1325XLT update testing

[K.O.]

I usually get my mail around 4pm or so...

I still need to notch it to let it sit back in the tube and will take the time to do it slow and get it just right.

so in the next couple days I will know what my effort brought me.

I could not help taking another look at expectations from another angle. (yep one more time)

After trimming the poppets I should end up with a valve volume of about .1-.13

so I will start with .1 @ 10 pumps, 

I get theoretical  1252 psi @ a conservative 60% efficiency

which gives an average psi with an 18.75" barrel of 688

If you look at the chart for .25 in this thread that gives about 29 fpe  with a .203 port (an oblong .187 is what I did It is .220 through the valve and transfer port)

http://www.airgunhome.com/agforum/viewtopic.php?p=78260

BUT  that is at 100%

so if you look at Wyomans chart for a .22 valve and barrel you will see that a 24" .22 barrel wants a .29 or so valve well so does a 18" .25 barrel

I did not do the math but based on a slightly flatter curve for the .25 efficiency  I think the .1 valve will give .85 as an efficiency factor(E.F.) which gives

http://i1249.photobucket.com/albums/hh508/WyoMan/Pumper%20Power%20Plant/1322efficiency_zpsb0e2f3c4.gif

24.6 fpe at ten pumps  H&N FTT 20.1 grain at 745 fps

I think that is actually what the pump should easily achieve  1250 psi is not that hard and I used a low efficiency for the pump...


Now here is the thing I think the pump can handle up to about 1800 psi...

with the .1 valve that is 1879 @ 15 pumps using a .65 E.F.

go thru the whole rigmarole again and I end up with  34fpe and 875 fps with the 20.1 pellets

there is probably a whole wormhole in my logic but I can not find it...

In the real world though if I get 625-650 I will feel like I did ok.

BUT

big hopes do have a bit of a reason behind them...

?

[K.O.]

well the bad news first

456-463 fps average over 15' @ ten pumps is what I got this morning when I tested.



So what is the good news,

well my project has problems.

I can hear you saying how the heck is that good news?

They are easily fixable and should provide some very substantial gains


The first problem,

 I broke the beautiful .220 I.D. transfer port that Big Bore Bart made for me and my substitute only is .180 I.D.

If you go back to the  FPE vs. Caliber and Port Sizes thread you will see that alone might  cost me about 5 fpe/90-100 fps.


The second problem,

I need to pick up an oversize bolt oring I get a puff of air past the bolt not real strong but there, at the least it is costing me 20 fps and maybe

30-50 fps.


The third problem

I  used the 2100 exhaust poppet and I think it is blocking flow some I should have used a 13xx poppet it has a longer shaft and will open more fully.

this one at ten pumps could be costing me some fps but honestly it is hard to tell...

three out of ten times I got just a burp of retained air at ten pumps and at 11pumps, 3 out of 3 shots a more substantial burp.

so no testing beyond 10 pumps until I get a 13xx poppet but I am pretty sure it will dump 15 pumps when I do.



One other thing I can do that I have not is to put a pin in the intake poppet as a guide and to take up a bit of headspace passage is .25 long

that should buy me a few more fps,  because of the light valve spring(cock before pumping) pump effort  feels effortless so the smaller

passage will not be a pain...

that is the state of things right now.

I looks pretty good for hitting 600 fps at ten pumps and I just may get a lot more at 15

[Big Bore Bart]

Kirby, Kirby, Kirby,      I'll make another......... out of aluminum.    (probably should have used it for durability anyway)   What's the final depth of the barrel recess? 
   The choked  T-port is causing some of the air retention, but the longer 13xx poppet won't hurt
 The bolt O-ring is costing you a lot more than you think.   When I don't get my bolt seated properly on the .22, sometimes the pellet doesn't make it to the target. 

   Actually the performance is not that bad considering the problems.

[K.O.]

well I thought I had it trimmed just right  but when I tightened the breech and barrel hose clamp it was just a touch to long...

Hey Bart I appreciate the offer but I took my vernier to ace and found a perfect brass fitting while unsuccessfully finding just the right o-ring

It has an I.D. of .220 and an O.D. of 250 can you believe it,

I mean exactly what I needed...

one of these  http://www.grainger.com/product/ANDERSON-METALS-Insert-46M542

[K.O.]

Took the exhaust poppet from my 1377  and he dumps  15 pumps now have not tried more yet cause the blow by at the bolt is worse now that I fixed the other probs.

Tomorrow I will try tape at the bottom of the o-ring groove but part of the problem is the bolt will fit all the way inside the barrel just barely.

I think I will look and see if I have some tubing to slip over the bolt that is closer to the right diameter.


"Actually the performance is not that bad considering the problems. "

yep got a stock 1322 beat already

[K.O.]

Still having sealing problems

But it will dump 25 pumps with no retained air

even with the leaks I am getting a 20 or so fps gain for each 5 pumps...

10 pumps  502 fps

15 pumps  524 fps

20 pumps  554 fps

25 pumps  576 fps

I do not think I got the transfer port perfect and may have a slight leak there also this time

I am getting a stronger blast from the  bolt  even though it is a bit better sealed so yep before the transfer port and 2100 poppet was really

holding things back.


I will do a cornstarch test for the transfer port but the main problem for now is sealing at the bolt...

Making head way though...

I think my valve volume is a bit large to hit 600 at ten pumps once I get it all sealed but it might be close.

I also think I did not  have the pump cup shimmed quite enough before and now have it slightly over shimmed and that cost me some 15-20 

fps on my 1322 before I got it just right.

but for right now my focus will be solving the bolt problem the others a pretty much whipped...

I am getting a pretty stout blast but is it a  100-150+ fps blast.

[K.O.]

Almost forgot won a new old stock 766/2200  piston for 10 bucks on ebay.

[K.O.]

More good news bad news...



the good,

I hit 16 fpe (15.99 actually)
 
Got all the leaks fixed....   (2 layers duct tape under bolt o-ring re-milled tport seat slightly)

It will dump 30 pumps...

Still room for improvement...



the bad,

fixing the leaks did not gain me  much at all


pumps      fps

5            385
6            405
10          493
15          535
20          549
25          566
30          593



the good,

The barrel is only ported to .187 and a very slight oblonging to it,

I believe I will get at least another 40 fps at 10 pumps and just maybe 50-65 if lucky,

My 1322 with similar valve size and a 4" shorter  barrel I gained about 40 fps going from a .140 port to a .160 port.

this will surpass that size gain slightly...


the valve after all the work has a volume of  about  .1256 and with more adventuresome milling up in  the nose could go as high as .14

I am glad Bart did not get adventuresome  this time though,  I did not fit the valve to the pump cup  before sending him the valve 

I feel  this one is perfect for a .22 version which just might be my next project.



I opened the  valve nose that Bart made from a 760 nose to .4 from .36 all the way to the check poppet ledge ,

the check poppet is 2/3 original size, is drilled out some and has a guide pin.

the exhaust poppet was also treated the same and is a 13xx poppet

Bart hogged out the exhaust end of the 2100 valve for me and ported it to .2  through out ( that is why I should see good gains from porting

the barrel it is the only choke point).

So the concept is working well and at 30 pumps I have not found the top end yet so it may be possible to hit 600 fps or better at ten pumps

by simply putting larger poppets back in... (and what I lose will be off the very top end)

I feel I am getting close to the top end because pump effort after 20 pumps  is about what it was at ten stock for the 2100b...



left to do,

Get the pump cup shimmed just right ( maybe some small gain maybe not)

finish the barrel porting.  (should see some substantial gains).

Adjust valve volume to taste  ( could easily get 600 at ten pumps IMO)(but what top end cost)?




I realized I could go flat top for fewer pumps but like the relative idiot proofness/durability of the pump cup once shimmed  just right...

so far I feel it was worth doing  and for all the very optimistic and pessimistic ramblings I shared in the beginning and throughout my gut told

me I would get  about  20 fpe and guess what I think that is about what I will get...

So yep about 20 fpe for about  $100 and the fun of tinkering  not bad...

[K.O.]

I can not say it enough...

Thank you Bart could not have done it without you.

and thank you to those that post that which teaches (I think you know who you are).

[Big Bore Bart]

   Turn the barrel-breech assembly upside down and make sure the pellet is clearing the T-port.    Then get a 1/8 or 3/16 chainsaw file, break it in half, and use it as a pull file to oblong the T-port forward.   


   Btw  Your welcome   Bart

[K.O.]

I measured fps with 2 microphones 6" from muzzle an 6" from tin can into my pc into audacity and is a very  accurate  Time of flight chrono.

Velocity is average over a measured 5 yards.

Chair gun says add about 20 fps for muzzle velocity

Thanks for the hint Bart. I have a Dremel grinding bit also and was thinking of using it

http://www.dremel.com/en-us/Accessories/Pages/ProductDetail.aspx?pid=453

[K.O.]

porting done, port is now  .187 x .220


well dang I guess 620-625 fps or so is all I am going to get for now...

porting did not hurt but only helped a small bit.

I ran up against the limits of the valves volume and from my fps is I would say a larger valve volume would help from ten pumps on up

 around ten pumps I am getting close to 30 fps per pump, by fifteen pumps 10fps and by twenty 5fps.

I can probably squeeze another .019 ci  out of the valve  which would take it from  .126 or so to .144 or so but looking at Wyomans  charts(@

Capof) I am guessing that would give a 3-4% gain which is about  20 fps.

speaking of which I need to figure out the algorithm and make one of those charts for a 1325...

 

I think I could squeeze  between .17- and .19 ci out of a full size 760 nose and 2100 exhaust.

I would have to sleeve the pump tube which would mean  a redesigned sear.

and then that would get me a pretty flat shooting 700 or so fps...  Maybe...

I will be checking my work for the next couple days  but other than the metal piston  I think it is  I got what I got... and 17.3 fpe does beat

my 1322 by about 5 fpe.


but for now oh well 550 fps at 15 pumps will have to do...

[Big Bore Bart]

   Try a 13xx striker with the 2100 spring,it may open the valve a bit quicker.   I just weighed my spare 2100 part at 29 grams.    Is the 13xx lighter or heavier?    I can see that the 13xx striker is shorter in the nose, so it will have more travel, and more energy

[K.O.]

Hi Bart I appreciate the input.

I switched to a 13xx striker when I switched to a 13xx exhaust poppet.

I could add some lead in the spring hollow and add a bit of weight and preload, but it will already dump 30 pumps with no retained air.

That leads me to think that is not my problem.

So that leaves me two areas pump efficiency and  valve volume to barrel volume efficiency

In a few I will take as an analytical look at those two from my results as possible...



One thing I have noticed is that up to 10 pumps is the valve/pumps sweet spot after that it starts to struggle and gains shrink after 15

Mail just came early and my 766/2200 piston just got here my 1377 pistons are not stuffed yet but I wonder if just the metal piston and its

brand new pump cup will help? 

I think I will do a quick 10-15-20 pump test and then stuff the 13xx part and test again but honestly I think the stuffed plastic 2100b piston is

not a big part of the problem.  ( the metal piston even with no gains is worth it just for the wiper)

That will have to wait till tomorrow though.

I am hopeful but skeptical  that I will see significant gains...


I do think a lot of it is the valve volume and can see how to  increase it from the .1256 it is now, to close to .16  and maybe get 660-670 fps

at 20 pumps.

Well any ways the efficiency right now compared to what Bobs graphs show is possible is about 60 %, rather than 85%  which was my guess

that the valve/barrel efficiency would give.

I think I will talk to Wyoman and try to get his help developing a chart instead of guesstimating because it would be easy to be off by 10-15%.

even the chart can just be to give an educated idea.

[Big Bore Bart]

  Kirby have you pinned the valve?   The valve moving even .005-.010" will reduce the pump efficiency at higher pressures.   30 pumps of a 2100 is equal to 20 for my custom, and it will not dump 18.  It does however have a flat-top setup.    I have some testing to do, post results later.

[Big Bore Bart]

   Just did 6 shots of Gamo TS-22 with the custom.   Average of 668 fps for 21.8 fpe @ 15 pumps.   Kirby You should be getting similar #'s with the 20 grainers you have.   

   Download SoftChrono  and give it a try.  http://talonairgun.com/forum/viewtopic.php?f=16&t=522   It may be your timing is off.

[K.O.]

Softchrono downloaded but I get class not reg, need file MSSTDFMT.DLL

[Big Bore Bart]

  Solution is halfway down here.  http://talonairgun.com/forum/viewtopic.php?f=15&t=436&sid=3c2de659735aac78929ad4bbae585948&start=40

 

[K.O.]

just got the chance to get 6 shots in

pumps    fps

10        513
15        561
15        563
20        588
20        583
25        609

this could be the new pump cup but I guess that the plastic piston even stuffed was not up to the job... and was at least part of the problem.

I just picked up an 8 32 tap and set screws yesterday...

[K.O.]

the 13xx portion of the piston is not stuffed yet.