I have been shooting Hornady 150gr.sp bullets in my 308 with iron sights and getting good groups at 75yards.I ran into some 180gr.rn sierras and thought i would load some up and see how she liked them.All my 180gr. rounds hit at least 4inches to the left.Is this common for a different weight bullet to shoot wide like that?
i had time to double check the little rifle today and she was still nailing the target perfect with the 150grainers......I guess this tells me my rifle likes the 150s better than the sierra 180s with irons?I cant move/drift my rearsight enough to play withthe 180s.I had thought that the heavier bullet would hit up or down not sideways.........Could another brand of 180gr. hit to my point of aim or not likely?,whats your thoughts and experiances with the lite & heavy bullets in your Favorite caliber Pet rifles
The 180gr.bullet in a 308 really makes it a thumper.....Iwould love to have a 358!

its a rare thing for a rifle to shoot different loads to the same point. what you are experience is normal

I don't think this is normal. I would think that the groups would open up for some loads and tighten up for others. But not shot 4 inches off at only 75 yards. I have tested many loads with a pistol at 50 yards and they al impact the same place, some bigger and some smaller but the center is always about the same some low groups or high depending on extreme velocity change. In fact I don't know what would cause a load to group left that much except a bad bullet. Jim

No, Jim, that's commonplace. The bullets are leaving at a different point in the barrel's vibration.

A bad bunch of bullets could cause a large group, but not a shift in impact point.

Rifle barrels move quite a bit while bullets are traveling down them. Part of the movement is what pistol shooters are (or should be) well aware of, the gun's movement due to recoil while the bullet's still in the barrel. As with a pistol, that motion is different depending on how the gun's supported, so it'll shoot to different points of impact shooting off a bench or shooting offhand, or on the bench it'll be different depending on whether the shoulder's snugly against the butt or not, and different shooters will seldom shoot to exactly the same point of impact. The other big part of the movement is more apparent in rifles with long, slender barrels than it is in shorter barrelled pistols. The barrel vibrates when the cartridge is fired, and the muzzle whips around in an oscillatory pattern. If you can get bullets to consistently exit while the muzzle's at a point in its vibration where it's reversing its motion, moving little, groups will tend to be small and consistent. If they exit at a point where the muzzle is moving rapidly in the middle of a swing, impacts will be all over the place.

If one load tends to exit while the muzzle's swing to one side, and another load exits while it's swung to the other side, the point of impact will shift quite a bit.

Any time you change any component expect different results.

The worst i ever saw was back when winchester came out with the control feed again,i think it was around 1990?,i bought a supergrade 30-06.Everytime i tried to shoot the black box winchester supreme silvertips that barrel would throw those bullets all over the place at 100yards.I could shoot the federal premiums and the hornady interloks and get little tiny groups....Never tried win supreme after that again in 06.
I also found out sometimes if i have a too lite grip the recoil would jump up and i would shoot high everytime!
Iam in the process of testing different loads on this 308 and the hornadys are giving me excellent groups i think i will say with them... Will match grade brass help get the most accuracy out of the little rifle?Thanks for the help!

I have experienced different weight bullets shooting as much as 8 inches high/low, and usually with a difference L/R also. I have also had some that shoot almost to the same POI. Just goes to show that you can't really predict the results, just make changes according to them.

Hey Ricochet, Good to see you back.
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Hey BBH, Ricochet described the situation well - harmonics.

If you think of the Muzzel moving in an elongated Figure " 8 " which can be leaning to the right or the left, you will get an idea of what is going on at that end. As Ricochet said, the trick is to get the Bullet leaving the barrel at either one end of the " 8 " or the other.

Now, with the 150gr-ers the " 8 " may be leaning to the right and you are sighted in for them. Then with the 180gr-ers, the " 8 " may be skewed to the left.

If you change the Load or change the Powder, you might(or might not) get the 180gr-ers to Impact closer to the 150gr-ers. Just deoends on the harmonics.
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quote:

Will match grade brass help get the most accuracy out of the little rifle?

Maybe. Depends on how closely alike your current Cases are. I do a full Case Prep and Weight Sort mine before I get the first shot through a new rifle just so that is never a question in my mind.

It builds confidence in my Final Loads and to me that is worth it. And since it is "my time" to use as I see fit, I do it.

Even changing powder can cause this to happen. My .338x74 shoots 2" high & to the left when I load H4831sc vs my std. load of RL19.

Yes expect a point of impact change with just about any change of weight or brand or point style of the bullet.
I have a 30/06 that when sighted in shooting its favorite load of 56 grains of IMR-4350 and a 180 grain bullet in WW brass will shoot about 3" higher and 2" left with only changing the brass to Remington and no other change to the load.

I don't intend for this to sound smart, but I have had (and still own one...) two different Remington Model 700s in .270 that would/will shoot 100-grain, 130-grain and 150-grain bullets all to the same POI at 100 yards.

I have to wonder how "rare" that really is.

D, there are the rare ones that will do this. My .260ai is such a rig, but when we say same poi, I'm talking within 1/2moa. Some rifles/bbls. are just picky. That's one reason I handload.

[QUOTE]Originally posted by Steel Slinger:
I have experienced different weight bullets shooting as much as 8 inches high/low, and usually with a difference L/R also.

I second it. roger

Hey BBH, Forgot to mention it is really simple today to have two Loads sighted-in for the same rifle. Most Scopes have the ability to "Zero" the Horizontal and Vertical Dials. If not, you can still do this process anyhow.

You just select the Load you intend to use the most for your Hunting and Zero the Dials for it, if your Scope will do that. Then note those Dial positions on the Load Box, whether or not you can Zero the Dials.

If the secondary needs some Scope adjustment, get it sighted in and record on its box the Dial Settings for it.

When you switch back and forth between Loads, I can recommend going 1-2 clicks past the Setting you are going to, and then back up those same 1-2 clicks.

The 270 and (I think) the .375H&H were both highly touted for their ability to shoot different bullet weights to the same point.

My .338WMag does this quite nicely. Most of my loads will stay centered with differences in impact height between 200-275gr. Now the 200gr loads I have to run noticably under max or the POI shifts higher and to the right and groups open up noticable with each grain increase in powder. Doesn't matter as the "slow" 200gr. will still nail a varmint size critter at 300yrd.