Home Forums Hunting & Shooting Ask The Gunwriters Horizontal impact between different grain bullets?

How typical is it for different grain bullets to impact differently in the horizontal plane? In several cases in my experience, well tuned loads with different bullets will have (small consistent groups) but 1.5" or more apart horizontally on the same day. Much less vertical dispersion was present. FWIW the rifles were a 30'06 shooting 180s vs 165s and a 6mm shooting 95s and 105s. There was little or no wind so that would not be responsible for the difference.

Thanks.

Very typical. The different weight bullets cause differing vibrations upon firing. Look at a barrel like a cantilevered beam. A flag flag pole is an example. Would hitting a flag pole other different weight hammer cause it to vibrate differently? That is an example

Not at all uncommon.

Different grain?

Rye? Barley? Wheat?

A lot depends on the rifle, including both barrel contour and bedding. Thinner-contour barrels often result in variations in point-if-impact of different bullet weights, especially if they're free-floated. But New Ultra Light Arms rifles tend to shoot a wide variety of bullet weights to very close to the same POI, even with lighter-contour barrels. Their very stiff synthetic stocks are bedded to contact the barrel evenly throughout the length of the forend. A good example is my NULA 24 .30-06, which puts 150 and 200 grain bullets about an inch apart at 100 yards--vertically, not horizontally.

Heavier barrels are also far more consistent with various bullet weights, even when free-floated.

My .260, with a Lilja sporter weight barrel, puts just about all loads at the same point horizontally, but 95 grainers print 1.5" higher than 130 grainers with my loads. My .223, with a fairly heavy factory varmint barrel, shoots 50 grain and 53 grain Vmaxes to the same spot vertically, but the 53 grainers are 1.25" to the right of the 50 grainers. The original factory barrel on the .260 put 95 grainers and 120 grainers (didn't use 130s then) within an inch of each other, vertically dispersed...but the 120s shot higher.

I just had one change with the same weight bullet. 30-06 M700 150TSX with IMR4320. 150TTSX with H4895 shot 3 inches right at 200 yds. This rifle shoots everything from 130's to 220's to same POI.

Standing by for corrections...................

The tip of a free-floated barrel oscillates in a figure-8 pattern, not just straight up and down; thus, you can have lateral shifts in POI, even with the same bullet weight.

I have experienced different POI with the same bullet but a different powder

I have a .30-06 and use two loads in it. One load is a 165 grain Hornady SP loaded to the max. The other is a Hornady 150 loaded in the middle range. The vertical difference is almost 5 inches. The main reason for the difference is the recoil. The 165 has much more recoil and thus higher POI.

That is perfectly reasonable even if the two powders have the bullet leaving the barrel at the same speed.

Perhaps I should have given more detail. The 6mm rifle is very accurate with both loads, consistently showing <0.5 inch groups with either load- but those groups are 1.5 inches apart horizontally with next to no vertical dispersion noted at 100 yards. The rifles barrel is a moderate sporter weight. I found it odd that the barrels apparent harmonics demonstrate such a large horizontal component relative to vertical.

Thanks

I have had that happen. Most recently my BigBore 94 shoots 200 grain bullets 10" higher and 5" more to the right than 255 grain bullets. I have also had horizontal and/or vertical shifts in bolt guns especially when free floated. Lately I have started to pick one load and bullet weight for a rifle so I have less to worry about

In my experience the individual rifle makes the biggest difference. Some of my rifles shoot a variety of bullet weights close enough. Others need to be re-zeroed for any minor change.

Temp-sensitive powders can make a big difference as well.

I got into temp-resistant powders after finding a VERY accurate load in one of my .270s shifted 3 inches to the right (and a little higher) at zero Fahrenheit compared to 70 degrees.

One 270 of mine, shoots the 130g Sierra btsp and the Speer 130g bts very, very well. Issue is that they have 6" different point of impacts.

I am shooting a Rem 700 in 223 that I have zeroed for 55 Grain Sierra HPBT using PP Varmint. 55 Grain Vmax with Varget has that same POI. 55 grain Sierra soft points with Varget have a POI 2.5" to the right and 2" high. All are accurate loads.

my buddy and I went to the range yesterday with his 30-06, a Ruger with laminated stock and factory muzzle brake. Anyway we were shooting in the rain at 200 yards. Fixed 6X Leupold .He bought a box of everything Big Ray's had. We started with 165 grain Ballistic tips . I could get 1.5" out of them. Then went to 180s. Couldn't find the hits at first. They were 9" lower. Switched to 180 Barnes. They were 8" lower than 165s. 200 grain trophy bonded were about the same. 220 round nose also.
Back to 165s Ave they were back to 8-9" higher than all the others.
Some horizontal displacement as well but only 1-2" in all. Never would have believed it had i not seen it