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Thread: The R18 Mk2 Review Pt 2 Live Fire Reliabllity and Accuracy Results

  1. #251
    Super GunNutz Bartok5's Avatar
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    Barrels are standard AR15 pattern, but with an enlarged Gas Port. The Gas Port, mated with the standard, adjustable Gas Block will ensure reliable feeding with all brands of ammo and bullet weights, to include compatible calibre changes.

    Being standard AR pattern barrels, rebarrelling for the purposes of a calibre change will be a simple do-it-yourself matter of unscrewing the 4 bolts securing the Barrel Nut and swapping over the Rifĺe-length Gas System. Barrel changes for the purpose of installing a shorter barrel may be problematic in terms of finding a compatible Carbine-length Gas System. My testing will not cover such a conversion, which is best left to the tinkerers to attempt.
    Last edited by Bartok5; 11-30-2021 at 02:31 PM.
    Mark C

  2. #252
    Super GunNutz Bartok5's Avatar
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    Quote Originally Posted by ColdLead View Post
    Hey Bartok, in your opinion is it worth the wait to have a dust cover, or is the seal between the receiver and the bolt good enough the cover wouldn't do much?
    The seal is pretty tight between the Bolt Carrier and the Ejection Port, moreso than competing designs such as the Bushmaster ACR. Personally I don't see the Dust Cover doing anything more than the current fitment between the Carrier and Receiver Walls. I won't be waiting for the Gen 3, if that tells you anything....
    Mark C

  3. #253
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    Quote Originally Posted by Bartok5 View Post
    Barrels are standard AR15 pattern, but with an enlarged Gas Port. The Gas Port, mated with the standard, adjustable Gas Block will ensure reliable feeding with all brands of ammo and bullet weights, to include compatible calibre changes.

    Being standard AR pattern barrels, rebarrelling for the purposes of a calibre change will be a simple do-it-yourself matter of unscrewing the 4 bolts securing the Barrel Nut and swapping over the Rifĺe-length Gas System. Barrel changes for the purpose of installing a shorter barrel may be problematic in terms of finding a compatible Carbine-length Gas System. My testing will not cover such a conversion, which is best left to the tinkerers to attempt.
    Do you have carbine length piston from a WK or MCR available to compare against the diameter of the one on the R18 Mk2 against? If they are identical you should be able to use the replacement carbine, mid, and rifle length pistons available for other platforms with the R18.

    Glad to hear the gas block is adjustable from factory. How is the adjustable gas block secured to the barrel? An issue with an over-gassed competitors firearm is the fasteners on the non-adjustable gas block loosening over time, causing the gas block to rotate sidewise on the barrel, which in turn causes enough strain and twist on the piston rod that it eventually snaps from the abuse. Hopefully the gas block is well secured, and the advent of using an adjustable gas block and rifle length piston means there is less force to loosen things up to begin with.

  4. #254
    CGN Regular vultr's Avatar
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    If I took a standard AR barrel for a caliber conversion, would I need to open up the gas port?

    Thanks Mark.
    "A gun is not a weapon, Marge, it's a tool. Like a butcher's knife or a harpoon, or...or an alligator."

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  5. #255
    Super GunNutz Bartok5's Avatar
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    Quote Originally Posted by vultr View Post
    If I took a standard AR barrel for a caliber conversion, would I need to open up the gas port?

    Thanks Mark.
    Difficult to say, but I doubt it. A calibre conversion Barrel will have a Gas Port unique to that calibre and ought to run just fine so long as you adjust the Gas Block to balance the action a tad on the over-gassed side. The only reason that SAI is opening up the standard AR .223/5.56mm Gas Port on the stock barrels is to ensure functionality under the worst conceivable conditions. This includes the use of Steel-cased ammunition, which is typically underpowered. The Gas Block will be factory-adjusted to ensure that the rifles are properly gassed at the operating system.

    Unfortunately I do not have a WK180 or WS-MCR carbine-length gas system to compare against the R18s system. In addition to having to integrate with the Gas Block, the Operating Rod diameter and length would have to be compatible where the Op Rod enters the Upper Receiver to butt up against the Bolt Carrier. That seems like an awful lot of commonality between different manufacturers to hope for, but I could be wrong and everything might work splendidly together. I simply cannot say.

    The R18 Gas Block is secured by 2 x Hex Cap-Screws on the underside. I do not know if the Barrel is dimpled to correspond to the Screws, thus preventing rotation. The Cap-Screws are Loctited during assembly. Neither Gas Block on my test rifes has loosened nor shifted position over the course of 710 rounds on the one rifle (and 260 rounds on the other).

    Accuracy and reliability testing will continue tomorrow, to include 3 different match loads. I have cleaned the bore on the higher round-count rifle in order to give the (expensive!} Match ammo the best possible accuracy potential. Watch and shoot....
    Last edited by Bartok5; 11-30-2021 at 08:01 PM.
    Mark C

  6. #256
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    Quote Originally Posted by Bartok5 View Post
    Unfortunately I do not have a WK180 or WS-MCR carbine-length gas system to compare against the R18s system. In addition to having to integrate with the Gas Block, the Operating Rod diameter and length would have to be compatible where the Op Rod enters the Upper Receiver to butt up against the Bolt Carrier. That seems like an awful lot of commonality between different manufacturers to hope for, but I could be wrong and everything might work splendidly together. I simply cannot say.

    The R18 Gas Block is secured by 2 x Hex Cap-Screws on the underside. I do not know if the Barrel is dimpled to correspond to the Screws, thus preventing rotation. The Cap-Screws are Loctited during assembly. Neither Gas Block on my test rifes has loosened nor shifted position over the course of 710 rounds on the one rifle (and 260 rounds on the other).
    Thanks for the info! Its great to hear the gas block has not shifted; if its not dimpled, as you say, hopefully the thread locker, the gentler action from having a tuned gas block compared to the competition, and the softer recoil impulse form the rifle length gas piston will keep it nicely in place. The 700 round count is already approaching the threshold where a loose gas block would be apparent; when the competition has piston failure, its around thousand round mark or so, so I think the R18 is looking good.

  7. #257
    Super GunNutz Bartok5's Avatar
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    So, another fairly successful day at the range. Wealther was overcast with an ambient temperature of +6C throughout. 340 rounds were fired through the primary Test Rifle, bringing the total round count to 1050. In addition I fired 100 rounds through the Alternate Test Rifle to confirm consistent accuracy between the two samples. Neither rifle demonstrated superior accuracy and results were identical between the two samples for all intents and purposes. Both rifles functioned with 100% reliability. Note that I cleaned the Barrel of the Primary Rifle in preparation for today's accuracy testing. Aside from that however, the rifle's internals and gas system have not been maintained at any time during the 1050 rounds of test-firing to date. Reliability testing (without further cleaning) will continue with the Primary Rifle until such time as I run out of ammo or reliability falters. I will of course, report either occurrence.

    The results of accuracy testing were acceptable, but not as good as was hoped for especially when it came to Match Grade Ammunition. Average resuts for PMC XTac 55 grain 5.56mm Ball hovered between 2" and 2 3/8".







    The R18's 1:8" Twist Pencil Barrel doesn't seem to particularly like the heavier 77 grain HPBT bullets found in the IVI LE load. Groups with this heavier load averaged 2 1/4" to 2 1/2".







    Finally the Match Grade ammo. First up was Federal Premium .223 with a 55 gr Nosler Ballistic Tip. The result was a mediocre, but acceptable 2 1/4" .





    Next up was 53 gr .223 Hornady V-Max Superformance Varmint with a very similar 2 1/4" group.





    The final load of the day was Nosler 77 gr .223 Hollow Point Boat Tail Match with a group measuring 2.5". It is worth noting that all of the declared group sizes are inclusive of "fliers" which in many cases expand a 1.5" 4-round group to 2+".






    The accuracy, at 2-2.5 MOA is acceptable for a pencil barrel, but is still not optimal. Properly free-floated, the Barrel ought to perform better than it has to date. The apparent problem is fliers - usually one or two per five-round group. Those fliers typically open up the groups from 1.5 MOA to 2 MOA+. So what's causing those fliers? After careful examination of the Test rifles I believe that there are two issues at play. The degree to which each of these functional issues is impacting accuracy I cannot say for certain. What I can say with some assuredness is that the issues are legitimate. The first is that the Gas Block is impacting the Handguard during firing. The clearance between the Gas Block and the Handguard is inadequate such that Barrrel Harmonics/Whip is causing the Cap Screws in the Gas Block to mar the inside of the Handguard through the anodizing down into the bare aluminum. This suggest significant force behind the Gas Block when it strikes the Handguard. The plan is to have SAI reduce the bottom profile of the Gas Block to create additional space between the Block and the Handguard such that contact during firing is eliminated. Note the proximity of the Gas Block to the inside of the Handguard in the following photos:








    The second issue at play is the Barrel profile. I believe that the "pencil" profile lacks the necessary rigidity to withstand intereference from the operation of the Gas System. In their quest for balance and weight savings i believe that the SAI Engineers went too light in the Barrel profile between the Chamber and the Gas Block. I have recommended a beefed up circumference between the Chamber and the Gas Block and a new custom Barrel is being created specificallly for Accuracy Testing. For comparison sake, the original AR180 Barrel measures .665" in front of Chamber and .625" at the Gas Block. The R18 measures .565" at the front of the Chamber and .555" at the Gas Block, indicating that the current R18 Barrel is .1" thinner in profile than even the original lightweight AR180.





    I will continue with Reliability testing on the Primary Rifle pending production of the Medium profile Barrel , the reduced-profile Gas Block and further accuracy testing. I would like to reach 1500 rounds without maintenance of the internals (less the Barrel which was cleaned at 710 rounds). I will advise when the new Barrrel and Gas Block are ready and installed for further Accuracy Testing.
    Last edited by Bartok5; 12-02-2021 at 12:35 AM.
    Mark C

  8. #258
    CGN Ultra frequent flyer Paul_T's Avatar
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    Good write-up and comments, thank you.

    FWIW the gas block vs handguard was an issue with the first bunch of WK-180's. I sent mine back to have the block milled and it seemed to reduce odd 'fliers'.

    Here are marks from the original setup. The other side was the same


    A few more ounces won't kill the rifle if they decide to stiffen the barrel but I'm thinking most commenters here were looking for it to be lighter and not bothered by 2.5-3MOA which would be typical of an MCR anyway.....

    Ref the match ammo I'm surprised the heavy bullets did not perform a bit better with 1:8. Any 68 or 69gr match ammo in your kit bag?
    Last edited by Paul_T; 12-02-2021 at 12:58 AM.
    "No matter where you go - there you are"
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  9. #259
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    Thanks for the continuing updates and the detail that you include. The fact that there are a few things to update or improve, and the response from the manufacturer to improve the design in certain areas will build confidence in the brand.

    P.

  10. #260
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    I for one, am excited about this product coming to market. Godspeed. I donít mind paying for quality. Seen lots of $700 m305ís with thousands of $ of accessories and mods hanging from them in the past. Cry onceÖ

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