Any thoughts putting HK416 gas system onto 180b build?

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fozzyh

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I got the upper and lower from SBI and after doing research on the current 180b rifles finding the gas vent on the 180b is annoying. The BRN-4/HK416 gas block is 0.75" and the 14/16" gas block are front vented. The piston rings on it would reduce wears on the piston well and only need to replace the piston rings if needed.
The gas block and piston will be used, may need a custom piston rod and reuse the rod sleeve and spring.
BRN4-Parts-Diagram.jpg

I'm trying to order a set of the gas system components from US, if the HK416 piston rod is long enough I may end up cutting the original piston rod to accommodate the 180b. The bushing on the upper receiver might need some enlargement or need to drill the hole bigger to install a custom bushing if they are not at the same height.
After that the only thing left is adjust the gas port size to find out what size works.
Does anyone has any thought of it?
 
Gobc said:
Neat idea, but it seams for the cost and hassel, you could just get a better gun to begin with.
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But the ar180b seems to be the only option now in Canada since they banned the AR15. And the ATRS isn’t an option for me as I’m not in Alberta or SK. To pair the 416 gas block with ar15 barrel will be a lot more easier compared to other guns.
 
what's your budget? There are other guns besides AR15 pattern rifles. You have the bren 2, or the APC223 if your budget is there. Normally I wouldn't suggest those rifles, but I wouldn't be surprised if the price tag of your project would reach the cost of these rifles.
 
Gobc said:
what's your budget? There are other guns besides AR15 pattern rifles. You have the bren 2, or the APC223 if your budget is there. Normally I wouldn't suggest those rifles, but I wouldn't be surprised if the price tag of your project would reach the cost of these rifles.
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Actually I have an APC308 and a NR bren2 ordered but would be interested in a ar15 style platform that have more aftermarket parts available.
 
Could be made to work. The center-to-center height on the MR556 gas block is 20.5mm, or .807". The WK180 is about .832" or ~21.13mm. However, gas journal loaction is different. MR556 is located ~8.05" from the barrel extension face, while the standard AR15 Carbine length is only ~7.862".
 
Blastattack said:
Could be made to work. The center-to-center height on the MR556 gas block is 20.5mm, or .807". The WK180 is about .832" or ~21.13mm. However, gas journal loaction is different. MR556 is located ~8.05" from the barrel extension face, while the standard AR15 Carbine length is only ~7.862".
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Thanks for the info, I’m trying to build a mid length gas system one so may need a custom rod. As for the carbine length system the rod on 416 is longer to reach the bolt so cutting to fit 180 is easier. Enlarger the bushing hole and adjust the gas port would be simple on the carbine length. I’m gonna to have another barrel to tryout the carbine length after getting the parts.
 
If you've got those, then go for this project. However, what have you considered the Sterling Arms R18? It's a premium WK180C.

Btw, how do you like your APC308? I love mine.
 
Blastattack said:
Could be made to work. The center-to-center height on the MR556 gas block is 20.5mm, or .807". The WK180 is about .832" or ~21.13mm. However, gas journal loaction is different. MR556 is located ~8.05" from the barrel extension face, while the standard AR15 Carbine length is only ~7.862".
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That's some great info, do you have the outer diameter of the MR556 barrel nut and diameter of the piston rod where it goes into the receiver?

Standard AR barrel nut is 1.367-0.007"
 
The MR556 barrel won’t work as the extension is longer than the ar15 barrel. You can use an ar15 barrel with 0.75 gas block journal. The brownells website listed the 416 gas block as 0.75.
 
There are no compatibility information for r18 i can find online. So I got a pair of 180c/ws-mcr compatible receivers to make it easy find parts. My APC308 shoots great and very accurate, the gas system is vert similar to the 416 one but the parts and measurements for the B&T gas system is difficult to find and I don’t want to take it apart.
 
My assessment is that you may just buy a CZ Bren if you desire government grade reliability.

if the gas block piston opening is not lined up with the receiver open, you will get push rod shearing - think about this, the push rod is tilted if the holes are not 100% lined up.

And HK MR223 BGC has a different mass from the AR18. Very likely this will turn into all work and no result
 
Also about custom push rod. Push rod is the number 1 enemy of all these new manufacturers. Many cannot get right in the first or second go, sometimes even the 3rd go. They need to be heat treated correctly or some choose to brute force it by thickening the rod.

So making custom push rod is not something I will toy with, unless you are mentally ready to see broken rod and has no issue with making new ones until getting it right.
 
greentips said:
My assessment is that you may just buy a CZ Bren if you desire government grade reliability.

if the gas block piston opening is not lined up with the receiver open, you will get push rod shearing - think about this, the push rod is tilted if the holes are not 100% lined up.

And HK MR223 BGC has a different mass from the AR18. Very likely this will turn into all work and no result
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I will try to start with the 416 rod and carbine length barrel, the 416 rod is longer than 180's, cutting it should be fine. for the line up I'm thinking of making a brass bushing with hole slightly off the center. Then the gas port adjustment is all needed.
 
DaveMachine said:
Pretty sure you can buy gas system components for the BRN180 from Brownells. Have you considered that option?
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Brownells doesn't have gas block for sale, you can only get it buying a complete upper, and the whole upper is prohibited here as it fit onto ar15 lower. Importing one would be a hassle to get the upper receiver removed.
 
Blastattack said:
Barrel nut is 35mm -0.009/-0.034. The piston rod is 5.7mm +0/-0.048
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Oh nice, that should mean more clearance with the smaller AR barrel nut (34.7218mm)
This may allow for the manufacturing of a piston rod guide/spring retainer that could locate in the WK style bushing orifice with minimal receiver material removed to allow the rod to clear at the lower height over bore.
 
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