hey guys. got a bit of a problem. im shooting a 7mm rem mag, 26" lilja, and 180 bergers. my powder charge is 70.2gr of H1000 and CCI 250. the chrono read 2920-2928 for 6 shots. took it to 1210 yards and had a 8"wide x 24" high group for another six. ran the numbers through LRH's G7 calc and it gave me a true MV of 2995. can i trust my chrono? and how do i get rid of this vertical?
chrono'd velocity and vertical string
- Thread starter shawnb
- Start date
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8" wide at 1,210 yards is 3/4 MOA that is fantastic. On a NON-muzzle brake rifle my experience has been that vertical is from muzzle rise or an inconsistant pressure on forend. But with a 3/4 MOA wide group, it seems you are doing everything right. Barrel temp that I've experienced will affect both directions of your group. You're there just got to tweak something small. I put muzzle brakes on all my big guns and shot better with the brake, and I Boran Nitride coat all my bullets and it keeps the barrel dramatically cooler and reduces friction and barrel wear. Remember if you coat the load you have now the chamber pressures will be lower and velocity also. Coated bullets will require more powder but will end up with a higher velocity. I used to send my bullets to Superior Shooting Systems to be coated, but now they offer a complete TBN kit for you to do it at home in your tumbler. It's great to save the shipping both ways and be able to coat and load when ever you want and not wait for them to be coated and shipped.
I fired 3 over 5 min then went and checked. Then 3 more. Maybe a muzzle brake is a good idea. Is there one around that is "quieter" than others? The trigger is factory. Prob set around 3.5#. So that may be another issue. But if it's around 2995 like the program says maybe I can lover my charge and get less recoil and safer pressures
The brake I use on everything except 338 and the 50 is a Miculek. If you or less than 30 cal. get the 1/2x28 AR-15 brake, and when they thread the barrel then they will install it and enlarge the hole/bore of the brake to the proper size while it's chucked up in the lathe. Purists say this is the best way because a predrilled brake could not be inline with the threads. My gunsmith said it is actually pretty common. If the muzzle brake is not perfectly centered it will screw-up the bullet flight. And a few thousands will really affect the group. What I was talking about with inconsistant pressure on the forend was sometimes people will hold down harder on the forend and the next shot loosen up a bit and go high. With a good brake you don't even have to touch the rifle forend. There is not a quiet brake that works, my experience has been the louder the better. If it's not redirecting the gases it's not working. Here's a pic and a link to the 338 brake I had built, it's amazing, but a 91lbs of felt recoil rifle needs a brake. But you can get 3 Miculeks for 1 of the custom built brakes.
Here's their website scroll down Home
I have used this and if you enter the data right, it is amazingly close. Handloads.Com Ballistic Calculator
