Silencers: a question or three

[meles meles]

Do any of you clever oomans know:

1. What pressure is likely to be experienced at the muzzle of a rifle firing a standard 7.62x51 mm round ? (In, say, a 26 inch barrel)
2. What the temperature of the gases will be at that point ?
3. What volume of gas is produced by a standard 7.62x51 mm round ?

[kennyc]

Do any of you clever oomans know:

1. What pressure is likely to be experienced at the muzzle of a rifle firing a standard 7.62x51 mm round ? (In, say, a 26 inch barrel)
2. What the temperature of the gases will be at that point ?
3. What volume of gas is produced by a standard 7.62x51 mm round ?

I have no idea, but I do know that it gets difficult to see the target after 8-9 rapid fire rounds due to heat shimmer

[ovenpaa]

Hmm.. interesting questions. I was discussing moderators and brakes tonight and there has been some suggestion that a well designed Mod will give slightly higher MV's.

Regarding pressure QL suggests

Cartridge : .308 Win. (SAAMI)
Bullet : .308, 155, Lapua Scenar GB491 7073
Useable Case Capaci: 49.057 grain H2O = 3.185 cm³
Cartridge O.A.L. L6: 2.905 inch = 73.79 mm
Barrel Length : 26.0 inch = 660.4 mm
Powder : Vihtavuori N140
Charge : 46.5 grains = 3.01 grams

Estimates of the progress of combustion:
NR.: x(in.) Z(%) v(fps) p(psi) t (ms)

0 0.00000 1.27 0.0 3626 0.0000
1 0.00001 1.30 0.8 3729 0.0007
2 0.00003 1.34 1.5 3833 0.0026
3 0.00010 1.38 2.3 3936 0.0054
4 0.00022 1.45 3.8 4142 0.0087
5 0.00043 1.51 5.2 4322 0.0127
6 0.00077 1.60 7.1 4578 0.0172
7 0.00127 1.71 9.4 4885 0.0223
8 0.00199 1.84 12.1 5242 0.0279
9 0.00298 1.99 15.1 5649 0.0340
10 0.00429 2.15 18.7 6117 0.0404
11 0.00599 2.34 22.7 6645 0.0473
12 0.00815 2.57 27.3 7257 0.0545
13 0.01085 2.82 32.7 7951 0.0620
14 0.01417 3.11 38.7 8731 0.0697
15 0.01820 3.43 45.5 9599 0.0777
16 0.02304 3.80 53.2 10572 0.0859
17 0.02878 4.21 61.8 11649 0.0942
18 0.03553 4.68 71.5 12838 0.1026
19 0.04340 5.19 82.2 14142 0.1112
20 0.05252 5.77 94.1 15559 0.1198
21 0.06300 6.41 107.3 17098 0.1285
22 0.07498 7.11 121.9 18762 0.1372
23 0.08858 7.89 137.9 20539 0.1459
24 0.10396 8.75 155.4 22430 0.1546
25 0.12126 9.68 174.5 24422 0.1634
26 0.14063 10.70 195.3 26514 0.1721
27 0.16224 11.81 217.7 28689 0.1808
28 0.18624 13.02 242.0 30940 0.1895
29 0.21282 14.32 268.0 33239 0.1982
30 0.24214 15.72 295.9 35577 0.2069
31 0.27439 17.21 325.6 37928 0.2155
32 0.30976 18.82 357.2 40278 0.2242
33 0.34845 20.52 390.6 42601 0.2328
34 0.39065 22.33 425.8 44875 0.2414
35 0.43657 24.25 462.8 47079 0.2500
36 0.48643 26.27 501.6 49200 0.2586
37 0.54043 28.40 542.1 51209 0.2673
38 0.59882 30.63 584.2 53095 0.2759
39 0.66181 32.97 627.9 54846 0.2846
40 0.72965 35.40 673.1 56443 0.2932
41 0.80257 37.93 719.7 57879 0.3020
42 0.88082 40.55 767.7 59148 0.3107
43 0.96466 43.27 816.9 60247 0.3196
44 1.05435 46.08 867.3 61171 0.3284
45 1.11747 47.99 901.4 61688 0.3344
46 1.15380 49.03 919.8 61886 0.3377
47 1.19072 50.05 938.3 62044 0.3410
48 1.22825 51.07 956.7 62161 0.3443
49 1.26642 52.07 975.2 62240 0.3476
50 1.30525 53.06 993.7 62282 0.3509
51 1.31507 53.31 998.3 62287 0.3517
52 1.32492 53.56 1002.9 62289 0.3525
53 1.32739 53.62 1004.1 62290 0.3527
54 1.32986 53.68 1005.2 62290 0.3529
55 1.33048 53.70 1005.5 62290 0.3530
56 1.33110 53.71 1005.8 62290 0.3530
57 1.33172 53.73 1006.1 62290 0.3531
58 1.37170 54.70 1024.5 62272 0.3564
59 1.41240 55.67 1043.0 62220 0.3597
60 1.45383 56.62 1061.5 62134 0.3629
61 1.49604 57.57 1079.9 62017 0.3662
62 1.53903 58.50 1098.4 61869 0.3695
63 1.58284 59.43 1116.8 61691 0.3728
64 1.62749 60.34 1135.3 61484 0.3761
65 1.67300 61.24 1153.8 61249 0.3794
66 1.71941 62.13 1172.2 60987 0.3828
67 1.76674 63.02 1190.7 60700 0.3861
68 1.81503 63.89 1209.1 60387 0.3895
69 1.86429 64.75 1227.6 60051 0.3928
70 1.91457 65.60 1246.1 59691 0.3962
71 1.96589 66.44 1264.5 59309 0.3996
72 2.01828 67.27 1283.0 58906 0.4030
73 2.07178 68.09 1301.4 58482 0.4065
74 2.12643 68.90 1319.9 58039 0.4100
75 2.18225 69.70 1338.4 57577 0.4135
76 2.23929 70.49 1356.8 57097 0.4170
77 2.29758 71.27 1375.3 56599 0.4205
78 2.35717 72.03 1393.7 56085 0.4241
79 2.41810 72.79 1412.2 55556 0.4278
80 2.48040 73.54 1430.7 55011 0.4314
81 2.54412 74.28 1449.1 54452 0.4351
82 2.60931 75.00 1467.6 53880 0.4388
83 2.67601 75.72 1486.1 53295 0.4426
84 2.74428 76.42 1504.5 52698 0.4464
85 2.81416 77.12 1523.0 52089 0.4502
86 2.88571 77.80 1541.4 51470 0.4541
87 2.95898 78.48 1559.9 50840 0.4581
88 3.03403 79.14 1578.4 50201 0.4621
89 3.11091 79.79 1596.8 49553 0.4661
90 3.18970 80.44 1615.3 48897 0.4702
91 3.27046 81.07 1633.7 48233 0.4743
92 3.35324 81.69 1652.2 47562 0.4785
93 3.43813 82.30 1670.7 46885 0.4828
94 3.52519 82.91 1689.1 46201 0.4871
95 3.61450 83.50 1707.6 45512 0.4915
96 3.70613 84.08 1726.0 44819 0.4959
97 3.80018 84.65 1744.5 44121 0.5004
98 3.89672 85.21 1763.0 43419 0.5050
99 3.99584 85.76 1781.4 42714 0.5097
100 4.09765 86.30 1799.9 42006 0.5144
101 4.20222 86.82 1818.4 41296 0.5192
102 4.30968 87.34 1836.8 40583 0.5241
103 4.42011 87.85 1855.3 39870 0.5291
104 4.53364 88.35 1873.7 39155 0.5342
105 4.65038 88.83 1892.2 38440 0.5394
106 4.77044 89.31 1910.7 37725 0.5446
107 4.89397 89.78 1929.1 37010 0.5500
108 5.02108 90.23 1947.6 36296 0.5555
109 5.15193 90.68 1966.0 35583 0.5610
110 5.28665 91.11 1984.5 34871 0.5667
111 5.42540 91.54 2003.0 34161 0.5725
112 5.56834 91.95 2021.4 33454 0.5784
113 5.71563 92.36 2039.9 32749 0.5845
114 5.86746 92.75 2058.3 32047 0.5906
115 6.02401 93.13 2076.8 31348 0.5970
116 6.18547 93.51 2095.3 30653 0.6034
117 6.35205 93.87 2113.7 29962 0.6100
118 6.52397 94.22 2132.2 29275 0.6168
119 6.70145 94.56 2150.6 28592 0.6237
120 6.88473 94.89 2169.1 27915 0.6307
121 7.07406 95.21 2187.6 27242 0.6380
122 7.26971 95.52 2206.0 26575 0.6454
123 7.47196 95.82 2224.5 25914 0.6530
124 7.68110 96.11 2243.0 25258 0.6608
125 7.89745 96.39 2261.4 24609 0.6688
126 8.12133 96.66 2279.9 23965 0.6770
127 8.35309 96.92 2298.3 23329 0.6855
128 8.59310 97.17 2316.8 22699 0.6941
129 8.84174 97.40 2335.3 22077 0.7030
130 9.09944 97.63 2353.7 21461 0.7122
131 9.36662 97.85 2372.2 20853 0.7216
132 9.64375 98.05 2390.6 20253 0.7313
133 9.93133 98.25 2409.1 19660 0.7413
134 10.22986 98.43 2427.6 19075 0.7516
135 10.53991 98.61 2446.0 18499 0.7622
136 10.86206 98.77 2464.5 17930 0.7731
137 11.19693 98.93 2482.9 17370 0.7844
138 11.54521 99.07 2501.4 16819 0.7961
139 11.90759 99.20 2519.9 16276 0.8081
140 12.28483 99.33 2538.3 15742 0.8205
141 12.67775 99.44 2556.8 15217 0.8334
142 13.08720 99.54 2575.2 14701 0.8467
143 13.51410 99.63 2593.7 14194 0.8604
144 13.95945 99.72 2612.2 13697 0.8747
145 14.42429 99.79 2630.6 13208 0.8895
146 14.90977 99.85 2649.1 12729 0.9048
147 15.41709 99.90 2667.6 12260 0.9207
148 15.94756 99.94 2686.0 11800 0.9372
149 16.50259 99.97 2704.5 11349 0.9544
150 17.08367 99.99 2722.9 10908 0.9722
151 17.69243 99.99 2741.4 10477 0.9908
152 17.89850 100.00 2747.5 10337 0.9970
153 18.38613 100.00 2761.4 10020 1.0118
154 18.87376 100.00 2774.9 9720 1.0265
155 19.36139 100.00 2787.9 9436 1.0411
156 19.84902 100.00 2800.5 9167 1.0556
157 20.33665 100.00 2812.7 8911 1.0701
158 20.82428 100.00 2824.5 8668 1.0845
159 21.31191 100.00 2835.9 8437 1.0989
160 21.79954 100.00 2847.0 8217 1.1132
161 22.28717 100.00 2857.7 8007 1.1274
162 22.77480 100.00 2868.2 7806 1.1416
163 23.26243 100.00 2878.3 7615 1.1558
164 23.75006 100.00 2888.2 7431 1.1699
165 24.23769 100.00 2897.8 7256 1.1839
166 24.38150 100.00 2900.6 7206 1.1880
Muzzle

[tikkathreebarrels]

Do any of you clever oomans know:

1. What pressure is likely to be experienced at the muzzle of a rifle firing a standard 7.62x51 mm round ? (In, say, a 26 inch barrel)
2. What the temperature of the gases will be at that point ?
3. What volume of gas is produced by a standard 7.62x51 mm round ?

Peasy,

1. Enough to push said projectile some considerable distance at a not inconsiderable velocity and with energy in correspondingly equal measure.
2. Hot, especially if you've still got powder burning up the barrel and creating a muzzle flash.
3. Probably a surprisingly small amount.

Why you ask these trixksy questions glasshopper?

[meles meles]

Thanks ovenpaa, that's most useful. Much appreciated.

Why do we ask such questions? Simples. Like most things manufactured by oomans, existing moderators are woefully inefficient and horrendously overpriced. Badgers could easily make better, but to do so we wanted to ensure that we properly understood the baseline conditions.

[ovenpaa]

Speak to the Ex Skydiver, occasional poster on this forum, he is also striving to develop the ultimate moderator and is well worth bouncing ideas off. He is also a confirmed sheddist like myself

[1066]

There's a lot of good information about moderatorsHere Have a dig around, there are some interesting fact and figures.

[1066]

And loads of info here:
http://guns.connect.fi/rs/linx.html

[meles meles]

Thanks for the additional information oomans. We've started frying the chips...

[Blu]

Gents may I suggest that before you tell the badger anymore, ya'all have a read of this.

http://badgercorporation.com/?page_id=264

I find the last paragraph particularly disturbing. It seems that our friend the Badger may be more of a ...........MOLE..... than a Badger. sign01

Blu