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Post by DBinNY on Sept 26, 2008 22:41:48 GMT -5
R'man, here's one for your favorite load from PointBlank. I entered a PBR of 7" (to get +3.5 at 100 yards) and played with the BC until it approximated your drops. Note that the BC (.236) is significantly less than the published .291 but remember that these things change with velocity. If I understand it correctly, the faster you push it the more the initial air resistance and the lower your BC. Based on the output I'd say your actual trajectory would be within one inch of the table values out to 300 yards. I'm talking about vertical trajectory here and not wind drift. I guess the conclusion is that this is probably a very useful tool for filling in the gaps but there is no substitute for knowing actual drops at key distances (i.e., one near the peak, one at your maximum range and one in between).
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Post by Rifleman on Sept 27, 2008 3:10:23 GMT -5
First of all thanks to Realhunter for helping me out posting my drop tables. I now have them added to my original post. Makes it better having it all in one place. DbinNY What you were able to do on the Point Blank program was interesting. I have a difficult time using that program getting it to do what I want it too. My problem is that I cannot get it too calculate on a given zero range, as it always defaults to calculating a Point Blank Range. Of course that is to be expected I suppose, as it is called " Point Blank". The program is useful of course, but as a target shooter I have never been a fan of PBR zeros. I am used to working off a zero range at a given 100 yd increment and then adjusting off of that. Either making an adjustment of the sights or using features of the reticle. It just helps me with the math. I notice on your very nice picture that the program shows being plus 3.49 at 100 yds which is correct, minus .86 of an inch at 200 yds which is incorrect for my purposes as I am using a 200 yd zero, and minus 18 inches at 300 yds which is correct. Compare this to my corresponding table: On my table I show being plus 3.5 at 100 yds which is correct, zero at 200 yds which is correct, and minus 14.91 at 300 yds which is incorrect compared to actual shooting results. I messed around adjusting the BC, but to get the correct numbers at 200 and 300 yds, it leaves me incorrect at 100 yds, showing impact way too high. No doubt overall your program is calculating things closer to real world then mine is. If we could just get your program to calculate on a set zero of 200 yds instead of defaulting to a Point Blank Range calculation we would likely have just what I am looking for.
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Post by Rifleman on Sept 27, 2008 3:16:50 GMT -5
Sorry DW , in response to your question: Ballistic coefficient used- .291 Sight height- 1.5 inch Intervals- 25 yards Max range- 500 yds Muzzle elevation-0 Temperature- 50 degrees F Altitude- 400 ft above sea level Crosswind -10mph Wind direction- 90 degrees
Hopefully with the recent edit that is not so easy to miss.
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Post by Rifleman on Sept 27, 2008 3:33:53 GMT -5
With all the talk of BC's, programs, drops etc we have skipped over something. [glow=red,2,300]Notice the energy of that load! [/glow] At 100 yds it is hitting like a freight train with over 2700 foot lbs! At 500 yds it is still packing a punch with over 900 foot lbs.
I really appreciate the terminal capabilites of this load. I am thinking which of the deer I have shot with it to tell you how impressive it is, but it is hard to decide on which ones to tell you about. I guess I will just tell about a few ;D
First deer I killed with it was right at last legal shooting light. Hard quartering away, 135 yds, walking away. Downhill at about 15 degree angle. I hit the deer just forward of the ham, and bullet exited through far shoulder. Muzzle flash prevented me from seeing where the deer went. For a second I thought I missed. Got down there and deer was piled up on the spot. About a 165 lb buck.
Shot a doe on the run at about 40 yds. She was slammed! Blood and gore spray about 15 feet behind her all over the ground and trees. High shoulder hit, complete pass through.
Then one little button buck I shot by mistake. I thought it was a yearling doe even after obseriving for awhile. I don't like to shoot buttons, but it happened. I like to shoot yound deer as I primarily like to eat tender deer. I enjoy a big buck as much as the next guy, but when I shoot anterless deer, I go for the little ones if I can. This little guy was screwing around on the other side of a wood lot at about 140 yds. I kept trying to get a shot through the trees, but he was moving around alot. Finally I got about 8 inch hole to shoot thru with my crosshairs right below the heart. I was darn near lying on my back to get the angle. I shot that deer and he ran like a scalded jack rabbit a good 100 yds. I thought what in the world is going on! But the good thing was he ran towards the road and made the drag much easier. I had hit him right through the heart though, and he just did not know it. It was kinda funny compared to most of the other deer I have killed with this load, but it just goes to show you that you have to shoot more then one deer to really get an idea on how a bullet performs.
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Post by runningdog on Sept 27, 2008 10:45:51 GMT -5
Thanks Dwight, this information is very helpful to many of us. I printed it out and plan to use it for various powders.
Thanks very much
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Post by DBinNY on Sept 27, 2008 20:55:35 GMT -5
OK R'man, I set the "targ dist" to 200 yards which set the zero at 200 (do not calculate PBR). I forgot to set temp to 50 but played with the BC until the predicted trajectories at 100 and 300 were just a shade over 1/2 an inch off. This is likely as good as we are going to do with this program. Remember that these things are just mathematical models that attempt to explain reality. They are not perfect but they do a pretty good job.
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Post by Rifleman on Sept 28, 2008 11:53:25 GMT -5
That is probably as good as we are gonna get, Thanks Db
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Post by chapmangleason on Sept 28, 2008 14:48:25 GMT -5
Excellent Rman, about the only thing I could add to your post is terminal performance. I know when I first got introduced to this bullet by Rick (Tar12) that I had questions about terminal performance. You and Rick answered that in this post, which I put on my Web site: tinyurl.com/3z5oqtI think that content should be integrated into your origonal post for completeness. As always, excellent organized info on this bullet. Chap Gleason
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gjs4
Six pointer
Posts: 50
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Post by gjs4 on Sept 29, 2008 19:42:44 GMT -5
couple questions...
AA 5744 45 grs- 2080 fps
4759 44 grs- 2042 fps
Is 5744 really faster than 4759?
Can some one print out the ballistics for these loads beeing (250fps slower)?
thanks...and great work
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Post by Rifleman on Sept 30, 2008 2:07:25 GMT -5
Chap- Not the dreaded PDF file! Can't do a thing with it.
GJS4 , those were the numbers guys actually posted from Chrony reports. Notice they are very close and the 4759 charge is one grain less then the 5744 charge. Also a change in sabot or primer can also make quite abit of difference in velocity as well. As far as ballistic tables, in the original article you can see links to different free onlice ballistic calculators and all the data you need to print out all the tables you would like to.
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Post by chapmangleason on Sept 30, 2008 16:59:08 GMT -5
Chap- Not the dreaded PDF file! Can't do a thing with it. I figured you would have the content bookmarked or knew what was said about terminal perormance since you and Rick did most of the posting on Terminal Performance. I do agree the PDF that I have is not the most readable. Sorry for that. I was a very important discussion for me, since I had read about the 70% weight retention I was fearful of fragmentation, but 40 kills between you allied those fears quickly. Chap
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Post by Rifleman on Sept 30, 2008 23:13:20 GMT -5
Not a problem on your end Chap, my puter just likes to lock up on PDF files. Why I have no idea.
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Post by chapmangleason on Oct 1, 2008 7:15:32 GMT -5
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Post by CORVAIR on Oct 2, 2008 11:13:23 GMT -5
Dwight and others,
Isn't there a program to calculate any bullets "true" B.C. using the readings of two cronographs, one set about 10ft. from muzzle and one set at 100 yards? Wouldn't that help acquire an honest bullet B.C. for the BO?
I know that Big 6x6 has done this to calculate SST and Parker 275BE's "true" B.C. values over on the Modern Muzz. site(white board).
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Post by forester on Oct 2, 2008 14:26:43 GMT -5
Dwight and others, Isn't there a program to calculate any bullets "true" B.C. using the readings of two cronographs, one set about 10ft. from muzzle and one set at 100 yards? Wouldn't that help acquire an honest bullet B.C. for the BO? I know that Big 6x6 has done this to calculate SST and Parker 275BE's "true" B.C. values over on the Modern Muzz. site(white board). You can do that, but the value would still be imperfect unless you could somehow have 2 chronos perfectly calibrated to each other and in identical light conditions, and the shot would need to pass the same height above the sensors on each chrono. Additionally, true BC will vary from one gun to the next because of the differences from one barrel to the next. Exbal with it's trajectory validation function does a pretty darn good job of making accurate drop charts for changing atmospheric conditions after you have gone through the process under precisely known conditions.
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Post by Rifleman on Oct 2, 2008 15:27:31 GMT -5
I am sure there is a way Corvair, but By the time we go through the motions one can shoot and find out actual drops for his gun and load.
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Post by thelefthand on Oct 2, 2008 20:10:23 GMT -5
Yeah, I'm sure there's a program some where that will do it. The only problem with that is shooting over the chrony at 100 or more yards. You really need to do a 5 shot string at each distance so that you get a good average. A 5 shot string will cover 94% of your normal variation on a given day. That would eliminate the need for two chronographs.
Mark
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Post by CORVAIR on Oct 3, 2008 4:56:06 GMT -5
Dwight,
Not trying to hijack your thread, just adding some thoughts.
This has been a very,very informative thread on the BO and I appreciate the fine reading you have presented to us all Dwight.
I do believe though that Barnes might have overstated the B.C. of the BO.Some of the comparative readings your ballistics program has calculated seem to bear this out as the B.C. calculations are significantly lower.
Here is some of the data that Chuck(Big 6x6) collected on several bullets w/two identical Chrono's:I do not know the advertised B.C.'s of these bullets.
big6x6 Site Administrator
Joined: 17 May 2005 Posts: 5197 Location: Athens, AL Posted: Sun May 21, 2006 3:23 pm Post subject: New Ballistic Coefficients...
-------------------------------------------------------------------------------- This morning I wanted to put to rest the actual BCs for some of the new polymer-tipped bullets....
These BCs are calculated using actual velocities taken using identical Pro Chrono chrnongraphs at zero and 100yds. All bullets were fired from the same Savage 10ML-II stainless/laminate. All velocities were measured using the same charge of 40gr SR-4759. The listed BC is an average of 3-shots/readings. I tried to keep all factors as close to being the same as possible....
The BCs are closer than you may think!
The "players" from left to right: T/C 250gr Bonded Shockwave, Barnes 250gr T-MZ, Traditions 275gr T-Shock XLR, T/C 300gr Bonded Shockwave, Knight 290gr USS-PTBT, Barnes 285gr Spit-Fire.
From lowest to highest: 250gr Bonded Shockwave- 0.197 250gr TMZ- 0.207 275gr T-Shock XLR- 0.214 275gr Barnes XBP- 0.224 (added 06/28/06) 300gr Bonded Shockwave- 0.239 290gr TMZ- 0.240 285gr Spitfire- 0.251
I included the 285gr Barnes Spitfire because it has always given me some of the highest BCs around for a .45cal bullet. It still is the BC champ. _________________ Chuck NRA Endowment Member
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