Bimodal bullet pattern from Savage 110 HS 338 Lapua

Recently I bought a new 338 Lapua in the Savage 110 HS Precision stock. I mounted a EGW one piece mount with ARC 30mm rings and a SWFA SS HD 5-20X50mm scope. All the rings and base screws were carefully cleaned, locktited in place and torqued at the time of install. When I started shooting I noted a Bimodal distribution of the 3 shot load development groups I was shooting. Sometimes 1 should would start then the next one approx 1" high and then the 3rd would return to the same hole as the first shot. Other times it shoots 2 bullets in one hole then the 3rd 1" high. I have seen this over and over for a while now. I assumed it was either bedding or scope mounts so I took everything back apart and re installed the scope (the fine base screws were not quite as tight as I would have liked upon removal so perhaps the recoil had loosened them up some. Then I also bedded the entire action and floated the barrel. After all this was finished I was anxious to get back to the range with my hand loads. Starting with Retumbo and 300 grain Nosler and Berger bullets I started launching them and the very first group was right on POI. NExt shot in the same hole, third shot approx 1" high again. This repeated throughout the 6 three round groups.

I am still getting some .5"-.75" groups but a few are opening up to 1"-1.5" at 100 yards. I realize this is pretty good but with the rifle showing me it can do two bullets in the same hole, I want 3 in the same hole. other than swapping out the scope to a different rifle I dont know what else to try. I have loaded lots of different powers, bullets, cases, primers, seating depths etc etc.

Thoughts?

How long between shots? Could the barrel be warming up? Also might want to check the loads with a chrono. You might be having an issue there.

I wonder about a little bullet run out on some loads. The rifle seems very accurate, so I wonder about ammo issues.

Sounds like a load problem to me. Check case capacities for volume and weed out the odd balls. This has always helped shrink groups for me.

Something in your shooting technique? How much repositioning between shots?

Maybe you're just getting larger groups than any 2 shots show.
For sets of five 5 shot groups the largest/the smallest group in the sets will average 1.91. Means that on average, the largest group is 1.91 times as big as the smallest. Group size varies-a lot.
I don't have the ratio for 3 shot groups. Maybe I can do the arithmetic.
joe b.

I have thought about the barrel warming up but if it was stringing them vertically they would continue to grow taller right? Sometimes the third shot goes back to the first hole. Others it is the third shot that goes high. I feel sure it is not my shooting (dont we always think that). I shoot left handed and since this is a right handed gun I can cycle the bolt with my right hand and the left secures the rifle in the bags without moving it much.

I am hand weighing every charge of powder to within .1 grain but I do not check bullets or cases for weight. I have on occasion used the chronograph to see if that helped me but I am getting pretty good shot to shot data here too. Sometimes as low as 10 fps differences sometimes higher like 20-25 fps variation.

I am shooting one lot of 338 lapua brass and they are all measuring fine in terms of length. Most of them have not been shot more than 1-2 times now and I am neck sizing them.

Runout could be an issue I guess as I do not check for this, never have. I know that is a good next step for me on all the cartridges I load for. I also do not check cases for capacity. Do you use powder for this or water? Can someone point me toward a link with more info on concentricity and capacity?

I would try to take every shot like it's your first shot. Do the same routine before every shot and try waiting 2-3min in between. Competition shooting is all about consistency between shots. When shooting groups you need to think this way. Usually vertical stringing has to do with breathing.

I know I'm saying this without knowing your experience, but just trying to say apply all the fundamentals for every shot. If you are the least bit uncomfortable it will throw off that shot.

Another thought is that you mentioned you had a couple different brands of projectiles. Do you have them in separated from each other to ensure you aren't firing a nosler for 2 shots then a berger on the 3rd? If not separate and label everything, so that there is less thinking to do on the firing line.

I have not started reloading yet myself, but have shot for score in the Corps numerous times. The inconsistencies in everything you do leading to each shot beats a lot of good shooters.

Sent from my AT100 using Tapatalk 2

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Originally Posted by LoneWolf

I would try to take every shot like it's your first shot. Do the same routine before every shot and try waiting 2-3min in between. Competition shooting is all about consistency between shots. When shooting groups you need to think this way. Usually vertical stringing has to do with breathing.

I know I'm saying this without knowing your experience, but just trying to say apply all the fundamentals for every shot. If you are the least bit uncomfortable it will throw off that shot.

Another thought is that you mentioned you had a couple different brands of projectiles. Do you have them in separated from each other to ensure you aren't firing a nosler for 2 shots then a berger on the 3rd? If not separate and label everything, so that there is less thinking to do on the firing line.

I have not started reloading yet myself, but have shot for score in the Corps numerous times. The inconsistencies in everything you do leading to each shot beats a lot of good shooters.

Sent from my AT100 using Tapatalk 2

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+1 You shouldn't be mixing bullet types if you are trying to be that accurate. And I think you might also think about neck tension. You didn't say what brass you are using but even Lapua can be somewhat inconsistent. What I mean to say is you might want to measure and separate the cases by thickness. Unless of course you neck turn.

Will a boatail projectile with that much oomph even stabilize at 100? What happens at 1000. 338 federal for 10-300,

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Originally Posted by rotts4u

Recently I bought a new 338 Lapua in the Savage 110 HS Precision stock. I mounted a EGW one piece mount with ARC 30mm rings and a SWFA SS HD 5-20X50mm scope. All the rings and base screws were carefully cleaned, locktited in place and torqued at the time of install. When I started shooting I noted a Bimodal distribution of the 3 shot load development groups I was shooting. Sometimes 1 should would start then the next one approx 1" high and then the 3rd would return to the same hole as the first shot. Other times it shoots 2 bullets in one hole then the 3rd 1" high. I have seen this over and over for a while now. I assumed it was either bedding or scope mounts so I took everything back apart and re installed the scope (the fine base screws were not quite as tight as I would have liked upon removal so perhaps the recoil had loosened them up some. Then I also bedded the entire action and floated the barrel. After all this was finished I was anxious to get back to the range with my hand loads. Starting with Retumbo and 300 grain Nosler and Berger bullets I started launching them and the very first group was right on POI. NExt shot in the same hole, third shot approx 1" high again. This repeated throughout the 6 three round groups.

I am still getting some .5"-.75" groups but a few are opening up to 1"-1.5" at 100 yards. I realize this is pretty good but with the rifle showing me it can do two bullets in the same hole, I want 3 in the same hole. other than swapping out the scope to a different rifle I dont know what else to try. I have loaded lots of different powers, bullets, cases, primers, seating depths etc etc.

Thoughts?

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This is the kinda thing that can drive a reloader crazy. Looking for a .25-.50 5 shoot pattern "everytime" out.
This is something that "to me" is so subjective.
Thru the yrs Ive tried everything from changing aol/anneling cases/perfect bullet to case run out/same brass/new brass/neck sizing only and even sanding down the mandrel down by .001/triple cked trickle charge/crimp-no crimp/powders/bullets/primers/same temp/atmospher while reloading and shooting/no wind conditions etc-etc-etc......
Sorry for the rant................
IMO...The 1st thing I like to do when trying to achieve the holy grail after my R&D on load testing/chronographing is I,ll vise the rifle in order to take human element out of the equation. A rock solid bench/properly vised rifle. without a dought, there is no movement of the rifle/rig when the rd cuts loose. After that...I can start blaming everything and anything else.
Good luck on your quest. If you do find something that cured your wondering rds then let us know. Im always open for more insight
The road to consistant perfection or even semi perfection is full of pot holes for sure.
Good Luck...be safe

i would try shooting at 400 yds and see how it does there. that will give you a truer picture as to how it will do further out.
as for runout try seating the bullet partialy, then rotate the case about half a turn and finish seating.

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Originally Posted by LoneWolf

I would try to take every shot like it's your first shot. Do the same routine before every shot and try waiting 2-3min in between. Competition shooting is all about consistency between shots. When shooting groups you need to think this way. Usually vertical stringing has to do with breathing.

I know I'm saying this without knowing your experience, but just trying to say apply all the fundamentals for every shot. If you are the least bit uncomfortable it will throw off that shot.

Another thought is that you mentioned you had a couple different brands of projectiles. Do you have them in separated from each other to ensure you aren't firing a nosler for 2 shots then a berger on the 3rd? If not separate and label everything, so that there is less thinking to do on the firing line.

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Its not really vertical stringing because sometimes its the second shot that goes high then the third goes back low, other times it is the opposite.

And no there is no mixing of primer brands and case lot numbers much less projectiles. I lable everything and put the different loads in Mtm ammo boxes and even maintain notebooks on every handload I have shot dating back to the 80s so I feel pretty confident that there is no mixup in loading or anything simple.

In most of my other rifles I am able to get consistant .5" 3 shot groups and a Savage 223 FLCPK often does better than that so I also feel pretty confident that its not me pulling the shots etc. The 110 HS is a big heavy rifle with a nice wide forearm that nestles very nicely in the sandbag rear and sand bag on a rest up front.

yep..... .224 imo often do give great small and tight patterns after some R&D.
Personally...I cant speak for the 338...but Ive found that in 308, it help,d to slow down the rd. On the flip side Ive read where other shooters are the opposite.
That rifle you have is my dream rifle. Love,d to have one so I could be in the same shoes as you right now...tweak here and a tweak there with a little more $$$ here and there.
Curious.....what powders have you tried?

these type cartridges are designed to perform well at longer ranges. most serious long range hunters and target shooters
are concerned more about performance at 4 or 5 hundred yds than they are at 100. some guns do well at all distances and
some dont. 100 yds with these type guns is for initial load work up and checking sight zero.

As others have said, stretch it out and see. I have a .308 that actually tightens up all the way to 300 yards. Barrel harmonics can even play a role in this. I would try and get the loads a little closer than 25 fps deviation also. You might look at neck tension.

Ive been shooting from 100 out to 1K @ 100yd intervals with great results. My train of thought for shooting accuratly out to distance is....nice and tight at 100 equals nice and tighter flight out to distance.....

anything less then a 5 shot "group"... isnt a "group"...

You have chosen 3 shot groups for load development.There is nothing statistical that argues for or against using 2 or 3 or 5 or 10 shot groups to measure accuracy, where accuracy = average group size.
With any number of shots per group, there will be variation in group size from group to group. Some groups will be larger than others. The ratio of largest/smallest groups in a set will increase as the number of groups in the set increases. More groups gives wider variation.
Your groups vary from .5-.75 to 1-1.5, inches. This is to be expected. Happens with all guns and shooters-with the variation different from gun to shooter.
You may be trying to solve a problem that doesn't exist, trying to eliminate variation in shot location that is inherent in the process. Nobody shoots one hole groups all the time.
For example, at the IBS 100-200 yard Nationals in 2012, Sporter, 5 shot 100 yard 5 group match, 1st shooter smallest = .113, largest = .195; 2nd shooter smallest = .098, largest = .220--all inches. That's variation.
Getting AVERAGE group size down is hard enough, getting VARIATION down is much harder/impossible.
If you record all group sizes and post them here, maybe I can be more definite.
joe b.

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Originally Posted by joeb33050

You have chosen 3 shot groups for load development.There is nothing statistical that argues for or against using 2 or 3 or 5 or 10 shot groups to measure accuracy, where accuracy = average group size.
With any number of shots per group, there will be variation in group size from group to group. Some groups will be larger than others. The ratio of largest/smallest groups in a set will increase as the number of groups in the set increases. More groups gives wider variation.
Your groups vary from .5-.75 to 1-1.5, inches. This is to be expected. Happens with all guns and shooters-with the variation different from gun to shooter.
You may be trying to solve a problem that doesn't exist, trying to eliminate variation in shot location that is inherent in the process. Nobody shoots one hole groups all the time.
For example, at the IBS 100-200 yard Nationals in 2012, Sporter, 5 shot 100 yard 5 group match, 1st shooter smallest = .113, largest = .195; 2nd shooter smallest = .098, largest = .220--all inches. That's variation.
Getting AVERAGE group size down is hard enough, getting VARIATION down is much harder/impossible.
If you record all group sizes and post them here, maybe I can be more definite.
joe b.

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+1....well said joe

Average, largest group/smallest group
with 5, 5 shot groups, the largest will average 1.91 times the size of the smallest
number 2 3 4 5 6 7 8 9 10
of groups shot shot shot shot shot shot shot shot shot
shot groups groups groups groups groups groups groups groups groups
2 1.84 1.53 1.42 1.36 1.32 1.30 1.28 1.26 1.25
3 2.59 1.92 1.70 1.59 1.52 1.48 1.44 1.42 1.39
4 3.33 2.24 1.92 1.77 1.68 1.61 1.57 1.53 1.50
5 4.10 2.52 2.11 1.91 1.80 1.72 1.66 1.62 1.58
6 4.93 2.77 2.27 2.04 1.90 1.81 1.75 1.69 1.65
7 5.82 3.01 2.42 2.15 1.99 1.89 1.82 1.76 1.71
8 6.82 3.24 2.55 2.25 2.07 1.96 1.88 1.81 1.77
9 7.94 3.45 2.67 2.34 2.15 2.02 1.93 1.87 1.81
10 9.23 3.66 2.79 2.42 2.21 2.08 1.98 1.91 1.85

In general accuracy refers to the ability to "hit what you are aiming at " (bullseye when shooting), and precision refers to the uniformity of the result (group size when shooting). Depending on what you are doing (shooting, or producing a product or service) one of these parameters can be more important than the other. In any case as Joe says the more you do and observe the result, the more variable it will appear to be. As a result it can be difficult to determine if the answer you get this time is really different than last time (eg this group vs last group). As a matter of interest shoot 20 shots at a target and then "randomly" pick any 2,3, or 5 (meaning how many you may shoot for a group size) and you may be surprised to see this is what to expect for group-to-group differences in a perfect world. Or shoot 7 3-shot groups at one time and see how much the point of impact changes between groups, esp at greater distances. All this makes it tough for a shooter to determine whether he is making improvements or not for load development, rifle work, etc. Usually after a little load development I continue to find out the weak link is me as a shooter, so I have focused more on technique than anything else (esp with a Savage).

What makes this bullet distribution interesting to me is that on all my other rifles that I have shot dating back to the late 80s, there is usually a different pattern (random) bullet distribution. Meaning sometimes the second or third shot is high, left, right, low etc etc. In the case of this particular rifle it is almost always the same. Two shots in a three shot group basically in one hole, then one of the 3 shots will be approx. 1" high.I almost never get holes to the right or left or low of the first shot.

the rifle seems to be capable of delivering 2 shots in a very small one ragged hole, then there is always this 1" high shot then it returns back again to the same hole. Its not just the size of the group that is interesting but the propensity to repeat this same pattern group after group as if something is moving between two spots. I have heard others talk about scope mounts, rings etc etc causing this but as mentioned earlier I checked all of that.

The only thing I have not done is swap the scope for another 30mm tube scope and see if it does the same thing. Most of my scopes are 34mm but I do have a Nightforce 5-22x56 on another rifle I could pull and see if that has any affect or not but that seems remote to assume the scope internals are moving due to the heavy 338 lapua recoil

I'd suspect the scope, although I was having the 2 in one hole and flier just like you with a .308 rifle. I ended up switching powder and re-testing seating depths.

You might just want to shoot a 20 shot group over 30 minutes time, and if the group is no bigger than an inch I would be very happy.

I have continued to have this bimodal bullet distribution and yesterday after shooting I noticed something as I was cleaning the rifle and I am wondering if this could cause any issues. Where the bolt handle attaches to the bolt on this rifle it attaches via a center allen head screw that holds the bolt handle through its center to the bolt. Mine was loose and it allowed the bolt handle to wiggle around some. Could this loose bolt handle have been effecting how the bolt holds a round in the chamber? I would have thought the locking lugs up front would determine that but I am still scratching my head to figure this out. Since this original posting I have had 2 different scopes on the rifle too and none of that changed anything and of course I checked the mount each time as well.

I have a 300 win mag that does the same thing. Usually shot number 1 and 3 are touching and shot number 2 is 3/4" high. I don't remember where but I read that this can be caused by a bad factory recoil lug. I pulled it apart and am waiting on a new one.

Group of five I always have one flyer high and right... Always...

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Originally Posted by Gatr

I have a 300 win mag that does the same thing. Usually shot number 1 and 3 are touching and shot number 2 is 3/4" high. I don't remember where but I read that this can be caused by a bad factory recoil lug. I pulled it apart and am waiting on a new one.

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I had my recoil lug replaced with a ground flat one during the re-barrel also I bedded the rifle into the stock anyway so that should have taken care of any lug issues right?

The loose bolt handle could be a possible problem,easy to fix. Hornady makes a nice concentricity for about a hundred bucks,not sure if that cartridge will fit in it though. I got one for xmas last year and check all my loads with it.