New project starts, 2240/13xx/MK177 = 13xxWT @ 20+ fpe (hopefully)

K.O. · October 22, 2014, 08:52:11 PM

My early bday present is supposed to get here today...

A Tan MK177

will shoot it for a few days and see want it can do but then begins its journey to becoming more... (I am not into the tacticool, I do not want my pellet gun #1 to be weak #2 to look like a weapon designed for killing people )

so it will be pulled apart to see what possibilities it actually has as the power plant for a 13xx...

http://www.gatewaytoairguns.org/GTA/index.php?topic=74715.0

K.O. · October 25, 2014, 10:23:02 PM

Ok so I did stage one and modded it as a MK will be testing soon...

The Mk 177 has a Barrel length of 16.75". I have my 1377 hitting 755 fps on 20 pumps with a 18.75 barrel and ~.12 ci for valve volume.

If I put a that .177 barrel on my 2100/13xx hybrid I am pretty sure with its ~.13 ci valve it would be hitting about 760-790 fps with 7.9g CPHP @ 11 pumps and 800+ @15... Based on 750 fps @ 15 pumps with 14.3g CPHP... it does have a 22" barrel but I feel it is not as important going down to .177)

Ok so stock here is what my MK was getting

pumps 7.9g 7.4g

6 520 541
8 559 590
10 612 642
12 632 672
14 675 692

I did do a bit of preload on the striker spring and retested and no change I even did one 20 pump shot but only got 630 fps...

I measured the transfer port size and it was .140", so I knew that was not holding it back...

I had looked at the sound of the shot and saw striker bounce and had a MK valve spring well I put 2+2 together and figured it was a part of the problem...

In my mind we were dealing with a valve size of about .07- .1 (stock13xx, Stock 2100) so I thought the valve not dumping cleanly was really costing...

I figured just get the right spring in the valve and maybe add a bit of volume(if possible) and all the other mods and should be able to get about 800 fps.

Well,

I finally took the Mk's valve apart...

WOW I found the valve that I have been hoping for stock minus the poppets(but not spring) it is about .17 ci and with all out work (reduced poppet size and bore rear portion of exhaust side out to .5 from .4 (about a .63 section)) it looks like a ~.25 ci valve is possible... and that is without making an extension... and at .74+ for an O.D. it looks like it would fit in a Discovery tube...

Since it is staying a MK for a while before becoming a hybrid and it will stay a .177 I took up some space with an extra .5 size intake poppet
to get a valve volume of about .15-.16 (less pumping than .17)

this also allowed me to use a 13xx sear spring to replace the MK's over done valve spring (stronger & longer than 13xx striker spring,to limit power?)

next I looked at the valves exhaust throat it was .2" and the exhaust poppet shaft .12" since they determine flow out of the valve...

not good...

you have a .8 throat feeding a .14 transfer port you would be better off with a small transfer port to keep charge velocity high... and with a large valve it makes no sense other than keeping velocity down...

The large valve can afford to eat air and still be a faster charge velocity than the choked setup that is stock IMO...

So,

Bored the exhaust throat to .220" and turned down the poppet shaft to .95" so now I have .125" feeding .140"

I then rounded the corner to help flow...

Last time I had it apart I pulled the magnetic bolt probe out until it seated a CPHP just past the breech port and it still clears the clips...

it IMO is way to fat at .11 in a .177 bore it is blocking almost 60% of the bore...
as soon as I get done typing I will be replacing it with a thinner steel probe of about .06-.07...

almost forgot I stuffed the piston with some large nails I forgot what size... 20d..?

So I have reassembly and testing ahead of me... 10 min to do the job it is as simple as the 760... But testing will have to wait till late today or some time tomorrow.

Any one want to venture any guesses as to how it does at 6,10,14, 18, 20 pumps.... with 7.9 CPHP

14.3 for atmospheric pressure

pumps psi @70 eff @60 eff My optimistic fps

6 580 497 610
8 773 663 670
10 967 829 730
14 1354 1160 790
18 1740 1492 825
20 1934 1658 850

wish me luck

Brutuz · October 25, 2014, 10:32:20 PM

Thanks for posting and good luck

K.O. · October 26, 2014, 01:41:59 AM

Thanks for the well wishes

some early results

had a little time for testing but had to stop with only one shot at each and did not get 8 & 20 pumps

pumps fps

6 577
10? 623 (might have miscounted)
12 708
14 752
16 776
18 798

I am still getting hammer BOunce (below pic at 16 pumps)

so I will be taking it down one more time, I will remove the collar that I put on the spring guide portion of the end plug for spring preload and smash one or two Jsb 25g Kings in the back of the striker for preload and weight...

Maybe it will help..? Or do I just need 5 more inches of barrel?

or both

K.O. · October 26, 2014, 02:20:01 AM

Just hit a soup can bottom almost dead center at 30 yards 14 pumps with 7.4 points and it was with my 2nd shot first trying to hit the can...

because the sights are 2.6" above the bore and the fact that I was zeroed for 10 yards with 7.9g CPHP (pre mods)I knew my 30 yard shot would be high

so I used my first shot as a ranging shot and it hit dead center about 6" high dropped my aim point and bam almost right on...

Long time since I used the m16 style peep and post but I guess I still can...

Gippeto · October 27, 2014, 04:53:02 AM

Quote from: K.O. on October 25, 2014, 10:23:02 PM
next I looked at the valves exhaust throat it was .2" and the exhaust poppet shaft .12" since they determine flow out of the valve...

not good...

you have a .8 throat feeding a .14 transfer port you would be better off with a small transfer port to keep charge velocity high... and with a large valve it makes no sense other than keeping velocity down...

The large valve can afford to eat air and still be a faster charge velocity than the choked setup that is stock IMO...

So,

Bored the exhaust throat to .220" and turned down the poppet shaft to .95" so now I have .125" feeding .140"

Just a small point...you're not actually comparing port area.

.200" throat and .120" stem have an effective area of .0201 sq.in.

.140" transfer port has an effective area of .0154 sq.in.

.220" throat and .095" stem have an effective area of .0309 sq.in.

Keep after it.

Al

K.O. · October 27, 2014, 06:02:59 PM

Hey you are right,

The embarrassing part is I am the one talking about, pi are squared...

I do suffer from concentration probs and it shows sometimes even on the basic stuff...

I do still think opening the exhaust throat to .22 from .2 will help it only cost about 4 psi over the .2 throat and will feed the transfer port better IMO.

I figured the above with a .15 valve and 1500 psi (about 18-20 pumps).

also,

I forgot to shim the pump cup and wonder just how much it is costing at the higher pumps I am pretty sure it is compressing enough to cause a bit of headspace

I also did not sleeve the intake passage but with a big valve well it might be .06% or just a few fps.

I think it is not to bad but have a feeling that the above and striker bounce just may be costing me 20fps or more...

it goes from gaining 42fps to 22 fps per pump to 11fps per pump rather quick.

I will test some more tomorrow...

and then most likely try the fixes if the above # are confirmed.

I was going to wait to get the 2240 parts to turn it into a 1377wt for the fixxes but my curiosity gets the best of me...

BDS · October 27, 2014, 09:46:49 PM

Hey KO... sorry, but you lost me on the ultimate "morph" of this gun.

What will it be when you are done? Steroid MK177? Or some other variant? Or, all the "guts" put into another gun entirely?

What's your thoughts on all that plastic and sheet steel on the MK after many sessions of 15+ pumps? Will it survive?

K.O. · October 28, 2014, 02:08:04 AM

hey Brian will respond more later and explain but have to do some running around...

step one is a steroid MK 177 and I just got about all it has to give sort of... and want to share todays results...

shimmed the pump cup .035 with a guitar pick and smashed two JSB 25g pellets into the back of the striker(necessitating shortening the spring guide portion of the end plug .25")

pump effort after ten pumps is a bit stiff and past 14 may be a bit hard on the gun I did not go past 16 pumps.

more complete numbers to follow later but

at 16 pumps 7.4g pointed 859 fps, 7.9g CPHP 831 fps, Winchester 9.75g pointed 738 fps.

just a little headspace makes a big difference...

K.O. · October 28, 2014, 06:52:28 AM

There are 2 mods that I forgot to tell about. I zip tied the barrel to the pump tube close to the barrel support/breech and made a solid pump pin.

I forgot to do a few drops of oil so did in the middle of testing... so a few are a bit low plus I think the cup seated to the tube better with a bit of use. (I think)...

pumps 7.9g CPHP 7.4 points 9.75g points

4 492
5 540
6 579 617
7 601
8 643,666 694 608
9 686,702
10 692, 722 753 669
11 743,744
12 755,783,779 782 692
13 787,785
14 795,798 826 719
15 815
16 831,827 859 738

It has a bit of space taken up by an extra 2/3 size check poppet that I should have left out it looks like... 20fps ?

For an all out .177 or as a .22 and .25 there is a .6" or so section that is .40" that could easily be opened up to .5" I am guessing 20+ fpe as a .22 or .25...

I really want to go all out with a disco tube, this valve(with an extension) and piston and a 2100 linkage to see what I could get...

Does any one know how much a Disco air tube runs?

it will have to wait till next year tho...

I need to think about the pro and con of 66 linkage vs 2100 linkage also...

I was hoping the MK had it in it... when I opened the valve I was like OH YEAH...

I feel the plastic shell of this thing can hold up to 10-12 pumps for a good while...

I will be getting the 2240 striker and end cap to turn this into a 1322WT shortly but for now I am all

how much does a 2240 striker weigh? the MK striker can in at 45 grams pre pellets in the back...

K.O. · October 28, 2014, 10:30:21 PM

As for the ultimate morph for this particular power plant it will have the valve bored out, it looks like I will get about .23-.25 c.i. when done.

It will then get a 1322 breech and pump grip after cutting 1" off of the back end off the pump tube,

It will use a 2240 striker cocking pin and end plug. I am guessing about 825-875 fps with 14.3 CPHP in ~25 pumps with a 22" barrel.

I also have a .25 barrel I will try on it...

I did this to see about what the valve could do tuned at close to stock volume(- an extra .6 size check poppet) ...

But in the end I want to use a disco tube with a 2100 linkage and MK piston with an extended valve to get an 800+ fps .25 in about 16-20 pumps... ??

K.O. · October 30, 2014, 08:56:55 PM

well It's first post mod groups at 20 yards was very good and not so good on purpose... all with 10 pumps

I did the first group with Crosman pointed (by the quarter) with the front post sight as far up as it would go without being loose and flopping around... aim point was bottom of bottom target

then I did the top with CPHP 7.9g with the front post adjusted to be on target...
no further adjustment on the bottom with the Winnie 9.75g points...

so I added some painters tape inside the screw on post ( a very small amount)...

It did the trick and thing were going well... as good or better than the 7.4g group

but yesterday it suddenly stared spraying around about 4" and it is not the sights... and since testing have not gone past 10 pumps...

I guess the plastic frame is just not up to the job...

took yesterday off but may look to see if I can spot a fix soon...

BDS · October 30, 2014, 09:46:00 PM

Good luck! Looking for the shotgun pattern problem can be tough but, your first inclination is probably the right one... lot's of plastic and lot's of pumps don't usually play well together, it's the reason I dumped my Webley Rebel Pumper, it would do nearly 700 fps in .22 caliber (and pumps 6 through 10 waere a monster) but, all of the plastic shrouds and inner moldings holding metal valves and pump linkage were not up to the hi-pressure task.

K.O. · October 30, 2014, 10:46:02 PM

I am not very worried about getting it accurate again as a MK it would just be to see if I can...

I just need a 2240 striker cocking pin and end cap and it will be a carbine 1322WT... My 1322XLT is still going strong as a 700 fps in ten pumps .22 long carbine. 13xx/2100 tube

It has even handled 12 and 14 pumps here and there. the 13xx platform is much better all around. Besides I do not like what high sights/scope does to a short range weapon...

but yep, it just did not handle going from a 600 fps at ten pumps to a 720 fps at 10 pumps rifle very well.

I also have recently a new used 2100b it did though all I did is add a old style metal piston...

http://www.gatewaytoairguns.org/GTA/index.php?topic=76905.0