Home Forums Reloading Big Game Rifles curious issue

shooting some test loads yesterday i had one wierd issue.
when i was shooting a 4 shot string i had 2 holes in one and then 1/2" to the side another 2 shot group. each group was barely larger than the caliber but there were 2 distinct groups. both exactly the same in elevation.
what causes this?
i had a very small POA so i dont think i could have been shifting my aim.

My impression is that one there is a bedding issue that once the gun achieves a certain heat level it "stresses" some due to the heat and achieves a new POI.

Try some five or six shot groups with the same interval between shots and see what happens.

If that was a single occurace I doubt it means anything.

That can happen with inconsistent primer ignition. The ones that go off like they're supposed to cause grouping in one area while those that don't cause a group in another area.

the 41gr group was scattered in a 1" block.
the 41.5 group was what i listed above
the 42 gr group was similar to 41.5 but a bit tighter and the groups were spread verticle and not horizontal, but still two distince seperate groups with holes within holes.

Your test progression could be moving between accuracy nodes.

given your additional info, I'd agree with mathman.

Be curious what 0.1gr increments between 41.5 and 42.0 would do.

I would say you have a bedding issue...so do this to check..

Number your holes as you shoot them.

Does it print one shot left, then the next right, then left again, then right. 1rt, 2lft,3rt, 4lft?

If this is what your telling us, bedding is the problem.

Is your barrel floated? Check that first.

I also had the recoil block of wood behind the recoil lug, split, causing the same shift in impact you see. Had a devil of a time finding that problem.

Shooter error.............

MM

Could be any of the above and I'll throw out one more. It could be brass sized with inconsistant headspace. A couple of years ago I went to the range with brass that had a slight crush fit when closing the bolt and some with about .002" headspace that chambered like butter.
My purpose was to see which was more accurate. I didn't find an accuracy difference but what I did find was that I got two horzontal groups....the crush fit to the left ...the hunting type ammo to the right. About 2" apart at 200 yds. So to this day I try to prep ammo one way or another...but don't neck size ammo that might have slightly varying headspace that could give me a combination of the above.
I have run my experiment past another experienced shooter here on the forums and he said he had seen the same thing between fitting the brass two different ways so I guess it is a possible phenomenon.

Parallax can do that when you line up behind the scope with slightly different head position. (I've done it.)

none of the problems you guys have addressed have ever show up with the dozen or so steyrs exactly like this one that i have owned.
barrel is fully free floated.
rounds were all sized at the same time and trimmed to spec.
scope is mounted the same as others so i have the same POV each time.
i have pulled the "now" fire formed brass. resized , trimmed and reloaded it w/ the same charge and will head out to the range tommorow PM. As well i plan on using a smaller point of aim. perhaps 1/4" black dot

shot her again today with fireformed brass. still showing a tendancy to string both verticle at times and horizontal at other times. never both.
i think its a scope issue. perhaps a loose erector?

Nighthawk may indeed have it. Does your scope exhibit parallax, and if so, do you have the ability to dial it out? A friend was recently having grouping issues, discovered he had parallax at 100 yrds, and has rectified the problem by making every effort to center his eye behind the scope. He is happy now. Another solution for him would have been to move his tagets out to 160 yards where his parallax disappears.

Even my lowly 22 LR units carry adjustable objectives, and folks are amazed at what I can do to long range, 1 1/4 inch wide ground squirrels. Very few shooters are even aware of that issue.

Not saying that it's the answer, but just throwing out another option. I believe that I often create a "third shot out" situation by concentrating and (unconsciously) gripping the rifle differently after having the first two shots touch.

i dont grip the wrist when testing loads i pinch the trigger against the rear of the guard.

not the scope. still stringing. no bad. each group is a 1.25" verticle line. i think i will add a pressure point in the forend with weather stripping.

Use something firm to shim. Traditional advice was to wedge business cards between the barrel and forend, that way you don't have to disassemble. If it works, make a permanent pad. If not, easy to remove. Could do the trick, hard to predict just what a particular sporter weight barrel will like.

5sdad makes a good point. I have one rifle in particular that demands a firm hold on the forend for best accuracy when shooting over sandbags.

I am amazed that no one has mentioned WIND. Are you shooting with wind flags? It doesn't take a lot of wind to move a bullet 1/2" at 100yds. Also, verticle is a good indication that your load is not in tune with your barrel. Try a couple different loads and see if the verticle goes away.

Matt Guthrie