I have no way to measure the speed of my bullet. I am hoping that someone can get be close. The cal. is 223, sierra 69 gn bullet with a BC of .305, 22.8 gn of IMR 4064, seated at 1.880 to og, CCI primer, RPR with a 20"barrrel. Do I need more information to get a speed estimation? I need this information to use in a bullet drop calculation.
Help with bullet speed
- Thread starter wanttobe
- Start date
Roach , Thanks so much. Entered all the inf. an got 2690, This should really help for I was sure have some problems yesterday at the range. Zero at 100 yd., 2 clks up was 3/4 high at 200 yd. Didn't seam correct but that what it was. Scope was 1/4 per clk. Not knowing where I was hitting I could not ring 12" steel 300 and 400 yd.
Get yourself a ballistics app like shooter. Adjust the velocity until it matches what your holding, or dialing up.
Jarhead6870
Gold $$ Contributor
I'm not sure how you determined your 200 yard elevation values but based on what you've given us, when put into a program, the numbers I get do not jive with what you're getting. Based on a 69 grain sierra bullet going 2690 fps with a 100 yard zero, the elevation drop at 200 yards is 4" which equates to 2 MOA, which with a 1/4 MOA value per click would equate to 8 clicks. 300 yard drop is 15.6 inches requiring 5 MOA and 400 yards has 36.7" of drop needing 8 3/4 MOA. These values are close as atmospherics can cause a difference in dialed elevation depending on your location and weather conditions. Hope this helps.
Jarhead, You are right on. as I said I was having trouble with the numbers I was getting. An as snret said it turned out to be the shooters problem. What cause the problem was the last time I was shooting I was shooting at 200 yds. and when I return home I was checking two of my rifles and resetting the turret caps to zero where I had made some adjustments at the range. on the rifle in question my last shots were at 200 yds, that where I made my mistake, I moved the turret cap back to zero causing my true zero to now be 200 yds. When I when back to the range Sunday started shooting at 200 yds so I move my turret 7 clks up, that would have been the correct data if zero at 100 yds. Was not on paper, kept moving down till I was 3/4" inchs high, that was 2 clks up from zero. Those numbers were correct for at 200 yds. zero, 2 clks would get me to 3/4" high.So thanks for all the help and comments, it was just a very dump mistake on my part for I have been shooting for many years. This will help me going forward.
I use that bullet and load according to Sierra's accuracy load info of 25.3 g of Varget. With a 16" 5.56 NATO chamber, I get about 2,720-2,735 fps and going to 25.5g, 2,740-2,750 fps at the muzzle. I set the overall length to 2.300". The recommended (just to fit most factory magazines) is 2.260". In my .308 IMR4064 produces about 1% to 1.5% more velocity over Varget for the same load. All else being equal, a 20" barrel should be about 3.5% to 4% faster than a 16".
snert
Silver $$ Contributor
now that makes sense
Ned Ludd
Silver $$ Contributor
Obviously, having a chronograph is the best way to know your velocity. However, if you don't have access to one, one thing you can do is to put a few shots into a dirt berm, rather than at a target of some kind. Even if you're off by a couple or three feet, it's usually possible to spot the dirt splashes and get dialed in, especially if you have someone spot them for you. Many ranges have enough twigs, rocks, and/or broken shotgun clays laying on the berms that you can usually pick out something as an aiming point and work from there.
Once you're mostly dialed in, you can fine tune the elevation/windage on the actual target without wasting a lot of rounds just trying to get on the target. At that point, inputting your drop, atmospheric, and bullet data into a ballistics calculator such as JBM Ballistics will allow you to adjust the velocity input until the drops match what you actually observed.
Once you're mostly dialed in, you can fine tune the elevation/windage on the actual target without wasting a lot of rounds just trying to get on the target. At that point, inputting your drop, atmospheric, and bullet data into a ballistics calculator such as JBM Ballistics will allow you to adjust the velocity input until the drops match what you actually observed.
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