|
Post by rbinar on Apr 21, 2009 22:09:28 GMT -5
This may be going off thread, so I apologize if I should have started a new one, but all the reported loads/MVs above reminded me that I have a question about the chronographing you guys do. I have an Oehler 35P that I have had quite a few years. I normally set it up so that the middle screen is at 12' from the muzzle, but have also set it at 20' at times. I have not been doing the math to correct instrumental to actual MV. Mostly using the chrono to help me work up loads for my own use, and not to compare loads from other sources. Now, I'm thinking that I should be doing the correcting for any load numbers I might post here. How do you experts do it? I have also had to shoot with the time feet (as opposed to inches) from the bench. My normal distance is 30 feet or 10 yards. I used a numer of ballistic programs to get an idea of how to adjust for muzzle speed. I found that for the bullet we shoot (BC of 1.9 to .3) and the velocity normally used (2100 to 2700fps) the speed change predicted was always between 30 and 40fps at 10 yards. So I began using 35fps as a correction. With the screens you can use a fraction of that number and get very close. At 12 feet that would be 14fps
|
|
|
Post by sagittarius on Apr 21, 2009 22:09:51 GMT -5
Excellent shooting, Rich. Congratulations! Look forward to seeing more pics.
|
|
|
Post by Harley on Apr 21, 2009 22:13:39 GMT -5
Boarhog, speaking just for myself, I set my first screen up at 10 feet from my bench. The rifle muzzle is probably about six or so inches into that. I'm guessing that's pretty much where most others set up, so give or take a little bit we are all reporting from the same perspective. Actually, though, there is probably a great deal of variation among the different chronys, so you just have to take the numbers a bit on faith.
Harley
|
|
|
Post by boarhog on Apr 21, 2009 22:43:23 GMT -5
My last range session, I needed to move the screens out farther than usual due to a shadow thrown over them by the firing line roof. I was barely able to reach 20' for the center screen because that's all the cables would reach. If I can get the same type coax, I can solder up extensions to set them as far as needed. I have plenty of male and female 1/4" plugs and jacks. If I had that option, I could quit worrying about tree shadows also.
|
|
|
Post by Harley on Apr 21, 2009 22:48:15 GMT -5
Boarhog, I don't know that this is a concern for you, but I needed to replace the cable between my Shooting Chrony and the remote readout. Although it appeared to be a modular, six-conductor telephone cable, I could not make it work; finally called Shooting Chrony and was told that although their cable was listed as a "telephone" cable, it was actually a specialty cable that had to be ordered from them.
Harley
|
|
|
Post by Jon on Apr 21, 2009 22:48:40 GMT -5
Rich, It looks like things have finally worked out for you. I'm impressed. You are probably one of the most devoted people that I've been lucky enough to talk to. I finally got some help to go to the range Sat. I've got basicaly three m/l to sight in and see how we both do. Thanks again for the great work you did for me. Jon
|
|
|
Post by wilmsmeyer on Apr 22, 2009 5:05:27 GMT -5
I use a real laymans approach to correcting for actual MV. If I look at a chart, I see that a .21 BC bullet starting at 2600 fps crosses the 100 yds line at 2190 fps. I see that it lost 410 fps over 300 ft. That equates to 1.37 fps per foot average. Since velocity loss is greater in the beginning I round up to 1.5 fps between my muzzle and the chrono. Since I normally set the chrony at 15 ft, I add 22 fps to all my averages.
Is this a big deal? Probably not, but it's closer to reality then what the screen says.
DB, I didn't look at your old post but wonder how close I am. I'm sure you were more scientific then me.
|
|
|
Post by fowlplay on Apr 22, 2009 9:03:41 GMT -5
Congratulation Richard, I'm glad the new barrel is working out very well for you. Just be careful. I feel boredom will set in after a few more shooting sessions. You might want to consider another 50. ;D Steve
|
|
tick
Forkhorn
Posts: 61
|
Post by tick on Apr 22, 2009 15:17:17 GMT -5
Great shooting Richard! Seems like Nitro and myself are about the only ones on here sold on Reloader 7 but we both prefer it over 4198. You might want to give it a try. Glad to have you back!
|
|
|
Post by smitty on Apr 22, 2009 17:10:29 GMT -5
60 - 65gr of R7 has also shot very well in my Pacnor 45. 65gr got me in the mid 2700fps range but my barrel is 28"
smitty
|
|
|
Post by Richard on Apr 22, 2009 19:22:49 GMT -5
Thanks to all for the kudos and the load information. Actually, I had Re-7 vials already loaded in 60, 61 and 62 gr. increments. I just did not have time to shoot all of them ;D I definitely wanted to shoot dave d's 56 gr. H4198 load and in fact, shot 10 of them with obviously excellent results. And, I also wanted to try some duplexes and other than the 10/70 load, which was stressing the sabots and gave my worst 5 shot group (2.2" ) I fired a total of 28 shots. (love that cool rod Edge!) I will be looking for loads that will get my velocity up into the 2600 fps range with sub MOA accuracy. Next on my list is to make a point up die for the .40 XTP's (tomorrow ) I definitely like the idea of the .50 Pac-Nor and its obvious that Jeff is getting excellent results with his...........its just that for target shooting and deer size game, which is all I can foresee doing, why beat myself up? No doubt if I were going to do a moose or bear hunt, the .50 would be the way to go. Richard
|
|
|
Post by pposey on Apr 23, 2009 22:03:32 GMT -5
Very nice,, see shorter barrels are good
|
|