7 mag grouping issue, longish distance

[7mmfan]

I have a handload that I shoot out of my 7mag, have been using it for years with great success. Have never had a need to shoot more than 150-200 yards, but recently have begun hunting more open ground and see the potential for 300-400 yard shots.

At 100 yards, I group consistany inside 1". At 200 I'm a little bigger than that.

Today I went to the range and shot at 300. I couldn't find a hole on paper. I felt very good about all my shots, no jerking/flinching, just solid squeeeeeze boom.

What could be happening between 100-300 that would cause me to not be on paper. My ballistics chart shows me only dropping about 4 inches between 100-300, so I highly doubt I was shooting low.

Load is a fairly hot load at 63gr IMR4831 with a 154gr Hornaday Interbond.

Guy at Kesselrings today told me he felt the bullet could be losing speed and stability, but I just don't think thats the case. Any thoughts?

[bobcat]

How big was your target? Was there any wind? Did you only shoot at 300 yards today?

[jjhunter]

Did you shoot a 100 or 200 yard target today?

[7mmfan]

Target was plenty large. 10" above and below and had same targets to either side so if it was drifting because of wind I would have hit. There was some wind, but my partner shooting his 7 mag at the same distance at the same time put together a perfectly normal group.

I shot at 100 to verify I was still on, and had a great 3 shot group. Did not shoot at 200 like I should have.

[CAMPMEAT]

My 308 did the same thing. Found out the scope was bad through process of elimination.

[BOWHUNTER45]

Try that exact load with a 160 gr partition ...I wasted a lot of time and money trying to figure out my friend T3 in the 7mag ..so I bought some partitions and it ate them for breakfast ...

[big t]

 Try moving your target out 35, 40 yds at a time until you group starts to change and keep zeroing as you proceed out to you desired range of 300 or 400 yds. As long as your group is good at 100 I would start at that distance.
  Make sure everything is tight (scope, rings etc.)  I looked your load up, as close as I could get to it in my Nosler book and you should be good there.
  I've been reloading since 1973. Doesn't make me an expert by any means however I believe you are shooting over your target as the slug is still climbing somewhat.
  Hang in there you'll find a remedy for it. Get back to me and let me know how you do.
     

[big t]

Forgot to mention to make sure your scope is mounted square with the barrel. like this +
                                                                                                                              O
and not like this x.
                        O
Even a very slight off center and it will vary quite a bit at a longer distance.

[7mmfan]

I have been thinking a lot about a slightly heavier bullet and seeing if this improves grouping. I have shot 162gr SST's out of it and they did very well. I will double check the squareness of the scope and all fasteners. Thanks.

[Karl Blanchard]

Like has been stated before, make sure everything is tight and make sure your reticle is not canted.  A few seemingly small issues like that won't show at 100 but magnify greatly at longer distances.  Small variances with gun/load can make ballistic calculators pretty inaccurate.  Also try shooting your buddies gun.  Not saying it is you, but if you can't hit with his either then you could eliminate beating your head against the wall and spending a bunch of money trying to remedy your current rig.  Good on you for hitting the range and practicing longer distances also!  Lots of guys just print out a drop chart using the velocity off the back of the ammo box and think they are good to go.  Prior planning and preparation prevents piss poor performance

[Karl Blanchard]

I have been thinking a lot about a slightly heavier bullet and seeing if this improves grouping. I have shot 162gr SST's out of it and they did very well. I will double check the squareness of the scope and all fasteners. Thanks.

  Pretty good odds that the size of the slug isn't the issue.  Those 154's have a good b.c. and the caliber itself is a great long range platform.  I shot 150's out of mine and it was a tack driver at longer distances.

[7mmfan]

Great suggestion BLRman, way to make a guy think about the obvious answers to his problems! If I had not done a fair amount of long range shooting before with other firearms, I would definitely consider that. I have never run into this problem before where a seemingly accurate load and good group just disapeared at distance.

[BUTTER]

You really gave limited information on your grouping my 300 with factory  ammo I have set at  2 inches high at one hundred its dead on at 200 and about six inches low at 300 I am guessing your dead on at a hundrerd?

[Karl Blanchard]

24 or 26" tube?  Have you ran the load through a chrony?  Most reloading data for the 7mag is based off of a 26" tube.  If you have a 24" pipe you should be subtracting about 35fps from your velocity.   Also, do you know how high your reticle is from the center of the bore (sight height)?  That can make a big difference in point of impact as well.

[7mmfan]

I'm sighted in 2" high at 100. Gun is a 26" barrel, don't know how high the reticle is above the center of the barrel, will have to check I guess