Loved the video but didn't understand hardly any of it lol. I just enjoy reloading for my hunting. This guy (sorry I don't know your name) explains things so I understand most of it. I'm still learning, but I'm never going to amount to much, but I get a buzz out of gleaning little bit here and there that just might just help improve my reloading. THANX.
Hey Keith like the vids! Sounds like a trick question, lol. The 108 EH has a short BT and a long BS. The BS at .408 may limit the ability to drive faster to reach ELR. The BT at .185 may limit the flight to reach ELR. You didnt mention MV but at 3000 fps your velocity at 1100 yds would be below the 1500 fps threshold at which the box numbers are generated; therefore, your BC's are no longer consistent. IMHO
I believe it was the guy from backfire that looked at advertised BC's in a video and found that match bullets were very accurate as advertized but hunting bullets were not. The reasoning being match shooters will test, as you have and hunters are less likely to do so. Hunters are apparently more likely to just look at advertised BC's and pick something high so the manufacturers are "loose" with their box numbers
i don't see a company like berger playing those tricks. but i guess you never know....honestly its not that hard to check if you just look it up in bryan litz library (book or subscription)
@@Sageofthe16 Wouldn't it make sense then for Berger to just test the dang BC? You are basically saying they don't bother testing hunting bullets and guess at a BC and call it good enough forever.......I highly doubt Berger does that.
@augerprecisionfirearms3247 quite the opposite. they know what the bc actually is, but the marketing guys look at noslers hunting bullet bc and print a higher number on the box than nosler has, because joe bob buys the best. but joe bob never tests.
Whats the average distance hunters are taking shots? I've noticed a trend on content where longer shots are taken on game. Has that average range been increasing with hunters? Does anyone have internal sales #s from retailers that can identify strictly hunters and their buying preferences? Will that data show a clear preference by hunter for bc over anything else? If you found a population of hunters that showed a clear preference for bc over everything else, would the range they shoot at have gotten longer as a result of boxed ammo/bullets? Have any idea what caliber that hunter had previously shot? Did they buy a new gun within the purchase dataset timeline? Analyzing why people do things is often an exploration of belief and brain farts than actions based on data driven anything.
I think there may be something to this. Keith, do you have another rifle/barrel (preferably a 3 or 5 groove) that you can run the same test, that is to shoot the bullets in comparison side by side. This may be an example of stacking tolerances as well: a particular batch of bullets in a barrel that maximizes bullet deformation, and violá you get a different BC. Just guessing at this genuine stumper. Fwiw, I DON'T believe that Berger is sloppy or misleading with their published BC's for hunting ammo, as some have suggested.
May be getting some yaw in the 108 at some point in flight for whatever reason. Yaw is more bullet drag . I think of a thrown football when i think of bullets. A wobbly thrown football slows down and will not travel as far, even when thrown with great effort.
Are you using just 1 bc number or multiple bc numbers? Litz gives about 5 bc variables at different speeds which gives a better picture throughout the flight.
Batches of bullets may have something to do with the bc. I’ve shot Berger 30cal 175 vld hunting from my 308 for years and different batches of bullets have all been the same weight on my scale but all different batches had different shapes. 30 thou different from longest to shortest bullet and different boat tail lengths. The bc just can’t be the same with those shape changes which are quite noticeable to the naked eye even without measuring tools
Bullets that are more radical in design longer ogives more tapered boat tails , short bearing areas VLD types can experience extra drag when striking higher air density and pressure patches along the trajectory path . This extra turbulence causes the real in flight BC to be lower than would otherwise be predicted for that velocity boundary . Also no single BC can accurately describe a full trajectory and when a bullet is modeled you get a long list of BC's right along that trajectory that vary considerably . What some manufacturers do is quote the highest BC in the list , others might quote an average of the list and others might quote three BC's at different velocity boundary along the trajectory which is the most accurate way . What you have done is just find the more accurate average BC for the bullet and conditions .Also long boat tail bullets that have a short bearing area can suffer from more in bore yaw than bullets with a longer bearing area especially if they are not entering the lands concentrically . That can also upset the stability of the bullet and lower the BC . This is a model of a basic flat base Protected Point hunting bullet I make and you can see the long list of BC's along the full trajectory . G6 Drag function seems to fit this bullet better than G1 . So some manufacturers quote the G1 number even though a different drag function could be more accurate because it's more impressive . If you see G1 .5 BC you think wow , but If you see G6 BC . 3 you feel disappointed . Caliber: 0.308 in Nose Length: 1.740 cal Meplat Diameter: 0.350 cal Ogive Radius: 6.000 cal Drag Function: G6 Boattail Length: 0.000 Base Diameter: 1.000 cal Total Length: 3.060 cal Rotating Band Diameter: 1.000 cal Core Depth: 0.246 cal Jacket Thickness: 0.060 cal Jacket Length: 3.060 cal Bullet Weight: 144.00 gr Boundary Layer: Laminar-Turbulent Jacket Specific Gravity: 8.900 Core Specific Gravity: 11.500 Muzzle Velocity: 2650.0 ft/s Distance to Chronograph: 0.0 ft Sight Height: 1.50 in G6 BC numbers are always smaller than G1 numbers but predict a similar trajectory . Coefficients Table * Mach CD CDα2 Clα Cmα Clp Cypα Cnpα G6 BC FF 0.500 0.225 3.378 2.345 2.065 -0.0101 -0.245 -0.194 0.214 1.043 0.600 0.226 3.490 2.345 2.068 -0.0101 -0.245 -0.194 0.210 1.064 0.700 0.228 3.611 2.356 2.099 -0.0097 -0.245 -0.170 0.208 1.075 0.800 0.230 2.798 2.367 2.131 -0.0093 -0.245 -0.146 0.209 1.069 0.850 0.231 2.876 2.422 2.181 -0.0091 -0.260 -0.100 0.212 1.054 0.900 0.236 2.929 2.477 2.231 -0.0089 -0.275 -0.054 0.217 1.029 0.925 0.259 3.199 2.529 2.266 -0.0089 -0.314 -0.008 0.211 1.059 Wobbles 0.950 0.284 3.473 2.582 2.301 -0.0088 -0.352 0.037 0.215 1.039 0.975 0.306 4.759 2.665 2.325 -0.0085 -0.337 0.052 0.229 0.976 ^ 1.000 0.368 4.899 2.748 2.349 -0.0081 -0.321 0.066 0.219 1.022 Trans Zone 1.100 0.478 5.375 2.952 2.179 -0.0077 -0.275 0.098 0.209 1.070 1.200 0.481 5.938 3.005 2.181 -0.0079 -0.245 0.094 0.209 1.072 1.300 0.486 6.467 3.053 2.122 -0.0079 -0.245 0.098 0.202 1.108 1.400 0.491 6.334 3.108 2.054 -0.0079 -0.245 0.100 0.195 1.147 1.500 0.484 6.219 3.170 1.976 -0.0079 -0.245 0.102 0.192 1.163 1.600 0.476 6.123 3.202 1.880 -0.0081 -0.245 0.103 0.190 1.177 1.700 0.467 6.048 3.234 1.784 -0.0084 -0.245 0.104 0.187 1.193 1.800 0.459 5.993 3.266 1.693 -0.0086 -0.245 0.105 0.184 1.212 2.000 0.443 5.952 3.330 1.523 -0.0090 -0.245 0.107 0.178 1.260 2.200 0.427 5.660 3.356 1.385 -0.0088 -0.245 0.108 0.170 1.313 2.500 0.403 5.421 3.394 1.178 -0.0086 -0.245 0.109 0.160 1.399 3.000 0.370 5.489 3.314 0.921 -0.0083 -0.245 0.112 0.146 1.536 3.500 0.342 6.016 3.245 0.947 -0.0082 -0.245 0.112 0.136 1.639 4.000 0.321 6.844 3.176 0.973 -0.0082 -0.245 0.112 0.130 1.720 4.500 0.304 7.795 3.115 0.997 -0.0081 -0.245 0.112 0.125 1.787 5.000 0.291 8.666 3.115 0.997 -0.0081 -0.245 0.112 0.121 1.847
possibly the thinner jacket taking more damage from the rifling? I haven't shot the 108 eh but have a pile of 105 and 109 hybrids. 105 bc tryed for me at .279 the 109 at .300 both from 6 dashers. 105 at 2880 the 109 at 2960
Keith, if you can’t figure it out what chance do us mortals have haha! Seriously though and only a guess…I believe that pushing “heavier” for caliber bullets with thinner jackets at faster speeds may actually deform bullets at launch and may cause them to deform and “hunch” over. (Only way to know though is to get out and test which is what you do and thank you for that) Basically creating a slightly shorter bullet. LMK your thoughts.
Could be a slight wobble. I have a dead nuts BC with the ELD-Xs or to 800. Then it drops velocity like a son of a bitch. There could be a slight jacket variation that only shows up at longer ranges.
Hunting bullets have a higher copper-to-lead ratio than target bullets. That could explain why a heavier bullet with a sleeker form factor isn't necessarily going to have a better BC than a target bullet consisting of mostly lead.
Obviously this turns out not to be " apples to apples" comparison, whether be the bullets themselves or the stated ballistics. I would like to entertain you with Isaac Newtons law of gravity and its part in the ballistics and the coefficient of friction of air. That's as far as I got in physics. Always liked the concept but just not that smart. Good head scratcher though. Love the videos.
Are you using the CDM or box BC on the Kestrel? I personally use the CDM and have seen the data line up on 105, 108, and 109s up to 1350+. Pleasure shooting with you last weekend.
I ran the 108 EH the tail end of the 2021 PRS season and got my best finish ever at the PRS finale with them. I think I ran them at close to the box BC and had them trued out at 1200. However, I wouldn't sweat the ballistic differences between bullets. I shot unpointed 105 hybrids at 2830fps at Blue Ridge in the wind last weekend and they did great. Lots of PRS matches being won with 105's in the low 2800's these days.
Perhaps the center of mass is located such that they don't stabilize as well as they should and there is a lower BC as a result. Too far back or forward.
Could be the distribution of internal weight of the bullet? Imagine a solid ring of led about 1/8" thick within the center of the bullet. Now you have a balanced bullet front to back. Okay, now imagine sliding that same 1/8" ring all the way to the back end of the bullet. You shifted the balance toward the back of the bullet. Could it be something like that?
Different bc's at different velocities?...ie..when bullet slowing down?...I think sierra list different bc's for difference speeds... Bit behind me...that's my only thought.. Love the learning
Here is an example BC from Sierra for the .264 107gr TMK (.445 @ 2200 fps and above .455 between 1600 fps and 2200 fps .415 @ 1600 fps and below). The data given is not really useful if you are trying to figure out generated dope issues between 2700-2900fps. If you want to figure out why the calculated dope is different between your 5" barrel and 24" barrel this data might be helpful. I'm not even sure most ballistic calc apps have the option to add in multiple BCs.
Bullets are deformed by rifling in the barrel. With a thinner jacket, might the rifling imparted to the bullet change the BC more than the target bullets? It would explain why closer ranges are similar, but further distances are different.
Keith, I took a look at Berger's data, and something is amis. The EH has both a shorter nose and a shorter boattail, which means that if you were to drop its weight to 105 grains, it should have a lower BC than the Hybrid Target bullet does. And even if they had the same nose and boattail, which you need for calculating increased BC by the bullet weight ratio, then multiplying HTs G7 BC by that ratio gives the EH a G7 BC of 0.283, and not the 0.287 claimed by Berger. But since the EH nose and BT are both shorter than the HT, I would expect, at a SWAG, that their BCs would be about the same, with the extra weight of the EH having to make up for the lower form factor, the shorter nose and boattail have. So I think your rifle has it right, and if you used your acoustic TOF measurement to compare BCs initially, some sort of precision problem occurred with it. The only way I can see a chance of Berger's numbers being right is if the secant portion of the EH nose has a much larger radius than the HT has, thus bringing the form factor back down.
I'm fairly new to shooting and have been using Hornady 140ELDM (6.5 Creedmoor) with the Hornady 4DOF app on my phone. My problem was the data from 4DOF gave a 2MOA low setting and I was unable to find any fault in what I had inputted to 4DOF. Hornady do allow an "Axial form factor" to correct for elevation but this only sorted about 1 MOA of error. A few weeks ago I had a notification from Hornady saying they had updated the BC's of their bullets to allow for the effect of using a muzzle device! Hey Presto, half of my problem vanished. Could this particular bullet be also sensitive to muzzle device? Or have the manufactures changed their test procedure?
Keith, I agree with others that part of this effect could be how your particular barrel interacts with this bullet and that the thinner jacket and 4 groove barrel could be causing the surface of the bullet to get more deformed, thus altering it's effective BC. Another possibility is that you are not adequately sampling this difference to really tell. For example, at 1k yds, the 108 is dropping 30.4moa, and the 105 is dropping 31.3moa. If you add MV dispersion and measurement error, rifle group dispersion, and environmental dispersions, these two groups will likely mostly overlap. You might have to take a lot of shots to really resolve this difference confidently.
I think it's the thinner jacket and your twist rate amd/or groove/land geometry causing the BC loss for your platform. I'm running a 24" Krieger tight bore (.236 bore vs standard .237 bore) 4 groove with a 1:8 twist for my 6mm GT (AR-10) and 2890 fps at the mizzle with 108 Elote Hunters matched the box G7 BC perfectly, trued out to 1,200 yards. I do use the Custom Drag Model in Applied Ballistics on my Kestrel, just because it's available.
The next opportunity you have to shoot with a high resolution radar you will be able to get a good BC value, but since you have actual speed and DOPE I would trust your own testing. Another approach would be to give Berger or Litz a call and see what they say.
I found that the box BC on certain hunting bullets is higher than tested in reality. Match bullets' BC tend to be môre accurate. Confirming the Backfire video findings.
It could be possible that the tangent ogive is close enough to the G5 form factor, instead of the G7 secant model, that the calculated BC is in error if using the G7 value.
Berger hunting bullets are generally excellent for target shooting.... However... Their published data has not always been correct. Even things like bearing surface length, etc. Talk to them, they'll sort it out and correct the data.
i ran out of 109s last year too. Tried the 108 EH on a whim and they shot great, maybe a little tighter than the 109s. I didn't see any ballistic difference. I use AB SW on my PC to do my range card - not a Kestrel. I shoot 850-1000 yd benchrest so it's not a giant deal to do the range card ahead of time - we get sighters so you just need to be close enough to see a splash and get centered-up. I'd check all inputs in the Kestrel - heading of fire in particular. And make sure the pressure/temp looks right. I've seen guys have to fudge the BC or MV to get agreement when that wasn't the problem and they had multiple bullets or loads or guns in their Kestrel and got things crossed-up. If the 108EH were off that much it would be all over the internet.
As I understand it a ballistic coefficient is a function of several inputs, velocity, shape, length, sectional density, add all those influences up and shake mildly, rotate at extreme speed, expose it them to the extreme variables of wind (speed and direction) and calculate it from the data revealed by shooting long known distances. The gun has the inputs of rotational speed and velocity, other than those inputs, the bullet doesn't care. The BC ends up being more a function of the ability to fly cleanly through the air, it is what it is, the manufacturer may have not calculated to the parameters you are operating in, the saving grace is, you are able to reverse calculate through your shooting data, a mystery but now you know. You could go to the degree of comparing the bullet in question to one of known BC, in an optical ,comparator if you could find one, but again, I believe you said you obtained the value through your results.
Maybe, at that weight of bullet, the harmonics of that barrel do not " come up" or react as other bullets. The " barrel flex" when you shoot? Just my guess, I really do not like to blame the bullet....especially berger. Just my guess. Great vid. Look forward to finding out if you solve this issue
Lets say for whatever reason, these bullets have a slight imbalance in them. More lead to one side inside the nose or something. They could have an identical defect and you wont easily see this on the target as group dispersion, but what it may do is introduce a wobble that is just enough to impact the BC and this is why the BC is lower than advertised, but consistent.
I never trust an advertised BC, but I do use it as a starting point for long range testing. There is no replacement for Data On Previous Engagements, you have to test everything and (to quote someone famous) believe the target.
It is just possible, since this is a hunting bullet, that the published BC is for ranges shorter than 600 yds. Another possibility is that this bullet attack angle follows the curve of the trajectory differently than the other bullets. Some bullets will not point downward as the range increases. At short range they can "ski" on the trajectory and in effect drop less than initially thought, but at longer ranges the lower BC causes more velocity loss and the bullet drops more. You need to shoot heavy paper at 1000 yds. or greater and see if the bullet hole is round or constantly oval. Have viewed this a few times in a trench range where the bullet flight seems to flatten between 300 and 450 yards, and then seems to drop faster than expected. Do not have equipment to measure this, but it does happen. It is similar to a submarine that descends until it reaches a temperature gradient and then refuse to decent any more until enough ballast is taken on. Then once it has penetrated the layer the submarine suddenly descends and the crew has to rapidly de-ballast the vessel or they descend to crush depth.
Not in this case. Berger and Applied Ballistics both share the same Chief Ballistician who Doppler tests all of this stuff and develops custom drag models for the application, and then also slaps the G7 BC on the box. I suspect this is a barrel to bullet interface issue that may be exacerbated by the thinner jackets of hunting bullets as compared to match bullets.
@@ewathoughts8476 well, you're obviously a ballistician, so I'll just leave you to your wall of text that could have been simplified with, "have you considered aerodynamic jump" even though that's not what the problem statement in the video is.
It is part of the chamber flag. I pull it tight around the right side knob on the scope (on the Kahles it's the illumination knob) and then over the bolt handle. It keeps the bolt up against the chamber plug and everything neatly in place.
@@winninginthewindCan you get away from the Kestrel for the calculations? Other shooters have written about the kestrel going apesheet at long ranges in some applications. It would be nice to try this. Would be nice to get Litz's superduper radar on this but I do not know how far it would even read. I would be one that believes certain bullets, for whatever reason, fly better (or worse) at different speeds and that could mess with BC calculations based on drop at a specific distance. Just a note... I seldom ever use box BCs when I get serious. I start with 5 BCs from Litz and fine tune from there.
... Bryan Litz, Chief Ballistician for Berger Bullets is also the Founder and Chief Ballistician for Applied Ballistics. All of the drag curves in use on the Applied Ballistics application came from Bryan's work with actual Doppler radar traces of actual bullets being fired from actual barrels. All of Berger's G7 BCs on their boxes came from that source. And per this video, the Kestrel had to have its BC "trued" to match the bullets fired from this particular rifle. Kestrel uses Applied Ballistics... This isn't a case of an incorrect value; this is a case of an interaction between the barrel's lands and grooves and barrel's twist disturbing the jacket in some way that is causing a slightly adverse impact on the G7 BC. The video is asking if anyone can guess why. I suspect that it's twist rate and the specific geometry of the lands and grooves in this particular rifle effecting a thinner hunting jacket more significantly than the thicker jackets of the match bullets.
Backfire picked up the same issue with hunting bullet BCs not matching the advertised BC but the competition bullets do. All manufacturers he tested seemed to be guilty. The worst offender seemed to be Nosler. I wounded a springbuck at range with a low impact though the leg with a Nosler Accubond bullet. I could not explain why I hit low. After finally recovering the springbuck, I went back to camp to recheck zero and speed. Nothing had changed. Its starting to make sense now.
Mr. Litz has been using Doppler radar to verify real world G7 BCs for all of Berger's bullets for quite some time now. He set the standard for manufacturer accountability in BC but every single barrel is slightly different so you will still need to true your data to your rifle if you're trying to shoot out to transonic ranges and beyond. It's the latter step that's causing concern here, not misrepresentation of the G7 BC on the box.
being out by 2-3% should not matter if you are only hunting to 3 - 400m max, but I suspect the G7 BC of the .308 150gr Accubond bullet is more than 10% off the mark. All my competition bullets have verified BCs out to 1250m, but I never realized that I would have to go through the same effort for hunting bullets.
FYI, Strelok is a Russian app, the US has a sanction against Russia thus it was removed from the app store. if you already have the app your in luck however you will not receive any updates. Hope some day soon sanctions will be removed.
He's using Kestrel and Applied Ballistics, which has drag curves developed by Bryan Litz, Chief Ballistician for Berger Bullets and Chief Ballistician and founder of Applies Ballistics. He's trying his BC at long range, as one should always do for their particular load and rifle. He HAS a valid G7 BC. He's asking why it doesn't match Litz's BC for THIS bullet when it does match up for every OTHER Berger bullet being fired. How is Strelok going to do anything for him that he hasn't already successfully done in Kestrel and Applied Ballistics?
@@ftn5546 I have no idea what he is using. I dont know what his stability factor is or anything. If the bullet is not stable, all factors are pretty much worthless, regardless of which app is used.
Center of mass is different causing the bullet to fly nose up or down affecting the BC, Irregardless of external shape of a bullet, the center of mass can be different, but you know this.
Thinner jacket more plastic deformation into the grooves more change in the BC (loss) when fired. You’d think that would be baked into the cake of Berger’s BC numbers, but you’d need to validate the barrel specifications used in their testing to really know (bore diameter and groove diameter).