THanks for these numbers, very interesting. I assume you are using sea level for your numbers or did I miss that data?
I am ata 3500 ft and our humidity is generally in the 10 to 20% range most of the year. SOmetimes even less like now.
I did find a problem in your numbers. At 1500 yards you list velocities at 1953 and 1883 fps respectively for the two test loads. A difference of 70 fps.
At 2000 yards you list velocities of 1557 and 1453 fps, that a differnce of 104 fps???
At 2500 yards the velocity spread is 62 fps
At 3000 yards the spread is 16 fps
At 3500 yards the two are idential.
I figure the 2000 yard figures are a typo in some way as its pretty hard to hit the afterburners between 1500 and 2000 yards. [img]/ubbthreads/images/graemlins/grin.gif[/img]
STill from what I am seeing in your numbers, yes the faster round slows at a higher rate then the slower bullet, BUT, it is never overtaken over the 3500 yard bullet flight. Instead the velocity advantage is just continually and consistantly deminished until the two rounds flatten out at the same velocity at the same range.
Am I reading your numbers correctly???
With the humidity changes and altitude changes I an using, I would agree with your numbers from what I am seein with actual tests in the field.
What I am most concerned about is the max range before the bullet drops out of super sonic velocity. I have not seen the 300 gr SMK survive this accurately in my testing. From your numbers we see that the faster bullet will reach out 250 yards farther while still being supersonic compared to the slower pill.
Honestly, in the real world shooting, THis seems about right from my actual testing.
I could really care less about how the two compare velocity wise, I am concerned about the range at which they drop out of super sonic flight and your numbers relate very well to what I have actually seen in my tests.
Good reading and discussion!!! Your still all above me with these numbers but I like reading them [img]/ubbthreads/images/graemlins/grin.gif[/img]
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
No one has talked about accuracy either!!!! What if my gun shoots 1 moa groups at 3100fps, bahhh
Then the same gun shoots .2 moa at 3400fps so now what load do i use? My faster load outshoots the slower load, hmmm. This is what i have found in my testing. There are more factors at work here than just what the trajectory curve is and how fast the bullet slows down. I have talked with Trigger Fifty about the 375-408, sure it has a higher BC bullet, but he never states the accuracy. All i could get out of him was somthing like 1 moa. It maybe due to the lost river bullets, the Sierra bullet may fix that, but no one knows just yet. I was told this many years ago, a bullet shot at a high speed will hit the ground the same time a slower bullet will, (all things being equal) This relates to a flatter shooting rifle will fall off fast due to you dont have to add the extra moa the slower rifle needs. But i have heard that is why we adjust our scopes for are varied ranges. He also talks about shooting not knowing the range, well im pretty sure most of the long range hunters here wount take a shot at an animal not knowing the distance, therefore what is the difference if i have to make an adjustment to the faster falling projectile?
If im shooting a Elk at 1000yds and my rifle is sighted in at 100yds, my MOA adjustment is +16.5moa A elk pops out at 1500yds well im not going to take a pot shot with out figuring the drop change. This situation will have to be delt with no matter what gun or cartrige your shooting. But what i am more concerned with is "will my gun hit the kill zone at the distance i am tring shoot?" "Will i have enough Energy to do the job?" I dont see the benifit of a 3000yd gun that shoots 35" groups or worse. Kill zone on a big elk is in the 18" range, therefore 1800yds would be the longest shot that should be taken. This is where supreme accuracy takes over, if you have the same rifle that shoots .5moa with a 3000yd range then you will have somthing.
I maybe rambling, but this is just my opinon for hunting game. I have never shot a cartridge like the 338-408 improved versions before, They are fast and have high energy to long kill distances. The accuracy for a big gun is phenomial to say the least, Kirby can attest to that.
Well anyway, i wish Trigger Fifty good luck on his rifles, i hope they will shoot as good as the 338 cal rifles do. I have had the reamers in my shop for 4 years just waiting for bullets, and Lost River Bullets are not an option for me.
I am very pleased that in some areas my formula correlated with your actual application results. I am extremely impressed that you caught the deceleration ratio discrepancy at the 2000-yard range, do not kid yourself, this stuff is by no means above you. That was no typo, that is just evidence of application vs. theory. According to Sierra, the B.C. of the 300-grain SMK abruptly changes at 1800 fps; this figure is not in correlation to the constant decline in the FC (frequency of collision) variable. The faster bullet did not speed up; it just did not cross the deceleration factor until sometime after the slower bulletís program had made a parameter adjustment causing a spike in its ratio of deceleration. (sorta like hitting a bug in cyberspace [img]/ubbthreads/images/graemlins/grin.gif[/img]). I did use altitude as a factor, but the air temp, humidity, pressure and barometer figures are an average of atmospheric conditions at 3500í obtained from a GOOGLE search. (Iím too lazy to call the Billings airport.) The cyber model atmosphere was constructed from perfect little cubic particles that were forced away from the meplat at a 168į or a 192į angle and simply ceased to exist after rising or falling .169Ē from the bullets centerline. In other words there was very little resistance past the oglive and no posterior turbulence effect. I did not allow for any pitch or yaw from the projectile and also no gravitational pull. I omitted these factors just to compare the deceleration and energy depletion ratio and because Iím lazy. This example should prove three things: 1.) Your observations through experience are likely correct. 2.) If the bullets become unstable the increased drag could affect the faster bullet enough to bring it to sub-sonic velocity sooner than the lighter load. 3.) Doing math calculations like this on a weekend indicate I do not have a life [img]/ubbthreads/images/graemlins/grin.gif[/img]. I think a 6.5 Allen Xpress would solve that problem!
This thread is very entertaining, if not somewhat off the original subject, I hope it continues.