Build Started: Hammerli 850 Max Efficiency Tune @18-ish FPE?

[imadunatic]

I also took a few minutes to take care of a couple more creature comfort/accurizing issues:

First up, my grand plan inline ASA turned out to be a real pain, could barely get needle nose pliers on it, and even then it wasn't good.

This was the stock on/off knob installed in the gun, you can see it's dang near impossible to reach:



So, one piece of aluminum and some lathe time produced a new knob that would actually extend up and around the regulator up to the bonnet set screws:



Extends out beyond the forearm just enough :



Next was locking the barrel down. Looked at many ideas, but I figured 3 #8-32 SHSS (even in the white metal) would be the easiest way to lock up the barrel. Wouldn't want to get ham fisted with the allen wrench, but it doesn't even pretend to move in the receiver now:



After all this, I came up from the basement to find sunshine and hardly a breeze... so I remounted the scope, sighted it in and then proceeded to shoot this 8 shot string at 22 yards:



Turns out she can cook too!!! Just to be sure it wasn't a fluke, I backed it up with this 8 shot group:



A little wider, but, right at this point in time I am nearly ready to say mission accomplished. The only things left on the to do list are a bottle support/built in sling mount (I found this on someone else's build, I can't remember who, but I'm borrowing the idea, so thank you!) and a barrel shroud (1" aluminum is supposed to be here tomorrow for that).

Couldn't be happier with it right now. Just need a good efficiency run to see how much of a gas guzzler it is.

This mean a ton of shots at 3000psi fill.

I think you're exactly right Fabio... I am definitely looking forward to a full shot string just to see how much we're talking.

[imadunatic]

Efficiency testing tonight.... For some reason my power slipped back down to 17.5 FPE, which is a little less than I would prefer. I'm going to wait until I have time to shoot it off the regulator before I decide what I want to do.

In it's current form, I'm getting 1.52 FPE/ci 1.39 FPE/ci (fat fingered a number I think) and using about 12.5 psi per shot, which means my shot count should be in the neighborhood of 175 shots from 3000-800 psi (assuming I'm just off the knee now and I can extend my usuable shots to 800 PSI).

Since this is a plinker, and now technically the most powerful airgun I own, I'm really tempted to just leave it where it's at and see if I like it. I would certainly like to bump it up closer to 20 FPE, but I can't negate the fact that my efficiency will most likely go down as I shim the hammer spring (I think it's still a little light based on a fairly wide ES), but this rifle only has about 200 pellets through it, so I'm not calling it broke in yet.

It's not over yet.

Kevin

Edit: Bumped the shim to .060" and it landed right at 18.6 FPE @ 1.32 FPE/Ci, gonna shoot it there for awhile and see what happens.

[Hobbyman2007]

Nice work Kevin. Never had one of the 850 rifles but always wanted one. Retail up here is nearly 400$ right now . Unless I see one used for a good price ,I'll have to live through your tinkering. Enjoy the new rifle .

[imadunatic]

Nice work Kevin. Never had one of the 850 rifles but always wanted one. Retail up here is nearly 400$ right now . Unless I see one used for a good price ,I'll have to live through your tinkering. Enjoy the new rifle .

Thanks Denis.

I feel you there. My wife paid $180 shipped for this as a refurb from airgun depot (early christmas present for me), that really is the right price; I can't see spending the full $300 (retail here) on it even as sweet as it shoots. I think it will always have it's place in the cabinet once I'm done with it though. It seems well built, and it's encouraging to hear other members like Fabio talk about having their 850 for 8 years and still loving it.

Kevin

[Tucobenedicto]

Yes,my .177 850 is still up and running and is very accurate, i love it.
Like i sayed,there are much more options around now,but if one can catch one for a good price i still suggest to buy one.
A lot of fun,even out of the box.

[imadunatic]

So the permanent bottle showed up today, lo and behold, it was at 775 PSI right out of the gate with the stock coil spring in it. It just happened I wanted to try this pressure with the .060" spring shim, so I loaded up 3 clips and proceeded to shoot this string:

Description: hammerli 850 775 psi hpa jsb eh 18.13 efficiency testing
Notes 1: start 1500 psi
Notes 2: end 1175


#   FPS   FT-LBS
1   702   19.84
2   700   19.73
3   700   19.73
4   698   19.62
5   704   19.96
6   700   19.73
7   701   19.79
8   705   20.01
9   704   19.96
10   703   19.9
11   702   19.84
12   701   19.79
13   703   19.9
14   700   19.73
15   700   19.73
16   705   20.01
17   695   19.45
18   689   19.11
19   696   19.5
20   689   19.11
21   691   19.23
22   685   18.89
23   689   19.11
24   690   19.17

That is the new current record for my tune, which is 1.58FPE/CI.... That is pretty spectacular considering I also bumped the average FPE up to about 19.6 with this regulator set point. Also, my extreme spread for the first 2 clips was 7 FPS or about 1%, I need to investigate that third clip and see what is going on with that. Makes me think the pellets might be getting damaged or something.

My shot count from 3000 to 750 PSI should be in the neighborhood of 160 which is enough for me to not even bother switching over to CO2 in the summer months.

None the less. Still being amazed by what a few PSI can do to the efficiency and power of an airgun.

[Tucobenedicto]

Very nice results Kevin,maybe the last shots are close to regulator setpoint?
I would test a string starting from an higher filling pressure to see.

[stalwart]

Yes,my .177 850 is still up and running and is very accurate, i love it.
Like i sayed,there are much more options around now,but if one can catch one for a good price i still suggest to buy one.
A lot of fun,even out of the box.

I have a magic number in mind, that will put one in my stable... even if it takes years. Did some reading, for a customer's project, and saw a *lot* of love out there.

[imadunatic]

Forgot to post my print of the extended knob (for the future builder of course!)...

Edit: Apparently really slacking. I've also attached a print and pics of the wrench needed to open up the valve. I used 2 #6 SHCS for the pegs, worked perfectly, just be careful when you open the valve, the spring has a fair bit of preload and stuff goes flying everywhere.

[stalwart]

Nice!

[Tucobenedicto]

Kevin,want go deep in the 850? A couple of years ago i modded the valve with a different stem,this allowed me to run the standard spring with a 1800psi setup.the great advantage is a low cocking effort and a lighter trigger.
Attached a drawing (metric) and some pictures
You can get the idea.
There is another mod around made by fivestar45 (anthony) with a classic poppett and a new valve cap,but i don't have Anthony skills and tools,so this is my way 

[imadunatic]

Fabio,

You are enabling the sickness. Lol.

Does the valve seal with the o ring on the washer? I've read other discussions on the tapered valve seat design, the consensus was that it took more hammer strike to crack it open, but it sounds like you're seeing the opposite?

Is it just because that stock poppet oring is so soft that it takes a ton of movement just to break the seal?

[Tucobenedicto]

Yes,the valve seal with the o ring on the washer,you can see better on the pdf attached.
The 90° angle on the stem was an arbitrary choice but worked for me.this setup is inside my 850 and still consistent without leaks after two years or more of shooting.I thinkered about a flattest angle,but i had no reasons to do that.
A conical valve spring works better with my stem,the standard spring tend to bent a little and misalign the stem.not a big issue with the valve screwed on the rifle.
This valve works with the standard hammer spring shimmed about 2millimeters giving 21fpe at 1800 psi on my .177 850.
The rifle becomed more quiet too,i think it waste less air then standard valve.
You are correct,the standard poppet require a big strike to break the o ring seal so a very strong hammer spring is required to run 1800-1900psi

[fsae99]

Kevin,
If you going to make this make 2, 1 for me.

Fabio,

You are enabling the sickness. Lol.

Does the valve seal with the o ring on the washer? I've read other discussions on the tapered valve seat design, the consensus was that it took more hammer strike to crack it open, but it sounds like you're seeing the opposite?

Is it just because that stock poppet oring is so soft that it takes a ton of movement just to break the seal?

[imadunatic]

Kevin,
If you going to make this make 2, 1 for me.

LOL. I've stuck it in my notes, not quite to the point of modifying the valve innards like this. That will probably be stage 2 for me depending on what kind of performance I'm seeing out of my current setup. I am guessing I could finish hogging the front of the valve out with this as well since this poppet is much easier to crack.

Fabio,

Again, thanks for sharing. I've saved your print and pics, no guarantees I won't have questions if I start down that road!.

[Tucobenedicto]

No problem,i am around.You can also try to convince Anthony-fivestar45 to make a new cap and stem for you  his mod is great.

[imadunatic]

No problem,i am around.You can also try to convince Anthony-fivestar45 to make a new cap and stem for you  his mod is great.

I can definitely make the parts, it's just a matter of deciding how far down the rabbit hole I want to go.... Looks like the hardest part of Anthony's is the new threaded cap, not too terrible, but admittedly it's been about 10 years since I cut a thread in the lathe!

I'm almost where I want to be power wise now, but having a more efficient poppet with a lighter hammer/spring couldn't hurt a thing in my quest for efficiency.

[Tucobenedicto]

My first itention was to replicate Anthony work,but my lathe is not equipped for thread cutting,so i reversed the design looking at a theoben and an hatsan valve.

[Snaptrap]

Getting ~20 fpe @ 775 psi boggles my mind.

Congratulations!

[imadunatic]

Well, the .177" 850 showed up last night. Pretty much going the same path I did with the .22. Initial velocity with no other mods (775 psi HPA and CO2) on the .177 is about 650 FPS with JSB 10.34. My goal is closer to 800 (16 FPE) for this build, curious to see what it takes to get there.

I did notice this trigger is slightly different than my .22, I think some adjustment is in order, or possibly the pseudo 2-stage mod. I can really find the break point like I can on my .22 (it's a little creepy) so I'm guessing this is what everyone talks about when they say it needs some work in stock form.

Still, happy to have a little sister to the .22, thought I was partially wasting my time during the .22 build, but the trigger time since has made me realize it's well worth the time investment; one of the nicest rifles I own.