.315 MOA, my best group yet with my build.

L

longarm21

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My build which started out with this: (Rem 700 PSS .308 w/ HS precision stock, terrible rings, terrible base, Super Sniper 10x scope)
rifle2_zps57fe1b81.jpg


Is now this: (add AICS, Sightron SIII FFP 6-24x52 MIL/MIL, 20 MOA badger base, Nightforce ultra low rings)

IMG_2046_zpscdb1ef43.jpg


So the other day after fouling the barrel, I managed to pull this group off at 100m from the bipod with 5x 168gr Nosler Custom Match factory rounds.


IMG_3345_zps7804ac1e.jpeg



I'm excited to see what handloading and some smithing work will have in store for the rifle. Next step, start load development, Atlas bipod w/AICS adaptor, bolt knob and possibly some lapping? Suggestions for how I can tune it further?
 
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Glad you are enjoying the optics. Can't hit what you can't see.

Out of curiousity, would you remeasure your group again. Assume the orange bar is 1/2". You group is just a schnick wider. My SWAG would say 0.6" outside width.

So if it is 0.6" - 0.308" for the bullet, leaves you with a 0.292" c to c dimension.

Now divide that by 1.1 as you are at 100m (not yards), you get a group of 0.26MOA.

So maybe, give that group another measure...

Jerry
 
My understanding is that its :
1. Take your outside to outside measurement.
2. Subtract your diameter of bullet.
3. Divide that number by 1.047
Equals MOA
In which case .638 - .308 / 1.047 is .31518
 
You can glass bed the action, rework the trigger to a crisp 2.5 pounds. I would not lap the bolt lugs... that usually just laps tapers and does not fix anything. You have a good shooter, keep the locking lugs lightly greased and enjoy it...
 
longarm21 said:
My understanding is that its :
1. Take your outside to outside measurement.
2. Subtract your diameter of bullet.
3. Divide that number by 1.047
Equals MOA
In which case .638 - .308 / 1.047 is .31518
Click to expand...

It's late so maybe my math is clouded by the drink...

1.047 INCHES is the physical distance of 1 min of angle at 100yds. This becomes 1.151" at 100m (assume 110yds equal 100m - actually a schnick less but ... you can do the perfect math)

So, if your group measured 0.638", then my math gives...

0.638"-0.308" = 0.33" center to center group distance (the height of the triangle). Now we divide that by the distance 1.1 as we end up using the yard MOA values most often (that 1.047" stuff)

0.33 / 1.1 = 0.30MOA. My math gives you a tighter group. Now if those calipers tightened up just a hair, you are in the 2's... :)

Regardless, that is some fine shooting and even more important, DEAD FLAT for vertical. That is going to be a very interesting load to see shoot at 300yds, and beyond.

Jerry
 
longarm21 said:
My understanding is that its :
1. Take your outside to outside measurement.
2. Subtract your diameter of bullet.
3. Divide that number by 1.047
Equals MOA
In which case .638 - .308 / 1.047 is .31518
Click to expand...

Actually, what you should be subtracting is not the bullets diameter but the measured hole that the bullet makes in the paper you are shooting your group on on that particular day.

Chances are you will find that the hole (or bullet marks outside the actual hole) will be smaller diameter than your actual bullet size due to the paper stretching and shrinking as the bullet passes through.

Splitting hairs here, but if you wanted exact group measurement that's how one would go about it.


That being said I do the same and subtract the bullet diameter.

Always makes my group size smaller. :D
 
longarm21 said:
unless its -40 I can't see it being that much smaller! What causes this drastic an expansion/contraction?
Click to expand...

What causes the hole in the paper to be smaller than the bullet ? It's the point on the bullet. The bullet point breaks the paper and the bullet pushes through, without the paper being completely removed. A wad cutter would do a more complete job. The type of paper used would likely affect the size of the remaining hole as well.

NormB
 
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