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P-12 project

April 26 2017 at 7:32 AM

Abrackeen  (Login Abrackeen)
YF12

So I picked up a P-12 dirt cheap a few weeks ago. My goal is to be as efficient as possible as roughly 30 fpe.

The rifle came to me and would not hold air. No big deal. Ordered new o-rings from The O-ring store. Replaced all OEM o-rings with Buna 70D o-rings and no more leaks.

I've had a .22 Polygonal blank that was supposed to go on my Homebrew rifle, but I couldn't help myself. Turned it down from .630 to 15mm. I picked up another project midway through turning the barrel down and I had loosened my compound. I completely forget to retighten it before my finishing pass and my tool bit in and now I have a barrel that fits, but is ugly as sin. There goes selling the rifle, but at least most of it is hidden by the shroud. Instead of the normal metric threads on the barrel I went with the standard 1/2-20 UNF for attachments should I remove the shroud.

Built a custom 1" shroud to cover the newer longer barrel. Also added a custom pickle that when combined with the shroud makes the pup extremely long. I have nosy neighbors so I can deal with the extra length if it keeps them from complaining.

I had a P-12 in the past and regulated it via a HuMa regulator. I also regulated this rifle, but I went with a Robert Lane Regulator set at 135 bar. I've used his regulators in many rifles and have always had excellent results.

I replaced the OEM hammer spring with a slightly shorter and weaker spring. Not sure of the exact details as it was all I could get my hands on in a pinch. The goal was to eliminate some hammer bounce. It worked ok, but I can still hear some bounce.

I ran this string tonight. The rifle is freshly reassembled from the regulator install and these are the first shots. I tossed four errors out. The regulator has some settling to do, and I believe the hammer is inconsistent as well. Overall I'm happy with where it's at, but I'm hoping y'all can help me get the count and consistency up.

Created: 04-25-2017 22:39:51
Description: P-12 .22 Polygonal (4 errors removed)
Notes 1: JSB Exact Heavy
Notes 2: 3000psi start
Distance to Chrono (FT): 0.50
Ballistic Coefficient: 0.033
Bullet Weight (gr): 18.130
Altitude (FT): 738.0
Temp: N/A
BP: N/A
Shots
# FPS FT-LBS PF
68 860 29.78 15.59
67 876 30.90 15.88
66 869 30.41 15.75
65 875 30.83 15.86 off regulator
64 891 31.96 16.15
63 889 31.82 16.12
62 895 32.25 16.23
61 899 32.54 16.30
60 899 32.54 16.30
59 902 32.76 16.35
58 904 32.90 16.39
57 900 32.61 16.32
56 902 32.76 16.35
55 890 31.89 16.14
54 900 32.61 16.32
53 898 32.47 16.28
52 897 32.40 16.26
51 897 32.40 16.26
50 895 32.25 16.23
49 897 32.40 16.26
48 891 31.96 16.15
47 891 31.96 16.15
46 886 31.61 16.06
45 890 31.89 16.14
44 883 31.39 16.01
43 876 30.90 15.88
42 888 31.75 16.10
41 881 31.25 15.97
40 878 31.04 15.92
39 880 31.18 15.95
38 881 31.25 15.97
37 883 31.39 16.01
36 877 30.97 15.90
35 890 31.89 16.14
34 883 31.39 16.01
33 874 30.76 15.85
32 883 31.39 16.01
31 882 31.32 15.99
30 888 31.75 16.10
29 880 31.18 15.95
28 881 31.25 15.97
27 876 30.90 15.88
26 888 31.75 16.10
25 889 31.82 16.12
24 881 31.25 15.97
23 878 31.04 15.92
22 887 31.68 16.08
21 886 31.61 16.06
20 884 31.46 16.03
19 879 31.11 15.94
18 883 31.39 16.01
17 880 31.18 15.95
16 890 31.89 16.14
15 889 31.82 16.12
14 888 31.75 16.10
13 880 31.18 15.95
12 879 31.11 15.94
11 879 31.11 15.94
10 884 31.46 16.03
9 893 32.11 16.19
8 888 31.75 16.10
7 893 32.11 16.19
6 880 31.18 15.95
5 886 31.61 16.06
4 888 31.75 16.10
3 884 31.46 16.03
2 886 31.61 16.06
1 912 33.49 16.53
Average: 886.63
StdDev: 8.99
Min: 860
Max: 912
Spread: 52
True MV: 888.16

Here she is in her neighbor friendly configuration.
[linked image]


 
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AuthorReply

robny
(Login robnewyork)
YF

looks great

April 27 2017, 10:19 PM 

how long is the barrel compared to stock? id bet an airtube extension would not only serve the obvious purpose, but also make it appear more baalnced


    
This message has been edited by robnewyork on Apr 27, 2017 10:21 PM


 
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Abrackeen
(Login Abrackeen)
YF12

Barrel length

April 27 2017, 11:46 PM 

Barrel is as close to 23.8" as possible.

I've never actually thought about a tube extension. Shot count is pretty decent, and if I ditch the extra attachment it's not near as good looking.

 
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robny
(Login robnewyork)
YF

yes, thats quite a few

April 29 2017, 6:52 PM 

shots per fill. so no real need for the extension whatsoever

 
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Abrackeen
(Login Abrackeen)
YF12

2nd string

April 27 2017, 11:56 PM 

Shot another string tonight. I had to use H&N 21.14's since I mistook a few tins of .25 Cal for .22 cal.

First thing I noticed while cleaning after the first string was a couple baffle strikes. I reamed all of them out and retested. No more strikes. I also had suspicion that my hammer and spring were causing issues. I didn't pull the hammer, but I did change the spring back to stock.

I shot this string and it looks like I need to check for the hammer binding. If that doesn't solve the issue I'm going to switch over to a HuMa regulator and see what happens.

Created: 04-27-2017 22:23:11
Description: P-12 .22 Polygonal
Notes 1: H&N Barracuda Match 21.14gr
Notes 2: 3000psi start
Distance to Chrono (FT): 0.50
Ballistic Coefficient: 0.038
Bullet Weight (gr): 21.140
Altitude (FT): 738.0
Temp: N/A
BP: N/A
Shots
# FPS FT-LBS PF
59 836 32.81 17.67
58 833 32.58 17.61
57 837 32.89 17.69
56 846 33.60 17.88
55 837 32.89 17.69
54 811 30.88 17.14
53 835 32.73 17.65
52 823 31.80 17.40
51 830 32.34 17.55
50 811 30.88 17.14
49 825 31.95 17.44
48 831 32.42 17.57
47 824 31.88 17.42
46 821 31.65 17.36
45 816 31.26 17.25
44 816 31.26 17.25
43 832 32.50 17.59
42 832 32.50 17.59
41 830 32.34 17.55
40 839 33.05 17.74
39 822 31.72 17.38
38 824 31.88 17.42
37 827 32.11 17.48
36 821 31.65 17.36
35 830 32.34 17.55
34 822 31.72 17.38
33 820 31.57 17.33
32 823 31.80 17.40
31 833 32.58 17.61
30 816 31.26 17.25
29 831 32.42 17.57
28 824 31.88 17.42
27 828 32.19 17.50
26 825 31.95 17.44
25 830 32.34 17.55
24 822 31.72 17.38
23 810 30.80 17.12
22 819 31.49 17.31
21 828 32.19 17.50
20 819 31.49 17.31
19 831 32.42 17.57
18 818 31.41 17.29
17 827 32.11 17.48
16 829 32.26 17.53
15 823 31.80 17.40
14 829 32.26 17.53
13 827 32.11 17.48
12 817 31.34 17.27
11 814 31.11 17.21
10 805 30.42 17.02
9 822 31.72 17.38
8 831 32.42 17.57
7 807 30.58 17.06
6 825 31.95 17.44
5 824 31.88 17.42
4 820 31.57 17.33
3 821 31.65 17.36
2 816 31.26 17.25
1 815 31.18 17.23
Average: 824.41
StdDev: 8.18
Min: 805
Max: 846
Spread: 41
True MV: 825.65

 
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Ron Robinson
(Login compressive)
YC

Sounds to me like

April 30 2017, 1:55 PM 

You're on the right track for improving consistency, but your quest for shot-count was over with the first string (not to mention that second string). Seeking OVER seventy-some-odd shots per charge is downright greedy!

 
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Abrackeen
(Login Abrackeen)
YF12

Shot count

April 30 2017, 7:15 PM 

Ron,

I believe you're right about being greedy with the count. I don't ever see myself needing near that many shots. Turning the power up is tempting, but I've got a .25 AT-44L that covers any higher power I might need. With the extended shot count I'm getting it looks more and more like I'll be selling the .22 FD-PCP as the P-12 is easily tuned to meet any power level up to 50 fpe with the current settings.

I'm honestly really surprised that it was as high as it is. The first P-12 I had, had the same mods (HuMa regulator though) and would only do about 40 regulated shots at 30fpe.


 
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