sabotloader

Ran a quick chart this as requested...

I use 1860 as the velocity - 110 grains of T7-2f loose. The request was for 150 grains - pellets. I do not shoot pellets so I do not have a definitive velocity, but 1860 should be in the area

Chart was computed using these facts:
1. Scope mount - sight height 1.75"
2. Elevation 4000 ft.
3. Temp 50
4. BC of the bullet estimated @ .250 (might be a bit high)

Hope this is useful to someone...

mike

Pglasgow

Based on drop, theactual B.C. of the Hornady 385 GP conical simply can not be the published B.C. My biggest concern about this is not the drop but how much energy I'm delivering at range. Recently, I increased charge so gain a little more energy downrange.

If I had a friend with a chrony, then we could get better data. Randy Wakeman did some of his own testing, chrony to chrony for 100 yard B.C.'s.

http://www.chuckhawks.com/bc_not_exist.htm

Where he said:

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sabotloader

Pglasgow

Hard to believe they are actually that low --- 250 BC's... BC is based also on velocity I wonder what Randy was shooting... That's why Precision Rifle can get and advertise their BC's so high.

Big 6x6 does the best job testing BC's that I have seen. He has checked the SST/SW and I know he was over .200 but I can not remember what, I could e-mail him and ask him.

mike

Pglasgow

I don't know if they are really that low. But I have a sense that they are for a 100 yard avg BC and 100 grains 777. Almost none of the bullet manufactures are being honest about ballistics coefficients. Randy has ranted on this with several articles. If you look at the PR website you'll find that they calculate B.C. three ways:

http://www.prbullet.com/bal.htm

They go on to say:

So if chrono to chrono says .205 but the program calculates .345, the experiment and experience is totally ignored and the "tie", that is, the out of thin air BC goes to the bullet. Their flattest shooting bullet test by Toby Bridges seems to be a joke too. Based on the weights and the ballistics you posted in this thread, there is no conceivable way, even with their published B.C.s, they could have shot that "flat".It would seem that Toby just aimed a little higher with the PR bullets.

lemoyne

I believe we all know that the BC changes with the velicity,so different muzzle velicities will give different answers.
Just to add a bit with my old,old chrony and my Omega Z5 a winchester 209 and 125gr APP-FF I get a BC of .210 for a 250 SW. I don't have a program so I did it with a calulater. The way I try to check the answers is by shootin and seeing if the trajectory at 150yards matches my answers. Lee

Pglasgow

I'm pretty much doing the same Lee. But at slower velocities and BCs in the value I have to deal with in full bore conicals, the difference in drop at 150 yards is far more than what you are having to deal with using your load. And the difference in energy at range is much more significant. When I run the numbers, the difference between .184 or .210 for BC is .320 inch at 150 yards with your load. I'm using 2150 for the muzzle velocity, is that about right? If the load is faster, the difference is less, slower, it will be more.

In any event, a drop change of a little over 1/4 inch is a little difficult to observe at 150 yards and could be swamped simply by an incorrect estimate of sight height or being just one or two yards off on the range. You are an excellent shot and report the load consistent, so you may try putting the chrony in front of the target and getting an average 150 yard velocity. Then you can go here http://www.eskimo.com/~jbm/calculations/bcv/bcv.htmlto calculate the BC. Just enter your avg muzzle velocity,your avg 150 yard velocity, and450 ft for the distance and it will calculate your B.C.

Phil

lemoyne

I averaged 5 shot groups both for velicity and center of group location.
Since my group at 150 was 2.2 inches and vertical you are right about the .25 of an inch.
Also I am chicken to try and use the chrony @ more than 100yd its to easy to throw one.
Lee

Wolfhound76

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I'd get a second opinion. He doesn't like SST's.

Pglasgow

I know what you are saying! Then maybe try 100 yards or 75 yards.

Pglasgow

I honestly can't believe you wrote this. Would you suggest that Randy Wakeman "fudged" his chrony to chrony tests? It would seem to me, that a chrony to chrony test is about as unambigious and "free of opinion" as anyone can find. For my part, irrespective of whether Randy likes SST's, I trust that he didn't misrepresent the data or "lie" about it.

Phil