I purchased 8lbs of CFE 223 to load 223 ammo I looked at hodgdon a reloading data center and it said min. Load for 77 grain bullet is 22.5 with a velocity of 2627fps and max load was 24.3 with a velocity of 2811fps so I loaded ten rounds starting at the min and worked my way up to max loading in .5 increments. I'm shooting a larue obr 18" 1-7 twist so I went to the range and used the magneto speed v2 I shot 5 of each load and recorded data when I got home I checked the data that I had vrs the hodgdon data and this is what I got
22.5 grains avg. 2291
23.0 grains avg. 2364
23.5 grains avg. 2442
24 grains avg. 2515
24.3 grains avg. 2566
I don't understand the huge difference I'm using 77 grain nosler custom competition. And the accuracy wasn't good either I'm sure if I was getting the bullet moving fast the groups would tighten up. Any help would be greatly appreciated. I searched all over the web and this site but couldn't find anything.
Thanks
First of all, greater velocity does not automatically equal tighter groups. All that really does is allow it to maintain supersonic speed for a little greater distance, and also spend an exceedingly tiny, shorter time in flight where wind can influence it. There are several different ladder tests described on this site that all have the purpose of finding a node where the barrel is always pointing in the same direction as the bullet exits. Various forces cause the barrel to whip up and down, and in a circular pattern as you fire it. That means that to a very small degree, the barrel is literally pointing at a different point than you think it is, and that change happens many times in a small fraction of a second. For different bullet weights, powder charges, barrels, bedding, bullet bearing length, neck tension, and other variables, there are nodes where the barrel is moving less than other times. This helps with your consistency, then you just have to correct your zero.
I am shooting a LaRue 5.56 OBR w/20" barrel but a 1:8 twist. So far, I have found that it doesn't like 80gn SMKs or even 80gn JLK VLDs, but it loves 77gn SMKs. Currently I am running 25.0 gn of Varget. I am CDO about my loading. I skim necks, normalize primer pockets, anneal every firing, and sort my brass to .1gn On my bullets I trim meplats, repoint, and coat with HBN. I weigh my powder to a single kernel of Varget. I do several other things, but you get the picture. On my last load test, for a group of 10 I had an ES of 15 and an SD of under 5 through an Oehler 35P proof chronograph. I'm not a great shot, but a friend of my son has gotten 5 of 5 in a .72" group at 200 yd with this setup.
For reasons I do not completely understand, the velocity changes do not track linearly with powder changes. I ran groups of 10 at 23.5gn and .5gn increments to 25.5gn and got velocity changes of 77, 61, 44 and 47 starting at 2603fps. It's all part of the fun of our second hobby, reloading the stuff for our first hobby.
