bullet weight and harmonics

[elginrunner]

Gun gurus,

I've found that my .308win likes the 168 grn bullets at 2500-2575 fps. I have a good selection of bullets for target shooting and hunting, so I never varied thinking, If it's not broke don't fix it.

Now I have a .223 rem,700 remington), and It does very well with 55 grain bullets keeping a 1/4' group at 100 yds. I'd like to try 40 and 50 grain bullets.

My question is your guns speed sensitive? Should I be seeking a specific velocity, or will the bullet weight/bearing surface affect the harmonics different for each weight/profile? I hope this post made sense..... : )

Brock in AR

 

[j_22250]

what powder/primer and bullet are you shooting? you need to speed that thing up for sure if your gonna hunt with it. i had mine dialed in at around 2650 and you could see the bullet in flight at night time a few more grains of varget and that problem was fixed and it still shot 1/4 moa. if your shooting magnum primers i would recomend you to switch to standard. your on the right track about matching harmonics and all as you say. you might have better luck with a lighter bullet,150) and faster velocities. most .308 usually like bullets in the 165-175 weight range. yours may however have a slower twist. do you know what the twist is in your rifle.

 

[BoydAllen]

You need to do a load workup for each bullet. If you load at the range, and shoot over a chronograph and wind flags, on a day when conditions are favorable, You can get a lot done in a short period of time. Start with a pressure series, one shot each, carefully shot, on the same target. After you find your top load, go back to a point where differences in powder did not seem to matter as much, load in the middle of that range, and play with seating depth. BTW I always do my pressure series with the bullet as far into the rifling as I would ever go, sort of a worst case situation for pressure. Most times, there is more to be gained from small changes in seating depth than with small changes in powder charge. Most of my loads have the bullets seated longer than 'touch'.

 

[elginrunner]

J 22250,

on the .308 I've loaded 3031, 4064, I4895, varget and TAC. The old savage likes em' all so long as the speed is the same on the 168's. I've harvested many, deer with that speed, but some bullet do perform better than others....,1 in 10' twist) Currently using the Amax for all round duty.


On the .223 it has a 1 in 12' twist. Since reading some good articles I've decided to move to the lighter bullets. Thats what got me to thinking about the harmonics.


Boyd,

I spent the morning loading 50 grain hornandy 2245's in 1/2 grain increments. Starting a 24 grains of TAC, to 26 grains. I'll use this as a starting point and look to see if my speed theory works out....Was going to the range today, but its raining, and I'll think I'll wait to a sunny day.

 

[BoydAllen]

One tip, I think that .5 grains steps are too large for a .223. I would use .3 max. Where were you on seating depth, and do you have anything between you and the target to keep track of what the wind is doing?

 

[j_22250]

how much do your groups open up with hotter loads? you should easily be able to get at least 2700fps with good accuracy out of your savage. one thing i've noticed with mine is that if it is not jst absouloutly clean it wont get those 1/4' groups. with a clean barrel it takes 2-3 shots before it starts same hole groups. after anywhere between 9-15 shots they start to open up. even though they're not in the same hole they are all still touching,so around 1/2'). that's what i've noticed and it could jst be me. either way no need to keep wasting ammo 1/2' groups are plenty good for hunting. i usually clean after 50 shots unless it's hunting season. if your content with your current load then jst keep shooting what you got. you're right, you jst have to keep experimenting till you achieve harmony. it's all about getting the right amount of spin at the right speed to get that bullet to fly jst right.