Hey guys! I'm struggling with an issue I hope I can enlist some help in solving. I am using Vihtavuori N140 as my gunpowder of choice for doing load development for use in an 18" 1in7" twist heavy-barreled AR15. I performed test shooting today. The 75gr Hornady HPBTs did great. Less than 1MOA, right on target, and I suspect that group size will shrink with practice. I'm fine there, I think I've got good data for that. The question is with 55gr Hornady FMJ with cannelure. Which I know won't perform as well as the 75gr due to my barrel twist rate, but it is cheaper and I'd like to have it as a bulk option (mostly so I can shoot it out of my other ARs that's built for CQC and not feel as bad about not using benchrest techniques, but still have it do reasonably well in my benchrest AR should I choose to use it then).
The main question: Why does the load data in Vihtavuori's guide for handloading 55gr fmj .223 list a higher maximum load than the maximum load for the same powder in Hornady's handloading manual (9th edition)?
https://www.vihtavuori.com/reloading-data/rifle-reloading/?cartridge=7
Vihtavuori's maximum load for 55gr fmj Hornady bullets is 26.8 grains of N140 powder. That is a bit higher than Hornady's maximum load of 25.7 grains of N140 powder for the same bullet. Why is that discrepancy present? I safely shot 25.9 grains of N140 powder today - ten shots, five shots each at 100 and 200 yards. Is it safe to load an AR15 (5.56 chamber) to the maximum load of 26.8 grains of N140 powder that Vihtavuori suggests? Is it wise to do so?
I ask because I wasn't entirely pleased with any of my 55gr groups today at either range, and I've actually achieved better results with Frontier Hornady .223rem 55gr HP Match ammo, which has a velocity of 3240fps on the box. I estimate the aforementioned 25.9gr load to be most likely just under 3200fps, but I don't have a velocimeter to check. My results were "okay" in some places, but I want my handloads to meet or exceed the performance characteristics of the Frontier, and I'm hoping that the higher velocities might give me more precise results where the loads below Hornady's maximum velocity didn't. One, maybe two loads came close, but not quite a match, and I'm tempted to try the hotter loads to see if those work better. I'm just worried that Vihtavuori's table is made with a bolt action rifle in mind rather than a semiauto, and I don't want to damage my AR as a result of personal ignorance.
Thanks!
The main question: Why does the load data in Vihtavuori's guide for handloading 55gr fmj .223 list a higher maximum load than the maximum load for the same powder in Hornady's handloading manual (9th edition)?
https://www.vihtavuori.com/reloading-data/rifle-reloading/?cartridge=7
Vihtavuori's maximum load for 55gr fmj Hornady bullets is 26.8 grains of N140 powder. That is a bit higher than Hornady's maximum load of 25.7 grains of N140 powder for the same bullet. Why is that discrepancy present? I safely shot 25.9 grains of N140 powder today - ten shots, five shots each at 100 and 200 yards. Is it safe to load an AR15 (5.56 chamber) to the maximum load of 26.8 grains of N140 powder that Vihtavuori suggests? Is it wise to do so?
I ask because I wasn't entirely pleased with any of my 55gr groups today at either range, and I've actually achieved better results with Frontier Hornady .223rem 55gr HP Match ammo, which has a velocity of 3240fps on the box. I estimate the aforementioned 25.9gr load to be most likely just under 3200fps, but I don't have a velocimeter to check. My results were "okay" in some places, but I want my handloads to meet or exceed the performance characteristics of the Frontier, and I'm hoping that the higher velocities might give me more precise results where the loads below Hornady's maximum velocity didn't. One, maybe two loads came close, but not quite a match, and I'm tempted to try the hotter loads to see if those work better. I'm just worried that Vihtavuori's table is made with a bolt action rifle in mind rather than a semiauto, and I don't want to damage my AR as a result of personal ignorance.
Thanks!
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