Scopes and bullet drop???

Guest · Post by **Guest** » Mon Oct 31, 2011 2:17 pm

If i use a rifle scope BDC for 7.5 Swiss caliber on a rifle that shoots 223/556 caliber bullets; how far off will the scope be with regard to bullet drop over different distances?

Is it possible to use a BDC scope for a rifle of a different caliber with at least some success???

Thanks for any help with my questions

:)

Rover · Post by **Rover** » Mon Oct 31, 2011 4:53 pm

Q1: Try it and see; too many variables.

Q2: Yes.

Levergun59 · Post by **Levergun59** » Mon Oct 31, 2011 10:46 pm

If you handload and choose the right bullets and propellent charges, you can make it work with just about any bottleneck cartridge. I assume this scope was set up for Swiss military ball ammo.
Chris

Guest · Post by **Guest** » Tue Nov 01, 2011 6:31 pm

it depends on what you are trying to shoot with it, ie how big the target is. It would be very hard to match the bullet drop from calibers that are so different. Ive been trying to replicate the bullet drop of australian military rifles with the same caliber rifle in a bolt action with a longer barrel but so far havent been able to

Levergun59 · Post by **Levergun59** » Tue Nov 01, 2011 6:59 pm

guest,
If you are looking for more speed in a short barreled rifle, try the double base powders from Vitah Vouri. They can add up to 200fps and should compensate for the short barrel. Their are computer programs that will also make a guesstimate of what to load to duplicate another bullet drop. You need to enter all the bullet BC's, bullet drops, velocities ect. It will get you very close to where you want to be.
Chris

muffo as guest · Post by **muffo as guest** » Tue Nov 01, 2011 7:11 pm

th military 556 is actually very slow. Problem is i dont have the info on what powder is used or even what size projectile it is. It looks to me like a 55 grain fmj but if i load a 55 grain projectile and match the muzzle velocity the bullet drop isnt anywhere near the drop of the army rifle

Levergun59 · Post by **Levergun59** » Wed Nov 02, 2011 12:10 am

The 7.5x55 Swiss army round or GP 11 is a 174gn FMJ with a ballistic coefficiant of .505-.514. It has a muzzle velocity of 2560fps. I just checked through Sierra's offerings and the 190gn Sierra Matchking has a BC of .505. Although you can't compare BC's from any different bullet manufacturer, this will get you in the ballpark. You launch this bullet at 2560fps and your scope will be close. You will need a 1 in 7 twist barrel to stabilize this bullet. If you play around with the powder charges, you will be able to duplicate the stadia wires on this scope. Hope this helps
Chris

j-team · Post by **j-team** » Wed Nov 02, 2011 4:10 am

muffo as guest wrote:th military 556 is actually very slow.

M193 55 grain FMJBT @ 3250 fps
M855 62 grain FMJBT @ 3025 fps

Slow? Compared to what?

Muffo · Post by **Muffo** » Wed Nov 02, 2011 4:25 am

Talking about Australian military rounds. which i was told were 55 grain rounds but i think they are more likely 62. they only have 1 round not 2. 3001fps. I would consider 3200fps on a 55 grain 223 slow. 3400 would be more normal but i guess that isnt taking into account the short barrel

mika · Post by **mika** » Wed Nov 02, 2011 6:46 am

I think it's both possible and useful, but you need to familiarize yourself with your loads and the reticle. With some effort you'll find how to best use or for your benefit. If you can accept that the distances are different, you don't even need to develop special loads.

Also remember that even a matching load won't work with the reticle If the sight/barrel line offset does not match. But also there, your "own rules" can work. It's quite difficult to get exact results with bdc, but If you don't expect that and use the reticle to your own benefit understanding what's going on, they can be nice.

Mika

j-team · Post by **j-team** » Wed Nov 02, 2011 1:37 pm

Muffo wrote:Talking about Australian military rounds. which i was told were 55 grain rounds but i think they are more likely 62. they only have 1 round not 2. 3001fps. I would consider 3200fps on a 55 grain 223 slow. 3400 would be more normal but i guess that isnt taking into account the short barrel

3200fps is quite normal in a .223 with a 55 gr projectile. The Steyr AUG has a 20" barrel, same as M16A2. I just looks short because it's a bullpup design.

You would need a .220 Swift or similar to get 3400fps with a 55gr projectile.

Muffo · Post by **Muffo** » Wed Nov 02, 2011 5:07 pm

Yeh 20 inch is relatively short. my friends Remington 700 with 26 inch barrel was getting just over 3400 out of a 55 grain. 220 swift should get way more than 3400. not sure exactly what speeds it will achieve but my 223wssm will push a 52 grain projectile at almost 4200 So i would have thought the 220 swift would have got close to 4000. Any way, what i was saying about the army rounds being slow was a little misinformed as I was told they are 55 grain rounds and that would explain why i was having so much trouble getting a 55 grain round to match its bullet drop. And since making that post i found info saying they are 62 grain projectiles that i couldnt find the first time i searched