.25 AV Avenger

[avator]

As for the tuning.. I think I might put a bit more hammer spring into it.

I'm not an experienced tuner so if you have suggestions, I'm open to them.

[avator]

After going back through this thread and looking at what I had done as far as adjustments.. I think I need to increase the reg setting back up to around 2300 or more. I think that would level the string out a bit and lower those numbers at the end of the string.
Pretty sure I won't get the full 7 12 shot mags from a fill when it all shakes out.

[TorqueMaster]

Let me just say this.. I have a love/hate relationship with Triggertreat's spreadsheet.
I love it for ease of use and the amount of information it puts at eye level.
I hate it for the same reason.... It shows how bad the tune is on this Avenger. 
Looks like I got some work to do.

I'm puzzled by the muzzle velocity alternating high-low-high-low so consistently.  There has to be an explanation for that.  I'd guess you were switching ammo on every other shot -- light-heavy-light-heavy.  Hopefully someone has seen this pattern before and knows what to look at first???

[avator]

Let me just say this.. I have a love/hate relationship with Triggertreat's spreadsheet.
I love it for ease of use and the amount of information it puts at eye level.
I hate it for the same reason.... It shows how bad the tune is on this Avenger. 
Looks like I got some work to do.

I'm puzzled by the muzzle velocity alternating high-low-high-low so consistently.  There has to be an explanation for that.  I'd guess you were switching ammo on every other shot -- light-heavy-light-heavy.  Hopefully someone has seen this pattern before and knows what to look at first???

I am as puzzled as you... all pellets were from the same tin. I think the regulator was being goofy at the 4360 fill pressure. Here to fore I only filled this gun to 3900 but I wanted to see the results from a full fill. I'm going to try a few things before I call it a bad regulator. Admittedly I'm not as experienced with regs as many here.

[splitbeing]

Far less experienced than you, Bill, but I have had the experience of a 1/8 turn of the hammer making a significant difference in ES but not changing the avg fps much.  Not saying that will happen, just that it sometimes does.  Might be worth running a mag or two at the high ES pressures and making small hammer adjustments in search of a sweet spot.

[avator]

Far less experienced than you, Bill, but I have had the experience of a 1/8 turn of the hammer making a significant difference in ES but not changing the avg fps much.  Not saying that will happen, just that it sometimes does.  Might be worth running a mag or two at the high ES pressures and making small hammer adjustments in search of a sweet spot.

Yep, I have a few ideas in mind.
Tomorrow I'm going to start fresh and degas the gun. Then I will follow the manual instructions and turn the reg screw all the way clockwise to close it the open it 1/4 turn (counter clockwise). According to the manual this resets the reg.  Next I'll air the gun up to max (300 bar = 4360 psi) and continue counter clockwise until it's set at 2300. I'll run that string and make HS adjustments from there.

[nervoustrigger]

The velocity jumping around like that on a regulated PCP is usually symptomatic of too little hammer strike.  In this case another clue is at the end of the string where we see the wild swings disappear and the velocity begin climbing.

A third factor is just a guess but I'm thinking the Avenger will very likely yield a velocity somewhere in the 800's with a relatively lightweight pellet (25gr) on a 2100psi setpoint.  The fact it's down in the high 6's to mid 7's is suspicious.

The solution would be to either increase hammer strike, reduce the regulator setpoint, or some combination of the two.  Then find the proper balance by adjusting it to the velocity knee...meaning gradually increase hammer strike until the velocity no longer increases, the back off the hammer strike until the velocity declines to about 97% of that maximum.

For example, let's say you find the max velocity is 890fps.  Back it off to 890 * 0.97 = 863fps.  When adjusted in this manner, the velocity should be much more consistent.

[Back_Roads]

 Yup Jason set you right I just did this with my M16 as I saw similar fluctuation  I added hammer spring, as Jason described. I then used a vibra tite like substance on the hammer spring adjuster threads,  to lock down that setting.

[avator]

Thanks..
So I'll start with giving it more HS today. It's very possible that the HS backed off because I don't remember getting this many shots before.
I'll first need to see what pellets I have enough of to run strings with... I pretty much burned the Benjis yesterday. I should have some weighed cast pellets. If not I'll have to make a run of them.

[avator]

Grabbed a refill on the coffee and I'm in the castin' shack. Got the pot and mold oven on and coming up to temps. I'll get a couple hundred poured and see what I have for weight consistency. I may as well just keep going today to build up a mess of them.

[avator]

First batch in the tumbler. Pot reloaded and coming back up to temp. I'll run another batch of around 100 then cull and weigh.

[avator]

I made an error in that string I posted...
That is an incorrect pellet weight. I listed it out of memory because the weight is not printed on the tin. The actual weight of the Benjamin pellet is (according to what site you trust) 27.8 not 24.7.
I am culling these cast pellets to 27.2 - 27.4.
My cull rate was not very impressive on that first pour. I got about 50% yielding 54 pellets within my tolerance.
That should improve over the next couple runs.

[avator]

Should be enough for a couple runs...
I still have more to tumble and cull.

[avator]

I sneaked out to the shop this morning before Betty Lou was awake enough to define the ToDo list... "dang" the torpedoes.   

I put 3k in the gun and watched the reg pressure as I dry fired a few shots. The gauge was sporadic. It would drop way below set pressure the sometimes recover fast and sometimes slow and maybe not even back to set pressure.
I know I was shooting faster than it would sometimes completely recover but I didn't know because I was watching chrono numbers and not gauges.

I saw somewhere about resetting the regulator and the process was to completely degas the gun, adjust the reg to 0 (clockwise) then back it back out 1/4 turn (counter clockwise). Then air the gun to max (300 bar) and adjust reg (counter clockwise) to desired set point. In my case, I set at 2200 psi.
Next I went in one full turn on the hammer spring.
I fired the gun several times and watched the gauge.... it functioned flawlessly. Barely bounced and recovered almost instantly.

[avator]

Enter chrono....

First of all.. let me be completely transparent here...
The original string I posted was with the (reported) 27.8 marketed Benjamin domes. I never weighed them for consistency and I don't have enough let to get a good read on them.
This string is with my cast 250 27 NOE Hunters using wheel weight lead at 700f. I sorted and culled them to 27.20 - 27.40. So you'll notice that I entered 27.30 as an average in the spread sheet below.

[avator]

The first thing you might notice is the shot count..
I went from 82 shots <> until it was well (maybe 4m or 5 shots) off the reg.
This string went 58 shots until I was visually at the reg setpoint of 2200 psi. That's where I stopped.
The ES is 26 at 3.26%. Average 37 FPE <>.

[avator]

Ok... let me point out...
That pellet weight.. remember? 27.20 - 27.40.
How much of that spread can be attributed to that varied weight range?
I culled 50% so I'm not happy tightening up that weight range much farther. I mean, I'd rather be shooting than pouring and weighing 200 pellets to get 100 gooderns, let alone lowering acceptability.
And I certainly don't want to pay today's stupid prices for good .25 pellets to shoot targets with.   

Oh BTW... I put all 58 of those shots in a 1" hole at 35yds. and I wasn't even focusing on accuracy.

THIS GUN CAN KEEL !!

[TorqueMaster]

That's the stuff.  Resetting the reg woke it up to behave better for sure.  ES went from an awful 83 to a reasonable 26.  It'll get even better with a bit more hammer spring to flatten the gradual MV rise you've got there.

[avator]

That's the stuff.  Resetting the reg woke it up to behave better for sure.  ES went from an awful 83 to a reasonable 26.  It'll get even better with a bit more hammer spring to flatten the gradual MV rise you've got there.

Yep, I figured another half turn or so. That would still give me 4 full 12 round mags.

[splitbeing]

That's the stuff right there. Welcome back, Avenger!