Posted: 1/20/2015 12:05:49 PM EDT
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I picked up a bushnell ar optic for .223 with the bdc
Its now mounted on a rem 700 308 . What ammo can i use in 308 to give me close to the same flight as .55 Gr .223 ? Thanks |
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55 gr. 223 velocities are all over the place, so more detail than that is needed.
I've found 77 gr 5.56 and 175 7.62 to match pretty closely wrt elevation, and roughly around 25%-33% more windage correction required for the 77gr. As long as you know the reticle subtensions, chrono the loads and use a ballistics program, you can make a note of the variations between guns. |
| You're asking how to use a wrench as a screwdriver however there is an answer. 110 grain .308's should have a pretty decent match to 55grain. BC's are close and so is MV. It'll keep you pretty well on out to 300m. I use 110gn round nose .30 carbine bullets for some things but you'll get a better trajectory match with 110gn TAC-TX or another pointy .308" 110 grain pill. You can get them going 3150fps from the .308 case pretty easily. The .30 cal pointy bullets have a slight BC advantage but the .223's have a slight MV advantage. It all evens out pretty nicely for short to intermediate ranges. |
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Quoted:
You're asking how to use a wrench as a screwdriver however there is an answer. 110 grain .308's should have a pretty decent match to 55grain. BC's are close and so is MV. It'll keep you pretty well on out to 300m. I use 110gn round nose .30 carbine bullets for some things but you'll get a better trajectory match with 110gn TAC-TX or another pointy .308" 110 grain pill. You can get them going 3150fps from the .308 case pretty easily. The .30 cal pointy bullets have a slight BC advantage but the .223's have a slight MV advantage. It all evens out pretty nicely for short to intermediate ranges. Not a bad idea as long as the gun groups with the light stuff. He would still be locked out of the bulk of factory ammo though without correction. Way to think out of the box 
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Download Strelok+ Pro ballistic soltware. Dirt cheap. It has the reticle. If you know your load velocity and bullet BC, and some other variables if you really want to be precise, and in addition to giving you a drop chart, it shows you a through the eyepiece view of your reticle with yardage for each subtension mark. It works with any load, any caliber, and any reticles ofvthe hundred or more in its catalog.
This is your reticle in the 3-9-40mm scope version used with a theoretical 7mm 168 grain hunting bullet at 2650 fps. Of course, I just randomly picked a bullet and load data I already use in a particular bolt action rifle (.280 Remington), particular ambient temp, altitude and such. Your load with a .30 caliber bullet with different BC and velocity will be different. The drop will be different. I didn't try to run your data because I don't know your bullet weight, BC or velocity from your barrel. But, this shows what the software can do. Note how, with this example the holdover points do come close to 200, 300, 400, 500, 600 yards. That was accidental and should not be expected with a .30 cal bullet with different BC and velocity.. What you want is the best performing ammo with accuracy, trajectory and terminal performance and then learn the holdover yardage, rather than choosing ammo just because it matches the scope BDC. That would be putting things backward. Select your load based on what is most accurate in your rifle and best for the type of shooting you intend to do, rather than trying to force less accurate or less effective bullets to match your scope BDC marks. 
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| Zero the scope normally at 100 yds. Then try that setting at 200 yds. Put the crosshairs on the point of impact and use that as the reference for the bullet drop. On a Nikon P-223 its pretty easy as that scope has several horizontal lines for bullet drop already there. As for windage that always requires experimentation. |