficult of the three to disassemble and clean.  To split the receivers 2 screw drivers are needed.  The lower receiver remained fairly clean after the test, but the 556 vents its gas under the handguard, fouling the upper half of the rail system and the SS parts badly.

3rd in group.

Lower Receiver


Bolt


Upper Receiver and Ejector


Gas Recoil System


Upper Receiver Parts Complete




LeitnerWise SRT conversion (special rifle tactical)

This weapon is a mutt.  The upper is a Colt 16", 1/9", HBAR converted by LW to SRT configuration during the AR15.com group buy.  The upper had about 150 rounds through it prior to the test.  The lower is all RRA with a Ace Ltd. RET, H2 buffer/Wolff extra power spring (on the recommendation of SMGLee), Magpul CTR, etc.  The lower was newly built just prior to the test.


ACCURACY
25 yds. offhand  2-3"
50 yds. offhand  3-5"
50 yds. bench    2-4"
100 yds prone*   1.25" best group, 1.75" overall average.
Barrel- 1/9" twist rate, chrome lined.

* 100 yd. group was shot prone because I forget to bring a hex wrench to remove the Eotech.  I shot the group at home using a laser rengefinder to establish the distance.  

2nd in test group.







 


ERGONOMICS/CONTROLS
Trigger-Standard AR single stage trigger group.  3rd in group.
Safety/Selector- Ambi AR selector, positive and correct placement.  Best in group.
Charging Handle-AR with Tac Latch, stiff due to Wolff spring, allows for ambi function.  2nd in group with XCR.
Bolt Catch/Release-Standard AR, works for me. Best in group.
Magazine Release- Standard AR, good placement/function.  Best in group.
Cheek Weld-Good with proper high mounts and optics, many options available. Best in group.
Adjustable Gas System-No, LW system is self regulating.  Best in group.

Best overall in group.


OVERALL FUNCTION
The LW SRT conversion just feels good to me, probably because I'm so used to the AR platform.
All the controls are where I like them.  The recoil is slightly harsher than a DI AR, but with the H2 buffer/Wolff spring not by much.  The SRT weighs about the same as the XCR, but less than the 556.  Ejection was at 3 o'clock and 10' in a nice small area. There were 0 malfunctions of any kind.  

Best in group.


APPEARANCE
Quality parts make up this weapon.  Fit and finish are 1st class.  The LW 2 piece handguard is nicely machined, as are all the after market parts.  

Best in group.


CLEANING/MAINTENANCE
What a pleasant surprise when I disassembled the LW conversion.  The bolt and carrier still looked freshly lubed and clean,  unlike a DI AR.  The LW system vents it's gas under the handguard also but it was much cleaner than the 556.  All that was needed was a little wiping with a solvent dampened rag and a few patches through the bore and it was good to go.  

2nd in group.

Bolt and Carrier


LW Tappet System


Upper Complete




Robinson Armament XCR

When I ordered this rifle direct from RobArms I was told 3 weeks for delivery.  3 weeks to the day the UPS truck delivered it.  So much for the "2 weeks out" stories.  I ordered this weapon as the standard carbine with the optional 16",  1/8" twist  heavy barrel.  Total preparation to shoot this carbine was to throw on a Aimpoint, pull back the bolt and squirt in some Breakfree CLP.  I have plans to modify this carbine to my personal tastes, but that is for another post, another time.


ACCURACY
25 yds. offhand  1.5-2.5"
50 yds, offhand  2.5-4"
50 yds. bench    1.5-3"
100 yds, bench   7/8" best group, 1.5" overall average.
Barrel-1/8" twist rate, chrome lined.

Best in group.











ERGONOMICS/CONTROLS
Trigger-2 stage, very stiff initially but by the end of the test it was better, my guess is about 6-7 lbs. on the 2nd stage.  2nd in group.
Safety/Selector-Good location, shorter throw than AR, positive, not ambi.  3rd in group.
Charging Handle-Left side (FN style), functions as forward assist, loose in the receiver, didn't feel very solid like the 556.  3rd in group.
Bolt Catch/Release-Ambi, functioned perfectly every time, great location but was loose and rattled when not engaged.  3rd in group.
Magazine Release-Good location, easy to manipulate with index finger.  Loaded magazine won't insert with bolt closed(I spoke to RobArms and they told me this was due to the design.  The magazine sits in the magwell higher to assist with feeding.).  2nd in group.
Cheek Weld-Decent position, although lower than a AR, AR mounts and optics work better than on the 556.  But still not optimum.  The rubber covered upper portion of the folding buttstock is a little small in diameter for a comfortable feel.  2nd in group.
Adjustable Gas System-4 position, requires a wrench to adjust.  3rd in group.

3rd overall in group.


OVERALL FUNCTION
The XCR balances very well and is a natural pointer.  The recoil is a little stronger than the other two but that's because the gas system was left in position #4 per the instruction manual.  Accurate follow up shots were easy to maintain due to the low muzzle rise.  The XCR seemed to weigh about the same as the LW SRT conversion, and less than the 556. My wife said she really enjoyed shooting the XCR.  Shell ejection was brisk and to the 1 o'clock position about 20' out.  The XCR was very hard on the brass, smashing the case mouths 50% of the time. This might also be attributed to the gas setting. Also worth noting is the sturdy feel of the folding stock mechanism that locks only in the open position. There were 0 malfunctions of any kind.  The only problem found was with the upper receiver rail.  It appears to be soft,  The Armalite scope mount rounded off 4 points on the picitinney rail.  
This did not happen on the other 2 test weapons.  

2nd in group tied with the Sig556.

Marred Rail


Smashed Case Mouths


Folding Stock Mechanism




APPEARANCE
The XCR is a very business like rifle.  Fit and finish are well done and machine work is also very nice.  Texture and color of anodizing are dark and rich.  The rifle looks worth its cost.  The only down side are the loose bolt catch and charging handle that detract from the overall quality of the weapon.

2nd in group.



CLEANING/MAINTENANCE
The XCR is very simple to disassemble and clean.  The take down latch is at the left rear of the upper receiver and connected to the recoil spring.  Push it towards the muzzle and the receivers separate.  Drive out the pin at the hinge point and the receivers come apart.
All of the gas system and recoil parts come out the rear of the upper receiver for easy cleaning and inspection.  The XCR was dirtier inside the receivers than the other tested weapons.  I attribute this to all of the CLP I dumped in before shooting.  Most impressive is the simplicity and overall design of this weapon. Though time and rounds sent down range will be needed to prove its durability.  

Best in group.

Bolt and Carrier


Bolt Carrier Assembly


Bolt


Gas Recoil Parts


Gas Recoil Assembly


Upper Receiver and Ejector




Conclusions/Overall ranking

I am sure I have stepped on some toes, but that was not my intent.  I sought to evaluate and rate these weapons as fairly as possible.  As I mentioned previously I am not a professional gunscribe.  These are all fine weapons and one would be well served with any of them, it's all a matter of your preference.  My opinions are subjective as hell,
aren't yours?  Another area I didn't want to factor in is cost,  these are all expensive weapons and when you start customizing them the cost can rise significantly.  I'm sure there are other areas that need to be rated also,  and one area is more important than another to each of us.

I gave each weapon a numbered score in each category rated (with sub categories in ergos/controls).  With best being a 1 and worst a 3.  The lowest number total being the winner.

Sig556- Accuracy 3, Ergonomics/Controls 2, Function 2, Appearance 3, Cleaning/Maintenance 3,  TOTAL  11

LW SRT conversion- Accuracy 2, Ergonomics/Controls 1, Function 1, Appearance 1, Cleaning/Maintenance 2,  TOTAL  7

XCR- Accuracy 1, Ergonomics/Controls 3, Function 2, Appearance 2, Cleaning/Maintenance  1,  TOTAL  9                      


So according to my test criteria the LeitnerWise SRT conversion is the winner.  I think that what this comparison shows is what a great platform the AR still is with a little updating.  All three of these weapons are so close it's difficult to choose a winner.  What really matters is how  your weapon works for you.  

FLAME AWAY!!!!!    

P.S.  If any one wants to link this to SigForum or any other site, feel free.  

Firedog - great idea.  I'm really looking forward to your review (and if all three of those rifles are yours am also very envious).  Don't know much about the SRT, but have been debating between the SIG and the XCR myself.

If you'r having trouble posting entire review, you might try writing it as a separate word document, and then cutting and pasting it to the forum.  (I think that will work).  

Tagged to see finished version.

Cool man. Regardless of the outcome, you are clearly the winner

On a side note, damn your XCR looks plain!

I'm interested to see the final result firedog!  It appears your xcr has the heavy barrel, but I'm not sure...let us know =)

-mb

Excellent idea, good start....

OST, cool thread and cool gear!

Sucks that the complete report got lost in cyberspace.  Looking forward to gatting the rest of it as you post!  

For you guys who have replaced the flash suppressor on the SIG 556, does it come off easily or is it pinned or is there loc-tite on it?  I'd like to replace mine, but want to know what I'm getting into before I start.

Thanks!

Devin, that FS comes right off, no problems.

Quoted: Devin, that FS comes right off, no problems.

Thanks firedog!  

I'm enjoying reading your writeup.  Thanks for the time and effort you've put into it.

Nice post!  I am just getting ready to try my XCR HBAR at 100yds. I expect similar results.

I know many here don't care, but for us working fellows, how much did each of the guns run you?  I have only seen one Leitner Wise SRT and the guy was asking $2400 (then again, the local dealer was asking premium of $2300 for the Sig, XCR at MSRP though)

Also, thanks for an extremely informative and thorough thread.

Thanks for a great post!

Great post.

Please elaborate on the 556 needing two screw drivers. Was the fit just that tight or does it use screws instead of just push pins like the AR.

Quoted: I know many here don't care, but for us working fellows, how much did each of the guns run you?  I have only seen one Leitner Wise SRT and the guy was asking $2400 (then again, the local dealer was asking premium of $2300 for the Sig, XCR at MSRP though) Also, thanks for an extremely informative and thorough thread.

I paid $1830 for my SRT (6.8).  That was several months ago though.  I'm sure that price would be hard to find now.  
The price may come down eventually through economy of scale.  LWRC was recently given a very good reason to seriously ramp up production.  
I haven't had a chance to shoot it yet  (I've been pretty busy).  I am enjoying it vicariously through this review.
Should the opportunity ever afford itself, I would love to contribute a review.  This review sets a pretty high standard.

tag

itstock-556 with optic-$2,000, LW SRT with optic-$1,900, XCR HB no optic- $1,450 retail

loaded drum - screws in the front receiver hinge like the old style Colts.

It appears alot of the bad parts of the XCR are only because its not broken in yet. Trigger, recoil, bent brass.

Im suprised it was the most accurate, very comforting. The weak top rail i have heard before and i hope it is something that gets fixed.

Great writeup, I wish i was you.

Excellent review.  Thank you for sharing with us.  Great pics too!

This was one of the best reviews I've ever read on the internet.  Great pics of the guns.  

Thanks firedog!  Very good and informative post.  I enjoyed reading it and your pictures were excellent.

I recently read somewhere else a review of the 556 vs. XCR and the 556 in that review was actually more accurate.  I always like to see more than one review of a given system.

Thanks again for the review.

It seems that the xcr's heavy barrel turned in some better results than I've seen in reviews where the pencil barrel was tested.  It shouldn't be surprising that it improved a bit in this test.  Now that the rifle is obviously broken in, I'd like to hear firedog's opinions on the xcr's recoil when he cranks the gas setting to around 2, which is where it should be with the majority of the ammo he was testing.

BTW  thanks for the comprehensive review and all the great pics!

-MB

Hey Firedog...Out-f'ing-standing.  Nice work and thanks for taking the time to not only do the testing (and documentation thereof) but also sharing.

Fred

Thanks for all the replies, it was time consuming and I lost the post 1st time around.

All 3 weapons are so close it was difficult to rate them, I'm sure personal preference played into the rating to a small degree.  It really was splitting hair at times,  thats why there were ties.

PhantomGhost- You could be right, the trigger might smooth out some more, although it's decent now.  But I don't think the loose charging handle and bolt release will cure them selves.  The soft receiver rail worries me as the whole upper receiver is extruded and tempered to the same spec. Will it effect long term durability?  Only time and use will tell.
I doubt I'll ever shoot it enough to wear it out.  I'm hopeful the brass problem will sort out with a lower gas setting.

HeavyMetal- The wifes LMT 14.5" carbine (pictured 2nd pic from top in post) was along for a test standard.  I choose not to write it up as the post was so long as it was.  It would have ranked somewhere in the middle overall.  My wife said the XCR was her favorite of the 3 tested, but she still liked her LMT better.

Devin- I was surprised also.  I thought the 556 would be the most accurate.  Maybe with a different load it could be.  But I chose to only use 1 type of ammo, a known, consistent performer so it would be a level playing field.

TheMagikBullet- I'll try to do another post on the XCR after I've shot it some more and made some changes.

Once again thanks to all, I'm glad you all enjoyed it.  I've been lurking on the internet boards for awhile and thought I should contribute something.

Quoted: Great post. Please elaborate on the 556 needing two screw drivers. Was the fit just that tight or does it use screws instead of just push pins like the AR.

the front takedown pin is a screw that screws into a slotted head pin.  sorry I can't describe it any better than that!   Some have likened it to older commercial colt front takedown pins.  You do need screwdrivers to separate them.  The good news is that the standard swiss takedown pins fit just fine on the 556.

Firedog - EXCELLENT write up!

Praetorian55
Thanks for the compliment.  Where can I get a swiss takedown pin?

Quoted: Praetorian55 Thanks for the compliment.  Where can I get a swiss takedown pin?

I got mine from http://www.theshootingedge.com/  in Canada but last time I checked, they were out...

This is where I got the takedown pin for my 556...

http://www.sturmgewehr.com/webBBS/parts.cgi?read=190788

Firedog55,Thanks for takeing the time to post pics and giveing range reports you did a good job, I dont think(as you can tell)That people  going to flame you.  

I was under the impression that the LW piston drive would recoil more the heavier of a buffer you used and the heavier the spring you used.  Also it tends to short stroke with heavy springs.  LWRC has considered going to a reduced strength recoil spring for this very reason.  Are you getting failure to lock issues?  If not your gas port is excessively large... another factor that would increase recoil.

I also dont think this is ANY kind of an indication of the performance of the LWRC SRT in accuracy or recoil.  You are using a different barrel than they use, a different gas block than what they currently use, a different recoil spring and buffer, etc.  It is nice to see a review like this but people should not expect that to be what they will get if they buy a LWRC complete rifle.

..

DevL-I noted in the write up of my LW that it was a built up gun using a Leitner Wise conversion of a Colt upper.  Several LW owners that I talked to @SHOT '07  also noted the perceived increase in felt recoil over a DI AR.  It was suggested by one I respect that a H or H2 buffer and heavier spring might alleviate this.  It has with my carbine, to me it doesn't feel much different than any 16" with a carbine length gas system.  My carbine has exhibited no short stoke or any other issues with this combination.  I don't know if Leitner Wise enlarges the gas port when they do conversions or not.  I do know LWRC only use quality parts in their complete rifle builds.  I also think that I used equal quality components (RRA lower and parts kit, Magpul, KNS, Ace Ltd, etc for the lower, and a complete Colt upper).  I doubt that there is much difference between mine and theirs.  The piston conversion and bolt carrier are  parts of their design, installed by them to their specs.  This is what makes up the core improvement over a standard AR.   I am not trying to sell LW rifles, although I highly recommend their quality products.  I merely tried to relay how my conversion worked in comparison with the other weapons tested.  For post accuracy I will change the posts title.   I will try a standard spring/buffer and see how they function.

tag for info

oft

My LWRC rifle has a 11.5" barrel which is non standard so I am still having my gas port tuned to find the minimum size I can run an Enidine buffer at.  I am unsure of the exact gas port sizes they are specing at LWRC but was under the impression that the system needed less pressure to operate propperly.  My only personal testing was using the 9mm weight MGI buffer vs the Enidine H weight buffer.  In DI rifles the MGI limits recoil more than the Enidine due to weight.  This did not occur with the LWRC piston system.  The MGI had slightly more recoil and had the exact same cyclic rate on full auto.  This, according to LW is because of the self regulating action of the system.  The more force you exert against the cycling, the harder it will cycle.  Thus my questioning the H2 buffer and extra heavy spring.

Quoted: My LWRC rifle has a 11.5" barrel which is non standard so I am still having my gas port turned to find the minimum size I can run an Enidine buffer at.  I am unsure of the exact gas port sizes they are specing at LWRC but was under the impression that the system needed less pressure to operate propperly.  My only personal testing was using the 9mm weight MGI buffer vs the Enidine H weight buffer.  In DI rifles the MGI limits recoil more than the Enidine due to weight.  This did not occur with the LWRC piston system.  The MGI had slightly more recoil and had the exact same cyclic rate on full auto.  This, according to LW is because of the self regulating action of the system.  The more force you exert against the cycling, the harder it will cycle.  Thus my questioning the H2 buffer and extra heavy spring.

So does the Endine weigh about the same as a standard buffer?

DevL-  Makes sense to me,  next time I get to the range with it I'm going to bring a standard buffer and spring and try it .  Thanks for the tip.  I've never shot it with any other buffer set up than the H2/Wolff.

Firedog,
I had the same problem with the upper on my XCR. I attached some PRI rings and they crushed the rails a little, nothing serious but noticable. I did not tighten them down very tight at all. I e-mailed Robinson about this and Alex Robinson e-mailed me back saying that the uppers are heat treated/anodized by the same company that does alot of ARs, and to the same specs. He thought my rings might be bad. I tried them on an AR and even tightened them down as hard as possible and they didn't crush or even scratch the AR. Alex did say I can send him my upper but I ended up selling the rifle to a friend who didn't mind the "dings". I wanted an XCR with the heavy barrel and 1-8" twist anyway which is what I have now ( other one was the pencil thin barrel). Great job with the review. I really like the XCR but now I put rings on hand tight with some blue lock-tite.

Great review, thanks

Good review. I love my XCR and am currently purchasing A Leitner Wise SRT. I think I'll pass on the Sig

Firedog,

On the LWRC why was the H2 buffer/Wolff extra power spring reccomended? What BUIS did you throw on top?

Thanks for taking the time to conduct the tests, take the photos, record your observations ... and then spending even more time writing them down such that all could understand your results, approach and objectives.  Posting the whole kit-and-kaboodle here for our enjoyment and edification, firedog55, was above and beyond the call of duty.  I salute you.

A most excellent post firedog55...!

revilo8367- The H2/Wolff extra power spring was recommended to dampen recoil by another LW owner.  I can't say if it helps or not as I've not shot the weapon with a standard buffer/spring.  I am going to try it to find out.  Arms 40 and MI front sight used.

Thanks to all for the compliments.

I'm going to do some more range work with the 556 and heavier bullets to see if it will group better, I'll post the results.

Also I'll post on the XCR after I get done personalizing it.

Excellent work!  Some guys have all the fun.