why groups move horizontally with powder change?

[calpik]

First thing to check for is consistent cheek pressure. Whatever amount you use must be the same for every shot.

There is nothing to check. I have an issue and I know that - stock is too low and a little bit too long for me.

I want to remove buttpad and tape something on top of stock. The only problem with cheekrest is that it's going to interfere with cleaning rod. Not a big issue as I rarely clean the rifle, but anyway removing cheekrest and installing it back will harm "consistency"... ok, ok. i'm just being lazy...

[calpik]

calpik
I know , but like I used to tell people before I retired -
I did not write the book .
It you think a dirty primer pocket , flash hole , burnt
powder inside case or a combination of any don't affect
pressure , you are right up there with the press makers .
They think reloaders [ a lot do ] just decap and reload .
The rest of us waste our time and money by buying things
to clean the cases [ vibrators , tumblers , sonics , prep
stations , media , primer pocket reamers / cleaners ]
To me a dirty case is like using a 2 die set .

Absolutely agree. If someone wants top performance - everything has to be the same from shot to shot, from load to load. i.e. crystal clear brass, etc

But as I said: with my equipment I did not see any difference with dirty or clean brass, because my baseline is pretty low: 0.5-1MOA.
The only drawback of not cleaning - have to clean collet die relatively often or it will bind a case.

[tonyjr]

I spray lube the bottle necks before depriming .
This means 2 or 3 reloading sessions [ between 200 to 600
cases ] I disassemble and run thru sonic [ the dies ]
I have plenty of help , so not a big deal .

[slamfire1]

[LynnJr]

Actually Bedding was said in post 16 about a week ago.

[ar15barrels]

Noticed a strange thing, with some bullets/powder groups move horizontally more than vertically.

What's the reason of such behavior? (rifle is not bedded, 223rem, weatherby vanguard)

Shooter position behind gun.
Hand position on stock/trigger.
Trigger control.
Parallax adjustment.

[calpik]

alright... some new results:

I put some glue into the stock and screwed in action.
Now groups stopped jumping around on a paper, i.e. I still see horizontal movement of the POI with increasing charge weight, but not so much as it was before.

Now all groups (difference is 1 full grain of powder) are in the same area - 0.25inch away from each other.

I like that, but I don't like the fact that to get a descent group I need to put more powder (so "good spot" shifted from low charges to high charges). And they became more 0.9-1.2 moa in average. - i'm ok with that, but it was better before, so I want to get it back


questions time:
1. action sits supertight in the stock, but to get it there i have to push with a lot of force (or put the screw and tight). After that previous method of bedding job check shows that there is no movement of the barrel.
Should i remove some epoxy? to let it drop into the stock, instead of pushing it in

2. i also left some glue under the barrel (in front of recoil lug) - should i remove it?

3. should I play with action screws before damaging epoxy?