I got a little lost reading the thread which Mr. Roberts kindly took the time to evaluate the ACOGS according to BDC. I tried to figure out the one I should use and what the drops might be using my rifle.

My question is for a Fixed Carry Handle 14.5" Colt- the BDC calculations for this rifle using a fixed carry handle ACOG or using a Flat Top ACOG.
Is it better to use a Fixed Carry Handle Reticle ACOG as far as the BDC is concerned out to say 700 meters? Which is more dead on the Fixed Carry Handle or the Flat Top Carry Handle reticle if using the standard 20" style reticle patterns on a 14.5" barreled fixed carry handle?

I am just trying to narrow my choices as to which is more accurate on the fixed carry handle 14.5" set-up.

If anyone could help it would be appreciated and also which bullet weight.

Thank you,
Creeper





 

What are you going to be shooting with your short little 14.5 inch barrel flinging 55 grain bullets out to 700 yards?

Your distance to 2700 feet per second is like 70 to 90 yards if I recall correctly. Below 2700 ft/sec you're not going to get dependable tumble.

Even a 20" is good to like 170 to 200 yards IIRC.

People don't shoot paper targets with ACOG's so I'm assuming you're trying to shoot people - people who might be armed with a real weapon that can return fire from 700 yards away with some killing power!

Rather than "accurate" you really want to know which will be closer to the bullet drop marks. Range estimation plays a bigger role than where the BDC marks are at distances like that.

Heavy wieght bullets retain more energy out there but even then not much at all. A FMJ-boattail 55 grain bullet fired from a 24" barrel will be travelling 3240 ft/sec at the barrel and just 1940 ft/sec 500 yards later going from 1280 ft/pds of energy to just 460. The rifle zeroed at 200 yards will drop the bullet 38 inches at 500 yards.

The figures for 700 yards are even greater!

[url]http://www.federalcartridge.com/ammocat20.asp?s1=1[/url]

Well I normally don't shoot 55 grain out of my 14.5". However Mr. Roberts post said for 55 grain using 20" barrel fixed carry handle.

I am just trying to figure which ACOG with what weight of bullet is best combo with 14.5" barrel that is somewhat accurate out to at least 600 yards which the military has determined the 62 grainer good for on a 14.5"

Normally if I go past 400 yards I won't be using wimpy .223 (or for any distance defensive shooting), but would use one of my .30 caliber rifles instead.

However since these scopes have ranges out to 800 then at least which scope would be good for say 600 but using a fixed carry handle set up and 14.5" barrel as per military setup- that's all. They make one for the Flat Top but I don't have that luxury since my Colt has a fixed carry handle.

Creeper, I responded to your question in the BDC Chart thread also, check that out.



There is minimal difference between the Flattop ACOG BDC and the Carry Handle ACOG BDC for your setup. They both work equally well out to 550m or 600yds. Past 600 I can't say as I didn't do calculations that far. For your purposes; both deviate from the reticle about the same amount so go with whatever reticle you like best.

IF you ever plan to flattop in the future, the flattop BDC is designed to match your rifle exactly.

Speaking in generalities:

The Carry Handle ACOG BDC can be made to somewhat match almost any barrel, mount and ammo combo there is, though it starts to be a poor match with heavier rounds.

The Flattop ACOG BDC has a trajectory that is easier to match well to a wide variety of ammo; but doesn't work at all with some carry handle combinations (mainly 18" and longer barrels shooting 62gr or lighter ammo).

The .308 ACOG BDC seems to match the heavy rounds very well; but is a poor match for most common 5.56mm rounds.



Use whatever ammo you want to use and then figure out how to make the ACOG work with it would be my advice.