Is my barrel bent?

[peterw]

I was at the range with my first build (http://americanlongrifles.org/forum/index.php?topic=2503.0). Below are the first ten shoots (28 yards, offhand, 62g BP, .445 ball).

The group of 7 shoots (3-9) is ~3,5" below POA. At 55 yards the POI is ~ 8" below POA. I don't know why. The height of front sight and rear sight are equal (~11/32"). The crown looks ok. Is my barrel bent? What do you think?

[Randy Hedden]

Peter,

Why don't you go to the range again and try filing the front sight down a bit and see if it makes a difference. Personally my first thought would not be that the barrel was bent.

Randy Hedden

www.harddogrifles.com

[peterw]

Of course I will do it. I need to file ~ 3 mm to shoot POA at 55 yards. I expected this. I am surprised that it shoots so low with equal height of front and rear sight.

[Roger Fisher]

If she were mine I'd shoot her from a good rest on a 2" sq black block on white paper and hold at 6'clock at 25 yds. She will shoot low!  Then carelfully file that frt sight then shoot 3 or more shots then file (carefully get that top flat) then shoot etc til you get her in,.  You will probably have to drift the frt or rear sight to move the windage.  When she is cutting the same hole then move out to 50 yds etc.  take your time - then practice with her offhand!!!

Please keep us posted!

[Tony Clark]

Sometimes when a barrel is made the bore can end up to be a little off, not perfectly parallel to the outside of the barrel. Standard procedure when breaching a barrel like this is to place the runout so as it will shoot low allowing the front sight to be simply lowered till it shoots on without having to mess with windage or have a very high front sight. Regards, TC

[Dphariss]

I was at the range with my first build (http://americanlongrifles.org/forum/index.php?topic=2503.0). Below are the first ten shoots (28 yards, offhand, 62g BP, .445 ball).

The group of 7 shoots (3-9) is ~3,5" below POA. At 55 yards the POI is ~ 8" below POA. I don't know why. The height of front sight and rear sight are equal (~11/32"). The crown looks ok. Is my barrel bent? What do you think?

Was the bore perfectly centered in the barrel at the breech. It is not unusual for straight barrels like GM  to be off a little at the breech. Up and down is easy to fix. I would also point put that unless the barrel is tapered the front sight is always lower than the rear to bring the bullet up to line of sight at some point. The bullet starts to drop as some as it clears the barrel so if the sights are perfectly parallel to the bore the ball will be low at all distances, just farther and farther as the range increases.
If the sight notch and the rear face of the blade are 36" apart the front sight will need to be lowered .010" to raise the impact 1" at 100.  At 50 yards .010 will raise it 1/2 inch. 36" is 1/100 of the 100 yard distance and moving the sight .010" will move the POI 1". Sorter sight radius will require less metal removal. Longer sight radius more.
So measure the target from center of group to the point of aim and remove enough front sight to move it 1/2 the distance then shoot 3 shots to check it.
Continue till the impact is where your want the ball to strike. I would recommend 1" high at 50 to start this will be a little low at 100. 1 1/2 to 2" high should get you close to on at 100 but it requires actual shooting.

Dan

[Daryl]

 Ditto what Dan, Randy and Roger have said.

 I know there are forumlae for figuring how much to move a sight. I usually don't take a set of calipers to the range with me and lack a calculator in the tackle box as well - I merely tap the rear sight over a 'tich, and try it - it's usually pretty close to being right- if not, a tiny bit more or back as the case may demand.  Trial and error are easier to deal with than getting upset over why the math didn't work. Same with elevation - getting better and better at knowing how high to make the front to match the rear. This is more important with bead fronts and wide V rear sights but there is always a file in the box - for either a front blade or a rear notch or wide V - whatever's needed.

[northwoodsdave]

I may get myself tarred and feathered here, but I have a simple method I use before I get out on the range.

I use a laser bore sighter.  That way I know exactly where the bore is pointing, even if there is some runout, or if the barrel is slightly askew in the stock, or any of a hundred other tiny things that can effect aim have happened.

And I can do it all right in the shop, before I get out on the range.  I can use my range time to make small adjustments to the sights, since the big ones are already out of the way.

It's not traditional, but it sure is quick and easy 

David L

[Daryl]

Peter- moving the rear sight a bit one way or the other to centre the group is normal.  Different loads will give different windage as well as elevation impact to the group.  This is also normal.  At 50 yards, changing ball diameter or patch thickness or powder charges can give up to 2" change in windage if my rifles are normal and I think they are.  True, it is nice to have a load that "shoots centred" - sights centred on the barrel, that is.  Round & centred groups usually show the ball is leaving at the top or bottom of the barrel's harmonic movement.  Stringing vertically usually means the ball is leaving in the middle of the harminics or barrel whip and the different vertical points of impact are showing shot to shot velocity and pressure changes, which are also normal, where a little more or less powder usually drops the ball's departure at a high or low node in the harmonic movement.  This is getting rather technical and ML's usually don't give this type of problem - but - they do shoow left or right with different loads.

Suffice to say, if you are happy with the accuracy, move the sights to bring the group into the centre. With your pictured group, a bit left with the rear sight, and file some off the front blade to centre the group and bring it up.

I knew a guy who actually was a really good shot.  I didn't realize how good a shot he was until he sold his rifle and mentioned the sights.  He didn't win much, as he was afraid to adjust the 'adjustable' sights on his rifle. It shot to the left right from the factory - so for 10 years or so of shooting rondy's he'd hold off for the impact error - of course, holding off for various ranges didn't help him to be as consistent on targets as needed.  When he sold his rifle, he mentioned it shot about 2 1/2" to the right at 25 yards - always had - he'd never adjusted the sights to shoot centre.  I like competitors like that - gives me a changce.

[peterw]

Thank you for your advices. I filed down front sight. I will check it tomorrow at the range.

[Roger Fisher]

Thank you for your advices. I filed down front sight. I will check it tomorrow at the range.

Now, now Pete!!! That is something that should be done gradually at the range while shooting her (unless you are extremely sure of yourself)

[peterw]

..unless you are extremely sure of yourself

I am rather sure. Not extremely so I kept reserve of height.

[Daryl]

By all means - only adjust sight placement and height at the range.  The front is usually only .030" to .060" below the height of the rear sight, for a 50 yard zero.

1/2" to 1" high at 25yds will usually put the ball about 2" high at 50yds, and on at 75yds to 80 yds or so, depending on the load used. This will only be a couple inches low at 100 and is a good sighting for a hunting rifle.  For target/rendezvous gong shooting, a 50 yard zero is normal - zero at 25 and it will be very close to "ON" at 50.

[Darkhorse]

Speaking from experience with files and sights; It's best to shoot at a big big target for awhile while you work up your load. If you go ahead and file to point of aim with a load that seems right you'll likely be buying or making a new front sight before too long.

[peterw]

... The front is usually only .030" to .060" below the height of the rear sight, for a 50 yard zero.

This is what I expected. But it is not true in my rifle. That's why I asked. My front sight is 0.14" below height of the rear sight. Now my rifle shoot POA from the rest at 55 yards and ~2" above offhand. Here is picture - 55 yards, 62 gr/.445, offhand, 16 shoots (first 3 in the white with dull flint).

 

[Daryl]

... The front is usually only .030" to .060" below the height of the rear sight, for a 50 yard zero.

This is what I expected. But it is not true in my rifle. That's why I asked. My front sight is 0.14" below height of the rear sight. Now my rifle shoot POA from the rest at 55 yards and ~2" above offhand. Here is picture - 55 yards, 62 gr/.445, offhand, 16 shoots (first 3 in the white with dull flint).

 

I should have said - we make the front sight to be .030" to .060" below the rear sight for starting to develop loads. We generally find we have to file one or the other as well as to drift a sight one way or the other to centre the group.  Different loads require different wight heights.  Now it's time to adjust powder charges and patch thickness to find the 'best' load for the rifle.  You cannot PICK a load and demand the gun to shoot it the best. The rifle will tell you what it's most accurate load is - then you sight it in, just as Darkhorse said in his post.   

[Roger Fisher]

Or do you mean 'above the rear sight'?

I know it's cold up there now!!    Picky picky!