Rifle accuracy problem

[Matt44-40]

Hi guys,

I have a Howa 308 and I have been having problems with it from day one.

Problems found an fixed
1) loose action screws
2) barrel was touching stock (used a dremmel to make the channel larger)
3) bedded the action and put epoxy in forearm to stiffen
4) lined up the scope rings

Now it started grouping better, but if I shoot a 3 shot group, leave it for a few minutes and shoot again the POI would shift a bit.

In the picture the different colours represent the four three shot “strings” I shot.

I was testing loads and shot one shot of each load in each string. I just used my computer to put the three groups together to show how the strings moved.

Any idea of what can cause this?

Howa 308 heavy 20” barrel
Standard Hogue stock bedded and forearm strengthened
Silencer
150gr hornady interbond bullets
S&B brass
CCI 200 primers
Sonchem (local SA powder) 42.8gr, 43gr and 43.2 gr
70.25 OAL
Hawke Endurance 6-24x50

Illustration of strings


String 1 Blue
String 2 green
String 3 yellow
String 4 red

Shot with a dirty barrel after 8 rounds to sight rifle
3-5 min between strings, 1 min between shots


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[Tatume]

Try shooting five shot groups. The American Rifleman procedure is a good one; five five-shot groups. Consider the average of the five groups to be the accuracy of the rifle/ammo combination.

Assuming your target was at 100 yards, and those are one-inch squares, I would say you have a solid two-inch rifle (maybe better). That is a good hunting rifle, and should reliably make 300 yard shots.

[pietro]

.

Maybe not the case here, but a known accuracy issue with glass-bedded actions like the Howa is derived from not laying down a layer of masking tape as a spacer prior to bedding the rifle. (after taping, I apply wax as a release agent, just like the rest of the bedded metal)

The front, bottom & both sides of the recoil lug gets taped, which gives clearance after the bedding is cured and the tape removed.

( the rear surface of the rear tang likewise needs some clearance.)

.

[Mr Peabody]

I do like pietro said, works well

[tomme boy]

Your parallax is not adjusted right on your scope.

[375RUGER]

The fact that you had to fill the stock with epoxy to stiffen it, is a big red flag. Above all, with plastic stocks, place forearm on the rest at the same place each and every time, and use consistent pressure. You may find if you use your off hand between the forearm and rest, that will give you most consistency.
I wouldn't be messing with the scope during load development, it's close enough where it's at for load development. The point you're at now, I'd shoot a 5 shot group of each blue and yellow dots and then a 10 shot group ( or two 5 shot) of the best of those 2. There are a lot of other variables to play with also if you're so inclined. Once you find your load, fine tune the scope for where you want poa/poi. Once you have your load and poi where you want it, then determine if you really have a roaming poi.

[Matt44-40]

.

Maybe not the case here, but a known accuracy issue with glass-bedded Mauser 98 based actions like the Howa is derived from not laying down a layer of masking tape as a spacer prior to bedding the rifle. (after taping, I apply wax as a release agent, just like the rest of the bedded metal)

The front, bottom & both sides of the recoil lug gets taped, which gives clearance after the bedding is cured and the tape removed.

( the rear surface of the rear tang likewise needs some clearance.)

.

Hi Pietro,

I did it like that


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[Matt44-40]

Your parallax is not adjusted right on your scope.

Hi Tommy Boy,

I set the parallax by first adjusting the rear adjustment by looking through the scope into the blue skye and adjusted it until the crosshair was at it brightest. I marked it and did not adjust it again. Then at the range I adjusted the parallax knob until the target was bright.

Is this the right way?


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[Matt44-40]

The fact that you had to fill the stock with epoxy to stiffen it, is a big red flag. Above all, with plastic stocks, place forearm on the rest at the same place each and every time, and use consistent pressure. You may find if you use your off hand between the forearm and rest, that will give you most consistency.
I wouldn't be messing with the scope during load development, it's close enough where it's at for load development. The point you're at now, I'd shoot a 5 shot group of each blue and yellow dots and then a 10 shot group ( or two 5 shot) of the best of those 2. There are a lot of other variables to play with also if you're so inclined. Once you find your load, fine tune the scope for where you want poa/poi. Once you have your load and poi where you want it, then determine if you really have a roaming poi.

Hi 375,

The hogue stocks have a lot of flex, hence the stiffening of the stock. I shot of a steel rest. Might be that it moved a little between strings. Would a bipod and rear bag give more consistent results?

The rifle was quite far out after the bedding job and straightening the rings. So I got it to where it is now and I did not adjust again when I started shooting the loads.

I will shoot a five shot group and check if it roams again.


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[Matt44-40]

Here is the actual target I shot. From left to right it’s 42.8, 43 and 43.2. 43 is my calibrated load according to quick load. I shot alternating shots on each target to make sure the barrel temperature is the same for each shot of each load. So 42.8 was the first shot of every string, 43 the second shot and 43.2 the last.

I just placed the together of the previous image to see how the strings grouped and to see if it really drifted.

If I discount the last shot on 43 as a flyer it is probably not the worst group I ever shot.

Should perhaps load 5 of the 43 and shoot them in one string and see what happens.

The lowest ES on the loads was 42.8 at 32fps and 43 gave an ES of 42fps


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[samari46]

I have an older Savage 110FP heavy barrel in 308.And the stock is \was rynite aka plastic stock. That rifle drove me nuts. Stock flexed so much that the front action screw would loosen up. Tightening it up would last maybe one range session. Plus the plastic under the screw head got all chewed up from constant tightening. The stock under the front receiver ring was divided up into 4 boxes as part of the molding process. I literally packed those boxes with acra glass gel. Waited a week then did the finish work. Area under the front screw ended up getting a pillar bedded and that stopped all the movement. Kinda did the last part backwards, but it worked. Had some special ball Military LR with the 175 Sierra match King. Ten rounds 3/4" group. Going to see what a good wood Boyds stock will set me back. Have about 1100 rounds down the tube. You mentioned about tightening the rings. Whose are they and what exactly did you do?. I've never got the accuracy out of a 308/7.62 nato I felt I should get. I've 3 308's.
Rem 700 Sendero
Savage 110FP
Rem 40x 7.62 Nato as that is what's stamped on the barrel. Frank

[Matt44-40]

Hi Samari,

I have Thor dovetail rings and bases. The more I think about it the more I realize I might have over tightened the rings. Don’t have a torque wrench as they are crazy expensive in SA. Could over tightening or miss aligned rings torque the scope to the extent that it drifts?

Planning on properly aligning and lapping the rings. Wil try to borrow a torque wrench for the job.

The other thing that bothers me is the rings aren’t vertically aligned (assume it’s the holes in the action that don’t line up) when I put a spirit level on the rear ring’s bottom half and level the gun the front ring is not level. I assume this could put strain on the scope. I hope that lapping will limit this strain.


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[243winxb]

The quickest way to get better accuracy is change bullets. Sometimes.

The powder weight should have a larger spread, like 1/2 gr. Balance beam scales are only accurate to +/- 1/10 grain.

Changing col may make a bigger difference then 2/10 of powder.

[RC46]

2 thoughts:
#1 I built stocks (Fiberglass Composite) for 30 years and always had people coming to me with problems w/ Hogue stocks, injection molded stocks in general, as they all flex way to much to find consistent accuracy. Hunting accuracy ok, target never, after all what do you expect from a stock that costs $12 to make and was/is way over hyped by writers.
#2 did you check the twist of the barrel and match a bullet to the twist? and, how far are you seating the bullet off lands?

[pietro]

The other thing that bothers me is the rings aren’t vertically aligned (assume it’s the holes in the action that don’t line up) when I put a spirit level on the rear ring’s bottom half and level the gun the front ring is not level.

I assume this could put strain on the scope.

I hope that lapping will limit this strain.

Lapping will not help a gross mis-alignment.

Diagnosis involves considering many possible issues.


1) Check the bases with the scope/rings removed from the gun via placing a straightedge first atop, and then along the sides, of the mount bases - That should tell the a part of the alignment tale.


2) Some scope rings sets are sold with different thickness' of the bottom of the rings, to achieve the various different heights desired.

If the rings on your rifle don't have equal thickness', your ring set might have mixed height rings.


3) Borrowing/switching to a known reliable scope may show a deficiency in your scope.


4) When targeting the rifle, the rifle will move during firing if any portion of the rifle's metal or stock touches the benchtop, or a hard front rest.


5) Remove the silencer to determine if it's effecting accuracy or not.


6) Sometimes, though, a rifle's barrel just isn't accurate, no matter what's done with it.



.

[Matt44-40]

2 thoughts:
#1 I built stocks (Fiberglass Composite) for 30 years and always had people coming to me with problems w/ Hogue stocks, injection molded stocks in general, as they all flex way to much to find consistent accuracy. Hunting accuracy ok, target never, after all what do you expect from a stock that costs $12 to make and was/is way over hyped by writers.
#2 did you check the twist of the barrel and match a bullet to the twist? and, how far are you seating the bullet off lands?

Hi RC 46,

I am contemplating buying a different stock, but finances is a bit tight at the moment.

I have a 1 in 10 twist, which should work better with heavier bullets. When I got the rifle I tested 180gr soft points, 150gr monos and 150gr soft points and the 150gr soft points gave the best results. But that’s before I did all the work. Can the wrong bullet weight cause the drifting between groups? I originally discarded that possibility because the groups on their own were good and just drifting.

I am very far from the lands. If I load close to the lands I do not have enough seating depth on the bullet.


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[Matt44-40]

The quickest way to get better accuracy is change bullets. Sometimes.

The powder weight should have a larger spread, like 1/2 gr. Balance beam scales are only accurate to +/- 1/10 grain.

Changing col may make a bigger difference then 2/10 of powder.

Hi 243,

I used small increments to calibrate the node according to quickload. COL adjustment would have been the next step of I did not run into the drifting problem.


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[Matt44-40]

Lapping will not help a gross mis-alignment.

Diagnosis involves considering many possible issues.


1) Check the bases with the scope/rings removed from the gun via placing a straightedge first atop, and then along the sides, of the mount bases - That should tell the a part of the alignment tale.


2) Some scope rings sets are sold with different thickness' of the bottom of the rings, to achieve the various different heights desired.

If the rings on your rifle don't have equal thickness', your ring set might have mixed height rings.


3) Borrowing/switching to a known reliable scope may show a deficiency in your scope.


4) When targeting the rifle, the rifle will move during firing if any portion of the rifle's metal or stock touches the benchtop, or a hard front rest.


5) Remove the silencer to determine if it's effecting accuracy or not.


6) Sometimes, though, a rifle's barrel just isn't accurate, no matter what's done with it.



.

Thanks Pietro,

Will check the alignment. I got some alignment bars as well that you get in the lapping kit to check it with as well.

The shooting rest has some soft tape on the rifle rests. Will a bipod with a rear bag perhaps give better results?

Will try without the silencer and see if it makes a difference


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[dtknowles]

Your drifting seems to be mostly horizontal. Do you shoot over wind flags? The gun might be fine you are just not correcting for wind drift.

Tim

[Matt44-40]

Your drifting seems to be mostly horizontal. Do you shoot over wind flags? The gun might be fine you are just not correcting for wind drift.

Tim

Did not check the flags. Wind was pretty calm. But your right it might have been a factor. Would mild to moderate wind make a 2 inch difference at 100m?


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