I have been trying to develop a load with hornady’s 68 gr bthp with imr 8208 xbr. The more powder I added, the better it would group. However, the groups weren’t very impressive until I accidentally overloaded 5 rounds about a have a grain more than the maximum amount. Is it possible that if I used a powder that puts more speed on the bullet, such as cfe223, that it would group better than before? Or would the new powder change the harmonics of the rifle completely?
Faster 556 loads tighter groups?
- Thread starter Bj10
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My favorite load for .556 is 24.4 gr. of XBR8208 using a 69gr SMK. Get about 2820 on average out of a 16" M4. The word is to be careful with 8208 as it pressure spikes quickly. I just did some velocity testing with the Hornady 75gr bthp using CFE223 and TAC. TAC was faster. Results posed in another thread. Faster does not equals better groups.
So it should be fine to load past the maximum amount of powder for the weight of this bullet? I believe hornady’s manual said 22.8 and I loaded 23.5gr.
Depends on the gun, chamber, seating depth, outside temperature, etc. You have to test carefully in your own gun to make sure you can load over the published max loads. Don't ever take anyone's word their load will be safe in your gun.
Always work up and watch for signs but it’s pretty common most reloadera load over max to get best velocity and groups. It’s common for companies who produce reloading manuals to provide VERY conservative information. AGAIN, always work up from those safe numbers and if you venture past the max load just watch for signs.
Will the signs be pressure signs on the brass or is there oth signs to look for? Also I’m guessing I shouldn’t have to worry about wearing out the barrel too much because it is only 556?
Forget about barrel life. You will get about 4000 - 5000 rounds of sub MOA accuracy with any 223 or 5.56 no matter what your load is unless you have a chrome plated bore or your barrel has been nitride.
Give this a good read and then do it again.
https://www.primalrights.com/library/articles/understanding-pressure
Ditto here. 24.5gr of XBR and a 75gr ELDM's did the trick for me (LC brass and Rem 7.5's). I just haven't found a decent load with CFE223 and this bullet (consistent shotgun groups).
Hornaday and Hodgdon data is so conservative it's damned near useless (makes me wonder why they even publish the data, since it's so conservative that it literally pushes people to completely ignore the max charges...which is the whole point of published load data). You do burn/waste a fair amount of powder though, "discovering" their data is uber conservative.
Edit: A shout out of thanks to Scott Parks @ Vortex for the pointer.
Hornaday and Hodgdon data is so conservative it's damned near useless (makes me wonder why they even publish the data, since it's so conservative that it literally pushes people to completely ignore the max charges...which is the whole point of published load data). You do burn/waste a fair amount of powder though, "discovering" their data is uber conservative.
Edit: A shout out of thanks to Scott Parks @ Vortex for the pointer.
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