RETRO Arms - M4 Hop Up Chamber Reviews

3.9 Rating 7 Reviews

Retro Arms M4 Hop Up Chamber, produced from EN AW 2007 and EN AW 7075 aluminum. Designed to allow precise adjustment in 2mm range with step of 0.01 mm. Chamber is compatible with Retro Arms gearbox but will also work with standard gearboxes. We cannot guarantee precise fitment with other gearboxes.

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“Amped did a great job of shipping my order fast, and I was excited to receive my hop up. It works great and I get around 400 FPS on 80 psi, paired with a MR HOP 2021 70° maple leaf bucking. My only problem would be that I get a weird hissing noise coming from the hop-up when I put my mag in. The rotary arm is also very stiff so it's hard to adjust the Hop. If someone could help me with my problems that would be great. But otherwise, this hop-up is great! I recommend buying from amped!”

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Posted 1 year ago

Thank you for your wonderful review Elijah we appreciate your support! As for your issues there should be no hissing coming from your hop up they normally come from the nozzle. I would check to make sure the seal is good and between your nozzle and your hop up. I also recommend lubricating your grip line and dry firing the gun a few times to lubricate your solenoids! I hope these recommendations can fix your issues! -Tyler

Posted 1 year ago

“Oh where to start ? ;) I am very impressed with the quality of this hop up unit. It does come from the Czech Republic which I was surprised by. It says in the description that it does not come with the C-Clamp, well mine did, which I ordered the extra one anyway, no bid deal there. I have to say though that I am not impressed with how the adjustment wheel becomes tight once you start to adjust the hop up. I am not sure if this is due to the fact that I used a bigger spring, that I thought would provide more tension on the adjustment arm, or if it is due to the notches in the adjustment wheel itself ? Not a big deal tbh. I paired this with a 363mm Modify Hybrid tight bore inner barrel and a Modify Baton Ryusoku Hard Hopup and flat nub. At first I was having some feeding issues, but I think that was due to the harder bucking. Once I ran a mid through it of .3's it seemed to feed good. This went into a G&G Mk16 (Scar-L) and with the stock hop up unit and flat hop I was getting about 200-230 ish ft. There was no change in distance with this hop up, which I did not expect anyway, I just wanted a better( upgraded) hop up unit. I did how ever have to remove the 2 screw holders inside the mag well that secure the plastic factory hop up, that was not that hard to do and took like 10 min to do and to make it look nice. Reason the screw holders had to be removed is due to the fact that the adjustment wheel on the Retro Arms hop up is wider than the stock plastic one, so the upper and lower would not fit together all the way. I hop some one finds this informative and helpful as I had to figure it out on my own :)”

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Posted 7 years ago

“To begin this review I'll state that I ended up trading it to a friend for his prowin which wasn't fitting in his receiver. This hop up unit is machined very well. It is a lot lighter than it looks. The red is a lot more subtle than the photos suggest so don't expect a bright red "statement" when you open the dust cover. This unit will likely work well with an r-hop because the design of the wheel and hop arm make it very difficult for the hop up to walk back while it is under pressure. However, this feature also makes it very difficult to adjust the hop once it is under tension. Another small complain is that you have to trim your bucking or order the shorter retro arms bucking if you want to use a c-clamp. This isn't a huge hassle but it doesn't feel good cutting your $15 prommy purple bucking. On the flip side, the c-clamp isn't completely necessarily due to the innovative barrel nut. My final complaint is that due to the spring tension design, the 'forehead' of the unit is significantly larger than other units (such as the prowin) so this may have trouble fitting some upper receivers. It fit into my GC-16 Predator just fine but my 2015 CA M4 was another matter. I hope someone finds this useful.”

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Posted 7 years ago

“A little crunchy at first but gear grease fixed that! nice and smooth Super light Going to buy couple more!”

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Posted 7 years ago

“Great finish but sub par performance, with under powered spring and adjustment wheel that becomes to tight due to lack of spring tension. People with a prowin”

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Posted 7 years ago

“Feeds far better than my prowin ever did, really smooth dial. The collet ring is really cool and does a really good job locking thr barrel in. If thats not enough, the c clip is unique and has a notch to lock into the barrel as well. Only problem i had was i has to trim part of my bucking off, but that wasnt too bad. I would highly recommend this to anyone looking for a nice upgrade”

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Posted 7 years ago

“It is nicely machined and in my case feeds much better than a prowin. I've only had the chance to use it with k120s and the new g&g mags and they feed flawlessly in my ~35 rps dsg. I would recommend buying the hop up arm pack if you are looking to flat hop or rhop.”

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Posted 8 years ago