loads for semi-auto vs bolt action

jbmoose

May 01, 2009 22:17

I loaded some 223 rounds with IMR 3031 and IMR 4198 according to the Hornady book. They shot nice groups but didn't generate enough pressure to chamber the next round in my AR-15.[B)] I was told these powders burn too fast and should only be used for bolt-action rifles. A slower burning powder such as Varget or Win 748, I was told, work better for semi-auto's. My service rifle loads with IMR 4895 worked fine. I've also been told that some powders will work well in semi-auto carbines (16" barrels) but not rifles (20" barrels). Is this true? My 223 and 308 are both 20" barrels.

I haven't been able to find any load tables that distinguish between bolt-action loads and those for semi-auto.[:(] I need semi-auto loads for 223, 308 and 30-06. Are there any reliable sources for this? Trial and error seems an expensive and time consuming way to figure this out, especially with the limited availability of powder in my area. I don't want to buy powder, such as IMR 3031, that isn't going to meet my needs.

Any help would be appreciated. [:D] Thanks.

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  243winxb

  May 02, 2009 08:10

  Go to www.6mmbr.com and click on the 223 link. Click the Sierra blocks for both bolt or auto load data. IMR 4198 should work well with 55gr bullets in 223. You will find 308 info there also.

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  B17-P51

  May 03, 2009 09:45

  The newest Sierra book has load data for semi autos. Plus plenty of info on the reasoning and details for such. The idea is basically to duplicate military ballistics, as these rifles were designed as a military proposition originally. I shoot alot of Accurate brand 2230, 223 up to 308 caliber sized cases. I don't use it in the Garand, however.

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  sandwarrior

  May 04, 2009 16:47

  jbmoose,
  
  I was somehow under the impression I responded to this post. So, in fear of repeating myself I will venture on.
  
  The biggest difference between loading for a semi-auto and a bolt is for semi-autos you have to take the gas system into account. There is a range of powders and bullet combinations used that give the correct pressure at the port at the end of the barrel. The correct pressure is what gives the semi-auto viable velocity but still works the action correctly (enough pressure). Not slamming it back (too much pressure).
  
  You generally have to use a faster powder to keep from over-pressuring the port. Both IMR 3031 and 4198 are very good powders for the .223. You may need to clean your gas system or take a look at your charges to see if they are up to pressure to make your system work.
  
  -good luck

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