New hop up, reduced fps

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Anno

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Hello,

I am slowly making my way into the wonderful world of upgrades. I opted for a new hop up which for all purposes looked to be far better than standard design.

http://www.ak2m4.co.uk/internal-parts/hopups-rubbers/zci-prowin-style-cnc-hopup-chamber-m4 with Prometheus purple bucking.

I put this into my APS Boar tact m4 which has caused a number of issues. FPS drop and also a misfeed issue.

Previously the APS was shooting around 420 FPS, once I placed the new hopup in this dropped quite significantly to around 300.

Can anyone advise what the potential cause for such an FPS drop could be?

 
you may have fitted it badly, it could be damaged, it could have a bad airseal.

Remove it and refit, then use some PTFE tape around the bucking and barrel (only a couple of wraps) to create a better seal, then gently insert it into the hop chamber, maybe use a very small amount of silicon oil to aid fitting and don't force anything.

 
PT247 said:
you may have fitted it badly, it could be damaged, it could have a bad airseal.

Remove it and refit, then use some PTFE tape around the bucking and barrel (only a couple of wraps) to create a better seal, then gently insert it into the hop chamber, maybe use a very small amount of silicon oil to aid fitting and don't force anything.
Click to expand...
Cheers, I will give this a try tonight!

 
If it's misfeeding, try the BB drop test. With it assembled to the barrel and bucking, turn it over and drop a BB down the feed tube. It should drop right the way down and not hang up on the lip of the bucking. If it is then that can cause the misfeed and potentially the fps drop as the BB can fold the lip of the bucking over as the nozzle tries to push it into the hop. It might be a case of trying a different bucking. I know my Prowin doesn't like Prommy purple buckings, but seems fine with a Maple Leaf.

 
Hangtight said:
If it's misfeeding, try the BB drop test. With it assembled to the barrel and bucking, turn it over and drop a BB down the feed tube. It should drop right the way down and not hang up on the lip of the bucking. If it is then that can cause the misfeed and potentially the fps drop as the BB can fold the lip of the bucking over as the nozzle tries to push it into the hop. It might be a case of trying a different bucking. I know my Prowin doesn't like Prommy purple buckings, but seems fine with a Maple Leaf.
Click to expand...
Thank you, I have some other buckings I will give them a try as well. Appreciate the advice.

 
Keep us up to date with how you get on. If the BB does catch on the bucking on the way into the hop up then there are fixes, but they involve taking a Dremel to the feed tube. Much better to find a bucking that works. Then again this might not be the problem. Who would have thought that toy guns could be such a pain?

 
It might just be that your stock nozzle isn't compatible with the newt hop up as well and you may need either a new nozzle or to modify your current ones length

Could be your tappet plate is too thick perhaps and is sending the nozzle not far enough into the hop up to achieve good seal

It's best to stick with your stock hop up most of the time unless the one it comes with is horrendous and you are inclined to change it but....

That's just a couple more things it could be :)

 
Thank you all for the advice!

So I took it all apart, tried the BB drop test. Just for sanity sake I tried a few different combinations.

Barrel on it's own - Obvious results, BB fell through no problems.

Barrel with Bucking - BB fell through no problems.

Complete Barrel+Hop - BB get's stuck. 

It appears to get stuck on the nub window/ cut out. Hop was turned completely off.

I didn't have any spare bucking to try out so will order some others to test.

Can anyone suggest some bucking to try out?

I also noticed a slight tilt left and right with the hopup which I believe is due to the new hopup being slightly smaller in size. Once fitted, if I stick my hand into the mag chamber/hole I can move the hop left and right (the BB funnel would then be off centre). I am going to attempt to secure this in place with some padding either side to prevent any moment.

Thanks again people, appreciate it!

 
Last edited by a moderator:
That sounds like you are dropping the BB down the hole the nozzle goes into. With the hop /barrel/bucking assembled you want to try dropping it down the tube that feeds from the magazine. Also try this with the gun fully assembled. Sometimes the air nozzle can protrude into the loading tube just enough to cause a feeding issue.

 
Thanks @Hangtight will check with it fully assembled, didn't think about the nozzle location. 

Now I think about it that should have been something I checked in the beginning. 

 
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