desertloper

I'm trying to estimate a drop chart before heading to the long range.

I'm shooting an AR platform with an 18" barrel and I don't own a chrono.

Anyone know what muzzle velocity should be?

Nomercy448

If you're going to the range, just shoot it and make up a range card. It's really not possible to tell you in advance how fast it'll be running in your particular Ar-10, way too many variables.

Shoot it at 100, 200, 300, and 400 and you'll know everything you need to know about your velocity on that particular day at that particular temperature.

desertloper

Thanks for the response, I know what you are saying I'm just trying to estimate the information before hand.

My range access for anything over 100yd is extremely limited so in trying to have things estimated before going out.

I should probably just buy a chrono and get into reloading

alleyyooper

Appears as though you will be shooting factory ammo. You also didn't mention which weight bullet you have in mind. Lots of information needed to do a real in dept chart with out shooting at the ranges but I was able to find this chart.
http://www.gunnersden.com/index.htm....allistics.html


308 Winchester
Cartridge
Manufactures Bullet Weight Grains

Bullet
Sectional
Density

Bullet
Ballistic
Coefficient

Muzzle
Velocity
Fps.

Muzzle
Energy
Ft. lbs.

Recoil
Energy
Ft. lbs.

Rifle
Zero
100 Yds.

Bullet
Drop @
200 Yds.

Bullet
Drop @
300 Yds.

Bullet
Drop @
400 Yds.

Bullet
Drop @
500 Yds.


Hornady
110 .166 .290 3,165 2,447 11.62 0 - 2.9" - 11.2" - 26.6" - 51.2"

Winchester
120 .180 .256 2,850 2,164 11.47 0 - 4.1" - 15.7" - 37.2" - 72.4"

Nosler
125 .188 .366 3,175 2,798 13.97 0 - 2.6" - 10.2" - 23.7" - 44.6"

Cor-Bon
130 .196 .340 3,000 2,598 13.66 0 - 3.2" - 12.2" - 28.2" - 53.1"

Winchester
147 .221 .415 2,800 2,559 14.77 0 - 3.7" - 13.6" - 30.9" - 57.0"

Hornady
150 .226 .415 3,000 2,997 16.75 0 - 3.0" - 11.4" - 26.1" - 48.3"

Hornady
155 .233 .435 2,865 2,825 16.58 0 - 3.4" - 12.7" - 28.8" - 52.9"

Hornady
165 .248 .447 2,840 2,955 17.95 0 - 3.5" - 12.9" - 29.2" - 53.5"

Winchester
168 .253 .474 2,670 2,659 17.05 0 - 4.2" - 14.9" - 33.2" - 60.6"

Federal
170 .257 .284 2,000 1,510 12.12 0 - 10.0" - 35.4" - 81.0" - 152.6"

Federal
175 .264 .505 2,600 2,627 17.64 0 - 4.4" - 15.6" - 34.7" - 63.0"

Hornady
178 .268 .530 2,775 3,043 19.83 0 - 3.6" - 13.1" - 29.3" - 53.2"

Remington
180 .271 .402 2,620 2,743 18.76 0 - 4.6" - 16.3" - 36.8" - 67.8"




You also do not need to have a range many hundreds deep to do drop testing. Just do the drop amount at a 100 yard range.

Al

Nomercy448

Together with your previous comments, this is a non-sequitur. You don't NEED a chrony and don't NEED to reload just to shoot "long range". Reloading doesn't make sense - financially - for most people, as there are plenty of factory loads that will maximize the precision potential of any factory rifle, and the start up cost for reloading equipment takes a LONG time to pay back on a single cartridge (for a 4box per year shooter, it takes about 25yrs to pay back!!). Reloading doesn't guarantee that you'll be able to produce more precise (often mislabeled as "accurate") ammunition at any range, especially out of a factory rifle. A chronograph will only tell you the bullet speed wherever you place it in your trajectory, which most guys do at the muzzle. It will not, however, tell you a d@mn thing about what the bullet is going to do after that. You need to know your environmental conditions and your actual trajectory - found by test firing at range - and can't rely on published charts.

Bottom line: Go shoot it at range.

Very reasonable expectation, but it's not all black and white.

Which Hornady Super Performance 308win load/bullet weight are you considering? They make several in that line, from 150grn up through 178grn loads.

IN GENERAL - you can expect ~25-50fps of velocity loss for every inch of barrel, more often in the 40fps neighborhood. You can also expect that test barrels will be 24". And finally, you can expect the same 25-50fps loss for a sealed breach and bore rifle compared to a ported gas gun.

So...

If you're looking at the 150grn Super Performance loads, spec'd at 3000fps, you're probably looking at around 300fps of velocity loss at standard conditions compared to the factory spec (meaning not on a super cold day). Using Hornady's calculator (which doesn't jibe with their product page table), I show 48" of drop for the 150grn SST at 3000fps at 500yrds, whereas the same bullet at 2700fps drops 62". So you're talking 14" extra drop, without making any modification for density altitude or powder temperature.

It's really easier to take an extra box of ammo with you and do the shooting. At 300yrds, the 150grn SST will only have 4" of difference from 3000fps to 2700fps. If you dial in the 11" expectation for the 3000fps mark, then land 4" low, then you have your answer - you're NOT at 3000ps, you're slower than that. You can back into your muzzle velocity by shooting 5 extra rounds at varied ranges and confirming your drops.

CalHunter

That is some really wise advice and it will save you all the extra costs of buying reloading equipment, a chrono and whatever other extras you're considering. And if you're only going to average 4 boxes of ammo a year (you haven't stated one way or another but...), this would be incredibly wise and useful advice.

Nomercy448

For the OP, to the point of your "itch" to start reloading:

HNI Reloading Thread: Secant vs. Tangent Ogive - Check Nomercy448's post on the bottom of Page 2!!

Check out my post at the bottom of 2nd page of this thread - I give a breakdown of reloading fixed equipment costs plus variable component costs vs. factory ammo cost, as I mentioned above, 25yrs to pay back the equipment if you only shoot 4 boxes a year. And that doesn't even account for a chronograph - get $100 into a chrony, that's another 3-4 boxes of factory ammo, so add another year to the 25.

I started reloading as a kid under guidance of my dad, uncles, and grandpa's, and I thoroughly enjoy it. I reload a lot of cartridges and I shoot a lot more than 4 boxes per year out of most of them, so my fixed cost of equipment was paid back years ago, and I'm miles ahead on ammo cost vs. equipment - but it doesn't work that way for everybody.

CalHunter

And time. People always seem to forget that part.

The topic and info looks very good. Most people tend to shoot way more rimfire and shotgun ammo bird hunting than they do hunting something with a CF rifle. It's good to think ahead as to how much you'll actually use the equipment versus saving that money and spending it on something else.