7mm Rem Mag accuracy problem

[scooter1979]

Hey guys,
         Thought I would pick your brains on this one. Acquired a used Win M70 7mm Rem Mag Blue/Synthetic.  Checked it out pretty well, looks like it has been bedded and floated, trigger seems really smooth.  Threw together a few loads for it just to see how it would shoot.  This is where it gets a little interesting.  Put a scope on it, and went to the range.  Accuracy hovered around 2 1/2 in at 100.  Tried a couple loads and accuracy was no better.  So I changed the scope to one I had on another rifle thats a tack driver.  Still no better. Tried some different loads.  Tired IMR 7828, IMR 4350, both with 140 Nosler bt's, and IMR 4350 with some 120gr Vmax I had layin around.   Out of 6 shots at 100 with both the 140 loads only 3 hit paper.  Im pretty baffled at this point so just for kicks i shoot the vmax.  Brought target in to 50yd to make sure, it was fine 2 shots in 1hole, went back to 100 and 3 shots measured just under 3/4".  Only thing I can see the difference is a flat base on the vmax and a boattail on the BT. Ive heard of guns not shooting one or the other very well but nothing like this.  Any opinions would be appreciated.  Thanks guys.  If Ive left any information out just let me know. 
The first loads with the original scope used Re 22 and berger vlds

[Buckskin]

While reading your post my first instict was to recommend some heavier bullets and then you go and shoot the 120 VMAX at .75 MOA...  The VMAX's are probably my favorite varmint bullet and fly out of all the guns that I've tried with them but I haven't gone over a .223 with them.  I would still recommend jumping up to a 160 gr bullet like the accubond or a heavier bullet, you probably have a twist rate that would be more favorable for heavier bullets with that 7 mag.  Although there are so many more variables that could be contributing to your issue.

[shot1]

If it will shoot those Vmax then it should shoot the other bullets. You just have not found THE LOAD yet. Keep trying. By the way I have had a couple rifles that just would not shoot BT bullets either. With flat base they shot like a house a fire. One other thought I have is the cases that you are using. I once had a brand new Rem 700 SS in 7 mag and I bought 100 new Remington cases. I did run the cases through the FL sizer before loading them. But no matter what load I tried I could not get that rifle to shoot under 1 1/2" at 100. I was about to get rid of it when I tried one more load and by that time I had run out of NEW cases so I FL sized some of the once fired cases. Went to the range and upon firing the second shot there was only one hole in the target. I fired shot 3 and only one hole in the target. I fired shot 4 & 5 and only one hole in the target so I thought great now this rifle won't even keep them on the paper. Went down to get the target and found out that all 5 had gone almost into the same hole. Found out that with a case that had been fired at least once you could just about shoot any load and it was a tack driver. Strange isn't it. 

[DANNY-L]

I always had a good hunting load for my 700 with 140 nosler bt and imr4350 about 1 1/4"- 1 1/2" at 100. I recently switch to 154gr interbonds and h4831 and now I actually rip the hole when shooting for a group.

[scooter1979]

Hey guys, thanks for the input. Just to be sure of consistency I went back to the range with the vmax and have 3 3shot groups measuring in the .7s to the .9s. I've ordered 3 different bullets to try. 120gr btip(mostly to compare the boatail vs flatbase theory, 140 sierra flatbase and 162gr hornady sst.  I think that oughta cover most of the spectrum weight wise.  I was using mostly winchester brass, Ill fl size them and just use them only (winchester) and cci mag primers to keep the variables down to a minumum.  Ill try them with the 2 powders I've already used, and then maybe some h4831. 
Thanks again for the imput guys, I appreciate it
Scooter

[HL]

I could never get 120's to shoot accurately out of my rifle, but with 160's, it will hold 1/2-3/4" groups. this is using IMR 4831 near manual max load.
I have found, shooting the 7mag since 1984, that it prefers near max loads for best accuracy, no matter what the bullet weight.

[irold]

FWIW ...I have a model 77 Ruger.  With 160 Sierra Spitzer BTs and IMR 4831 it shoots 3/4" at 100 yds ( chronys just under 3000 )....if I do my part.  But for only 2-3 shoots then the groups slowly open up.  Soon as the barrel cools its back to 3/4 to inch groups again.  For a 5 shot group , it must be shot very slowly.  Doesn't matter to me....I very seldom shoot more than once or twice anyway. 
 
regards, irold

[scooter1979]

Thanks again for the input guys,  Seems its looking more and more like bullet weight, but I guess thats what magnums are for, shoving the bigger bullets faster.  Cant wait for the bullets to come in so I can give em a try.  Really hoping they groups tighten up with a heavier bullet.  Even if they do, it wouldnt explain the 120s shooting well and the 140s shooting awful.  Oh well part of reloading  .  Thanks again guys
scooter

[jhalcott]

 So how well did FACTORY loads shoot in this gun?? Maybe the case HAS to be fireformed to the chamber, but that seems unusual to me.Compare a fired case to a new one to see how much expansion and length you get. This could affect the internal capacity and performance of the round.

[Lloyd Smale]

heres my take on the 7mag. Its one of my favorite long range deer rounds but ive allways seemed to struggle trying to get tack driving loads out of any 7mag. Most ive owned are 1.5 inch 100 yard guns and to get them to shoot moa has been a struggle and a couple ive owned wouldnt do it period. Latest one is a ruger hawkeye and its looking to be one of those that just isnt going to do it. If it sounds like ive owned alot of 7 mags its true. the reason probably being i do like the round but have allways searched for that majical one that will shoot about anything into an inch. So far its alluded me.

[kennyd]

Since belted cases head space on the belt, maybe there is too much room in the chamber to always center the bullet.  The other thing to watch is how much throate you have.