What do you feel is an appropriate separation of POI for both barrels at 50 yards? One inch or less maybe? And what is a reasonable expectation for a DR?

quote:

Originally posted by LionHunter:
What do you feel is an appropriate separation of POI for both barrels at 50 yards? One inch or less maybe? And what is a reasonable expectation for a DR?

The same distance as the barrels are apart.

At 50 yds, I would think that the bullets striking on a common horizontal line within 1.5" or less would be quite acceptable.

Gary
DRSS
NRA Lifer
SCI
DSC

What you are looking for is not bullets individual POI, but where the center of each barrel's individual 3 shot group is in realtion to the other barrels center of group. The centers 1" to 1.5" apart on the same horrizonal level, with the POA half way between the tow centers. That is about as good as you can get in most cases. individual bullets from both barrels will cross into the other's group to 50 yds, and more so at 100 yds. the barrel centers of bore are no more that 1/2" apart at the muzzle of the rifle, but the groups of even a MOA for each barrel will merge with the other barrel down range. A perfect composite group will be slightly egg shaped along the horrizonal line thorugh both barrel's groups with the centers of each barrel's group being 1/2" to 5/8" on it's own side of POA of the sights in the composit group.

..........Hope that is at least as clear as Mississippi mud!

acceptable accuracy is one minute of a buffalo's shoulder at 50 meters.

quote:

Originally posted by 500N:

quote:

Originally posted by LionHunter:
What do you feel is an appropriate separation of POI for both barrels at 50 yards? One inch or less maybe? And what is a reasonable expectation for a DR?

The same distance as the barrels are apart.

Both Mac and 500N are saying the same thing. I think each could use some clarification so here it is (I hope):

The barrels should have POI's which measure, center to center, the same distance apart that the barrels measure apart, center to center, at the muzzles. Right barrel should print 1/2 of the center to center distance to the right of the POA and the left the same 1/2 distance to the left. This would be the same at 50yds, 100yds or at any range.

(Horizontal distance from POA is something that involves personal preference, some like the POI to be centered under the bead as one views the target, some like the POI to be at the top of the bead.)

As Mac describes, each barrel will have it own group when multiple shots are made. Some barrels are more accurate than others... But each will have some dispersion within a multi shot group.

For a particularly accurate pair of barrels, each with 1 moa potential for a three shot group, if the shooter can shoot well enough with the sights on the rifle and is a good shot, the potential is for the individual barrels to print about 1/2" groups at 50yds. We all read about lots of 1 moa bolt rifles, I believe they and 1" 100yd groups are a hell of a lot less common in the real world than on the internet, so that 1/2" group from each barrel is not going to happen with each rifle, even without shooter induced dispersion.

But, if your (preferably standing) bench rest is good and the shooter can see and shoot well, every rifle ought to be able to shoot 1" or so barrel groups. But the centers of the two barrel groups should remain only the distance from center to center between the barrels at the muzzle.

Given variations in dispersion of, say, repeated three shot groups from each barrel, and even ignoring any shooter induced dispersion, you can end up chasing your tail with a rifle that doesn't shoot very, very well. Add a half grain, no take away a 1/4 grain, oops, add back that 1/4 and a bit more...

Easy enough to do with a bolt rifle, even easier to chase your tail with a double.

So, when developing loads, which is not often since once you find them they are good for the life of the rifle, so long as the same powder, cases, bullets and primers remain available, I prefer to err, if I am erring, on the side of convergence rather than divergence.

My thinking is that some slight convergence is better than any divergence. A diverging load will shoot only larger and larger composite (both barrels) groups as distance from the muzzle increases. While a slightly converging load will shoot smaller and smaller composite groups until the POI's converge and then composite groups will grow until they reach the spread of the barrel centers at twice the distance the POI's converge.

For illustration, if the POI's centers ideally should be, say, 1" at all distances from the muzzles, but converge a bit so that POI's centers would meet at 150yds, the POI's would be within that 1" to 300yds, which is farther than I want to shoot with a double or any rifle.

If the same degree of divergence was inherant in the load, perfectly shot composite POI's at 150yds would be 2" center to center and 4" at 300yds.

Jeez, I have been windy tonight. Hope this helps,

JPK

Forget the 100 yard results as a benchmark of load development. Even the smallest front bead will subtend a 4" bullseye so that you are just guessing where you are holding.

Work at 50 yards to get the load right and then "practice" at 100 yards to hone your shooting skills.

quote:

Originally posted by bigfats:
Forget the 100 yard results as a benchmark of load development. Even the smallest front bead will subtend a 4" bullseye so that you are just guessing where you are holding.

Work at 50 yards to get the load right and then "practice" at 100 yards to hone your shooting skills.

Bead subtention of the target is why one should use a 6 o'clock hold when shooting targets in load development. Or try 500N's technique, described in one of the Searcy threads.

Holding at 6 o'clock on a round 4", 6" or 8" target at 100 yds, or at any distance, will enable the shooter to control for elevation, imo the more difficult proposition, as well as for windage. When stacking the target circle on the bead for a 6 o'clock hold it is easy to see when you're high and the bead is subtending the bottom protion of the target, the white of the background is easily visible between bead and target circle when you're low and the bead is below the bottom of the target circle. Easy to see when windage is off as well.

Most load development is easiest done at 50yds, or early on even at 25yds. But to get the loads right, you need to shoot at other, longer distances. Just use a 6 o'clock hold (for all distances.)

JPK

quote:

Originally posted by Dave Bush:
acceptable accuracy is one minute of a buffalo's shoulder at 50 meters.

If you happen to be shooting a Blaser S2 that is in fact true.

quote:

Originally posted by JPK:

quote:

Originally posted by bigfats:
Forget the 100 yard results as a benchmark of load development. Even the smallest front bead will subtend a 4" bullseye so that you are just guessing where you are holding.

Work at 50 yards to get the load right and then "practice" at 100 yards to hone your shooting skills.

Bead subtention of the target is why one should use a 6 o'clock hold when shooting targets in load development. Or try 500N's technique, described in one of the Searcy threads.

Holding at 6 o'clock on a round 4", 6" or 8" target at 100 yds, or at any distance, will enable the shooter to control for elevation, imo the more difficult proposition, as well as for windage. When stacking the target circle on the bead for a 6 o'clock hold it is easy to see when you're high and the bead is subtending the bottom protion of the target, the white of the background is easily visible between bead and target circle when you're low and the bead is below the bottom of the target circle. Easy to see when windage is off as well.

Most load development is easiest done at 50yds, or early on even at 25yds. But to get the loads right, you need to shoot at other, longer distances. Just use a 6 o'clock hold (for all distances.)

JPK

Plus 1 for the six o:clock hold

Absolutely on the six o'clock hold.

Regards