Sighting in my 308


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alana
February 10, 2012, 08:55 PM
Bought a new toy. Apart from the AR, which is set up with an Eotech, this is my only rifle - I shoot clays normally.

Spent an instructive hour sighting it in. This was at 100 yards using cheap (PPU) ammo off a bench with a front sandbag.

The last string I shot five - 1 through 5 - one after another in fairly quick sucession. You can see what happened. I then waited a few minutes while I wondered what was going on and took 6.

http://www.tr250v8.com/images/308/sightin.JPG

I'd been playing around on another target between the sight in shots and this set, and by the time I got to this set the barrel started out warm to the touch and didn't get any colder...

I'm not knowledgeable enough to know if this is normal or do I have a problem with the rifle. Anyone care to offer an opinion?

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12gaugeTim
February 10, 2012, 09:05 PM
Is the problem that your barrel was getting warm? Because this is perfectly normal.
If the problem is that you're losing accuracy as your barrel gets warmer, this is also normal. It should not impact your accuracy by much though, as many .308's have thicker barrels, and since the equation for specific heat is kJ/kg K , the heavier the barrel, the longer it will take to heat up.

alana
February 10, 2012, 09:08 PM
I'm guessing (or more accurately hoping) that's what it was, but it's not like it ever got hot to the touch. It was 35 degrees today and the thing only ever felt warm...

12gaugeTim
February 10, 2012, 09:19 PM
Actually, after evaluating your picture it appears you're getting vertical stringing. Im no expert, and I definitely cannot tell you how to solve your problem, but I'm fairly confident in my diagnosis. What rifle are you using?

bbrownie
February 10, 2012, 09:25 PM
benchrest shooters will tell you if it is stringing vertical add more powder.

alana
February 10, 2012, 09:31 PM
These aren't handloads. This is cheap 149 grain PPU ammo. Gun store didn't have any Federal and I bought this stuff to let friends who want to shoot play with it. I wasn't expecting it to group at all - I was more looking for a suggestion that it was close to the middle ;)

Gun is a Savage FLCP-K.

Edit: Never mind. 30 seconds of google on "vertical stringing" says it's often the shooter's technique that's inadequate - which I'll be happy to agree with - and that inconsistent position is a common cause. Since I couldn't get low enough on the thing and see through the scope, I had lousy cheek weld and was moving my head the whole morning. I'll reserve judgement until I get a cheek pad and try again...

Casefull
February 10, 2012, 09:56 PM
You are correct on moving around effecting the group. I would say that is half of the problem and match ammo will fix the other half.

TexasPatriot.308
February 10, 2012, 11:23 PM
refer to "combat zero or combat sight in" from miltry manuals to sight in your ARs, this starts at 25 meters, good for 100 meters. just google this or find a M16 or AR10 manual to get you started.

alana
February 11, 2012, 08:22 AM
It's a scoped bolt rifle. My AR is just fine.

LoonWulf
February 11, 2012, 01:50 PM
what model of rifle? what weight barrel?

My 7mm SPS would string 5 shots right off the bat end up with a 1.5-2" 5 tall group at 100, but only about .5-.75 wide. This was from a fully bedded action and a slightly floated barrel. I tried making a major gap between the forend and the barrel to see if it was touching during recoil, stiffening the forend, and changed bullets with full ocw work up. No change at all, and ive tried shooting this gun fast, and fairly slowly (minute or two between shots).
I ended up re-pressure bedding the forend tip, and re-worked up the ocw load (again). This time every group was right at 1" or better for 5 shots.

kaferhaus
February 11, 2012, 04:18 PM
Doesn't matter that it's not handloads. Change ammo until you find one that shoots round shaped groups. What the other poster said. Vertical stringing usually needs a bit more velocity to bring the groups into a round shape.

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