Hi All,

I have built an AR15 upper using a 16" barrel that is 1.00" under the handguards and .750 from gasblock to muzzle, 1/8 twist. I plan on using this rifle up to 500 meters. What weight of bullet would be the best to use/flattest trajectory? I have 3x9x36 mr/t scope.


MickeyJr.

Seirra 77gr OTM

But it aint going to be flat.

or there 80gr but it has to be single loaded.

77 and 80 would be your worst choices.  Not flat trajectories at all.  More drift and more drop... they are only good for LONG range not 500 maximum use.  Id look at 69 grain and 52 grain match loads.

Mick, Give the Hornady 75gr JHP bullet a try.

Semper Fi,
MHL555

Quoted: Sierra - 77gr for mag length ammo, 80gr for single load.

These bullets are designed for long range!  That's what we use at Camp Perry back to 600 yds.  The AMU is shooting 90's at 1000 yds with 1:6.5 twist.

Quoted: 77 and 80 would be your worst choices.  Not flat trajectories at all.  More drift and more drop... they are only good for LONG range not 500 maximum use.  Id look at 69 grain and 52 grain match loads.

This guy has no clue!  Although, the 69 gr bullets will make it if you load them hot.

168gr in an AR10
Edited toa add 77smk would be good

Quoted: Quoted: 77 and 80 would be your worst choices.  Not flat trajectories at all.  More drift and more drop... they are only good for LONG range not 500 maximum use.  Id look at 69 grain and 52 grain match loads. This guy has no clue!  Although, the 69 gr bullets will make it if you load them hot.

Yeah... but the entertainment value is high.

His maximun range is 500 yards... this means most of his shooting will be under that.  It is a fact that 77 grain ammo will have more drop than the lighter ammo at close ranges.  He is not asking what ammo has less drop beyond 500 yards.  I use 75 and 77 grain ammo exclusively but it has significantyl more drop at 100, 200, 300 yards etc.  Its a mathematical and physical fact.  A higher BC bullet starts out slower but ends up faster than a lighter bullet with inferior BC of similar construction. At close range the faster bullet will have less wind deflection and drop. Hope my cluselessness has entertained your smug uneducated self.

55gr will be the flattest to ~300yds; beyond that it will drop like a rock. The 77gr will drop more than a bullet in the 60s; but it is easy to figure out drop and harder to dope wind well.

Quoted: His maximun range is 500 yards... this means most of his shooting will be under that.  It is a fact that 77 grain ammo will have more drop than the lighter ammo at close ranges.  He is not asking what ammo has less drop beyond 500 yards.  I use 75 and 77 grain ammo exclusively but it has significantyl more drop at 100, 200, 300 yards etc.  Its a mathematical and physical fact.  A higher BC bullet starts out slower but ends up faster than a lighter bullet with inferior BC of similar construction. At close range the faster bullet will have less wind deflection and drop. Hope my cluselessness has entertained your smug uneducated self.

owned. nicely done.

Quoted: Mick, Give the Hornady 75gr JHP bullet a try. Semper Fi, MHL555

+1

Awesome bullets, and less $ than Sierra.  My reloading bench is full of red and grey (Lapua) boxes.  No green boxes yet (though I have tried them).

Try also the Hornady 68 HPBT Match.

Per Sierra Infinity Ballistics Program, realistic MVs assumed out of a 16" barrel:

Sierra 77 MK, 200 yard zero, 2600 fps MV

distance    trajectory      wind drift in 10 mph x-wind
50                 1.15                          .24
100               2.38                         1.0
150               2.05                         2.3
200               0.00                         4.2
250              -3.96                         6.8    
300             -10.03                       10.0
350             -18.46                       13.9
400             -29.50                       18.7        
450             -43.5                         24.3
500             -60.8                         30.9


Sierra 69 MK, 200 yd zero, 2900 fps MV

distance    trajectory      wind drift in 10 mph x-wind
50                .75                            .25
100             1.84                         1.04
150             1.64                         2.64
200               0.0                         4.36
250            -3.26                        7.00
300            -8.35                       10.36
350            -15.5                        14.5
400            -25.00                      19.4
450            -37.00                      25.3
500            -52.1                         32.2


Sierra 52 MK, 200 yd zero, 3100 fps

distance    trajectory       wind drift in 10 mph x-wind
50                .62                            .31
100             1.7                           1.3
150             1.56                         3.05
200               0.0                         5.66
250            -3.24                        9.03
300            -8.48                       13.9
350            -16.1                        19.9
400            -26.6                        27.3
450            -40.6                        36.3
500            -58.8                         47.0

I'll take the 77.  The drop difference is an insignificant 1.5" at 300 compared to the 52 gr, drifts 1 MOA less in a 10 mph wind, and hits a lot harder.

Nothing like cold, hard facts to kill an argument....

Quoted: Per Sierra Infinity Ballistics Program, realistic MVs assumed out of a 16" barrel: Sierra 77 MK, 200 yard zero, 2600 fps MV distance    trajectory      wind drift in 10 mph x-wind 50                 1.15                          .24 100               2.38                         1.0 150               2.05                         2.3 200               0.00                         4.2 250              -3.96                         6.8     300             -10.03                       10.0 350             -18.46                       13.9 400             -29.50                       18.7         450             -43.5                         24.3 500             -60.8                         30.9 Sierra 69 MK, 200 yd zero, 2900 fps MV distance    trajectory      wind drift in 10 mph x-wind 50                .75                            .25 100             1.84                         1.04 150             1.64                         2.64 200               0.0                         4.36 250            -3.26                        7.00 300            -8.35                       10.36 350            -15.5                        14.5 400            -25.00                      19.4 450            -37.00                      25.3 500            -52.1                         32.2 I'll take the 77.  The drop difference is an insignificant 1.5" at 300 compared to the 52 gr, drifts 1 MOA less in a 10 mph wind, and hits a lot harder.

May I ask why?

At 500y the 69SMK has only 1.3" of drift more than th 77gr (.26moa) yet the 69gr has 8.7" (1.74moa) LESS of drop.  It would seem the tradeoff (getting almost 2 moa less drop for 1/4moa more wind deflection) would be a pretty good deal.

Or is wind deflection that much more important when shooting at 500y?

Has anyone asked what he wants to do at 500yds ? Blast varmints ? Punch paper ? Knock down a Pepper Popper ? Drop a man ? The answer may better inform the discussion.

Quoted: Quoted: Per Sierra Infinity Ballistics Program, realistic MVs assumed out of a 16" barrel: Sierra 77 MK, 200 yard zero, 2600 fps MV distance    trajectory      wind drift in 10 mph x-wind 50                 1.15                          .24 100               2.38                         1.0 150               2.05                         2.3 200               0.00                         4.2 250              -3.96                         6.8     300             -10.03                       10.0 350             -18.46                       13.9 400             -29.50                       18.7         450             -43.5                         24.3 500             -60.8                         30.9 Sierra 69 MK, 200 yd zero, 2900 fps MV distance    trajectory      wind drift in 10 mph x-wind 50                .75                            .25 100             1.84                         1.04 150             1.64                         2.64 200               0.0                         4.36 250            -3.26                        7.00 300            -8.35                       10.36 350            -15.5                        14.5 400            -25.00                      19.4 450            -37.00                      25.3 500            -52.1                         32.2 I'll take the 77.  The drop difference is an insignificant 1.5" at 300 compared to the 52 gr, drifts 1 MOA less in a 10 mph wind, and hits a lot harder. May I ask why? At 500y the 69SMK has only 1.3" of drift more than th 77gr (.26moa) yet the 69gr has 8.7" (1.74moa) LESS of drop.  It would seem the tradeoff (getting almost 2 moa less drop for 1/4moa more wind deflection) would be a pretty good deal. Or is wind deflection that much more important when shooting at 500y?

Valid question.  Here's my take on it.  

Distance to target, as a rule, is MUCH easier to determine with a good degree of accuracy than the wind between you and the target.  You can use optical or laser rangefinders, range cards, or range estimating reticles to quickly and easily find it.  If the target is moving, it is readily apparent if it is getting closer or getting farther away.

We have no such aids to determine wind.  Even in a controlled range, with spotting scopes and directional flags, it takes quite a bit of experience to accurately dope the wind for that first shot.  Using a wind meter doesn't give you the total picture, since wind can and does behave differently between you and the target.  And the farther away that target is, the more opportunities for the wind to change and behave differently from where you are.

For those reasons, I'll gladly trade drop for wind resistance, even if the exchange isn't one for one.

That and the 77gr will have more velocity than the 69gr at range.

Quoted: That and the 77gr will have more velocity than the 69gr at range.

Not if the 77 starts at 2600 fps and the 69 starts at 2900 fps out of a 16" barrel.

At 500 yards, S 77 MK: 1532 fps, S 69 MK: 1603 fps.

They are within 10 ft-lbs of energy at that distance as well.