Windage Varience in diff .308 ammo

[Centurian22]

Ok, I'm relatively new to centerfire rifle shooting. I have a Savage Axis XP 20" barrel in .308 with the included Bushnell 3-9X40 scope. I have now shot five different ammo's through it: "HSM HPBT 168gr 7.62x51 (.308)", Federal Gold Medal Match sierra matchking 168gr HPBT, Winchester Super-X 180gr and 150gr, and one other cheap 147gr FMJ BT who's name eludes me at the moment.
Ok enough background, onto my question:

I would obviously expect elevation variances in the diff ammo's due to velocity, weight and other variables; however I have now experienced two Windage variations of 4" or more.

Starting with the HSM which I used to get on paper and sight in the rifle, the FGMM 168 was in the same spot, the Win Super-X 180 I couldn't get any consistent results from, the Win Super-x 150 POI was 4-5" left of the FGMM, then the cheap 147 FMJ BT was another 4-5" left from the super-x putting it 8-10" left of the FGMM! This was all shot from bench rest (no lead sled or anything like that) at 100yrds until the cheap stuff that I shot at 50 because I was having trouble with it (which turned out to be me because my wife produced a nice 1" group of 4 shots at 50yrds the second time she ever shot it (first was only two rounds just testing it out when I was sighting it in).

So what I'm asking and looking for here is this: is this much windage difference 'normal' or within reason between brands and weights of bullets? Or is it more likely user error such as inconsistent cheek weld or head alignment with the scope? I know that I need to just get out and put quite a few rounds of one type down range to work on and try to perfect my form (hold, cheek weld, trigger control ect). I will probably do this with the cheap stuff because it's alot easier on the wallet at $17 / box of 20 at my LGS compared to $26-$35 / box of 20 of the FGMM. Unless my wife got very lucky, the ammo seems good enough for initial practice until I get consistent and confident in my own abilities. Then I'll switch to my whitetail deer round of choice (possibly federal fusion 150 or win super-x 150) and get sighted and practiced for different shooting positions to be ready for the fall.

Thanks for any and all input, especially in regards to the Windage varience mystery!

Chad

 

[TonyAngel]

Centurian, it could be any or all of the above. Are you a proficient shooter? Were you shooting from a rest or sandbag with a good support for the rear of the rifle?

If you don't have much experience shooting a rifle for groups, your best bet might be to get someone that is more proficient.

 

[Centurian22]

I consider myself to be a moderately proficient overall shooter but as stated before just lack hands on centerfire rifle experience (shot plenty of BB and .22lr). I was shooting with a simple forend rest with the rifle against my shoulder and supported by my left hand under the stock.

Also I was just talking to someone who said its best to just pick on type of ammo one load and ONLY shoot that round out of that rifle for best accuracy and precision. I can see the advantage of this advice but find it hard to practically adhere to. I am hoping to use an inexpensive ammo to practice with first, a good hunting round as mentioned before as this is primarily my deer gun, and something known for consistancy such as the Federal GMM for precise paper punching and friendly competition. Am I 'asking too much' to be able to be consistent with three different rounds once I learn and record the zero's in relation to each other?

 

[Caliper_Mi]

First, check that the action is well bedded and action screws are tight.

However, with the wide variety in ammo that you are shooting, it is possible that barrel harmonics are causing the change in windage. The different loads likely result in the barrel vibrating differently as the bullet moves down the bore and the bullet exiting the muzzle at a different point in that vibration. Something in your rest setup may also respond differently to the differences in recoil between the rounds. The 4MOA you are seeing is only 0.067 degrees, so it doesn't take much...

 

[Haxby]

What size group can you shoot with the Winchester 150 grain loads?

 

[jmr40]

Make sure your scope is mounted so that the crosshairs are truly verticle. If not you may be canting the rifle.

 

[Centurian22]

My Best group was 1" with the FGMM 168gr @ 100yrds and slightly more than that (1.5-2") with the Win Super-X 150gr also at 100yrds.

As far as I can tell the cross hairs are vertical. I have only done a visual inspection of this but could double check it with a level and or plumb bob line.

 

[Haxby]

Maybe the point of impact was moving as the barrel warmed up.

Maybe cheap Remington or Federal 150 grain hunting ammo would shoot a little better than the Winchester in your rifle. 1.5" ain't bad.

 

[Centurian22]

Barrel warming wasn't a problem as each ammo was shot on a different day sorry for not clarifying that in the OP, but thanks for the idea!

As per my original posting, the groupings weren't my concern as much as the variation from one ammo to the next. If I put a large poster board 100 yards down range and shot each of the mentioned ammo's they would all group great (except the 180gr). But in very different places. Just curious if this is common.

 

[sniper762]

USING different weights of bullets will definately effect windage. heavier bullets buck the wind more than lighter ones even when they are of the same caliber.

 

[Haxby]

Some variation is not surprising. 4" or 8" is surprising.

Have you tried shooting the same ammo from the same box on different days, without changing anything (including cleaning) in between? If you find one hunting load that works every time out, you could stick with that one load.

 

[jmr40]

Some variation is not surprising. 4" or 8" is surprising.

That is what I'm thinking. I've seen an inch or so, but never this much. At 50 yards the wind hasn't had time to be a factor.

 

[Centurian22]

I am aware of the weight of bullet and velocity having an effect on the POI due to how much the wind affects it and how long the wind has to act on it but these were shot under similar little to no wind conditions, and with the exception of the 180 (which performed poorest) there was only an 18gr difference in the other rounds (168-150).

I have not tried same ammo same box different day no cleaning yet. Thanks for asking because that sounds like a good idea to try and narrow down some variables.

 

[goon]

Honestly, I'd call the shift in windage normal. I've been surprised to see different bullet weights hit at the same elevation but with a windage difference of three or so inches at 100 yards from centerfire rifles. It's possible that the different loads the OP is experimenting with have just introduced the extremes, especially if he's got enough windage in the scope to zero without problems.

I'd say you will probably have to experiment until you find a combination of a "serious" load and a fairly cheap practice load that hit close to the same POI. Or just shoot practice ammo for now and re-zero for hunting.

 

[sniper762]

was the 168 a hp match bullet? those have no lead in its nose and designed much longer for balance, therefore your barrel may not have a tight enough twist for the longer projo.

 

[chrome_austex]

Yeah, I've seen 2-2.5 MOA shifts in POI to the left and slightly down at 200y with some of my handloads on the same day/session. It can happen, if your're sideways at all in your stance, windage change are more likely as different makes of ammo will have slightly different recoil impulses and harmonics.

Usually, I attribute windage shifts in POI on different days to different prevalent wind and shooter position differences.

4" at 100y is a lot, but not out of the question, especially on different days. It takes a lot of practice to develop a shooter position that is consistent from day to day and session to session. Rifle cant (which I believe is more of an increasing issue beyond 100y) can be a major culprit, but also buttstock to shoulder position, shoulder angle to force, cheekweld, eye centering/parallax, even _lighting_ at the target can make a difference. Also consider that a wood stock can swell with humidity changes.

 

[USSR]

was the 168 a hp match bullet? those have no lead in its nose and designed much longer for balance, therefore your barrel may not have a tight enough twist for the longer projo.

Definitely not that. Any factory .308 barrel will be either a 1-12" twist (most common) or 1-10" twist, and either of those will work well with a 168gr HPBT bullet.

Don

 

[adelbridge]

Make sure your scope is mounted so that the crosshairs are truly verticle. If not you may be canting the rifle.

If you are shooting from different benches and your reticle isn't aligned 4" shift wouldnt surprise me.

I normally get about an .5-1" or so shift using different brands of the same weight. They all seat their bullets differently. They all have slightly different b/c's.

One range I go to doesnt let me go down range to change targets, they do it for you and judging group sizes from 100 yards away isnt exactly optimal. I am not sure what your range is like but it sounds like it is time to get scientific in your data gathering. bring a ruler, thermometer and wind gauge next time out.

 

[GJgo]

I shoot a lot of 308 & this doesn't suprise me at all. You have to re-zero for different ammo.

P.S. also try a box of FGMM 175 SMK, and see if it likes that or the 168s better. Then, just stick with that weight class & find the bullet it prefers.

 

[rehorne]

It's not really suprising. Different makers ammo will shoot to a different POI. There is to much difference in the loading process, different powders, charge weights, projectiles on so forth. Also the same makers ammo will vary from lot to lot. I always check my zero with lot changes. Even with my own match reloads.

 

[gamestalker]

I reload and have always experienced variations in both windage and elevation when going form one bullet weight to the next. When a particular rifle is zeroed with one bullet weight, and or, style you can expect to see a significant variation in POI when shooting a different bullet. Even if both bullets are producing the same MV, POI is often going to be quite different.

Recently I was printing some 1/2" groups at 200 yds. with 140 gr. BT's from a 7 mag.. After a good barrel cool down I printed a 5 shot group with some 110 gr. and they were printing about 3" to the right and about 4" high of center. I still got impressive grouping, just not any where near center. It's the nature of the beast and can be the result of multiple variables.

GS

 

[Centurian22]

First: thank you all for your opinions and tips on this topic. I'm so greatful to have such a huge and willing knowledge base to bounce these questions off of.

Sniper762: Yes, as stated in the OP the 168 was a federal gold medal match Sierra Matchking BTHP, my rifle has a 1 in 10" rifling which to my understanding should have no trouble stabalizing that round.

SIDE NOTE: should it be BTHP or HPBT? I've seen both but wish to use the proper way which I would think would be tip to tail and therefore HPBT.

Chrome: you confirm part of what I gathered, I need to practice my own consistancy before expecting more from my rifle lol. Also it's a synthetic stock with a free floated barrel.

Thanks for the reassurance that this is relatively normal or at least not too extreme. I'll try the FGMM 175's when I can but for now I think I'll stick to and play with the 147-168 range as those have given me the best performance and consistancy so far (compared to the 180's anyway), and are what some others with the same rifle seem to use as well. I don't foresee any need of the extra knock down power, especially not for the trade off of more expensive, harder to find, harder kicking, and poorer results from me and/or my gun.

GameStalker: sounds like some great shooting, also sounds alot like what I have going on with my factory rounds, so to hear that a similar thing is happening to reloads (typically much more consistent) is very reassuring and helpful.

Back to my follow up question about the advice I received on only shooting one type of round through the rifle: it sounds like from most people it's common practice to use different ammo and just re-zero and learn and adapt to the changes.

 

[goon]

Or you could learn to reload. I don't reload for precision but I don't thin I've ever shot a group from a rifle with my reloads that was over 2" and some were literally under an inch at 100 yards with open sights. Having three or four shot cloverleaf groups isn't uncommon.
And you shoot more for the same amount of money.
And you can tinker with your loads until you get what you want shooting where you want it to shoot.

 

[Centurian22]

I do want to start reloading it's just that a couple more firearms are higher priority than investing in everything to get started reloading.

 

[Centurian22]

I may have just found my 'perfect' ammo. At least what I hope will be perfect as long as my gun likes it as much as I do. Federal Power Shok .308 150gr 2820fps MV, and my local Wally world FINALLY got them back in stock and last I checked they were priced at about $16 per box. Far cheaper than I could find online. Same price I was paying for FMJ's. I'm crossing my fingers that they shoot well, I've done some research and they seem to be fine for whitetail sized game (with proper placement of course). After testing a box or two ill be buying out WM any chance I get until I have a 'good supply'.