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Dust · Member

Looking forward to the discussion on the 850 resource. Would like to see how you drilled out the B&A too.

rsterne · Moderator

Pretty simple.... first I removed the pin valve rod.... I chucked it in a lathe with the 88gr airsource end out, and drilled it to 5/16" and countersunk it (same as the "flowed" short fitting Roald sells).... Then I turned it around, (big end out) and drilled it progressively larger until the final hole was 5/8" ID to a depth of 1.7".... Depending on the taper of the drill, you may have to watch it so that you don't go too close to the small diameter where it shoulders down for the 88 gr. threads.... I left about 0.15" thickness minimum between the drill point and the shoulder.... There is about the same wall thickness left, which is plenty IMO....

Bob

Dust · Member

will you be making these for other people? Wink

rsterne · Moderator

Dust · Member

I guess I will be buying from Roald then.

rsterne · Moderator

Finally got outside.... 8 shot group at 25 yards:

C-T-C 0.40".... easily covered with a dime.... Mr. Green

Bob

Dust · Member

Ur dime looks weird Mr. Green

, but mine currently are brown and the size of quarters, so...

packrat · Senior Member

Great time o' day !!!!! that shot string with the 18.1 pellets is probably the straightest I've ever seen!! Jeez, NOW I gotta roll up all my pennies and get an 850.. 70 shots with such a low fps deviation... WOW!
I do notice though, that the gun is not very "carbine-like"...that may turn out to be a blessing for me Mr. Green

Dust · Member

I just found a short flow modded adapter for $30, but came back here. How much longer is the long adapter? Will it allow the regulator gauge to stick out the front catch instead of farther into the stock with a hpa tank? Also, do you think I could take the long adapter to competent machinist, and he could do what you did with your instructions? Or did Roald say that he would look into it, and I should wait for him to sell them.

Verado · Member

Just from the looks of it, I have the B&A adapter and with an hpa tank and reg it would stick out too far. I think it could cause alot of stress on the valve where it threads into the receiver. The B&A adapter puts the shoulder of a 9oz CO2 tank just at the area where the foregrip clips to the fore end

rsterne · Moderator

B&A make two adapters, and they are "about" an inch different in length, maybe a bit more....

Roald uses the short adapter with JDS regulator and the shoulder on the tank just touches the front of the stock.... If you use a 9 oz. CO2 tank (no regulator) and the long adapter, same position....

I used an 18 ci. tank and a Ninja regulator and the long adapter.... I got more volume between the regulator and valve (because I drilled out the adapter) which resulted in being able to get more power from less pressure.... The increased volume results in a higher AVERAGE pressure during the shot cycle....

I dont think the extra leverage of the longer adapter is a problem because my 18 ci. tank is lighter than the 22 ci tank Roald uses....

Bob

Dust · Member

Would you feel comfortable mounting a 22ci off of the long reg.

rsterne · Moderator

I assume you mean off the long adapter?.... I wouldn't worry about it unless you start banging the tank around.... a 22 ci. HPA tank and regulator is significantly lighter than a 9 oz. tank full of CO2 (I'm guess that is about 6 oz. heavier?)....

I personally would use a long adapter, 13 ci. tank, Ninja regulator, running about 1600 psi if I was starting from scratch.... and machine off almost all of the spring guide but use the heavy hammer spring.... You should get about 30 FPE and over 50 shots and have a nice light, well balanced combination....

I'm convinced that the extra volume of the drilled out long adapter is the key to improving the performance of the 850 on HPA....

Bob

Dust · Member

Being a .177, I doubt I would get more than 20 something, but I like the extra efficiency you are getting. I haven't bought anything yet. Do you think a competent machinist could do what you did with your instructions?

rsterne · Moderator

I am using a long B&A adapter drilled out to 5/8" ID for a depth of 1.7" (from the large end).... The small end is drilled out to 5/16" ID....

That's it.... no magic.... anyone with a lathe can do it.... Don't go too deep on the 5/8" hole or you will reduce the wall thickness too much at the end of the hole where the tapered end of the drill approaches the shouldered down section....

Are your building it for FT with a 20 FPE limit?.... If so, you should be able to easily get enough shots to do a whole match plus sighting & warm up with a 13 ci tank @ 1600 psi.... I have a converted 22XX PCP and I get 85 shots @ 20 FPE on a 13 ci. tank regulated at 1500 psi.... this with 10.3 gr. JSB Heavies....

Bob