Loading for a particular barrel length

[redbank]

I have load data for a 204 ruger. That data is based on a barrel that is 26". The gun I'm loading for is one of the ruger lightweigths with a 20" barrel. What should I do different. Is there any general rules that can help me. I should mention that I'm pretty green when it comes to reloading (if it ain't obvious).

Thanks,

 

[Varmint Hunter]

The first thing that you should do is verify the load with one or more of the current loading manuals. Never rely on load data that is given to you by " a guy at the range" or "taken off the internet".

Secondly, all handloads should be loaded at least 10% below the listed maximum loads found in the manuals. Once you have learned how to recognize the signs excess pressure than you can begin to load with succesively higher charges.

Handloading should only be done by persons who are knowledgeable in all the important little aspects of the hobby. If you are just starting out you should read, read, read. After that, it is a good idea to begin loading with the help of an experienced handloader. Once you get a good handle on handloading you'll probably be hooked for life. /ubbthreads/images/graemlins/grin.gif

To answer your question directly - Yes you "need" to start low and work up. Loads that are developed in one rifle may be dangerous in another. That is why you should always reduce your initial charge weight and load back up. You may also want to fine tune the load for peak accuracy in the other rifle.

You should also expect to see a drop in velocity of 150 ft/sec or so, due to the shorter barrel.

 

[redbank]

I have loaded for a little while, with quite positive results in my own estimation. But, I'm just not sure about certain items. Are there different burn rates of powders that are more advantageous to certain barrel lengths?

 

[abinok]

The only major differance you will have loading for the 20" is that you will have highest velocities using powders a step or two faster than the data published for the 26". For example... sorry... its not really directly applicable... if you found the books showed top velocities with H1000 with your given bullet, you should plan on using h4831, or H4350. The shorter the barrel, the faster the powder you should use for the given application. Obviously, there is a point of diminishing returns, but going from a 26" to a 20", ill bet 2 steps up the speed scale will be about right.
I loaded for a savage stryker, 16" (14"?) in 300WSM that with 200gr bullets, was getting good results from powders in the H414 speed class... certanly fast for the application, and certanly faster than what the books say will get top velocities in a rifle barrel.

 

[Ringman]

redbank,

I read a report by someone who did some testing in both hand gun and rifle. The fellow started with a long barrel and began to cut them off. He concluded that the highest velocity produced in the long barrel produce the highest velocity in the short barrel.

I like to test things so I would try maybe half a dozen powders.

 

[CPorter]

Like the other mentioned you will need to work up your own loads. That said, in general with a shorter barrel you will get lower velocities, I would guess maybe 125 fps with 6" less barrel, for the same load.

If you are a fan of the shockwave theory then the optimum barrel times change as well. 10 nodes are listed below for each barrel length.

26" 20"
0.88 0.68
0.97 0.75
1.11 0.86
1.19 0.92
1.33 1.03
1.41 1.10
1.55 1.20
1.64 1.27

To give you an idea what this means I have some data from Quickload below. Notice that the barrel time (ms column) changes from 1.31 to 1.133 as the charge goes up. According to the shock wave theory the more accurate load will be at 45.7 grains or 1.19ms barrel time. Quickload says a 20" barrel would be 240fps slower and in this case the same load would be at an accuracy node of 1.03ms



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

-6.6 90 42.7 3125 1518 38747 8763 95.1 1.31
-5.9 91 43.0 3147 1539 39591 8823 95.4 1.297
-5.3 91 43.3 3169 1561 40454 8881 95.7 1.284
-4.6 92 43.6 3191 1583 41336 8938 96.0 1.272
-3.9 93 43.9 3213 1605 42236 8993 96.3 1.259
-3.3 93 44.2 3235 1627 43156 9047 96.6 1.247
-2.6 94 44.5 3257 1649 44097 9099 96.9 1.235
-2 95 44.8 3279 1671 45057 9150 97.2 1.223
-1.3 95 45.1 3301 1693 46039 9198 97.4 1.212
-0.7 96 45.4 3323 1716 47042 9245 97.7 1.2
0 97 45.7 3344 1738 48067 9291 97.9 1.189
0.7 97 46.0 3366 1761 49115 9335 98.1 1.177
1.3 98 46.3 3388 1784 50186 9376 98.3 1.166
2 98 46.6 3409 1807 51280 9416 98.5 1.155
2.6 99 46.9 3431 1830 52398 9455 98.7 1.144
3.3 100 47.2 3452 1853 53542 9491 98.9 1.133