Inaccuracy going from lead to copper ?

[Surfdaddy]

I may have titled this wrong but I didn’t know how to phrase it.

I have a CZ bolt action in 7.62X39. I’ve been using PPU and PMC ammo and have got things sighted in ok (1” groups at 100yds). I’m going hunting this weekend and realized that I needed lead free ammo, so I got some DT tactical loads with Barnes TSX bullets. I could only get one box, so I got the bullets so I could reload in case I had trouble sighting in these and ran out. I’ve always knew that some guns like more loads than others, and I have had a little experience with this but not to this extent. With the DT loads I couldn’t keep it the groups with in a 12 inch group! I had cleaned the barrel since I shot 3 PMC rounds before to verify grouping and wanted to see if I could get a decent baseline with copper VS lead.
I also had loaded, just in case, and to see what would be the best load for this rifle. 3, 5 rounds batches of different powders and charges. 2015 at 27.5gr 28gr and 28.5gr. H4198 at 24.5 25.0 and 25.5. I got the loading data from Barnes and though they didn’t have the data for the 2015 I got it from the Hodgen site. The 2015 wasn’t as good as the H4198 but they also were not acceptable for hunting, an inconsistent 4” groups.
The question is what would be causing this inaccuracy? I’m not the best shot, primarily a shotgun shooter for the last few years, but I may be missing something.
By the way, all the cases are within .0005 length of the Barnes case dimension (1.518”) I weighed each powder charge to within +/- .1gr. and the OACL is 1.90 +/- .1

 

[Toby Bradshaw]

Perhaps the twist of your barrel isn't fast enough to stabilize the Barnes bullets, which are long for their weight (because copper is less dense than lead).

If you provide some specifics (bullet weights, muzzle velocities, twist rate) we may be able to help.

 

[stgw77]

.311" bullets works best in most 7.62X39 barrels...

 

[bigedp51]

Judging from the font size your using you may need solid copper laser guided braille bullets.

Sorry, I thought for a moment you cured my cataracts and then reality set in and I just needed more medicinal marijuana.

I have to go now and get some sleep, I have to patch the holes in my kevlar vest before I ref tomorrows game.

 

[Surfdaddy]

I’m using the Barnes 123gr .311 TSX bullets. I’m going to be hunting mostly Wild pig and Deer. In California the area I’m hunting is a lead free zone, very soon all of the state will be that way. There just aren’t too many options for lead free bullets that will I can find.

Sorry about the size of the font. It was my first post here and wasn't sure how big the default settings were.

They best group I got (around 4”) was with the H4198 and it was close to 2320fps. The 2015 was worse groups at 2180.
I thought about the bullet length but didn’t know if that would be a factor or not. I’ve heard and read nothing but great things about the Barnes bullets and never even considered the fact that I would be having trouble with this.
I guess with anything there is a learning curve. This one just happens to be at a bad time. I’m leaving on Friday for a hunting trip and I might as well use a rock if I can’t work this out. This is something that isn’t kept in stock at a lot of the reloading stores around here. So I got lucky find a box. I was really surprised that the DT Tactical loads didn’t work out.