Advanced Marksmanship I need help please

[Jtbaker1989]

Hey everyone. I have some questions regarding shooting at 400 yards. I didn't know exactly where to post this, so if its wrong I am sorry. I have a howa 1500 in .308 with a 20in barrel in a 1/10 twist with a Hogue OD green stock. The ammo I am currently using is hand loaded Sierra 168g BTHP matchking, lapua brass, 42.0g of varget, Remington primers with a COAL of 2.800. According to sierra load data, the velocity should be 2600. At 100 yards after firing 3 shots, the group is tight enough a quarter will easily cover the grouping.
Now today we shot at 400 yards off of sandbags. My grouping was horrible. We were shooting at a 12inch circle target and the rounds were landing about 6 to 8 inches from center but they were placed all over the target. It was almost making a circle around the target but again about 6 to 8 inchs from center. A friend who was shooting with me was running a 7mm using the same bullet as I, but with different powder. When I shot his weapon, I could get about a 3 to 4 inch group out of it. I am in no way a marksmen shooter but with the results I had with the 7mm vs my .308, something just doesn't seem right.
My question is, I am using the correct powder/bullet/COAL for this distance and beyond? What can I do different or work on to help improve the grouping for this weapon? Or is there something I need to look at on the gun that may be a issue? Thanks a lot for the input and help.

 

[roggom]

Few things:

You load is more likely in the 2500 FPS range at 42 gr out of a 20" bbl. Remember velocity has an effect on BC, no need to hotrod your load but there are a few more accuracy nodes above what you are shooting. A med node should be somewhere around 44.0-44.5 grains of varget.

Research and run a ladder test at 300Y. This will get you closer to the accuracy node you are looking for.

Lastly check the parallax on your scope. Could be the load, but also parallax can cause your groups to open at higher mag and longer distance.

Shooting Tip - Scope Parallax - YouTube

 

[Sako man]

Few things:

You load is more likely in the 2500 FPS range at 42 gr out of a 20" bbl. Remember velocity has an effect on BC, no need to hotrod your load but there are a few more accuracy nodes above what you are shooting. A med node should be somewhere around 44.0-44.5 grains of varget.

Research and run a ladder test at 300Y. This will get you closer to the accuracy node you are looking for.

Lastly check the parallax on your scope. Could be the load, but also parallax can cause your groups to open at higher mag and longer distance.

Unless it was was pretty windy that day I would think it's more your likely parallax than MV. But this guy is correct, 42g varget is going to be slow. for a 1/10 20" barrel try 175smks, it will love them. 43.5 to 45g Varget. Do the work up of course. But your ingredients are good.

I rest my rifle in a neutral position so it's naturally pointing at the target, I then move my head up and down (not touching the stock) while looking through the optic to make sure the reticle is tracking in the same plane as the target. Perhaps the video covers that.

 

[Jtbaker1989]

wow, thanks a lot sako man and roggom. That was helpful information. The day was alittle windy but when we shot the 7mm it was a much tighter group. I am in no way a expert in firearms so I do not know much on the different between .308 and 7mm. I will reset my scope again and go over the parallex again. I am kinda new to reloading and going over the sierra reloading manual it says max load for this round is 43.5 with a velocity of 2700. Their testing was done with a 26in barrel with a 1/10 twist. Thanks again guys for the information and help.

 

[tullius]

Not wind. Probably that damned Hogue tupperware flexi-stock. Bet you couldn't slide a dollar bill between the stock & barrel when it was on the sandbags..

How did you shoot your 100yd. group?

 

[Jtbaker1989]

actually we tried the dollar bill trick with it on the sandbags and off the bags. The dollar bill slide under the barrel both ways. On my 100 yard shooting, we rested on sandbags sitting in a chair. Same way for 400 yards.

 

[Sterling Shooter]

OP,

Call your shots. When shots are not on call, error is likely about not properly adjusting for the effects of wind. At 400 yards, either a half value 10 MPH wind or a full value 5 MPH wind would be worth about 2 minutes of favor, or about 8 inches of sight offset. Not countering for this non prevailing or switching wind could get the results you described. Error from shooter or gun would produce shots on call but not where desired.

 

[TimK]

Sliding a bill under the barrel means nothing with a flexible stock. Under recoil, the stock will flex, contacting the barrel and changing poi.

I'd guess parallax error as well.

 

[Jtbaker1989]

thanks guys for the information. Another question, the scope rings that I am using contain 6 screws per ring with 3 on each side. I use blue lockite on these but what should they be torqued to roughly? I believe each time I send a round down range the scope is moving on me.

 

[Enough Said]

Beyond the other variables that it may be, make sure you are torquing your screws to spec after every 50 to 100 rounds.

My groups opened unexplained one time and upon disassembling my rifle chassis, I found a loose block just forward of my mag well. Tightened everything up and went back to magic shooting.

 

[farrier]

get rid of the lock-tite on the ring screws and pull them apart. If the scope is moving with every shot, you'll have the scars on the scope to prove it. If these are quality rings, great, if not, get a good set of rings and torque to manufacturers specs, often around 15 in/lbs. The connection between scope and rifle has to be solid and trustworthy. Good lock.