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Old 05-13-2020, 11:43 AM   #1
Myzur   Myzur is offline
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A really odd fps problem

So I am running into a really odd issue.

Working on my cousin's HK417 to make it DMR worthy. I installed an R Hopped 6.01 Angel Customs barrel with a purple Prometheus flat hop bucking into the stock hop up unit (sadly this needs to stay due to proprietary parts inside the gun that prevent installation of anything different.)

Here is where the weird comes in, with the stock barrel and bucking it was getting 445 fps with a deviation of about 5 fps. But after installing the Angel customs with the Promy bucking everything stays the same until I actually put the hop up control arm in. Without the control arm everything fires fine with the same 445 fps and 5 fps deviation, but i put the control arm in with a flat hop nub and the fps drops to 290.

My thoughts are one of two ways:

The nub is a little too aggressive for the TBB and is jamming the bbs as they go through

The bucking is a bit too rough and when adding the hop up is gripping the bbs too much

I'm kind of stumped here. I am going to try a .modify bucking as that is a bit softer but if that does not work I am not sure which avenue to pursue.
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Old 05-13-2020, 12:05 PM   #2
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Throw away that piece of shit Angel Custom barrel and test the prommy setup with the stock barrel.
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Old 05-13-2020, 12:49 PM   #3
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I would love to but not my gun, just working with the pieces I have available.
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Old 05-13-2020, 07:01 PM   #4
 
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Try the prommy bucking with the stock barrel. I wouldnt be suprised if the problem is with the Angel Custom barrel and rhop install.
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Old 05-14-2020, 07:59 AM   #5
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Sounds like a pinch jam kinda thing with r-hop install.
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Old 05-15-2020, 12:19 PM   #6
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Have we not had conversations about pre-installed r hops in barrels? hahahaha.

If the rifle is shooting fine until you put the hop arm in, I would suspect a reshaping of the arm or nub setup is in order....that's if you choose to use the Angel customs setup at all. If it's what you've got, you can make it work, but 6.01 is already too tight.

That aside, it may be a case where the hop up arm may need to be ground down to allow for the new nub/bucking setup. Not overly unusual, really. Also keep in mind that with an r hop you're getting a lot of action from it so very minute adjustments in pressure will have great effect on the BB...in this case, it's acting like a brake.

Once you get the hop assmebled and the arm in place, have a look down the barrel from the hop up end and I bet you'll see the hop is already applied in the barrel window.
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Old 05-15-2020, 09:06 PM   #7
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Quote:
Originally Posted by Zero Roaster View Post
Have we not had conversations about pre-installed r hops in barrels? hahahaha.

If the rifle is shooting fine until you put the hop arm in, I would suspect a reshaping of the arm or nub setup is in order....that's if you choose to use the Angel customs setup at all. If it's what you've got, you can make it work, but 6.01 is already too tight.

That aside, it may be a case where the hop up arm may need to be ground down to allow for the new nub/bucking setup. Not overly unusual, really. Also keep in mind that with an r hop you're getting a lot of action from it so very minute adjustments in pressure will have great effect on the BB...in this case, it's acting like a brake.

Once you get the hop assmebled and the arm in place, have a look down the barrel from the hop up end and I bet you'll see the hop is already applied in the barrel window.
I honestly wish he would have let me make it but that gun is his new baby so he wanted it done professionally, but then went to Evike to get it. It is literally just the precut r hop patches found on Amped Airsoft put on an Angel Customs barrel.

You may know why but I swapped the Prometheus bucking for a Modify bucking and fixed the problem right out of the gate, shot up to 471 fps right away. I had previously ground down the arm to make the room needed not to protrude into the hop window with the flat hop nub and it was still dropping until I swapped out the bucking.

Now I just need to see how it lifts bbs, but i have 0 room to do that because the backyard is only 50 feet.
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Old 05-19-2020, 09:46 AM   #8
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I get it...in my books, 'professional' means done quickly for money. hahahaha
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Old 05-25-2020, 02:17 AM   #9
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I hear you there but I am not much better, I usually do the S Hop instead of actual R Hop because I have not found a good material to work with and it's super cheap.

So we have encountered a new problem, this R hop patch is overhopping .36s with no hop applied. The target weight was supposed to be .36s but that may not be an option. I am going to try to adjust the hop up arm to see if it is pushing the bucking too far into the window and then see where it sits, but at this point it's like splitting hairs to get at the problem.
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Old 05-26-2020, 12:36 PM   #10
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The whole idea of the r hop is splitting hairs...it's a pretty precise business. Yeah, you've definitely got some patch hitting the BB if you're lifting .36's with the hop off. Depending on the curvature of the material they used for the r hop patch, it could spin the BB with no hop applied as well. Normally I shape the patch both inside and outside of the barrel...
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Old 05-28-2020, 11:24 AM   #11
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Quote:
Originally Posted by Zero Roaster View Post
The whole idea of the r hop is splitting hairs...it's a pretty precise business. Yeah, you've definitely got some patch hitting the BB if you're lifting .36's with the hop off. Depending on the curvature of the material they used for the r hop patch, it could spin the BB with no hop applied as well. Normally I shape the patch both inside and outside of the barrel...
I am honestly to the point that I'm going to take off that patch and make one myself. The problem I am running into is the 417 has a really aggressive hop up arm and after reshaping it 3 times I am still having the protrusion problem. It is to the point that I need to start modifying the nub and I am always leery of that because any imperfections with the nub can wildly affect accuracy. I am really tempted to swap out the flat hop for an H nub but I am not sure how that would work in an R hopped system like that.
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Old 05-28-2020, 12:19 PM   #12
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Yeah I get that. Par for the course in R hops. The more of them that you do, you get a better feel for how it needs to go, but the first bunch are a real gong show. hahahaha

If you take the arm right off, does the patch protrude?
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Old 05-28-2020, 12:53 PM   #13
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Random input from someone who is far from experienced with r hop: make sure the bucking isn’t too thick. On a different platform I had a similar issue. But it was worse; zero hop and the gun wouldn’t even fire because the bb was stuck on the patch. I had confidence that the patch was NOT the issue. It was a faceless patch thats pre made for a pdi barrel. The SRS guys drool over them and use them quite often. I put this patch and barrel combo in a vsr to try something other than maple leaf, with a Nineball bucking. Everyone says the Nineball is “great for sealing”. But that’s because they’re THICC. I swapped to a random thinner bucking and now the gun shoots and hops bbs as it should. And yes I removed the contact patches.
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Old 05-28-2020, 01:38 PM   #14
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You MUST remove the contact patches. I use G&G greens exclusively these days. Super flexible, cheap as dirt, and they're everywhere. I turn them inside out and grind the bump off then when I install the bucking onto the barrel, it goes on upside down so that where the bump was is on the underside of the barrel and only smooth material goes across the hop window.
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Old Today, 02:23 AM   #15
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Hey Zero. When the arm is out of the hop up it sits perfectly smooth all the way down. I never shot it without the arm in, I guess I should try that at some point. With the hop in it sticks through ever so slightly that you would almost miss it if you weren't looking for it, but that's enough for it to go crazy.

Yeah Blind Sniper we had the problem in the beginning when I was using a Prometheus bucking that was already flat hopped from the factory. The fitment was so tight it caused the FPS problem that started this thread. I swapped over to the Modify Flat Hop bucking and the fps problem was gone in an instant and the fitment was perfect, though now I have this overhop problem so its trading one problem for another. Though I know what you mean about the SRS bucking because I own one too, it's great only as long as you have the fast hop curved nub to go with it. Those are too big for AEGs sadly or I'd use those as my bucking as I have yet to have a problem in my spring rifle.
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