Maybe I suck less than I thought I did. (POA/POI findings)

[adam_mac84]

So, this summer, I have mostly sworn off any factory ammo. I had gone exclusively to reloads of plated ammo last season, but shot factory in competitions. This spring, I started shooting cast boolits in training and plated in matches. And my last match, I did switch fully to lead.

Needless to say, 2017 I didn't have much factory ammo in my life [smilie=p: I have been so caught up this year in eliminating the lead that nearly everything I shoot have been test loads of some form, until I landed on a decent minor PF load with 231 and Titegroup that seemed decent.

Long story short, I have been beating myself up on some accuracy issues (pulling everything left), and today while shooting some B8 targets at 25 yards, I did shoot a couple with some cheapo 115gr Amscore that I picked up for like $8.50 a box to have on hand for others to shoot if they accompany me to the range.

Low and behold, I was able to actually keep things centered.

All of my cast rounds were going left. I also did a test where I aimed at the 4 oclock position with cast rounds. They found the center. Rode the right side of the rear sight with the post (POA at the X)... ended up centered. So everything needed to be compensated for being slightly left of POA. I of course blamed my trigger pull, and have been dry firing like mad the last few weeks, and thinking I was doing a pretty good job in the basement, but not having it translate to the range.

Until I shot the B8 with factory. Centered POA, Centered impact. And a good score from 15 yards (for me).

Pic in next post (I have to attach on my phone.)

Normal for a cast round to have a POI lateral to the POA? I don't mind much about up/down... that can be made up for easily enough with holdovers... but I am not a huge fan of Kentucky windage

[adam_mac84]

https://uploads.tapatalk-cdn.com/20171001/313abe2ae26d8972b0fe90840f0612dd.jpg

Left is cast. POA. Center x.

Factory ammo is Center x.
Middle lower target was x POA riding right side of rear sight in sight picture.

Target on far right is compensated POA.


Sent from my iPhone using Tapatalk

[runfiverun]

lateral, higher, lower.
different ammo has different POI.
same ammo different powder amount or deeper seating will do it too.

[sutherpride59]

Never experienced much of a poi change with factory vs cast but you might try harder lead or different sizing die and see what happens. I have a nice hollow point mold that when I use the hollow points they won't group better than 3.5" at 25 yards and are high in left, when I replace the pins and make them flat nose instead of hollow point they are dead center 1.5" groups at 25 yards. Almost as good as my SWC's. Keep in mind is shoot 45 and run major PF.

[adam_mac84]

I was not expecting lateral shift at all... knowing it is 'normal' makes me so much happier. This is after testing way too many loads, alloys, expanders, seating depths, diameters bla bla bla, and the leading after 200 rounds was very minimal. Bumping the sight a bit is the least of my worries at this point!!!!

[Digital Dan]

Adam, it isn't clear to me what style of gun you're shooting though I get the impression it is a handgun. Doesn't matter a whole lot either way thought peestols and rifles have different personalities and dance steps.

With very few exceptions a change of load in any fashion will prompt a change in POI. The reason is fairly simple. The firing sequence for any gun/load/hold is an exercise in chaos. Guns are dynamic tools that respond to minor change in nuance to pressure curve and peak, bullet weight, primer, powder charge, etc, etc, ad nauseum. You can develop a load that is equal to a given brand and lot of factory ammo, but it is a tedious process. OR, you can find a load you like, adjust the sights and move on.

Couple of points to illustrate the above. Rifle barrels droop. They are not the rigid pipe that most believe, and this is the primary reason you see bench rest barrels in the short fat iteration more often than not. It is called column stiffness. They still droop due to gravity, but just do it a little less. When the sear releases the hammer it unleashes a vibration sequence in the receiver and then the gun barrel. It is fairly consistent from shot to shot, but if you change primers, guess what? You have changed the vibration sequence. In a conventional rifle that vibration will resonate 2-3 times over the length of the barrel before the bullet exits the muzzle. Small groups come from making the chaos consistent. On target groups come from sight adjustment.

An illustration of this point is found on the target below. 4 load pairs, the only thing different in each pair is the bullet alloy. The only difference between the pairs is powder charge. Otherwise, same distance, same hold.

https://i.imgur.com/YkBD31K.jpg

[adam_mac84]

Pistol, Glock 34 with aftermarket barrel. I want to find a ransom rest to try from... but unlikely

[dverna]

I bought a sight pusher to address left/right POI issues.

I do not run different loads in the same gun very often. Once I have a load that works, I adjust for it.