375-408 CheyTac (Kirby Alert!!!!!!) question
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Jon A
Well-Known Member
[ QUOTE ]
Okay, I guess I am still just not seeing how the faster of the 2 identical bullets would go sub sonic first.
[/ QUOTE ]
Don't worry. Neither am I. I'm hoping Dean can explain that one a bit better. /ubbthreads/images/graemlins/wink.gif
Okay, I guess I am still just not seeing how the faster of the 2 identical bullets would go sub sonic first.
[/ QUOTE ]
Don't worry. Neither am I. I'm hoping Dean can explain that one a bit better. /ubbthreads/images/graemlins/wink.gif
Fiftydriver
Official LRH Sponsor
M. Sheep,
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. /ubbthreads/images/graemlins/grin.gif
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 /ubbthreads/images/graemlins/grin.gif
Kirby Allen(50)
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. /ubbthreads/images/graemlins/grin.gif
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 /ubbthreads/images/graemlins/grin.gif
Kirby Allen(50)
Black Diamond 408
Well-Known Member
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.
Dave
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.
Dave
Mountainsheep
Well-Known Member
Kirby,
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 bullet's program had made a parameter adjustment causing a spike in its ratio of deceleration. (sorta like hitting a bug in cyberspace /ubbthreads/images/graemlins/grin.gif). I did use altitude as a factor, but the air temp, humidity, pressure and barometer figures are an average of atmospheric conditions at 3500' obtained from a GOOGLE search. (I'm 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 168° or a 192° angle and simply ceased to exist after rising or falling .169" 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 I'm 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 /ubbthreads/images/graemlins/grin.gif. 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.
Dave
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 bullet's program had made a parameter adjustment causing a spike in its ratio of deceleration. (sorta like hitting a bug in cyberspace /ubbthreads/images/graemlins/grin.gif). I did use altitude as a factor, but the air temp, humidity, pressure and barometer figures are an average of atmospheric conditions at 3500' obtained from a GOOGLE search. (I'm 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 168° or a 192° angle and simply ceased to exist after rising or falling .169" 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 I'm 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 /ubbthreads/images/graemlins/grin.gif. 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.
Dave
Fiftydriver
Official LRH Sponsor
Thanks for the explination on the numbers.
I agree, this is a good conversation to have, if nothing else to open minds to ballistic performance. Mine included as much as anyones!!
Thanks for running the numbers.
Kirby Allen(50)
I agree, this is a good conversation to have, if nothing else to open minds to ballistic performance. Mine included as much as anyones!!
Thanks for running the numbers.
Kirby Allen(50)
duckinalaska
Well-Known Member
Dayyaamn,
Kirby Allen.... The Professor.
or The Gun Professor.
I think that I'm on to something here.
Brandon
Kirby Allen.... The Professor.
or The Gun Professor.
I think that I'm on to something here.
Brandon
triggerfifty
Well-Known Member
- Joined
- Oct 13, 2005
- Messages
- 50
Hi Dave, only time for a quick minute.
First, the BC of the 300 gr. Sierra bullet changes every single meter downrange, refer to the image of the different shots of the 773 gr. LRBT above. That curve represents thousands of BC values. Using a single, or even 3 BC values won't yield accurate results. The varying BC values in the data curve above are every 100 meters yes, but they are averages of BCs taken every single centimeter from 10 meters to about 5000 meters, more or less, depending on the shot, downrange. You guys are on the button with yaw and pitch characteristics. The "controlled spin" patent that LRBT has on it's bullets addresses this issue. Now many say it can't be done, but the YPG and APG ballistics guys disagree and said that it was effectively DONE.
I've attached a plot image from the YPG test. That fine (not so fine on this upload) line represents the stability of the controlled spin bullet during supersonic through transition and into subsonic flight. No bumps and dents in the line. As the bullet starts to yaw, the BC value begins to drop, sometimes the straighten themselves out, and the BC value climbs again, after transition, they always climb, some are higher in the subsonic range (BC) than they are supersonic.
Brains smoked, here's the plot. Last PS, the data string from 1 shot, printed in 10 cpi is 198 pages long. A different BC shows up 3-4 times per page, depending on how you buffer the data.
Also, once the bullet
First, the BC of the 300 gr. Sierra bullet changes every single meter downrange, refer to the image of the different shots of the 773 gr. LRBT above. That curve represents thousands of BC values. Using a single, or even 3 BC values won't yield accurate results. The varying BC values in the data curve above are every 100 meters yes, but they are averages of BCs taken every single centimeter from 10 meters to about 5000 meters, more or less, depending on the shot, downrange. You guys are on the button with yaw and pitch characteristics. The "controlled spin" patent that LRBT has on it's bullets addresses this issue. Now many say it can't be done, but the YPG and APG ballistics guys disagree and said that it was effectively DONE.
I've attached a plot image from the YPG test. That fine (not so fine on this upload) line represents the stability of the controlled spin bullet during supersonic through transition and into subsonic flight. No bumps and dents in the line. As the bullet starts to yaw, the BC value begins to drop, sometimes the straighten themselves out, and the BC value climbs again, after transition, they always climb, some are higher in the subsonic range (BC) than they are supersonic.
Brains smoked, here's the plot. Last PS, the data string from 1 shot, printed in 10 cpi is 198 pages long. A different BC shows up 3-4 times per page, depending on how you buffer the data.
Also, once the bullet
triggerfifty
Well-Known Member
- Joined
- Oct 13, 2005
- Messages
- 50
Dave, on the LRBT bullets, why no options for you? If I may ask.
Jon A
Well-Known Member
Thanks Dean, but that doesn't really answer the question. If the above bullet was fired at 900 m/s, would the 780 m/s and on portion of the velocity vs time curve be vastly different than the one above or would it just be shifted over a little bit? If the latter, then the speed of sound would not be reached as quickly, correct?
davewilson
Well-Known Member
Trigger, i'm sure i can answer that for Dave, it's because the bullets don't shoot worth a hoot! i know, i know, they shoot great. i'm sure every once in a while it seems someone will have a rifle that shoots em pretty well. but it's rare. just ask the fellow in Ohio that has been trying to get them to shoot for 3 years. he's got great equipement, a full tricked out heavy gun built by a good smith. did i mention he's gone through 20 barrels in this time and has never, ever, even once kept all the bullets on paper much less done well in a match. i think Dave's point was it doesn't matter if a bullet has a BC of 2.500, if you can't hit what you're aiming at.
I agree with you Kirby, this an interesting conversation. I am learning something new everyday. I never looked at ballistics in this fasion. I am trying to make sense of the whole thing. Anyhow, I hope the conversation continues. I am glad I posted this topic.
Kirby, I e-mailed you back regarding your recommedations for my 338 Allen Mag project, just wanted to let you know. I hope to hear from you soon.
Wildcat
Kirby, I e-mailed you back regarding your recommedations for my 338 Allen Mag project, just wanted to let you know. I hope to hear from you soon.
Wildcat
Black Diamond 408
Well-Known Member
My point with the Lost River Bullets are experience in the 408 cal bullets, these are the patented controlled spin, yes i have tried them in three different rifles. They shoot just ok, not anywhere close to match quality. The quality control is not good for a bullet that is priced as is. You never see a Lost River bullet win any long range match, why is that? Even with the special barrels made exclusivly for the LRB bullets, they still are only just ok. Now there is another bullet company making a similar 408 bullet, that will out perform the LRB in accuracy. My customers no longer use the LRB bullet, they prefer the other manufacturer's bullet. This is why i said, IF and When Sierra has something to offer, then you will have one awesome rifle, but then you will be back to the 300gr MK delema, lower BC bullet, but more accurate. All these curves and tangents don't mean a whole lot to the guy hunting big game in the 1000-1200yds, he just wants to know where to aim and see the bullet hit what he is shooting at. I know its a military sorta thing and they would be more interested, that is the whole thing behind Chey-Tac anyway, they want gov contracts. I told Warren Jensen the 408 will die without other bullet manufacturers in the mix, he then threatened to sue me for patent infringements. Chey-Tac and Lost River at that time wanted the Monopoly on the whole thing. I refuse to buy another LRB bullet.
triggerfifty
Well-Known Member
- Joined
- Oct 13, 2005
- Messages
- 50
Sorry guys, while i'm not a cheytac fan, the 408 DOES shoot. I've shot them all from gun #1 to now, dozens of them, built some of them. I shoot 338 250s and 270s, and have seen them shoot by navy shooters, army, and many other units. You ARE outnumbered on that. The internet "push" against these bullets is misguided i think. Dave, i believe you build a good gun, i also believe you are using barrels that are not compatible with these bullets. Lawton in Mt, builds them right. Just had an AI gun here shooting 270 gr. LRBT 338 bullets, and HE is convinced.
I know, I know, it' takes a special barrel, but isn't a specific twist a special barrel? Doesn't the M24 have a 1:11.25" twist for JUST the old 173 gr. M118 SB round? PLEASE come to an extreme range shoot in Idaho and LOOSE to these rounds. Just had a 4 day shoot here and all those guys were convinced. The only guns to hit the 2600 yard targets were shooting LRBT solids, a 375 rifle, a 408 rifle and a 338 lapua, shooting 270s. Results on are my website. Dave, what bullet are you shooting in your .408 guns? Please don't tell me that brass junk.
Respectfully,
Dean
Also, on these other guys that can't make them shoot. Can you hook me up with them? I'd like to know their gun setups. Tight bores that have to squeeze bullets to make them shoot won't do the solids, the FCSA shooters knew this years ago, they simply adapted.
I publish results with my guns and groups. Witnessed, this target was shot by the owner, with 3 witnesses. I built the rifle, 375 SOE gun.
Sniping Operations Executive
[image]http://www.snipingoperationsexecutive.org/375-408page.html[/image]
I know, I know, it' takes a special barrel, but isn't a specific twist a special barrel? Doesn't the M24 have a 1:11.25" twist for JUST the old 173 gr. M118 SB round? PLEASE come to an extreme range shoot in Idaho and LOOSE to these rounds. Just had a 4 day shoot here and all those guys were convinced. The only guns to hit the 2600 yard targets were shooting LRBT solids, a 375 rifle, a 408 rifle and a 338 lapua, shooting 270s. Results on are my website. Dave, what bullet are you shooting in your .408 guns? Please don't tell me that brass junk.
Respectfully,
Dean
Also, on these other guys that can't make them shoot. Can you hook me up with them? I'd like to know their gun setups. Tight bores that have to squeeze bullets to make them shoot won't do the solids, the FCSA shooters knew this years ago, they simply adapted.
I publish results with my guns and groups. Witnessed, this target was shot by the owner, with 3 witnesses. I built the rifle, 375 SOE gun.
Sniping Operations Executive
[image]http://www.snipingoperationsexecutive.org/375-408page.html[/image]
