CA SLR105 Issues - Low FPS/No Hop

[Cheesevillage]

So after a whole season with no issues, my CA decided to start shooting low FPS (280 vs 370). Hopup does not work no matter where it is set.

Styrak and I stripped the gun down and did some much needed gearbox maintenance. No parts, including nozzle and hopup body seemed in critical condition. After reassembly, the gun shot 350fps...kinda.

By tightening front furnature (or loosening and "resetting") and switching between my MAG brand magazines and a TM AK47 lowcap, we were able to produce the 100fps variances. It seems my gun is now super sensitive to mag pressures and positions.

Thoughts?

I was thinking maybe I should install a pro-win AK hop unit but am not sure whether the CA design is totally compatible.

[ehobbyasia]

Did you check your rubber?
it could be damaged, dirty or stuck.
also if you have left you hop up "on" in storage it will cause hop problems when you get it back into use.
it is basically a spring and needs to be turned off when your putting into storage.

also you have given you barrel and rubber a good clean and lube.
although to much silicone oil at the rubber can also cause problems.
can't see it being a mag problem though.

[Azathoth]

I don't recommend you lubricate your barrel. Occasionally when gunk starts to build up I use Hoppe's 9 or CLP to clean my barrels . If you are going to use windex/gun solvent route make sure that:

1) whatever brand barrel you are cleaning can actually take these chemicals
2) you completely take pull the barrel away from any other parts
3) you go in and clean out and residual chemicals with water

Springs naturally will lose their stiffness over time. This is compounded if you didn't try and reset the piston to rest between games or during our long winters (I detail strip all my guns during winter). Depending on the brand of the spring losing 20 fps is 'normal'.

You should dial your hopup completely off after each game to help keep the rubber supple, and keep it's original shape. Replacing a hopup rubber is akin to performing a oil change on your car. Every "X" rounds/timeframe it's due to a cleaning or will need to be replaced depending on the velocity you are shooting, the BBs, and the weight.

[Styrak]

Unfortunately none of that actually helps him. It's a very strange, peculiar problem.

[Azathoth]

Originally Posted by Styrak

Unfortunately none of that actually helps him. It's a very strange, peculiar problem.

No detail was provided. If the gun was in storage for the last year or winter ehobbyasia and what I have to say is the problem. After the gun was ripped apart and put together you're now at a different set of problems and situation.

Different magazines will give you different velocities. I have noticed that TM mags in my gun chrono lower than Pmags, and the different generation of Pmag also will chrono differently too. If I grab my mag and pull downwards after it's locked I will get 50-70 drop in velocity.

I don't know if a HOPup will fix the problem. My first test would be to do the earplug mod on the gun and see if that consistently corrects the velocities with the different mags. And if it does, that means you need to go back to ripping the externals apart and putting them back together to get fit and alignment correct.

As for your "no hopup" issue it was really answered in post 2 and 3. Look at your rubber, clean it, and if necessary replace it. Take apart your hopup unit, is something broken? Is the hopup unit seated firmly against the gearbox. Is the loading nozzle seating the BB too deep (past the nub) thus you don't get any hopup.

[Styrak]

This is an AK, not an M4, so different mags shouldn't matter much as there is almost no movement.

What's the earplug mod?

I could replace the hopup rubber and try that though.

[Slow]

If the hopup is not working, make sure that the hopup nub is still there.

[ViR]

Well, considering that CA SLR105's bodies are not very "consistent" I would blame this on the position of the hopup unit and gearbox. My issue(and many other people's) with SLR105 is that most of the mags do not fit properly at all or need a lot of shaving off. So I wouldn't be surprised that 1mm differences in mags will "push" your Hopup unit out of straight line with the air nozzle.

Question is why did it only started to happen now. Were the internals bolted down very hard when you first took the gun apart? If its too loose now maybe there is movement? Styrak are you stating generic AK facts or you have checked this AK? If you getting 100fps difference consistently between the mags it must the pressure of the mag and/or front end which dis-aligns hopup and gearbox.

[Styrak]

Problem solved.....I think.

I switched out the hopup unit for a metal SRC unit and 3 different midcap mags I tried (MAG AK74 plastic, TM AK47 metal, CYMA AK47 metal) shot 360fps.
I used the CA inner barrel, CA hopup rubber, SRC hopup unit, and SRC hopup nub.

So either the hopup unit is FUBAR somehow, or it's flexing with each different mag. I believe the problem is partially due to the fact that this gun has no plate in the body seperating the mag and hopup unit like TM/CYMA/most AK's do.

I'm recommending he buy a metal hopup unit.

[ThunderCactus]

+1 to new hop chamber

Spring wear is more dependent on actual use rather than tension. I kept a 420fps G&P spring fully compressed for 5 months and it only lost 3fps

And I've always stored my guns without resetting the hopup back to zero, never had any problems, never have to fiddle with my hopup lol

But lubing your barrel is bad, makes you lose accuracy

[Kokanee]

I own this model of AK as well; your problem does indeed sound like the mags are not quite a good fit and are pushing on the hop up chamber, forcing it out of alignment and creating an air leak.

I would recommend replacing the hop up unit and as well shaving some material off the offending mags locking hub to provide a correct fit. I had the same problem with G&P mid caps, disappeared once I took about 2mm off the rear hub.

Cheers

[Styrak]

Like I said I think a metal hopup chamber will solve the issue. He is ordering a Prowin unit.

[Kokanee]

That is all well and good, but unless the fitment of mags is addressed, the stronger hop up unit will just pass the stress onto another part instead of flexing like the plastic hop up unit, potentially causing more problems. It would be a bitch if the hop up unit mounting screws stripped their holes for instance...