+- 6.5 Grendel Forum (https://65grendel.com)
+-- Forum: 6.5 GRENDEL DISCUSSION FORUMS (https://65grendel.com/forumdisplay.php?fid=3)
+--- Forum: 6.5 Grendel Ammunition & Reloading (https://65grendel.com/forumdisplay.php?fid=10)
+--- Thread: Real Life Effect of Velocity (/showthread.php?tid=16006)
Real Life Effect of Velocity - Vetman1 - 04-19-2018
What is the real life amount of velocity change required to cause a significant change in terminal performance of the 123 grain SST?
What is the difference between a 25 FPS change in velocity when you are shooting a 123 grain SST? How would a load at 2400 FPS compare to 2425 FPS? How would both of those compare to 2450 FPS?
Basically, are you looking at 25 yards less killing range? Or is it more like 75 yards less killing range?
At what point will the slower Bullet drop significantly more than the faster Bullet?
Real Life Effect of Velocity - BluntForceTrauma - 04-19-2018
Basic answer: 25 fps makes no real difference to a game animal.
You can play around to your heart's content with different parameters by entering different data into the online JBM Ballistics Calculator.
Real Life Effect of Velocity - grayfox - 04-19-2018
Another option is to get the Grendel handbooks - they have a lot of info on expected ranges, terminal ballistics, and bullet performance at various velocities, for several types of bullets. Pictures and graphs.
Lots of good info.
Real Life Effect of Velocity - VASCAR2 - 04-19-2018
This is just my opion but as you get closer to the threshold for expansion the 25 FPS comes into play. Nosler has pictures of their hunting ballistic tip bullets at various velocties. At close to 1800 FPS a 123 grain SST has pretty small disruption of the tip of the bullet. At higher velocities you get more of a full mushroom but at very high velocity the bullet will shed weight and the actual diameter of the bullet will get smaller.
How much expansion is necessary for a clean kill is really dependent on shot placement. The Hornady 123 grain SST is well suited to the 6.5 Grendel velocities. Most 123 grain SST perforate a broadside deer unless the range is close, more velocity the bullet sheds mass which can inhibit penetration.
Me personally, I like to keep cup and core bullets like the SST above 1800 FPS at the target. Barnes recommends a minimum impact velocity of 2000 FPS with their monolithic bullets like TSX or TTSX.
Real Life Effect of Velocity - Vetman1 - 04-19-2018
Along these same lines, how much slower is a Lilja Barrel compared to other barrels with the same load?
Real Life Effect of Velocity - VASCAR2 - 04-19-2018
I don’t think you’ll know without a chronograph. Each barrel is unique and each lot of ammunition is unique within certain tolerances. To me it is like taking two exact cars and putting them on a dino, some will be better than others. You put another brand of car on the dino with the same rated torque and horse power it’ll still be different.
If your wanting to shoot at very long range it’s best to have a base line velocity for a particular load so you can use a ballistic calculator to calculate your drop. Most times I can’t see my misses to get my own dope for extended long range. In the midwest there is so much foliage where I shoot the ballistic calculator helps me get on target. When shooting steel targets I can see the impact and hear the hit. If I miss I can rarely see dirt or brush move. I usually can’t see the bullet contrail good enough to make corrections to get back on target.
Real Life Effect of Velocity - LRRPF52 - 04-20-2018
Vetman1 Wrote:Along these same lines, how much slower is a Lilja Barrel compared to other barrels with the same load?
Of all the Lilja barrels I've chronographed, with various loads, over the past 4 years, I haven't seen any appreciable difference between that and other barrels of the same lengths.
Hornady said they really like the predictable behavior of Grendel on target because it doesn't suffer from a lot of high speed impact challenges of larger case capacity cartridges, giving very uniform wound channels along the intended path of the POA.
As to bullet drop, once you have your zero, even the difference between a 2300fps load and a 2700fps load won't matter much within 200yds, and is only 2" difference with a 100yd zero.
Real Life Effect of Velocity - FloorPoor - 02-21-2020
When shooting animals at ethical ranges (300yardsish), 25 fps has zero impact on terminal performance.
Real Life Effect of Velocity - Double Naught Spy - 02-21-2020
I don't know that anybody has done any sort of step testing at 25 fps intervals to see how the terminal performance of a bullet may vary be interval. Are there threshold points that impact the level of expansion performance? Who would know?
I now from other materials failure testing than in some circumstances, changes due to stress may be on a continuum until thresholds are crossed and then radical changes may occur. How that might apply here is speculative at best. It may be that 25 fps intervals are too insignificant to matter at most velocities, that you won't see a significant change of terminal performance between two adjoining intervals. Then again, if nobody has studied this, who would know?
Combine that with the fact that how the bullet terminally performs may vary a good amount over a much wider range of velocity than 25 fps, not having explicitly consistent performance.
Real Life Effect of Velocity - BobinNC - 02-21-2020
Running a JBM Trajectory Calculation on the 123 grain SST:
@2400 FPS it drops below a 2000 FPS expansion threshold at 250 yds.
@2450 FPS it drops below a 2000 FPS expansion threshold at 275 yds.
Here you can run simulations yourself:
http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi
Real Life Effect of Velocity - A5BLASTER - 02-21-2020
BobinNC Wrote:Running a JBM Trajectory Calculation on the 123 grain SST:
@2400 FPS it drops below a 2000 FPS expansion threshold at 275 yds.
@2450 FPS it drops below a 2000 FPS expansion threshold at 250 yds.
Here you can run simulations yourself:
http://www.jbmballistics.com/cgi-bin/jbmtraj_simp-5.1.cgi
BobinNC I think you got your yardage figures in the wrong place. That are the ballistic app used gave you the wrong figures.
Real Life Effect of Velocity - imaguy3 - 02-21-2020
A5BLASTER Wrote:BobinNC I think you got your yardage figures in the wrong place. That are the ballistic app used gave you the wrong figures.
Yeah... Using 2415 in my strelok I drop below 2000fps at 300 yards.
That being said, and has been experienced and verified by Hornady. The SST performs well down to 1600fps, which with 2415 muzzle puts you out past 600
Real Life Effect of Velocity - Double Naught Spy - 02-21-2020
Bob, using the link you provided, BC of .51 (per Hornady), no wind, no target velocity, 123 gr. bullet, looks like with a MV of 2400 fps, it drops below 2000 by 250 yards (using 5 yard increments).
At 2450 fps, it drops below 2000 fps by 280 yards.
This app says with MV of 2400 fps, you drop below 2000 fps by 255 yards, 2450 by 285 yards.
http://www.shooterscalculator.com/
Real Life Effect of Velocity - BobinNC - 02-21-2020
Yes, I reversed the numbers above and now I corrected them. And those getting slightly different number used different heights above sea level and sight height above bore. Mines a measured 1.8" default is 1.5". That alone can make a slight difference.
Also I was not trying to say what the minimum expansion is for the 123 grain SST or what it should be, just that 2000 fps impact velocity was just an illustration of what an extra 50 FPS buys you which is about 25 yards. The further out you go, the less it buys you as velocity is a wasting asset.
Real Life Effect of Velocity - CJW - 02-21-2020
Fermat’s Last Theorem clearly states that an animal does not care how fast the bullet is going when it hits him!!!!!
What the animal does care about is where it hits him.
Real Life Effect of Velocity - 1Shot - 02-21-2020
The problem many forget or do not understand is that the down to velocity threshold that bullet companies give as the minimum velocity for expansion is for ANY EXPANSION. Most of those bullets at that velocity will just barely open the nose a little bit. To get what most would call expansion you need 200 fps or so more velocity.
Then you also have to take into account the bullet getting unstable at a certain yardage. The bullet depending on what twist barrel it is fired from will start to yaw below a certain velocity, usually below 1125 fps (speed of sound). A bullet that is yawing or is on the verge of yawing will often tumble on impact with flesh. A tumbling bullet, even an FMJ, will do considerable damage to flesh. That is the principle of the design of most FMJ military rifle ammo. Even back a far as WWII the M2 ball round with it's short flat base spitzer bullet would start to yaw and tumble between 4 and 6 inches of penetration in flesh even at close range. As a teenager I had a 1903A3 Springfield rifle and a man out the road a couple miles from my home raised cattle. There was a pack of dogs that had gone wild and started causing him problems and kill one calf. He paid me and a friend to kill these dogs. The first one that I shot was about 100 yards away facing me and was about a 40 pound dog. I was using the 03 with M2 ball ammo. I shot it in it's chest. Upon going to it it's rear end had a pretty large exit hole with lots of damage. We cut it open and could clearly see evidence that the bullet had tumbled causing lots of damage. I talked to my cousin that was still in the National Guard and was supplying me with a 250 round can of ammo every month when he went to muster and was a silver star awardee that saw a lot of combat on Korea about my tumbling assumption. He said yes that the M2 ball ammo definitely would tumble because he saw evidence on the battle field.
Jump ahead a number of years and out comes the M-16 with a barrel twist that would just stabilize the little 55 gr FMJ. When it hit flesh it almost instantaneously started to tumble and combined with the high velocity at shorter ranges created some pretty nasty large wounds.
So bullets do crazy things depending on construction, spin rate, at different velocities.
As has been basically said, out to the yardage that a Hornady 123 SST can stay above 2000 fps at impact it will not matter what velocity it was started out at if it is put in the vitals of an animal most likely the animal will die from the result with no problem.
Real Life Effect of Velocity - LRRPF52 - 02-22-2020
Plug in a .462 G1 BC for the 123gr SST if you want a more accurate external ballistics profile. The .510 G1 is more of a theoretical standard compared to the nominal G1 profile at higher speeds.
But yeah, 25fps is normally within the ES of most loads and won't matter a hill of beans within typical hunting distances.
Even a 10.5" Grendel pushing the 123gr SST at 2200fps will have effective expansion out to about 250yds.
Adding 25fps doesn't change that much.
Here's one of the charts from the Grendel Handbooks:
![[Image: Vol-2-Excerpt-300x326.jpg]](https://shootersnotes.com/wp-content/uploads/2014/01/Vol-2-Excerpt-300x326.jpg)