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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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