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Discussion Starter · #1 ·
I've been building a custom ca 25 for about a year just tinkering with it. It has had almost every part in it changed. My main problem is that it is not very consistent. I do not know how to make its Fps more consistent. For a while I had a silent piston head in it, but I removed that because I thought it would solve the problem. It helped a good amount, but I still can't get it fine tuned how I would like. I haven't chronoed it since I took out the silent piston head, but it had started with low Fps and as I pulled the trigger, it got faster. Each shot would have a higher Fps than before. This is still a slight problem, but not as noticeable. I have a guarder sp170 spring in it. I guess that the longer gearbox decreases the Fps that the spring could put out, but I believe my gun is maxing out around 500. Is there any way I could better the consistency? I have a replaced piston in it with the piston head from a magpul Masada. It has the stock cylinder head. Ca super torque gears for sr25. Amp t5000 motor. Systema hop bucking. Stock hop unit. Ca 6.04 barrel 509mm. And I assume the 11.1 30c lipo doesn't make a difference. It is cut to semi only.
 

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Discussion Starter · #4 ·
I'll try replacing the hopup unit. Any suggestions? And I thought that long range aeg section was for full auto? Correct me if I am mistaken. I am new on the forum, so I apologize in advance.
 

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Long range AEG section is for semi-auto DMRs. With all the influx of rifles on the market, it's just too difficult to keep adding sub-boards for every rifle. The AEG section is pretty much to cover everything.

Most of my rifles now, I use the Madbull hop up. They're great and not horribly priced. In the past, I've also used Systema, G&P, and Prometheus. Most of those have now been swapped to the Madbulls.
 

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Discussion Starter · #6 ·
Thank you very much for the input and clarifying the thread for me. I may have to pick up a madbull hop up unit. I use a polarstar nub since that was readily available at the time that I first got into building the rifle. I never could find a SCS at the time. I read vindi's thread, which is how I found the forum. I just hesitate to drill into my cylinder. The only other thing that I haven't done from the thread is shimming my hop up arm. Is the drilling into the cylinder necessary?
 

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No, it is just to balance the volume of air in your cylinder to the volume of air in your barrel to a more efficient amount to propel the weight of bb that you are using, so if you are heading towards the 500+fps mark and you are going to use .4 bbs in a 510mm x 6.04 or 6.03 barrel you will not be far off the mark with a full cylinder, if you read all of the guide it says that I'm limited to 350fps for most of my rifles, though the field regs over here are slowly starting to change, so with a lower power, using a lower weight bb, the cylinder volume doesn't need to be so great.


You should try the shimming first then if you feel you need to buy a new hop unit, but bare in mind that will probably require some form of shimming too to remove any play.

The whole thing about accuracy is maintaining consistency and in that you need to remove play and increase tolerences, tolerences that your average full auto queen is quite happy with, but we DMs find a ball ache :yup:
 

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First thing I would do is replace the hop up and see if that helps any. CA hop ups are notoriously bad and leaky.
There is nothing wrong with the CA hopup.I have the CA AR-10,essentially the same rifle,only preupgraded.I had poor compression at the hopup/air nozzle,and fixed it in mine in the following manner.

I bought the ICS boreup CH and PH.Reason?Because its an alluminum PH for strength,and a silent design for shock absoption.Also the nozzle stem is unique in that it uses nonboreup air nozzles.

VS studio double oringed nozzle for SR-25.Obvious reason here,seals the nozzle stem nicely

I next "shimmed" my air nozzle with Krylon Matte Finish.I used a digital calipre to measuree the inside of my hopup dia,and the outside dia of my air nozzle.In this way I could meter the amount of "shimming" to apply with thye Matte Finish.Fixing the air nozzle to the end of a barrel clesaning rod I held the nozzle upside down,and while slowly turning it I sprayed the nozzle with the Matte Finish from 3in's away.I allowed 1.5hrs drying time and sanded smooth with 300grit emery cloth between each of three coats.I was able to build the nozzle up to where it just fits inside the hopup.Mine chronos at 558fps with a Matrix 300% spring.This is with the stock CA hopup,barrel,and bucking.
 
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