Problems zeroing the same load as last year??? Advise?

[Pete112288]

So I finally had a break in my schedule that allowed for me to get out to sight in after shimming my rear sight. I went to the same spot to shoot as always in the past. The same powder, the same measure of powder, the same bullets, the same loading and shooting process but horrible results. I am off the same bench as before as well and the same type of target. Last year I was drilling a 3-3.5 inch hole in the target at 100 yards and 2 inch and under groups at 50 yards. Today everything was the same as before except for the shim under the rear sight. I just don't know whats up. The rear sight is still secured well and solid after the modification. At 50 yards only 3 of 10 shots hit an 8 inch circle. At 100 yards 1 shot missed the 2ft by 18" board completely and I had 2 shots on polar opposite edges of the target along with scattered shots all over. No pattern to them beyond an 8 inch group of 3 to the right of the bull. 23 shots, 4 hours of shooting, and I accomplished nothing but disappointment.
I shoot a Traditions Vortek with Great plains bullets. I normally shoot 90 grains of 777 FFFG but I even tried stepping it down to 80 because that's what I started with the first time I shot this load ever. Still no good results. Any tips or something I could be overlooking?
I love my peep sight but I may try going back to the fiber optic irons that came on it just to see.
The first load I ever shot through this were powerbelts and they did clover leafs at 100 yards off a bench. Then I had a bad experience with them on an elk and swore I would never go back. I was thinking about going with a sabot load to see if that would make a difference but I just don't have the money. After I zeroed last year I bought over 100 rounds of the GP bullets. Now I have all of those and they don't seem to want to shoot well. I just keep thinking it has to be a shooter issue but seriously missing a 2 ft board completely....

[barracuda163]

Sabots and more powder.  Not sure when your rifle was manufactured or even when vortek changed some hammer issues and cerakote issues. I've seen several first gen vorteks that had serious barrel corrosion. On the other hand if this was a scoped rifle with same issues, I'd say loose optics.

[one shot kill]

I learned this lesson the hard way. Couldn't get them to group. Found out 777 is really good at absorbing moisture. Bought a new can of powder and problem solved. Might be worth trying if you are using the same powder you had last year.

[Pete112288]

Ha, that would make sense. I hope this is not the case. I have half a pound left in this open container. But for a while I couldn't find any so Feb of 2014 when I finally found it I bought 3 and still have them. Hopefully the unopened ones don't have the same issue if this is the case.

[MountainDevil54]

if its the old same bottle, bad powder most likely. Ive never been a fan of T7 as it was very erratic for me.

Start with the simple stuff, look over the rifle, make sure all the screws are tight, including the STOCK bolt. Take  a look at the nipple, find a tiny drill bit that will fit into the nipple and scrape out the carbon. #11 and musket caps can really build up over time and  that causes issues with accuracy.

[Soady]

If the powders are sealed and stored in a dry/semi cool place you should be ok. Shoot a few rounds with the other powder and shazam, you are done! 

[PyroBlack]

Check the......

Powder
Front sight
Barrel grooves leading-up

Last November - right before Opening Day, I dispersed about a half-jug of 777 FFF all over my backyard lawn. Chose not to use my Omega on Opening Day because of it. Took my sidelock roundballer and a jug of real blackpowder instead.

I no longer use American Pioneer/Shockey Gold, 777 or Pyrodex, because of moisture concerns. I use real blackpowder (currently Goex FFF) and/or Blackhorn 209. Those two have the longest shelf-life, where moisture is present. Both of these powders can get very wet and recover 100% when dried, without loss of horsepower.