I am reloading for .223 I use H335 22.5 grains with a 69 grain sierra hpbt....my 3 shot group at 100 was good so that's what I use....I have never used a chronograph but another thread was telling about the necessity of one for accurate loads. I am shooting from a "custom" AR 15 with a 20" stainless varmint Hart barrel, 1:7 twist that was matched to my bolt. I ask because I am trying to get my dopes out to 600 yards and am slightly frustrated....not sure if my bullets are sporadic because I'm still new to the long range scoped rifle game or if my bullet is not the best for my particular rifle? One can go nuts trying to figure out what the issue might be! I am not sure if it's the powder or just that my rifle doesn't like the round or powder charge, etc.? The rounds are made on my hornady lock n load and I have had no issues with the rounds themselves as far as function, etc. How do I hammer out a way to fix this so I know it's me and not my bullet, powder, etc.? I liked the 69 grain projectile because it gives me a good overall weight and I can use it in my other 3 ar's without being too heavy for the ar with a 1:9 twist. If a Chrony is the way...can someone tell me how to use it and what I should be looking for? Or am i missing something else..?