bc for sb-4 mould

sumphre · Post by **sumphre** » Mon Mar 13, 2006 8:32 am

I am planning on purchasing ballistic software frm tmt enterprizes and
need to figure out the ballistic coeficient for my steve brooks .45 cal
530gr postell. anyone have a contact # for him or can i just enter the
dimensions into the software program.

MLR · Post by **MLR** » Mon Mar 13, 2006 8:47 am

sumphre:

Go to the links page on the Shiloh Rifle page. Brooks add is the first one.

Michael

sumphre · Post by **sumphre** » Mon Mar 13, 2006 8:58 am

i cant seem to find any links reference anywhere.

MLR · Post by **MLR** » Mon Mar 13, 2006 9:05 am

http://www.shilohrifle.com/links.html

there ya go

Michael

Kurt · Post by **Kurt** » Mon Mar 13, 2006 9:51 am

sumphre.

I don't think Steve can tell you, I asked him before on a couple of bullets from his moulds and he said I have no idea.

Kurt

Orville · Post by **Orville** » Mon Mar 13, 2006 10:47 am

go to www.uslink.nt/~tom1/index.htm

There is a B. C. istimater there and also a twist veris bullet length calculater there.

Dutch · Post by **Dutch** » Mon Mar 13, 2006 12:34 pm

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
sumphri
am planning on purchasing ballistic software frm tmt enterprizes and
need to figure out the ballistic coeficient for my steve brooks .45 cal
530gr postell. anyone have a contact # for him or can i just enter the
dimensions into the software program.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

You found me!!

I don't yet have the dimensions of the Steve Brooks 530 gr. Postell on hand so I can't help you right away

The Precision Ballitic software that is currently offered can estimate the BC for the heavy lead bullets that we use, but it does not do as good a job as the add-on package "Cast Bullet BC Estimator" that needs to be ordered seperately.
Add-on Cast Bullet BC Estimator

I would rather not commercialize on this thread so will send you a personal message with the details.

You may also use the TMT Enterprise's Website BC estimator, although it is still not quite as accurate as the add-on Cast Bullet BC Estimator.
OnLine B.C. Estimator

If you want an estimation of the BC now, and can post a good profile image of the bullet, I can scale it out and give you a pretty close estimate of what the BC should be.

Hope this helps.
Check you personel messages.
Tom Myers
Precision Ballistics and Records

Kurt · Post by **Kurt** » Mon Mar 13, 2006 3:21 pm

You are not going to get an accurate BC if you don't have a reading on the same bullet read over two chronographs, one at the muzzle and one down range no matter what software you are using.

Kurt

MLV · Post by **MLV** » Mon Mar 13, 2006 3:39 pm

Kurt: Dr. Oehler, the chronograph guy, and I did precisely that one time at his home in Texas. Except we used one of his Model 43 Ballistic Laboratories with breaking screens at a surveyed (to the tenth of an inch) 200 yards.

The BC we got THAT DAY in THAT HUMIDITY, etc. etc, for a Lyman Postell #457132 weighing 536 grains of 1-20 tin to lead alloy was .402. It was fired from a 30" Shiloh .45-70 barrel over 58 grains of Goex FFg with a velocity at 10 feet of 1082 fps.

It might interest someone to know that the Redding/Saeco #745 weighing 534 grains with all other variables the same gave a BC of .399. At 10 feet it was doing 1075 fps.

take care

Kurt · Post by **Kurt** » Mon Mar 13, 2006 4:43 pm

Mike;
That's pretty respectable BC, I retired that mould, I never could get it to print a decent group.
I was running a string with the .50 with 718 grainer's from a Brooks mould with the second Chrono set up at 200 yds

first shot after getting the sights set I got heavy fingered and set one off and wiped out the front and back sensors

Pact has always fixed this unit when I had a problem with free of charge, I just got it back from repair but I don't think I will ask for a new set of sensors

Kurt

RMulhern · Post by **RMulhern** » Mon Mar 13, 2006 4:52 pm

Well...IMO.... BC's don't mean squat anyway in BPCR cause the piece of lead we're puttin down range has got a trajectory akin to a manhole cover! And since the BC is constantly changing due to velocity loss.....what's the point?? The only thing that matters is that one go out and obtain zeros for various distances by SHOOTING AT THOSE DISTANCES....and let well enough alone!! Enjoy the smell and the smoke!!

MLV · Post by **MLV** » Mon Mar 13, 2006 6:27 pm

Sharpsman; Here's a question for you since you have a LONG range to shoot on. Do you ever notice that your sight settings change by the temp of the day? Sometimes we have seen in silhouette that on cold days with heavy air we have sight settings a few minutes higher at the rams than on very hot days. Same load & rifle.

By the way I agree with you on the general subject of BCs after mine and Dr. Oehler's little experiment. The lowest we got was .36 and the highest .40, which is very little change with vastly different shaped bullets.

Dr. Oehler's conclusion (and the man knows something about ballistics) was to pick your bullet by its groups and not by what it looks like.

Mike V.

PS: I'm still going to get that magazine to you. I just haven't received my new books yet.

RMulhern · Post by **RMulhern** » Mon Mar 13, 2006 7:51 pm

[quote="MLV"]Sharpsman; Here's a question for you since you have a LONG range to shoot on. Do you ever notice that your sight settings change by the temp of the day? Sometimes we have seen in silhouette that on cold days with heavy air we have sight settings a few minutes higher at the rams than on very hot days. Same load & rifle.

By the way I agree with you on the general subject of BCs after mine and Dr. Oehler's little experiment. The lowest we got was .36 and the highest .40, which is very little change with vastly different shaped bullets.

Dr. Oehler's conclusion (and the man knows something about ballistics) was to pick your bullet by its groups and not by what it looks like.

Mike V.

PS: I'm still going to get that magazine to you. I just haven't received my new books yet.[/quote]

MLV

You better believe zeros on elevation change from just a mere 8-10 degrees variation in temp!! Many days here in the summer when it's hot enough to fry and egg on the blacktop.....we'll start the day out early AM around 0600 with maybe 85F and by 1400 she's cookin at 102F to 105F. And only an idiot shoots in that kind of heat....even under a covered firing point it's absolutely unbearable!! From shooting much outdoor .22 smallbore....I learned long ago that not only does the heat variation make a change in elevation zeros but winds from varying angles will also effect elevation; left winds have an effect of lowering the POI and right winds do just the opposite! This is very noticeable shooting low velocity bullets of .22 caliber and I do believe it applies to these big/slow slugs we shoot in BPCR!! I shoot very little in July/August as the heat plays havoc with us down here just as wind/snow/ice effect you boys up there!!

Don't worry about the article....or the book! I have patience!!