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I purchased a new scope recently that is calibrated for 7.62 and it made me wonder about different caliber trajectories.

There must be some coincidental trajectory characteristics considering all the variations of different calibers. Has anyone ever seen a comparison? Obviously it would probably have to be for standard commercial offerings.

It would be interesting to know.

Thanks for any ideas or suggestions.

Jeff
 

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Would that be for 7.62X39, 7.62X54R, or 7.62X51 ?

Yes there are lots charts available for bullet drop.

7.62X54R net will give you trajectory info. for each type of military 54 R on the market in long and short barreled rifles.

However all that info. is not of any use unless you use the same ammo and same type of rifle.

What you need is info. for the type of rifle you will be shooting and a particular ammo that you will be using.
Cammed scopes for a particular cal. have too many variables, to give any info.
Type of rifle, type of ammo used, consistancy of the ammo, etc. etc.

ie. a scope made for a particular rifle in a particular cal. can be of use, but then the bullet weight is still a variable since a lot of ammo comes in diff. bullet weights.

What was the question again?
 

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Discussion Starter · #4 ·
Hey, thanks for the replies.

The specifics are along the lines of mounting a Trijicon ACOG on my M1a, which as we all know is X51 and I was wondering about the possibility if the graduations that it has would just happen to coincide with, (don't laugh), maybe 22 rimfire or some of my other calibers like a ruger 77 in 270.
 

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When speaking of rifle rounds, the external balistics of them are very SIMILAR (not same, but a great deal alike) if they throw similar weights at similar velocities, out to arround 300-350 yards. Beyond that, differnces start to become verry apparent.
.223/5.56mm, .243, .270. .308/7.62x51, 30'06, 7.62x54R, .300 Winmag, etc, etc, etc., are all very close together, within an inch or so, out to 300 yards with apropriate bullets fortheir calibres.

The "flatness" of a modern centerfire cartriges external trajectory, especially one to another, is often made far more of that it is worth untill you get into VERY HIGH velocities, and even then, it's not all that and a bag of chips.

Even a 4,000fps SABOT round I throw out of .308 is down to 2000fps @ 500 yards and almost 2 feet below line of sight, on a 300-yard zero, but, with a 316 yards zero, it is, according to a plotting program, within 3" of aimpoint vertically ("point blank") from muzzle out to 367 yards. It is my prarie-doggie round tho, once they are out of range of .22LR Stingers. :)
 

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How about altitude elevation?

This is a good thread about trajectories. However, I was wondering how much of a factor does altitude play with it? That is, are long-range [bullet] trajectories different at sea level compared to that at 5,000 feet?

I've shot low-powered rounds at long distances [200 yards plus] and noticed that bullet drop seemed to be less at the 5,000 foot elevation shooting areas compared to doing the same at sea-level.
 

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This is a good thread about trajectories. However, I was wondering how much of a factor does altitude play with it? That is, are long-range [bullet] trajectories different at sea level compared to that at 5,000 feet?

I've shot low-powered rounds at long distances [200 yards plus] and noticed that bullet drop seemed to be less at the 5,000 foot elevation shooting areas compared to doing the same at sea-level.
When you are a mile high, the air is thinner and accordingly the air resistence is reduced. Velocity doesn't drop as fast and bullet drop at any particular range will be somewhat reduced. Ain't usually a lot, though. Enough to measure, not usually enough to make a lot of difference in practice on game. On targets - best to zero at the altitude you'll be shooting at.
 

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The graduation marks on your scope will not coincide with anything printed anywhere.

There are too many variables involved.

You will have to test it out yourself, with YOUR rifle, and the ammo you will be mainly using.

No way around it.

FWIW 200 - 300 yds. is not really considered "long range"

Altitude does indeed have an affect, as well as several other factors. But unless you are in a mountainous area and plan to accend or decend considerable distance. Altitude is not a factor.

Temp. is a much greater factor. Also temp. of the ammo. Leaving ammo in the sun on certain types increases the pressure. Old Brit. .303 with cordite is dramatically affected by heat and sunlight.

Gravel, there was a TV sniper show, recently on long range and altitude effects. You must have seen it.
This type of shooting at high altitudes here in the states is rare, unless you are hunting mountain goats in Nev.

THe ammo you use will all be different at long range. Long range, at around 600 to 1,000 yds. or more.

600 yds. to 1,000 is usually considered "long range". It is relative.

At those ranges you will have to dope for wind and wind shears.

THe elevation adj. for bullet drop will depend on your rifle and ammo used.

Your Trijicon is an exc. scope, but it will require work to understand the bullet drop at different ranges, by trial and error with your ammo and rifle.
There is no "chart" or easy way to get a handle on bullet drop for the rifle, scope and ammo you will be using.

Any info. you get from someone using a diff. cal. or rifle is useless.

The type of bullet you use will dramatically affect the drop at different ranges. Different bullet grain weights will all have a different POI.

In gen. you can assume that larger bullets like 8mm and 30-06 will drop considerably at longer ranges. LIghter bullets like 7mm and may others, Sweded, 6.5X55 in milsurps have a flatter trajectory, but still need to be tested to see where POI is at long range. Unless you have ammo consistancy.

There is nothing similar in the drop of an 8mm and .223 bullet. At any range over 200 yds.

There are expensive bullets and cheap bullets. Lots of difference.

Not only in the way bullets are machined, but the weight, and materials used all make a huge difference in POI.

In milsurp the variances run the whole spectrum in 7.62X51. No way to get a handle on bullet drop unless you test it out in YOUR rifle.
 

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Let me give you an example. Of bullet drop and real world.

We have a 1' by 3' steel plate mounted at 1,000 yds.

To test any rifle and ammo, no matter if it is a $2,000 Armalite in .308 or $90 M/N with iron sights.

We use a spotter to see where the ammo hits in the dirt. Then walk the shots in.
Wind will give you grief and it changes constantly.

This way you get an idea of the POI of a certain cal. or ammo.

Temp. will make a difference. as well as other variables. So everytime the same rifle and ammo is used the procedure is done over. It only takes a few minutes, but there is NO getting around it, with fancy formulas or charts.

Too many variables.


You can get a head start, if you have a particular rifle with a scope cammed for a particular type of ammo . Like real snipers. Or people who buy these type of rifles for matches etc.

But, for most shooters that is not an option.
If you are shooting milsurps it is near impossible to have that kind of info. before you shoot.

Our club shoots all types of Milsurps at ranges up to 1,000 yds. and your M1 should be capable of it. If it has a good bore, crown, throat, and bedding, trigger etc.




Which model of the M1A and what is it tricked out with.
 
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