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RWS / Hammerli 850 HPA conversion??

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ErickP

ErickP

Member
Mar 10, 2017
12
0
Georgia, United States
Hi All,

I have a stock 850 in 177 and I'd like to convert it HPA. Is this all I need??

cf84343e197e3e8c571d1e04d72fc763.png




Or am I missing something?

The tank is regulated to 1100 psi output will I be ok without modding internals??

I've read on the forums some people mention a spring from Roald at the 850 store? 

Anyone with a similar setup that might be able to tell me what kind of shot count and fpe energy should be expected??

I was wanting to get a Gaunlet but I'm thinking this will have to do for now. I saw in the other forum that the release date has been pushed back. And even then I don't know how it will perform. 


Thanks in advance
 
Hi Erik,

I have an 850. I'm pretty sure that will fit with the adapter it comes with. Only thing is that it's not very high pressure. You're not going to get much of an increase in energy. Of course, it won't be affected by temperature the way CO2 is. 

I think these Air Venturi tanks are about $100, yes? For $250 more you could get it converted to HPA by Roald, which also includes the full tune. Will be shooting the 15.89 gr JSB's at 900 fps+ for 75 - 80 shots and it's regulated. Check out his web site, The 850 Store. 
 
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"chasdicapua"Hi Erik,

I have an 850. I'm pretty sure that will fit with the adapter it comes with. Only thing is that it's not very high pressure. You're not going to get much of an increase in energy. Of course, it won't be affected by temperature the way CO2 is. 

I think these Air Venturi tanks are about $100, yes? For $250 more you could get it converted to HPA by Roald, which also includes the full tune. Will be shooting the 15.89 gr JSB's at 900 fps+ for 75 - 80 shots and it's regulated. Check out his web site, The 850 Store.
Click to expand...
No, because his is .177. He might get more shots though. 

My 850 is a Roald conversion, and it is fantastic. I keep thinking about selling it, because my S510 is "nicer," but I just can't. It shoots too darned well. Action is silky smooth, and the trigger is awesome too. It shoots JSB 15.89s so well it's not even funny. 

A converted/tuned 850 is going to be a much nicer gun than a Gauntlet. If nothing else, it has a Walther barrel. Overall quality is most likely better too. 

i'm told mine is regulated at 1500 psi, not 1100. (To get 28 FPE)
 
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Erik, the Air Venturi bottle will fit with the adapter in terms of threads, but with the fill nipple sticking out like that, I think you'd have to cut some of the plastic on the stock away. Power will be about the same as CO2. 

Agree with Smaug that a Roald conversion would be better, unfortunately, he's not doing HPA conversions on 850's anymore as he can't get the parts. 

Chas
 
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I converted a .22 about 3 or just 4 years ago. I used a 22 cu in tank. There's a thread that I assume is still around on how to do it. With the .22 it was recommended to drill several small holes into the brass fitting that the tank adapter screws into to get max power. If yours is a .177 or if you're not looking for a ton of power probably not necessary. I was getting around 915 fps with 16 pellets with the regulator set at 1800 psi, and as others have said, super accurate. I used a Walther Dominator hammer spring based on other post I read. Replacing the HS was a royal pain in the &*%. I cut the end of the stock off to get better access to the regulator. It's butt ugly but I decided it wasn't exactly a work of art to start with.
The down side of the converted gun:
It was already a long AG, if you don't have an ldc on it now you'll need to get one cause it's gonna be a LOT louder, thus making a long gun longer.
Adding the tank made it very front end heavy.
Changing the hammer spring, which is a must, made it hard to cock.
Although it's as accurate as any AG I own, I wasn't shooting it much because it was long, front end heavy and hard to cock.
A few days ago I decided to replace the 22 cu in tank with a 13 cu in tank to reduce the front end weight somewhat. I also put some sand in a baggie and added it to the hollow stock to try to balance it better. Seems to help. I cut several coils off the hammer spring (don't remember how many) to reduce the cocking effort. I shot it unregulated starting from 1800 psi and found max power with the shorter HS was now achieved at 1575 psi and reset my regulator accordingly. It's now shooting 16 g pellets around 840 fps. It cocks easier and is much smoother. Still tinkering with it so I don't know about shot count yet. I was getting 72 with a 3200 fill. I'm sure I lost some with the smaller tank but hopefully not to many. 
One more thing. There's a small spring that always trying to pop out when you reassemble the trigger group. I couldn't see what purpose it served and finally decided to leave it out and see what happened. Works fine without it and goes together a lot easier.
 
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1100 will work fine, you just won't have nearly as much power. The good news is the hammer spring can be shorter which makes it easier to reassemble and makes cocking easier. When I was testing to determine where to set my regulator I started at 1800 and went down to 1375 psi. Here are a few of the results with 16 g pellets;
1800-914 fps
1700-901
1600-876
1500-850 
1400-833
1375-811 (low as I tested)
I'd guess you be around 750 fps @1100 with 16 g pellets and you'd get a ton of shots. If you decide on the conversion I'd order 2 springs. Use one to experiment with. Start by cutting at least 2 coils, test fps, then cut one coil at a time until velocity starts to drop, then cut your other spring down to just prior to the point velocity started to drop. 
 
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