HKPRO Forums banner

Weak 223 ammo in a 416

355 10
I have a 10.4" 416 upper with a 10" vented GB. Went to the range to sight it in with some pmc bronze 223 and it kept short stroking on me. Finally switched to the imi 77gr 5.56 to zero it after I got it sighted and it ran the 5.56 (as expected) just fine.

I didn't realize the 416 couldn't run weaker 223. Just wanted to know if anyone else has run into the same issue.

I'm sending the upper in to D. Wilson with an unvented 10" GB to swap out. He mentioned that the unvented one would allow the weaker ammo to cycle but again just curious if anyone else has tried running 223 through their uppers.

I did see the following thread and some members stated they had zero issues running steel cased (not my plan as I don't have any) but pmc bronze is known to be weak and I train with it so it'd be nice not to have to shoot my 5.56 ammo which is mostly factory match and some defensive stuff.


Thanks in advance
1 - 11 of 11 Posts

·
Registered
Joined
·
7,877 Posts
I have a 10.4" 416 upper with a 10" vented GB. Went to the range to sight it in with some pmc bronze 223 and it kept short stroking on me. Finally switched to the imi 77gr 5.56 to zero it after I got it sighted and it ran the 5.56 (as expected) just fine.

I didn't realize the 416 couldn't run weaker 223. Just wanted to know if anyone else has run into the same issue.

I'm sending the upper in to D. Wilson with an unvented 10" GB to swap out. He mentioned that the unvented one would allow the weaker ammo to cycle but again just curious if anyone else has tried running 223 through their uppers.

I did see the following thread and some members stated they had zero issues running steel cased (not my plan as I don't have any) but pmc bronze is known to be weak and I train with it so it'd be nice not to have to shoot my 5.56 ammo which is mostly factory match and some defensive stuff.


Thanks in advance
I shoot mostly .223 ammo through my MR's and SL8 as well as my other AR's . I've got an unfired 416 Upper that will remain that way . The PMC that I have tried has been underpowered . I shoot a lot of Freedom Munitions 223 that does just fine in all weights . I also shoot a lot of Norma and Magtech and Geco .
 

·
Premium Member
Joined
·
24 Posts
Discussion Starter · #3 ·
I shoot mostly .223 ammo through my MR's and SL8 as well as my other AR's . I've got an unfired 416 Upper that will remain that way . The PMC that I have tried has been underpowered . I shoot a lot of Freedom Munitions 223 that does just fine in all weights . I also shoot a lot of Norma and Magtech and Geco .
Thanks for the info!
 

·
Premium Member
Joined
·
24 Posts
Discussion Starter · #5 ·
I have a chopped Brownells barrel with a vented gas block and I run my reloads through it just fine. I know I’m running xbr8208, I believe 24gr, with a hornady 55gr bullet.
Any idea what size your gas port is (or does it not matter and does the GB port size matter in relation to allow for cycling of weak 223 loads)?
 

·
Registered
Joined
·
13 Posts
All of my factory hk416 uppers in 10.4" cycle all 223 and 556 without issue including lots of PMC. So given that, I'm assuming you have a clone build. Assuming you are using a hk red buffer spring and tungsten buffer your issues lies between the gas port on the barrel and whatever gas block you are using. Sounds like the gas port on the barrel was drilled too large. Which obviously cant be fixed. So i would suggest running a Waffen Burke gas block to possibly gain additional back pressure (with smaller vent holes) or switch to a non vented gas block. Your choice but either one will fix your problem. You should have zero cycling issues with all ammo once its tuned right.
 

·
Premium Member
Joined
·
24 Posts
Discussion Starter · #8 ·
All of my factory hk416 uppers in 10.4" cycle all 223 and 556 without issue including lots of PMC. So given that, I'm assuming you have a clone build. Assuming you are using a hk red buffer spring and tungsten buffer your issues lies between the gas port on the barrel and whatever gas block you are using. Sounds like the gas port on the barrel was drilled too large. Which obviously cant be fixed. So i would suggest running a Waffen Burke gas block to possibly gain additional back pressure (with smaller vent holes) or switch to a non vented gas block. Your choice but either one will fix your problem. You should have zero cycling issues with all ammo once its tuned right.
Mine is an AF date coded upper, not a clone. The guy i bought it from replaced the unvented gas block with a vented one, hence I've sent mine to D. Wilson to swap the vented with unvented. Also, I always used the HK spring and buffer when running the upper. 5.56 was not an issue with the unvented GB as I mentioned in my OP.

Anyhow, appreciate you sharing your input and experiences with your uppers!
 

·
Premium Member
Joined
·
24 Posts
Discussion Starter · #9 ·
Ahhh gotcha. Makes sense. Hopefully that original owner did not open the barrel port up. Assuming they didn’t, switching back to the 10” non vented gas block should remedy all your issues and that ammo should function properly. Best of luck
Thanks man! I'm a bit confused though. You mentioned that if the gas port was drilled too wide, that it would cause cycling issues. If that was indeed the case, wouldn't the gun still cycle with a vented gas block anyway? For example, if the port was .063 and was opened to say .070 crane spec (just using that since I have a 10.3 colt sized with that which cycles tula), wouldn't it cycle even with the vented gas block?

I'm not exactly sure how much the vented GB reduces the amount of gas so genuinely wondering
 

·
Registered
Joined
·
13 Posts
Sorry for the confusion. You are correct. I made a mistake in my wording. Your problem is actually the opposite. Not enough gas which is why it’s short stroking. From the sound of it, someone put a vented gas block on an upper that was originally non vented and they didn’t open up the port hole on the barrel. So you are losing gas out of the gas block vent that should be directed toward the piston and op rod. To properly run the vented block you have to open the barrel port larger. However, my personal recommendation since it’s a factory 416 upper is to restore it to original condition with a non vented gas block. It should cycle without issue once you do that. There are a lot of guys out there swapping parts that don’t actually know what they are doing. The original non vented hk416 uppers run extremely well. Again, sorry for the confusion
 

·
Premium Member
Joined
·
24 Posts
Discussion Starter · #11 ·
Sorry for the confusion. You are correct. I made a mistake in my wording. Your problem is actually the opposite. Not enough gas which is why it’s short stroking. From the sound of it, someone put a vented gas block on an upper that was originally non vented and they didn’t open up the port hole on the barrel. So you are losing gas out of the gas block vent that should be directed toward the piston and op rod. To properly run the vented block you have to open the barrel port larger. However, my personal recommendation since it’s a factory 416 upper is to restore it to original condition with a non vented gas block. It should cycle without issue once you do that. There are a lot of guys out there swapping parts that don’t actually know what they are doing. The original non vented hk416 uppers run extremely well. Again, sorry for the confusion
No worries man! I figured you meant what I said 😀
I'm in total agreement with you as far as leaving it factory and not opening the port on a factory barrel. Hence I sent it to D. Wilson just to simply swap out the GBs lol. I don't even trust myself or have certified HK armorers around me

Thanks again for the advice!
 
1 - 11 of 11 Posts
Top