Shooting position

gcp · Post by **gcp** » Sun Aug 11, 2013 1:54 pm

While shooting my 22 mag Marlin today at 100 yards I notice something of interest I thought warranted discussion. The lower 2 shots where shoot without changing shooting position, while the remaining 3 were shot after I got up to check the 1st two. I am surprised that by simply re-assuming shooting position, which should be constant for the most part, would make that much of a difference to POI.

blue68f100 · Post by **blue68f100** » Sun Aug 11, 2013 3:54 pm

Did you change the position of your forehand?

Post by **Bullseye** » Sun Aug 11, 2013 4:36 pm

This same type of circumstance can happen if you change your "cheek weld" position on the stock. Your eye is part of the aiming system and if the position of it is moved so does the impacts on the target. Ensuring that your cheek finds the exact same spot on the stock is key to consistency of performance.

R,
Bullseye

gcp · Post by **gcp** » Sun Aug 11, 2013 10:21 pm

On the forearm, not that I can think of but maybe I did instinctively. How does the forearm play into this? Let me explain, the target is bench rest with the left arm/hand wrapped around and supporting the back of the stock. Cheek weld should also have been the same but I was having trouble at 9X seeing out of the scope so maybe not. I think I’ll put a better scope on this Marlin because it’s accurate enough to deserve better glass.

On a related question, how can one reload rimfires? They continue to be hard to come by now days and are more costly than I like so I need a better solution as I really am enjoying shooting this 22Mag.

gcp · Post by **gcp** » Mon Aug 12, 2013 6:56 am

On second thought, and I do my best thinking while asleep

I believe blue is on to it! The sandbag under the rifle's forearm may have been elsewhere after I re-assumed my shooting position. The Marlin's barrel is floating but under it it's a cheep plastic stock so who knows what pressure points exist.

Georgezilla · Post by **Georgezilla** » Mon Aug 12, 2013 3:43 pm

There are A LOT of possible causes for POI changes during shooting.

In addition to what BE and blue noted (which are likely the causes seeing as you only fired 2 rounds), POI can change as a barrel heats up.

Often less expensive barrels are not stressed relieved post fabricating, and they are also usually button rifled in the traditional manner. Basically this creates unresolved stresses in the barrel that can manifest in a barrel's deflecting in a direction upon heating up. This is actually the reason why target shooters pretty much never use cold hammer forged barrels, they have A LOT of residual stress that is very difficult to relieve using traditional methods, so the deflection on most CHF barrels is significant upon heating (there are exceptions though).

Also, even if a barrel is properly stress relieved so that the thermal expansion is more or less uniform, there can still be POI changes if the barrel is not free-floated properly. Sometimes a cold barrel can be free-floated, but upon heating up the barrel can expand into the stock which causes a stress and deflection on the barrel. Lastly, really thin barrels tend to change POI readily even if it's floated and stress relieved well, a lot of factors go into that. I doubt any of these are the case seeing as you only fired 2 rounds, but just some things to keep in mind.

greener · Post by **greener** » Mon Aug 12, 2013 8:21 pm

Bullseye wrote:This same type of circumstance can happen if you change your "cheek weld" position on the stock. Your eye is part of the aiming system and if the position of it is moved so does the impacts on the target. Ensuring that your cheek finds the exact same spot on the stock is key to consistency of performance.

R,
Bullseye

A rifle basic that is lost with the advent of scopes.

Post by **Bullseye** » Mon Aug 12, 2013 8:49 pm

This situation still present with the use of of a rifle scope as your aiming eye position on the stock is relative to parallax errors through the optic. I have experienced it before during 3 position smallbore rifle competition shooting in an open class league which allowed the use of a telescopic rifle scope.

R,
Bullseye

greener · Post by **greener** » Tue Aug 13, 2013 5:53 am

Bullseye wrote:This situation still present with the use of of a rifle scope as your aiming eye position on the stock is relative to parallax errors through the optic. I have experienced it before during 3 position smallbore rifle competition shooting in an open class league which allowed the use of a telescopic rifle scope.

R,
Bullseye

That could be why the rifle that shot on target last time needs a bit of tweaking this time to get back on target. I'm probably not as careful with the scope as I am with open sights.

gcp · Post by **gcp** » Tue Aug 13, 2013 5:57 am

Excellent points guys, all of them.....and truer words were never spoken, we all tend to forget the basics in our continual quest for the magic load, barrel, stock, trigger...your poison...I know it's true for me at least.

bearandoldman · Post by **bearandoldman** » Tue Aug 13, 2013 8:47 am

Remember this old saying when you are really out for accuracy, sameo, sameo, sameo, and then sameo