30.06 - Accubond Load Issues

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RogueMontanan

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I have been trying to work up a Nosler Accubond load for my Model 70, 30.06. I have shot three ladders at this point and on all three ladders my POI is consistently between 1.5-1.75 inches left of POA.

My concern stems from the fact that my Nosler Partition group is dead center on the POA and slightly sub-MOA (0.90). I was hoping to work up a Nosler Accubond round that shot with the same center/zero with the better BC and tighter group.

I do not want to change the zero of the rifle, and would like to be able to shoot both rounds out of the rifle.

My COAL is 3.320", Barrel Twist is 1:10, and shooting at 100 Yards (rifle zero'd for 200 yards).

Any suggestions or explanation why the Polymer bullets are drifting left? I had chalked it up to barrel harmonics, but I tried to control for that by running the ladders at .5 and then .1 Grains each.
 
Welcome to the forum.

When the difference is left, usually it means you are a right-handed shooter and the recoil has increased or your position has shifted. For example, when I move from standing offhand or sitting position to prone, I always have to dial in about one moa of right windage. This is because, in prone, the butt of the rifle slips to the right on my shoulder, so the muzzle is pointed left, whereas it doesn't do as much of that when I am in either of the other two positions. Since slipping to the right starts before the bullet clears the muzzle, it changes the point of impact to the left.

That said, any degree of contact between the rifle barrel and stock can also cause such symptoms. Also, if you dialed in your zero with a stiff wind blowing from the left, the lower BC of the Partition will mean the wind moves it further to the right than the Nosler does (assuming similar muzzle velocities).

The way to tell if it is the gun or your body position that is the issue is to wait for a day with no wind and shoot using your weak side. If the problem goes away or changes direction to the other side, you will know it is your body that is raising the issue and you'll just have to remember to dial the windage difference in. It's no big deal. Use some paper white-out to mark the two zeros on the knob for quick adjustment. But if the difference remains the same, the gun and its stock bedding and barrel clearance probably need attention.
 
That is great information. I didn't realize that my shooting position had that large of an effect on the POI. Something I will definitely consider in the future. Most of my shots on animals have occurred either from off hand (using a tree as a rest), kneeling, or sitting. Very rarely do I shoot prone because I have found that it is a very unlikely position to be shooting from when hunting in my area.

I am curious though, wouldn't I see that same position or rifle bedding effect/difference with the Partition Bullets as the Accubonds? During the same session, shooting from the same bench position, the Partitions POI is Centered on POA (1.5-1.7" high) and the Accubond POI is 1.5-1.75" left of POA and 1.5-1.7" high).

I just disassembled the rifle and looked for any indications of wear or rubbing between the barrel and the stock but did not discover any. I have another ladder loaded up and am going to head to the range to see if I just haven't found the "sweet spot" yet.

I am starting to wonder if I may need to step up the grains of the Accubond to 165 gr. to see if it is a stability issue? The rifle is a 1955 Model 70 so from I can find it has a 1:10 twist rate but given the age it might be having trouble stabilizing the 150 gr. Accubond.
 
"...shot three ladders..." The ladder test doesn't tell you anything about the accuracy of a particular load. Only tells you where the POI is in relation to other loads.
However, the construction of a bullet doesn't matter for accuracy. It's the weight that matters. Are the two bullets the same weight? That alone will change the POI.
What's the load? Any new load needs to be sighted in. The chances of 2 loads impacting in exactly the same place are decidedly slim.
Your shooting position only matters if you're not shooting off a solid rest. If you've moved or recoil is causing it, the POI will not be consistent.
The only part of an Accubond that's a polymer is the point insert. The point doesn't matter for accuracy anyway.
 
I wouldn't worry a lot about the stabilization of the 150 AB. If you were shooting a Woodleigh 240gr PP bullet, then maybe.

As far as stock contacting the barrel, it prolly ain't something that you would be able to see. The best way is to take something like a business card (thicker that a piece of paper) and try to slide it down the barrel channel with the rifle assembled and properly torqued to the stock.

BUT, since it is an old M70 Winchester, I would not expect to have any contact.

The Accubond and the Partition are different bullets. I would expect that they would not shoot to the same POI.

Train yourself to adjust the optics to compensate for the difference. It isn't hard at all with a good optic. Now, if you have one of those old scopes on it that make you have to tap on the thing when adjusting, that's another story.

What powder are you using?
 
UncleNick gave some very insightful information and really have nothing else to add other than this. My only caliber I use for hunting has always been a 30-06 for more than 50 years. With the manufacture of new bullets to give them a better BC I found out that even though they may weigh the same, the shape of the bullet may cause different pressure levels because of bearing surface lengths. I used to only shoot Remington cor=lokt but than decided to use other bullets such as hornady, Speer and Berger, and they all shot different and I had to adjust as each had a different poi from my poa.
 
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In my experience switching loads can indeed change point of impact on the horizontal plane, not just vertical, and vertical and horizontal changes at 100 yards (most commonly used distance for sighting and grouping) are almost always more than what could be attributed to wind drift, bc, or velocity changes. I think it’s almost entirely to do with harmonics and specifically what some call “barrel whip”. Truly free floated barrels are orders of magnitude less sensitive to this. Heavier barrels are less sensitive than slender barrels. My 270 is truly free floating (and ugly - it’s an old savage 110 package rifle, the plastic stock was actually touching the barrel to begin with. I fixed it with a utility knife. It doesn’t really group any tighter now but I can feed it just about anything and it spits out real word 1.5-2 Moa groups from real world hunting shot positions with boring predictability. It’s never printed a one hole group. It’s never had a problem with any projectile or powder combo I’ve fed it. For what I use it for, it’s perfect, not fussy. I used to own a .300 win mag weatherby vanguard, still do own a savage 99 .243 and a Winchester 88 .308. None of these guns had free floating barrels. All were/are capable of about the same accuracy as my .270 BUT you had to figure out what they liked. Either they loved the load or hated it. The .300 and .243 have actually given me cloverleafs on occasion (so much for rear locking lever actions being incapable of bolt gun accuracy), but the .270 shoots acceptable groups with literally everything I’ve tried and all within a few inches of each other even out to 200. Once I had two different .243 loads that were both very good grouping loads but at 100 yards one load was hitting 8 inches higher and 5 inches left of the other. Sometimes you just simply can’t have it both ways and thus the “one load for everything” approach.
 
RogueMontanan said:
I have been trying to work up a Nosler Accubond load for my Model 70, 30.06. I have shot three ladders at this point and on all three ladders my POI is consistently between 1.5-1.75 inches left of POA.

My concern stems from the fact that my Nosler Partition group is dead center on the POA and slightly sub-MOA (0.90). I was hoping to work up a Nosler Accubond round that shot with the same center/zero with the better BC and tighter group.

I do not want to change the zero of the rifle, and would like to be able to shoot both rounds out of the rifle.

My COAL is 3.320", Barrel Twist is 1:10, and shooting at 100 Yards (rifle zero'd for 200 yards).

Any suggestions or explanation why the Polymer bullets are drifting left? I had chalked it up to barrel harmonics, but I tried to control for that by running the ladders at .5 and then .1 Grains each.
Click to expand...
This is my load I use in a Sako Finnbear in 30-06. Consistently a clover leaf pattern at 100 yards.

IMR 4350 – 53.0 gr – 3.340 COAL – Nosler Accu-bond 165 gr
 
A 10 twist should be fine for any common 30-06 bullet weights from 150-220 gr. You might have some issues with 125's, but 150's should be fine, and I don't think you'll find a bullet too long that will work in 30-06 that will be a problem.

Every rifle is unique. My 1999 production model 70 shoots 165 gr Accubonds better than any other load. I'm using a near max load of H4350. It doesn't shoot 165 gr Ballistic tips nearly as well. And I've not yet found a 180 gr load this rifle likes. Go figure!

Some rifles will shoot many different loads, even different bullet weights, close enough to the same POI at 100 yards that you don't need to change the zero. Others won't. Once again, every rifle is different.
 
Yeah unfortunately you may not get the same POI with different bullets.

Why do you need to have both? They are similar in performance... I say pick one.

Are the Partitions and Accubond you are testing the same weight?

Also, you will probably have a more meaningful ladder test at 300 yards than at 100 yards.
 
As mention 2 different bullets. One of my 30-06, I hunt with 180gr Partition. I have shot Nosler 180gr AB/180gr BT, I use same powder for all three (H-4350) but different amt powder for the 180gr Partition and AB/BT shoot same POI. The BT is about .020" shorter than AB, both have same BC/SD.

I haven't tried it with any other Nosler bullets and I do shot few AB in some of my hunting rifles.
 
I watched my #2 son put 10 165 grn Sierra Gamekings Hollow points into a group you can cover with a dime this Saturday, testing and zeroing for deer season.
Rifle is a Savage 111, bone stock.
Scope is a Burris C4
The load is 47 grns of IMR 4064, and the coal is book I believe.
Surprised me, I loaded that ammo for a 1903 I sold to a fella two years ago.
It shot 2" low and 2" right. Had to stop him before he ran out.. and he used two more rounds for a 2" high zero.
 
I am using IMR 4350, and my optics are vintage. 4x Leupold Pioneer on Leupold base/rings. Have to adjust the POA by adjusting the Base/Rings. Considering the rifle has been sighted in since 1956 when my grandfather originally locktited the base/rings in place I am REALLY trying not to touch it. I realize that this is the easiest fix when I find a load that solidly groups.

The Partition SP 150gr has shot well over the years (consistently in the .75 MOA group range), but I was hoping to load an 150 gr accubond that shot a little faster and flatter with the higher BC for less wind drift. The area I hunt is notorious for gusty winds.

That said I think I misspoke when describing my ladder test. I will describe my process below:

My initial Test: I shot 5 loads of 3 rds each at 100 yards. The loads where 0.5 gr difference from 56.2 Gr up to 58.2 gr IMR 4350. I zero'd in on the tightest groups 56.7 gr IMR4350 (0.69MOA) (but 1.68" Left and 1.68" High) the 1.68" high is nearly perfect as the rifle is zero'd at 200yards.

Second Ladder: I shot 5 loads of 3 rds each at 100 yards. The loads were 0.1 gr difference centered around 56.7 gr IMR4350. This time I found that ALL groups were between 1.6 and 2" left of center.

Third Ladder: I shot 5 loads of 3 rds each at 100 yards. The loads were again 0.1gr difference centered around the 57.2 gr load (2nd best initial group, but closer to center/elevation. This time I found that 57.3 gr IMR4350 had the best group center around the desired POI at 0.13" Left and 2.21" High. (A little high but my next test should help fix this, I hope).

Fourth Test: I am now adjusting my seating depth to decrease the jump distance to my lands. Because it is an older rifle I have extended my seat to max saami (3.340" on the 3 "base" cartridge), seated three at 3.360", and am going to use a OACL guage tonight to make sure that my old school measurement (smoking the bullet in an unprimed case and progressively seating it until there was no contact) was correct. I have 3 seated at 3.390" OACL (tip to base) for the 150 Gr Accubond is what I came up with for max OACL. I have decided to verify before pulling the trigger with the hornady OACL guage system because 0.050 seems little much even for a rifle of this age. I am hoping that the tighter seating tolerance will help bring the group solidly into MOA/sub-MOA range and bring the POI into the 1.6" to 1.8" high range (maintaining the 200 yard zero).

I know this is a LOT of work to avoid adjusting the scope POA, but I guess I have to admit to some sentimental attachment to keeping the rifle "As-Is" from when my grandfather set it up.

Finally, I feel that the max hunting range for this rifle/setup is solidly around 600 yards. If I need to shoot farther than that I know I need to build a different rifle with modern optics. It is on my "To-Do" list. And before I get a bunch of criticism, I took a 5x5 Bull with the Nosler Partition at 558 yards last year. Dropped in it's tracks. After reflecting on that event and thinking about everything that could have gone way wrong (strelok is great for playing games like "what if the wind had gusted as I shot"). I decided I really needed to try to develop a solid BT round with higher BC that was less susceptible to wind drift and drag/speed bleed, or I needed to re-evaluate and limit myself to 400 yard shots.
 
Contrary to Mr. O'Heir, a ladder test is NOT to show you POI shift.
A ladder test is a powder charge test.
I don't care where on the target my groups are landing. I'm just looking for the 3 closest vertical shots to tell me optimum powder charge.

After ladder test i do seating depth test for group size.

Then i adjust scope for that load.
 
Well, Mr. O'Heir is correct that the old Audette ladder is aimed only at vertical POI shift from consecutive shots, the idea is that if you select three or four consecutively incremented loads where the POI shift from one to the next was negligible. the center load of that range will all tend to hit the same vertical POI. The limitation is that doesn't preclude horizontal stringing. You can, however, measure a change in horizontal POI separately and see if you get a flat spot in that which overlaps the vertical flat spot. That, by definition, would be shooting tight groups.

The idea that bullet design does not matter to accuracy is a theoretical but not a practical idea. Match bullets are designed with thin jackets because those are easier to make with uniform wall thickness. The high BC match bullet shapes will fight wind deflection better than low BC shapes, helping precision. So there is some design difference when trying to make bullets capable of the highest precision.

The idea your shooting position doesn't matter with a solid rest would greatly surprise benchrest competitors who go to a great deal of trouble to figure out how to shoot the gun without disturbing its point of aim or making it recoil any differently from one shot to the next. They play with sheets of slippery plastic tape on their front rests to try to let recoil be as free as they can while it jumps to their shoulder. They have stops on their front bags to make sure the exact same amount of the stock is on the rest every time. I've also seen sporting guns that shoot much more poorly off the bench than they do in prone. That's usually due to barrel contact with the stock. I've beaten the bench with the prone position more than once using a rifle because with a tight leather sling with a good deal of tension on it. The configuration was simply better able to constrain the gun's movement.
 
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