Accuracy troubleshooting suggestions?

Good Day,

Kimber Montana .308, 18” w/DPT suppressor shooting Hornady SST 165 gr., 2700 fps, 200m zero (per sight in at 100m range at 2.8 inches high).

Was shooting at a target recently and was about 19 inches low at 350m, decent 5 inch group (shooting off of crossed tramping poles and my day pack under the rear arm). Did not try dialing to correct, but 19 inches low (or 3.9 moa) was correct according to my ballistics app (shooters calculator.com).

I then added a DPT muzzle brake (replaces end cap), a stainless blast baffle, and one more alloy baffle. Recoil is massively reduced, can pretty much stay on target after shooting even at 15x.

Last night I’m out on the hill, stalking in on a mob of 4 yearlings across a gully, when one spots me. I sat down in the tussock and ranged it at 335m, and figured it was a good opportunity to try a longer shot (almost always stalk to within 200m). Dialled 3.8 moa. Clean miss (son thought it may have been low but wasn’t sure). Two more shots before it ran off, both misses. Again, son thought they were low.

Should I re-chrono? Did I miscalculate moa? Would the two extra baffles and muzzle brake change (reduce) muzzle velocity very much? They didn’t significantly change point of impact at 100m, maybe 3/4 of an inch higher, but I haven’t tried shooting at distance (hard to get access to the farm with the 350m target).

Any other suggestions?

Thanks!

I wouldn't read too much into it if it was a 350m sitting shot.

You’ve changed your POI, which only magnifies the further out you get.

Re-zero your scope for the modified setup.

Zero needs to be checked after any change made.

Had a similar event happen to me, fortunately a mate was trying out his flash harry spotting scope and phone adapter so got it all on camera. Short version is that I was missing high by some margin.

I eventually came to the conclusion that I was shooting high due to not having a rear support. (I was crouched behind a bank) I have since shot at a target at a similar distance and all six shots would have taken the deer.

The lesson I learned that day is that if I wish to execute a shot at distance I need to be prone with something supporting the rear of my rifle.

Reduction in felt recoil can lower the point of impact by reducing muzzle flip - could be a large part of a 'miss low' at longer range. Need to recheck zero with the new muzzle attachment to know though. As someone noted, any change means a recheck.

Zero needs to be checked after you've made a change. Yes, extra baffles/muzzle brake can make a difference. Doesn't matter what ballistic app you've got, until you verify at known ranges they are only an educated fucking guess. Check zero at an accurately measured range.Better yet go along to a NZDA or NRA range and check zero and drops at verified ranges. Verify against app and modify app inputs until you get app outputs that coincide with actual results .Do tall target tests or whatever to verify your scope adjusts correctly per click/MOA or Mil. Until you do this you're pissing into the wind. And don't forget operator error/capability. Also...practice,practice,practice. I generally shoot at least 24 rounds a week when not doing pest control and still make the odd fuck-up, we're all human and stuff-up from time to time.

My 308 Kimber is very sensitive to "hold" even with a braked can. I have resolved to practice more.

IMHO there’s nothing to even talk about until you’ve re-zeroed after the suppressor changes?

My 308 20 inch barrel zeroed for 200yds is 1.5inch high at a hundy using150ssts 2900f/s.Using Hornady 165gr ssts .Theres only .5 inch difference for 400yds zero.Actually the 150gr ssts have a bit more energy than the 165gr.
As the boys have said rezero.
Iv just got a slightly bigger suppresser fitted,so I had to rezero.Heres the result,get yr 100mtr zeroed good first,then stretch the legs.
Attachment 272909
4 shots in one hole,one flyer,2 clks right,job done.
Thats with a thermal clipon on front of scope

Thanks all, truly appreciated. Just to be clear, I did re-zero, but only at 100m, and was using a rear support (sand bag).

I will re-zero at 100m using my go-to field setup, which is two crossed tramping poles (I have some attachments called Quick Sticks that lock them together) and my shooting arm/elbow on the frame of my daypack, and then do as Woods says: tall target tests, verify drop, clicks, etc.

In the tussock hills where I hunt, I can’t always get to a rock, and shooting prone is never an option. My goal is to consistently shoot to 400m off the poles (80% of shots within an 8 inch circle). We shall see!

I reckon if you going to spend $150-$200 on a hunting trip each time,say once or twice month.Go to the range befor each trip or 2.Fire 2 or 3 rds =$12 or so.Just to make sure yr rifle n scope are in tune.

Greetings all,
I have heard this tale over and over again over the last 30 years or more. Rifle zeroed at 100 metres or there about and being out at longer ranges when dialled resulting in missed deer. Step 1 is if you want your rifle zeroed at 200 metres then shoot it at 200 metres. Next check it at 400 metres to make sure your trajectory matches your dial up values. Don't have a range? Find out where your nearest NRA range is and make contact. Also as mentioned use exactly the same set up for zeroing as you do in the field.
Regards Grandpamac.

bang on Grandpamac on TV many years ago a certain idiot ( wont give name may not still be with us ) who thought he could hunt and present a hunting show zeroed a 25-06 Remington on a track before going hunting - looked like about 100 yd range - showed us target - it was at least 1 1/2 high and 1 1/2 to left - announces on TV near enough I knew he was an idiot from some of the stuff he did on show but after that just completely wrote him off as a bloody moron

Fire 10 rds at the range per month.You'll only need 2 rds to shoot 2 deer per month,all going well.

@Barry the hunter. I suspect I know who you’re talking about from early 2000’s. An idiot who got far too much air time. Has to be said though that we’ve got the same scenario with idiots on YouTube these days.

Another thought. Was the 2,700 fps chronographed in your rifle? It seems high for an 18 inch barrel.

Great advice per your previous post, thanks, will do. Almost makes me question the value of shooting at the range on sand bags other than measuring velocity and grouping, and confirming scope is still aligned.

It’s Hornady SST 165, says 2840 on the box, guessing 22 or 24 inch test barrel so I figured 2700 was probably correct?

I get 2712ft/s out of a 20" using Hornady ssts 165gr.Forget the box numbers.

Quote:

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Originally Posted by Trout

I get 2712ft/s out of a 20" using Hornady ssts 165gr.Forget the box numbers.

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Yup.

You did the right thing by shooting a group at long range and measuring the actual drop to get velocity (BC is negligible at hunting ranges, don't alter it from factory specs). The resulting velocity given by the app will be very close, but it will change a bit from the addition of a can/extra baffles etc. - probably not enough to make a hunting scenario difference under 400m. If you can chronograph the actual set up that's very nice but not essential.

I'd reiterate that these light rifles require absolute consistency of hold to shoot well, which tends to compound out on the hill where you're never shooting from a nice flat place. A different shoulder pressure or fore-end hold will move a shot at least 3-4 moa - so quite a bit at 300M +. Practise is your friend, at home dry firing is far, far better than none at all.

PS
My recently acquired 308 Kimber shoots very well if I do my part, and I'm getting 2730 fps from a 17" barrel with a DPT braked can. That's a very snotty load that is significantly faster than the factory ammo I tried.

After shooting tikkas 308s for 15yrs using the same ammo.You get to know their habits and how to be accurate with them.

The 2700 was based on a Garmin chronograph, average of about 10 shots ��

“I’d reiterate that these light rifles require absolute consistency of hold to shoot well, which tends to compound out on the hill where you're never shooting from a nice flat place. A different shoulder pressure or fore-end hold will move a shot at least 3-4 moa - so quite a bit at 300M +. Practise is your friend, at home dry firing is far, far better than none at all.”

Great points. That’s partly why I wasn’t too hesitant to put a heavier scope on it (upgraded from a VX3 4.5-14 to a VX5 3-15, maybe 6 ounces heavier), as well as the extra DPT baffles and brake, especially since I shoot probably half my animals offhand, say 30-100m.

For what it’s worth, I picked up one of these thingies for dry firing practice, it’s quite fun to use. It slips over the barrel and connects to an app via blue tooth. I records barrel movement before and after trigger squeeze, and gives you a trace and score of 0-100. There are different exercises, timed drills, etc. and you can make notes for each 10 round group. My son and I like to compete, and we’ll mix it up by adding 5 pushups before each shot, etc.

One thing I’ve quickly found was that pulling the rifle in to the shoulder firmly really improves my score, while utilising the sling doesn’t help (or hurt). Can’t say for certain that it translates into real world accuracy but a 50 round session the night before a hunt can’t hurt anything.

https://mantisx.com/

And with that aid you will perfect follow thru which is extremey important.

[/QUOTE]"One thing I’ve quickly found was that pulling the rifle in to the shoulder firmly really improves my score"[/QUOTE]

This is one of the most important things for shooting hunting rifles, especially lightweight rifles. This will help with shot consistency through all postions. Pull the rifle into your shoulder with the lower 3 fingers of your trigger hand. Doesn't matter if your style is holding the forend or two hands on the butt bipod style.
The barely hold the rifle style of shooting is bullshit with hunting weight rifles.

With my new GWs suppresser, I checked my 3" high at a hundy for 300yds dial up,even tho 4"high is my 300yd dial up for zero.I fired 5 shots,windy but only after elevation for 300yds.Elevation centre of group was 3-1/4" low at 300yds.4 clks is 3/4"×4=3".
So dial 4"up at a hundy up give me a result of 1/4"low zero at
300yds.Drop chart ballistics app spot on.
2.5"- 3" high at a 100yds is good for a 308 shooting out to 300yds
point n shoot deer.
Attachment 273186

400yds similar results,7 " dial up.Not good grouping in the NW wind,but deer have a big sholder broad side.
Attachment 273187

All my shooting off the bonnet of truck at the range n out on the river beds.Using a cheap $320 nikko stirling scope 2-10×50 and a very expensive Infiray CHV2 50 Clip on.Contessa 6 screws rings dont let anything move either,very good rings.
Attachment 273188

Yesterday while at the range I tried a wee experiment with my Kimber 84M 308, it's a pretty reliable 1.0 MOA or a tad better rifle WHEN it's treated with consistency in hold. Target is 3 different holds on the same aiming point. This rifle doesn't change POI when it gets hot, but in any case I stomped up the 100M to check each individual group to get some cooling.

Attachment 273190

95mm of vertical at 100M, that's gonna punish ya at 300M+. All individual groups 35mm or under. After this I went back to 300Y and sent 3 rounds into 85mm nicely centred over my point of aim.

Oops - photo tipped over, don't ya hate that!

Well that’s really interesting. I see that the bipod was the highest. I don’t use a bipod, but the rifle fore end sits at the intersection of the clips attached to the tramping poles, just below the handles. The clips keep the poles locked out at 30 degrees, and my front hand pushes the fore end against the poles, while the rear hand pulls the rifle into my shoulder. With my right arm on the daypack frame, it’s really steady, nearly as good as sand bags. Just need to get the 200m zero and work on being as consistent as possible with the hold. I’d guess I’m applying about 10 lbs of pressure at each end?

I wouldn't read too much into what went where, just that there's a considerable difference, so your sight in had better be validated at longer ranges using whatever hold you commonly use out on the hill.