Author Topic: Mrod: .177 to .20 (Read 6111 times))

triggertreat · « **Reply #40 on:** September 24, 2017, 11:38:04 PM »

Bummer on the bolt and hope the ear is ok. That is a really nice 1.84% ES tune that should keep the groups tight even long range.

Dairyboy · « **Reply #41 on:** September 24, 2017, 11:52:23 PM »

Yeah big bummer and not physically hurt but internally from the noise. No biggie though

avator · « **Reply #42 on:** September 25, 2017, 10:47:40 AM »

Typical for R&D. Looks great though.
That's an awesome string. Any future on getting a mag going?

ackuric · « **Reply #43 on:** September 25, 2017, 10:55:31 AM »

Seam? Was the bolt a 2 piece design? I would keep it 1 piece for the next one, or if you must 2 piece have them thread into each other. Good luck and glad you're okay!

-Matt

anti-squirrel · « **Reply #44 on:** September 25, 2017, 02:27:10 PM »

Yup, keeper for sure, Dillon. And OUCH! about the ear.

I concur with Matt- either 1-piece or threaded design.

I want to see more .20 PCPs. I think this is the way to go for HPA mid-power go-getters.

vanTeunenbroek · « **Reply #45 on:** September 25, 2017, 06:36:58 PM »

Progress is only to be had by trial and error..
Glad to hear you didn't have any major hearing damage.
Imagine such a thing happening to one of those bullpups!

Eager to see how it performs with the new bolt fitted.
I'll keep following your build for sure!

Dairyboy · « **Reply #46 on:** October 05, 2017, 11:39:25 AM »

Just an update the bolt and barrel are back with Roy and he's making one out of steel this time instead of the aluminum. Real excited to get this one back together and shooting!

Dairyboy · « **Reply #47 on:** October 08, 2017, 10:58:50 AM »

Got the bolt and barrel back last night! Gave the barrel a very good cleaning and am in the process of leading up the barrel but shot multiple sub MOA groups at 25yds with a variable breeze. Very happy with how it's performing. I had a 50gram MDS hammer and decided to throw in the 29gram hammer. Very nice shot. Cycle with very little spring preload as well. A joy to shoot. Have it tuned from 860-875 right now and it shoots great and quiet. Will run a full shot string when time permits but had 40 over the Chrony today with a 13fps spread (861-874) so very happy with it.

Dairyboy · « **Reply #48 on:** October 10, 2017, 12:31:01 AM »

Here's a full shot string I ran today. Accuracy is great new bolt functions perfectly. Not great on efficiency at 1.27 for the whole string but with such a low set pressure and a .140 TP I can't complain. Could I improve it? Absolutely but do I really need more than 75 shots at roughly 23fpe? Nope so will likely stay as is

(No this gun doesn't have the SS valve in it)

Created: 10-09-2017 04:41:03 PM
Description: .20 Mrod
Notes 1: 2975-1475psi reg set 1600ish +-25psi
Notes 2:
Distance to Chrono (FT): 2.00
Ballistic Coefficient: 1.000
Bullet Weight (gr): 13.730
Altitude (FT): 0.0
Temp: 68 °F
BP: 30.16 inHG
Shots
# FPS FT-LBS PF
75 860 22.55 11.81
74 859 22.50 11.79
73 862 22.66 11.84
72 865 22.81 11.88
71 867 22.92 11.90
70 867 22.92 11.90
69 870 23.08 11.95
68 869 23.03 11.93
67 869 23.03 11.93
66 873 23.24 11.99
65 869 23.03 11.93
64 867 22.92 11.90
63 869 23.03 11.93
62 866 22.87 11.89
61 867 22.92 11.90
60 870 23.08 11.95
59 869 23.03 11.93
58 871 23.13 11.96
57 872 23.19 11.97
56 867 22.92 11.90
55 869 23.03 11.93
54 867 22.92 11.90
53 862 22.66 11.84
52 860 22.55 11.81
51 867 22.92 11.90
50 868 22.97 11.92
49 870 23.08 11.95
48 865 22.81 11.88
47 865 22.81 11.88
46 871 23.13 11.96
45 861 22.60 11.82
44 866 22.87 11.89
43 868 22.97 11.92
42 868 22.97 11.92
41 867 22.92 11.90
40 864 22.76 11.86
39 870 23.08 11.95
38 868 22.97 11.92
37 871 23.13 11.96
36 ERROR 2
35 868 22.97 11.92
34 869 23.03 11.93
33 870 23.08 11.95
32 869 23.03 11.93
31 872 23.19 11.97
30 868 22.97 11.92
29 867 22.92 11.90
28 871 23.13 11.96
27 869 23.03 11.93
26 866 22.87 11.89
25 866 22.87 11.89
24 869 23.03 11.93
23 874 23.29 12.00
22 870 23.08 11.95
21 872 23.19 11.97
20 868 22.97 11.92
19 866 22.87 11.89
18 879 23.56 12.07
17 873 23.24 11.99
16 872 23.19 11.97
15 873 23.24 11.99
14 875 23.35 12.01
13 870 23.08 11.95
12 866 22.87 11.89
11 872 23.19 11.97
10 874 23.29 12.00
9 870 23.08 11.95
8 870 23.08 11.95
7 864 22.76 11.86
6 869 23.03 11.93
5 872 23.19 11.97
4 870 23.08 11.95
3 868 22.97 11.92
2 873 23.24 11.99
1 876 23.40 12.03
Average: 868.58
StdDev: 3.68
Min: 859
Max: 879
Spread: 20
True MV: 868.78
Shots/sec: 0.10
Group Size (IN): 0.00

jarmstrong · « **Reply #49 on:** October 10, 2017, 01:13:42 AM »

Looks like you have put together a pretty nice pest control tool.

OK who is Roy and how to I contact him, to see if he would machine a lothar walter barrel for me to fit my SPA P-16, if I sent him both barrels? Or how every he would like to do it.

jarmstrong · « **Reply #50 on:** October 10, 2017, 02:34:54 AM »

OK, I got off my lazy rear

and reread the post from start and found the answer and sent Roy a e-mail

avator · « **Reply #51 on:** October 10, 2017, 08:50:44 AM »

Thanks Dillon.... seems to have turned out just as expected.
You going to work on mags for it?

Dairyboy · « **Reply #52 on:** October 10, 2017, 11:04:47 AM »

Oh glad you found the info lol

At this time Bill no. First this barrel isn't able to use a mag with how the single shot is setup and second the single shot tray works really well for my needs so I'm happy with it.

avator · « **Reply #53 on:** October 10, 2017, 11:29:01 AM »

Good enough... I find myself using SST on all of my repeater guns when just plinking and adjusting. I like the mags when I'm patrolling the perimeter. Better than keeping a mouthful of pellets.... $:-\$

Dairyboy · « **Reply #54 on:** October 10, 2017, 11:42:06 AM »

Lol yeah can't say I didn't use to do that as a kid...

avator · « **Reply #55 on:** October 10, 2017, 11:52:16 AM »

Most of us probably did.

Motorhead · « **Reply #56 on:** October 10, 2017, 01:14:14 PM »

Dillon,
You may indeed find some more shots by refining the regulators set pressure.
It is pretty darn easy to find where the sweet spot is by doing this simple test ....
* Know what speed you want with what ever pellet you wanting to shoot.

Keep the hammer & stroke settings you now have and just do some fill pressure changes.
have the guns air tank down to @ 80 bar and take few shots over the chrony ...then fill tank in @ 10 bar increments taking a few shots with every bump in pressure.
Continue to do this until your at the KNOWN set pressure of regulator.

If you see a trend in velocity where at a lower pressure than your current reg setting the velocity equals too or exceeds that of gun with higher fill & operating under the regulators influence ... YOU REGS SET TOO HIGH.

Recently I converted my RAW TM-1000 to .20 cal where it had been a .177 prior. In use with the .177 having done said test the sweet spot was 128 bar or @ 1900 psi.
Once the .20 cal was fitted it appeared and sounding as if valve was not balanced right to the pressure & decided to run the test again ...
Was actually quite shocked that the speed of my .20 pellet ( JSB 13.6 @ 800 fps ) while at 128 bar was EQUALED & Surpassed when only at 100 bar ( @ 1500 psi ) !!!

** While at 100 bar the gun was actually shooting near 860 fps, so backed off the HST ( SSG equipped ) untill velocity was back at @ 800 FPS.

Now granted we who tune with regulators need to be well aware of setting up at or just under the self regulated bell curve & this is no different ... point being made here is that with the increased AREA of the .20 over the .177 is that the efficiency in pushing an even heavier 13.6 pellet over a 10.3 was able to be done with less pressure.

You very well may find the same thing that you don't require the same reg setting with .20 that you see with a .177 when the end FT LBS power rating is still the same between both calibers.
* My gun is for Field Target use and needs to be sub 20 ft lbs.

All said & done, with less hammer strike and a lower set pressure the efficiency became MUCH better, gained a bunch of shots per fill and muzzle report fell away too.

JUST SOME FYI ....
Scott

Dairyboy · « **Reply #57 on:** October 10, 2017, 01:26:08 PM »

Wow many thanks Scott!! I will definitely be playing with it some then. Good things to know for my other guns as well.

Dairyboy · « **Reply #58 on:** October 14, 2017, 08:39:38 PM »

Just in case anyone is wondering I freaking love this gun!! Took it out today on its maiden voyage on the dairy and it is just dead on every shot!! And by that I mean 4 head shots on sparrows at around 60-65yds IN A ROW

triggertreat · « **Reply #59 on:** October 14, 2017, 09:21:43 PM »

Those are fun shooting days for sure when you can do head shots on small birds at longer ranges. I have been there and smile for days later thinking about those shots. Glad your build turned out well!

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Mrod: .177 to .20

Author Topic: Mrod: .177 to .20 (Read 6111 times))