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

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I don't know if barrel flex or handguard flex is causing the contact between the gas block and the handguard. I suspect it is the handguard.
Maybe the vibration occurs after the bullet has departed.
But this obviously would contribute nothing to accuracy.
It would be interesting to mill a slot in the handguard so that the gas block cannot make contact, and retest for accuracy. This would be a simple modification to a lower cost component that would eliminate one variable.
 
If the the rifle is loaded on the bipod or on a sandbag, the handguard ( especially a thinner handguard like this ) will bend upwards and touch the barrel gas block if it is too close. First hand experience, this will destroy accuracy even with a thick handguard. This can be tested by applying pressure to the handguard where the rifle is rested.
 
greentips said:
If the the rifle is loaded on the bipod or on a sandbag, the handguard ( especially a thinner handguard like this ) will bend upwards and touch the barrel gas block if it is too close. First hand experience, this will destroy accuracy even with a thick handguard. This can be tested by applying pressure to the handguard where the rifle is rested.
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Wasn't there a class on exterior ballistics in the military about this?
 
smellofspentcasings said:
Wasn't there a class on exterior ballistics in the military about this?
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Not really. The key is not to put the gas block too close to a free floating handguard, or do some weird semi-quasi touching free floating. Either it is free floating with space for the handguard to deflect, or do what FN in SCAR16 and PWS in their old MK series did, ie, bolting the gas block in at least 1 axis to a rigid handguard.

One way to get around this is to adjust the location of the bipod to avoid touching that sweet spot. The handuard is more rigid near the receiver, so putting the bipod closer to the receiver may cut down the deflection.
 
tiriaq said:
I don't know if barrel flex or handguard flex is causing the contact between the gas block and the handguard. I suspect it is the handguard.
Maybe the vibration occurs after the bullet has departed.
But this obviously would contribute nothing to accuracy.
It would be interesting to mill a slot in the handguard so that the gas block cannot make contact, and retest for accuracy. This would be a simple modification to a lower cost component that would eliminate one variable.
Click to expand...

greentips said:
If the the rifle is loaded on the bipod or on a sandbag, the handguard ( especially a thinner handguard like this ) will bend upwards and touch the barrel gas block if it is too close. First hand experience, this will destroy accuracy even with a thick handguard. This can be tested by applying pressure to the handguard where the rifle is rested.
Click to expand...

greentips said:
The key is not to put the gas block too close to a free floating handguard, or do some weird semi-quasi touching free floating. Either it is free floating with space for the handguard to deflect, or do what FN in SCAR16 and PWS in their old MK series did, ie, bolting the gas block in at least 1 axis to a rigid handguard.

One way to get around this is to adjust the location of the bipod to avoid touching that sweet spot. The handuard is more rigid near the receiver, so putting the bipod closer to the receiver may cut down the deflection.
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The BRN-180 has a cutout for adjusting the gas system. I wonder if they designed the gas block to have more height in the vertical, up in the slot, thus preventing the gas block from bottoming out on the handguard when pressure is applied with a bipod or rest.

Would a carbon fiber handguard be less likely to flex and touch the gas block when heat and pressure applied?

Another way to test this is to use a split Mlok bipod that mounts each leg on the side of the rail -> amazon dot ca/Feyachi-M-LOK-Adjustable-Compatible-Hand-Guard/dp/B084Z5KN2C/ref=sr_1_2_sspa?keywords=side+bipod+mlok&qid=1638464283&sr=8-2-spons&psc=1&smid=A211XTRG8Z1K1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExNkZPR1ZBRlRHTjM4JmVuY3J5cHRlZElkPUEwMDc5MjkzUjY2SE1ORFFWSExVJmVuY3J5cHRlZEFkSWQ9QTA0NjAwMThNTzZSSzIwSzhRTE8md2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
 
Ustauk said:
Another way to test this is to use a split Mlok bipod that mounts each leg on the side of the rail -> amazon dot ca/Feyachi-M-LOK-Adjustable-Compatible-Hand-Guard/dp/B084Z5KN2C/ref=sr_1_2_sspa?keywords=side+bipod+mlok&qid=1638464283&sr=8-2-spons&psc=1&smid=A211XTRG8Z1K1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExNkZPR1ZBRlRHTjM4JmVuY3J5cHRlZElkPUEwMDc5MjkzUjY2SE1ORFFWSExVJmVuY3J5cHRlZEFkSWQ9QTA0NjAwMThNTzZSSzIwSzhRTE8md2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl
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That’s good in theory except the forces are downward so regardless of where the bipod is mounted the handguard will flex upwards countering gravity. Moving the bipod closer to where the handguard is attached will minimize the amount of upward flex. The best solution is going to be a smaller gas block or larger ID handguard to ensure maximum clearance to the free floated barrel.
 
All of this theorizing about whether it is the Handguard flexing upwards or the Barrel "whipping" during firing due to barrel harmonics is all well and good, but we pretty much eliminated the Handguard theory by firing the rifle with the Handguard removed. We balanced the rifle on the Barrel Nut to avoid interference with harmonics. The results were effectively the same, meaning that Barrrel Harmonics primarily account for the large group sizes due to "fliers". This is why I believe that the thin Barrel diameter, in conjunction with the violent movement of the Gas Piston, is primarily responsible for the random deflection.

No doubt the effects of the thin Barrel and Gas System are exacerbated by Gas Block contact with the Handguard. I strongly suspect that it is the Barrel whipping into the Handguard, and not vice-versa. I say this because the handguard is very rigid when tightly screwed down to the Barrel Nut. I can easily "bend" the barrel to touch the bottom of the Gas Block against the Handguard, and can do the same with upwards pressure on the Barrel. The barrel is not moving where it is sandwiched by the Upper Receiver and Barrel Nut - it is the barrel actually flexing that is causing the problem. Hence the requirement for a slightly thicker barrel.

The fact that the R18 Barrel is .1" thinner than the original AR180 is indicative of the likelihood that the SAI engineers went too thin between the Chamber and Gas Block where the flex is clearly occurring. I strongly suspect that a thicker barrel is required in conjunction with a reduced-size Gas Block to avoid contact with the Handguard. The combination of improvements should eliminate the "flier" problem, resulting in far better accuracy results more in line with the potential demonstrated by the R18 when fliers are discounted.
 
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Most float tube hand guards are made for ARs so they tend to interfere with anything larger than a gas block designed for the DI system.
That barrel, while likely being too thin, could also just suck for accuracy. For the expected price, the manufacturer really should be getting their barrels from a known, quality supplier (IBI?), especially since, as we all know, that is where the rubber meets to road.

I went out on a limb with the other (first) rendition of a re-worked 180b clone some time back and could get 10 rounds into 2". That was at a $1K price tag. This thing for the price should be kicking' it's a$s.
 
beltfed said:
Most float tube hand guards are made for ARs so they tend to interfere with anything larger than a gas block designed for the DI system.
That barrel, while likely being too thin, could also just suck for accuracy. For the expected price, the manufacturer really should be getting their barrels from a known, quality supplier (IBI?), especially since, as we all know, that is where the rubber meets to road.

I went out on a limb with the other (first) rendition of a re-worked 180b clone some time back and could get 10 rounds into 2". That was at a $1K price tag. This thing for the price should be kicking' it's a$s.
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And I suspect that the R18 will kick the competition's arse accuracy-wise once it is fitted with a stiffer Barrel. The R18 is a work in progress, whereas the WK-180 and (now $1600) WS-MCR are production rifles with several years of rolling improvements under their belts. The R18's demonstrated grouping potential (less fliers) varies from 1 to 1.5 MOA, ammo dependant. That ought to give the competition a run for their money.

Note that the WK-180 and WS-MCR are both fitted with stiff, medium-weight barrels. The down-side is that they are both ill-balanced, front-heavy beasts in factory configuration. SAI went with the "Pencil"-profile barrel from the outset in an effort to minimize weight and improve the rifle's handling characteristics and balance. The SAI engineers evidently went a bit too far in terms of the lightweight Barrel profile and wil have to stiffen things up somewhat. Watch and shoot as we see what changes a heavier-weight barrel brings to the ongoing R18 development.

The new Barrel is being manufactured as we speak and will ship from Ontario, so expect 2 weeks before we have new accuracy results. In the interim I will continue to ramp up the round-count with the existing barrel, which has more than enough practical accuracy for banging steel!
 
Bartok5 said:
And I suspect that the R18 will kick the competition's arse accuracy-wise once it is fitted with a stiffer Barrel. The R18 is a work in progress, whereas the WK-180 and (now $1600) WS-MCR are production rifles with several years of rolling improvements under their belts. The R18's demonstrated grouping potential (less fliers) varies from 1 to 1.5 MOA, ammo dependant. That ought to give the competition a run for their money.
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When did the R18 start to be developed. Has it been able to sit back and learn from the development of the WK and WS?
 
Northern Shooter said:
Is there an official date for the R18's release next year?
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Short answer is "No". The intent was to have the first production rifles rolling off of the assembly line as we speak, to the tune of several hundred rifles per month. The accuracy issue with the current "Pencil" Barrel has delayed things somewhat and production of complete rifles cannot occur until the accuracy issue is addressed. So, no firm date as yet.

Notwithstanding the above, production of test-proven parts and complete assemblies (eg Lower Receivers), is ongoing. Once they have the right Barrel and reduced Gas Block combination, production of complete rifles will Commence immediately - like literally as soon as Barrels are available there will be R18s for sale through The Shooting Edge.

Follow this thread for your best indication as to the start of retail sales. If not before Xmas, then certainly very early in 2022.
 
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On the 9 Hole Reviews Practical Accuracy Test for the What Would Stoner Do 2000 rifle, which also has pencil barrel, they mention the barrel has difficulty with consistent zero when using suppressors, adding the following in the comments:

9 Hole Reviews in YouTube Comment said:
Man i'd say the biggest issue with SOF use is with the suppressor weight causing the barrel droop. My retro Gordon Carbine has no issue like that and I suspect the reason is two fold: 1, the free float barrel with no secondary support point, 2, the Gordon using a reflex suppressor, giving it two points of contact to stiffen the barrel up.

Not saying that's a big issue for civvy use, but for SOF use, being unable to use a can is a no-go. It's also not that hard to solve with a fluted barrel to increase barrel stiffness.

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Not sure if this is similar to the issue with the barrel harmonics and the gas block/piston hanging off of it for the R18, but hopefully it is an indicator a slightly heaver/stiffer barrel will be of help. The WWSD has a lighter, non adjustable gas block and a gas tube hanging off it, so it can get away with maintaining accuracy with an extremely light barrel profile with no suppressor is involved. Hopefully we can see similar accuracy on the R18 with a slightly heavier barrel to deal with barrel harmonics and the weight of piston/gas block.

Assuming there's no outstanding issues between TSE and ATRS, it might be a good idea to have them send a barrel down while you wait for your Ontario manufacturer; it can be alternate local source, and people may want to source from there themselves if the R18 is ever released in build kit form.
 
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Ustauk said:
On the 9 Hole Reviews Practical Accuracy Test for the What Would Stoner Do 2000 rifle, which also has pencil barrel, they mention the barrel has difficulty with consistent zero when using suppressors, adding the following in the comments:



Not sure if this is similar to the issue with the barrel harmonics and the gas block/piston hanging off of it for the R18, but hopefully it is an indicator a slightly heaver/stiffer barrel will be of help. The WWSD has a lighter, non adjustable gas block and a gas tube hanging off it, so it can get away with maintaining accuracy with an extremely light barrel profile with no suppressor is involved. Hopefully we can see similar accuracy on the R18 with a slightly heavier barrel to deal with barrel harmonics and the weight of piston/gas block.

Assuming there's no outstanding issues between TSE and ATRS, it might be a good idea to have them send a barrel down while you wait for your Ontario manufacturer; it can be alternate local source, and people may want to source from there themselves if the R18 is ever released in build kit form.
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You raise some good points for consideration. It would seem that pencil-profile Barrels have their limitations, dependant on just how thin you go. One point to note is that the WWSD rifle gets away with a stationary Gas Tube and a low-profile Gas Block, whereas the R18 must contend with a much heavier Gas Piston literally slamming back and forth with every shot fired. The AR180B Gas System on the R18 exerts far more stress on the Barrel and Gas Block than a Direct-Impingement System's stationary Gas Tube. That is simply an inescapable fact of the operating system that was chosen for the R18 for uniquely "Canadian" reasons.

I am not privy to the relationship (if any) between TSE and ATRS, so will leave any such arrangement to the discretion of JR Cox. The barrels being sourced out of Ontario are high-quality tubes, air-gauged, stress-relieved, etc, etc. I am quite confident that a slightly heavier Barrel profile between the Chamber and the Gas Block will pay dividends in terms of grouping consistency. It ony stands to reason. The real question is "how heavy is heavy enough"? At the end of the day, SAI wants the lightest barrel that will provide consistent accuracy results. 1 MOA 5-round groups at 100m with Match-Grade ammo would be ideal. 2 MOA with bulk 55gr PMC XTac would be similarly acceptable. SAI are just not quite there yet. The good news is that "adequate" is not good enough for either SAI or JR Cox at TSE. Barrel and Gas Block refinement will continue until acceptable accuracy results are achieved, with retail sales to quickly follow ASAP.
 
SAI may also want to get the dimensions of the Brownell's BRN-180 barrel for comparison sake. It too uses a near rifle length gas port with piston and gas block, and they may have run into similar issues, so seeing where they settled on their final product may be useful. I couldn't find a picture of their 18.5" barrel, but here's one of their 16" barrel:

Brownells.com said:

Full sized -> https://cdn-fsly.yottaa.net/53ff2f503c881650e20004c9/www.brownells.com/v~4b.11a/userdocs/Miscellaneous/brownells-retro-rifle-line/brn-180-gen2/gallery/078-000-600i.jpg?yocs=p_E_
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Also useful may be the dimensions of the IBI barrels used by the previous but not longer produced premium 180 based offering, the Range Warrior Accessories RWA180B. I believe that my have also used a rifle length gas port. There weren't too many made, so it might be difficult to find a sample for comparison.
 
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Interesting to see that the BRN-180 has a much heavier Barrel between the Chamber and the Gas Block as compared to the "Pencil" Barrel forward of the Gas Block. I believe that is where SAI is headed with the revised Barrel....

E.T.A. I just measured the "Pencil" Barrel on my AR15 SP1 and it tapers from .675" in front of the Chamber, down to .610" before the Gas Block. It would seem that nobody goes below .6" Barrel diameter for successful pencil-profile Barrels. More evidence suggesting that SAI needs to increase the diameter of their Barrel by at least 1/10"...
 
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The WK barrel measured .75" in front of the chamber shank out to just before the gas port journal, then flared out to form a shoulder for the gas block. Gas block was standard .75", then tapered again to .65" to just short of the muzzle. I fear they cut too much out from the chamber to the gas block, and that was a carbine length gas system. Quite light, and yes, the rifle was nose heavy. I don't think there really is much to be able to mitigate that other than balancing the overall weight of the rifle out.
 
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