Change in POI? Causes?

[koauke]

I had my TVM Virginia out at the range today and for some reason it was shooting low. With a six o'clock hold on an 6 inch shoot and see target at 50 yards it normally it hits pretty much center. So 3 inches above my hold. Today I was hitting just below where I was holding.

I was using the same patch material, same ball size, same powder and charge I normally do.

I've seen posts on here that a touch hole can open up and cause this, but I've only had the rifle for just about a year. Would it wear out that quick?

Does weather have an affect on POI? Thoughts?

I may take it out again tomorrow to see if I get the same results.

 

[Grimord]

It could be caused by the stock shrinking or swelling due to temperature and humidity. Direct sunlight on a barrel, enough to warm it up, will also have an effect on poi.

 

[Billnpatti]

There are so many things that can cause this. It is true that the size of the tough hole can cause such things but, in your case, that is an extremely remote possibility. Such changes are not a function of the time you have had the rifle but on such things as the size of the charge and the number of shots. It usually takes many, many shots to wear out a touch hole liner. There are many other things that can cause a change in the POI such as changing lighting conditions. As the light hits your sights differently, it can cause the POI to change. If you are using a substitute powder such as Pyrodex of Triple 7, etc. they will deteriorate with age. A year on the shelf can make a difference in their performance. You may have been using the same size balls but, unless you weighed them, they can vary in weight due to having voids inside them or variations in the alloy from which they are made. Another possibility is that you may have changed the amount of lube on your patches. Lube can have an effect on your accuracy, it must be the same from shot to shot and it must be the same amount of lube on your patch shot to shot. Dutch Schoultz discusses this in his work on muzzleloading accuracy. Are you sure that the patch material is the same as you had been using? Is it from the same piece of fabric and is the fabric new or something from an old piece of clothing? Clothing wears differently in different parts and patches cut from these different parts will have a different thicknesses. Then there are such extremely remote possibilities as you having sighted in the rifle in the mountains of Colorado and then find that it shoots low at a range on the Gulf Coast. This would be caused by a change in air density. Ridiculously remote but mentioned just as an example.

Look at the simple things first to find the most likely answer. According to Occam's Razor, Latin: lex parsimoniae "law of parsimony") Among competing hypotheses, the one with the fewest assumptions should be selected. Or stated another way, the simplest answer is usually the best.

 

[azmntman]

Perhaps its you and not the gun? Eyes checked recently? Any injury, strain or weakening of muscles/shoulder, hands, back, neck, fingers?

I have that happen on occasion and finally found its my NECK (which has metal and hip bone in it). If I'm tired or stiff I hold the gun differently which changes my site picture.

That and the lube/patch issue? Powder as stated above if not real black (and assuming it is per mention of t/h liner).

SOMETHING Has changed, you or the gun. Keep us posted.

 

[Rifleman1776]

As others have pointed out, there are many reasons why an ml rifle can be cantankerous one day and a lover the next. Often the reasons cannot be pin pointed. Sometimes you can find the fix. Other times you can go just plain nerts :youcrazy: trying to find a solution. That is part of what makes this game so much fun. :rotf: Good luck.

 

[SgtErv]

I believe weather can play a big role.

I have strange days at the range sometimes. Honestly, I didn't fool with anything or worry about it much unless I'm getting the same problems/occurrences over the course of a couple or a few range trips.

The other day I was shooting pretty far to the left. I had no idea why. The next range trip I was back to normal ¯\_(ツ)_/¯ . The trip after that was normal, too, so I'm glad I didn't tinker with the gun any.

One thing I keep in mind is that nine times out of ten I am the least reliable factor in shooting my rifle

 

[BrownBear]

The most consistent reason I've seen for POI changes?

Shiny front sights on a sunny day.

If yours is silver or brass and the sun was reflecting off it even a little, try blackening the sight.

 

[smo]

Any head wind? Which I would think would have to be extremely hard to effect the shot that much at 50 yards. :idunno: Most likely a lube issue or simply positioning of the rifle. :thumbsup:

 

[koauke]

There was a slight breeze, but definitely not something I would think could make a difference.

The front sight is brass and I initially thought that the light reflecting off of it was the reason but as the sun moved and the front sight hit the shade it didn't change anything. It was 82 degrees out and I could feel barrel was retaining more heat than it has been over the last several months when I've been out with it. It was still grouping well, just low.

I've probably put at least 400 - 500 rounds through the rifle since last June when I received it. I stopped keeping track. I use 60 grains of 3f, .018 pillow ticking, and switched to a .495 ball over the last couple of months.

It could just be something I was doing and didn't realize it.

 

[hanshi]

They can sure change poi for seemingly no logical reason. My .45 which has always had a poi about an inch high at 50 yards. I took it out a week or so ago and it had a poi of 4-5 inches high at 50. The shooting line at the range I belong to is covered so sun isn't a factor. My neck is fused and getting more and more painful so maybe that's it. It's never done this before in all the years I've owned and fired it.

So many things can and do cause this to happen. What hasn't been mentioned, though, are gremlins, curses, tick bites on the stock, neutrinos, Klingon sensor waves and cussedness.

 

[Louisk]

Not to mention gravity waves....they were discovered by shooters long before the scientists!

As far as wind drift, Billnpatti gave me this link for a calculator a while back: http://www.ctmuzzleloaders.com/ctml_experiments/rbballistics/web_apps/rb_ballistics.html

It only calculates for a crosswind not a headwind. I was surprised how much difference a little wind can make.

 

[smo]

They can sure change poi for seemingly no logical reason. My .45 which has always had a poi about an inch high at 50 yards. I took it out a week or so ago and it had a poi of 4-5 inches high at 50. The shooting line at the range I belong to is covered so sun isn't a factor. My neck is fused and getting more and more painful so maybe that's it. It's never done this before in all the years I've owned and fired it.

So many things can and do cause this to happen. What hasn't been mentioned, though, are gremlins, curses, tick bites on the stock, neutrinos, Klingon sensor waves and cussedness.

. It hard to shoot good when you're in pain. To shoot your best you need to be settled and at ease.

 

[Grenadier1758]

Have you tried using the same balls you used to get the center group? The change in ball size can change vibrations in the barrel.

 

[dragnetbill]

Beyond the light reflection on sights there may be the targets to consider. Being frugal (cheap) I make my own informal targets on standard sheets of office paper; on a recent range session I posted one target that was a stick-on orange bullseye and one that I had stenciled an X on with magic marker; back to back five shot groups with the same load produced different points of impact (horizontal shift).
Far from scientific or conclusive but I believe that how my eye percieved the different targets may have produced the different points of impact.

 

[Loyalist Dave]

IF you altered your seating of the bullet..., a pressure difference might cause a different burn, thus slower MV = a little drop.

Sounds to me that perhaps over time the powder has just a tad moisture in it, and if it was a humid day as well..., then add the fact that a little, teeny bit of absorbed moisture might make it tougher to settle the powder, so you have a few grains less, all adding up to just enough of a lower MV to give you a little drop for your money..., :wink:

give her 65 - 70 grains and see if that doesn't change things up for you.

Remember:
Alle Fähigkeit ist vergeblich, wenn ein Engel in Ihrem Notenloch uriniert
All skill is in vain, when an Angel pisses in your touch hole!

:wink:


LD

 

[coloradoclyde]

 

[Billnpatti]

Love the flow diagram, Clyde. :thumbsup:

 

[hanshi]

. [/quote]. It hard to shoot good when you're in pain. To shoot your best you need to be settled and at ease.
[/quote]



Very, very true, my friend. And I know pain by it's first name and intimately. I have a high pain tolerance; but the chronic pain I deal with now is almost at my limit. Fused neck, scoliosis, degenerative spine disease and ra. Can barely pick up a glass of water without using both hands. I feel for you, brother.

Oh, did I mention the chronic fatigue that accompanies it all, can't walk very far and have to use a cane. You know what would make me feel better? If someone would build me a nice rifle (EL) for a Christmas present. :v: :dead: :hijacked: :idunno:

 

[coloradoclyde]

Love the flow diagram, Clyde. :thumbsup:

It's a blueprint for successful thinking... :grin:

 

[ohio ramrod]

Also known as "scientific method", Observation ,hypothesis, experimentation , results confirmed or rebuked. :idunno: