great article with information on barrel length and velocity

Sas874runner · Apr 18, 2014

http://rifleshooter.com/2013/12/300-win ... 0-win-mag/

I read this article and thought you guys may like to read this. Being as there is always a question about velocity and barrel length. Also notice how much the crown affects accuracy.

DrMike · Apr 18, 2014

We're seeing quite a few of these articles in recent days. It is a perpetual problem in the mind of those building a rifle. The article presents quite a thorough study that considers the major causes of potential error. Thanks for posting.

Sas874runner · Apr 18, 2014

Ya I thought it was interesting on how barrel length had always been the longer the faster but it shows how at one point a shorter barrel had slightly increased velocity

baltz526 · Apr 18, 2014

When I cut my bad shooting 24" vanguard down to 20" as a last resort experiment. Velocity loss was not bad at all with some loads. Several where less than 100fps loss. But a few lost closer to 200fps or higher. The most accurate loads in the 24" did improve. It went from a 2 1/2" best group rifle to this with load development.

This load in the 24" 2752fps average, in 20" 2687fps average. It shoots 150gr partitions loads pretty well But if you compare book velocity to my 20" results it is a pretty large drop. this is out of my log book 150gr Partition, ww-brass, Rem 9 1/2M, 80gr H4831, 2996fps average. Nosler list the max load at 81gr, 3318fps, 79gr 3224fps, 77gr 3155fps. My 77gr data out of the 20" is 2860fps A very large reduction.

baltz526 · Apr 18, 2014

PS: I wonder what quick load would say about my 150gr H4831 load?

SJB358 · Apr 21, 2014

baltz526":579wqfje said:
PS: I wonder what quick load would say about my 150gr H4831 load?

Seems very close to me?

Cartridge : .300 Win. Mag.(W)
Bullet : .308, 150, Nosler PART SP 16329
Useable Case Capaci: 86.642 grain H2O = 5.626 cm³
Cartridge O.A.L. L6: 3.340 inch = 84.84 mm
Barrel Length : 20.0 inch = 508.0 mm
Powder : Hodgdon H4831

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !

Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms

-10.0 93 72.00 2674 2381 40117 13300 87.1 1.182
-09.0 94 72.80 2707 2441 41466 13511 87.8 1.164
-08.0 95 73.60 2740 2501 42863 13719 88.5 1.145
-07.0 96 74.40 2773 2562 44311 13925 89.2 1.127
-06.0 97 75.20 2807 2624 45810 14128 89.8 1.109
-05.0 98 76.00 2840 2687 47363 14328 90.5 1.091
-04.0 99 76.80 2874 2751 48974 14525 91.1 1.074
-03.0 100 77.60 2908 2816 50643 14718 91.7 1.057
-02.0 101 78.40 2941 2882 52376 14908 92.3 1.040
-01.0 102 79.20 2975 2949 54172 15093 92.9 1.024 ! Near Maximum !
+00.0 103 80.00 3009 3017 56036 15275 93.4 1.008 ! Near Maximum !
+01.0 104 80.80 3044 3085 57969 15452 94.0 0.992 ! Near Maximum !
+02.0 105 81.60 3078 3155 59979 15624 94.5 0.976 ! Near Maximum !
+03.0 106 82.40 3112 3226 62062 15791 95.0 0.961 !DANGEROUS LOAD-DO NOT USE!
+04.0 107 83.20 3147 3298 64217 15953 95.4 0.945 !DANGEROUS LOAD-DO NOT USE!
+05.0 108 84.00 3181 3371 66447 16110 95.9 0.930 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 103 80.00 3184 3377 66995 15716 98.5 0.929 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 103 80.00 2794 2601 45810 14141 84.8 1.107