Come on out - It's safe now

[Jon A]

Re: Come on out - It\'s safe now

You would need to calibrate the two chronographs to each other by putting one right after the other and shooting over them to see if one consistantly reads higher than the other and by how much; then swaping their positions and doing it again. Hopefully you'd be able to find a repeatable pattern you could use to correct your velocities from one to the other. If they average the same but differ by a random amount shot to shot you aren't gaining a whole lot--but hopefully that wouldn't be the case.

Done with two good chronographs calibrated correctly, of course will be more accurate. But not many have access to two Oehlers. I don't think that means they should do nothing.

Doing it with one good chronograph is certainly better than nothing--which is what most are doing right now. When SD's are in the single digits and one bullet on average loses 30, 50, 100 or 170 fps more than another, you may not have a number down to the last .001 with enough statistical assurance you'd bet the mortgage on it, but you sure have better data than when you started. You'll be in the ballpark.

 

[LWolken]

Re: Come on out - It\'s safe now

I thought that HBC (Benchrest Central) did some testing on the 6mm wildcats and reported that the stated BC's were marginal at best? Obviously this doesn't mean anything for the rest of the bullets offered by Richard. I'm not one way or another on this subject. I'd just like to see repeatable comparisons. Would there be any merit with comparisons of bullets drop to another manufacturer at the same velocity and range? In other words can we skin the cat another way?

Lance

 

[Fiftydriver]

Re: Come on out - It\'s safe now

Thats what we have been trying to do but everytime someone posts any data from this type of drop testing all haties breaks loose.

Its accurate enough data to get a guy on target at extreme range but many feel it is not good enough to establish a BC off from. They may be correct, I do not know, all I know is I can hit the targets I shoot at using the derived BC values I get from bullet drop testing.

Hitting the target is about all I care about.

Kirby Allen(50)

 

[LWolken]

Re: Come on out - It\'s safe now

Fifty,

What I'm saying is rather than reverse engineer the BC figures from drop tables which we all know can vary quite a bit due to other factors. Why don't we just take a known competitor's higest BC bullet and shoot a Wildcat along side it and post the differences in drop. This would leave the numbers out of the equation but still give us a comparison that we can relate to.

Lance

 

[Mikecr]

Re: Come on out - It\'s safe now

I don't think there is much merit to someone else's observed drops by itself. Condition's or comparisons are really needed.
If somebody reports that a bullet requires less drop compensation than another, under same conditions, it means to me that the bullet has higher BC. Thats all.

If someone calculates a local/apparent BC of .XXX, but can't provide further -qualifying information, then I can't find a real use for it. There is just no way to back convert apparent BC from Montana into a sea level standard BC for comparison with other bullets without knowing the conditions producing the data.

It's all good to hear though. And queries for further info should not automatically be taken as an attack. Atleast, not from me. Questions=Interest.

 

[Matt27]

Re: Come on out - It\'s safe now

What qaulifying information are we after and what can be a consensus on how to go about getting B.C. figures that all can understand and agree upon?

Are we talking about having 2 chronographs?

Are there any programs out there that can convert to sea level from the conditions of where we(tester) are at at the time of testing?

 

[dakor]

Re: Come on out - It\'s safe now

I am planing on shooting a few bullets with High bc's when I test the 200's. I am going to shoot the 175 Sierra SPBT and Noslers 160 Accubond. No store around here has any Berger 180 VLD's and it could take up to 3 weeks to get them if I order them so I am going to see if I can find a box of 162 A-max bullets since they have a bc of .625. As for using two Chronographs I am just going to use the one Pact I have and move it to a couple of different ranges. As for Elevation I will be shooting at 850ft for the 300 yard target and the bench will be at 853ft. The target is 4ft tall so I should not be shooting at a down angle. I guess we will see what happends when the 200's get here.

 

[Fiftydriver]

Re: Come on out - It\'s safe now

LWolken,

When you have bullets of relatively equal bullet weight to compare that is a good idea at least for the individual to test bullets head to head.

In the case of the heavy wildcat Bullets, there is nothing out there that will match up of equal or similiar weights. Example:

156 gr ULD RBBT .257"
169.5 gr ULD RBBT .277"
200 gr ULD RBBT .284"
350 gr ULD RBBT .338"

Still you can take two different bullet weights, zero them at the same range, say 500 yards and measure mid range tajectory and say an 800 yard drop and be able to figure out which bullet is most ballistically efficent.

We have actually been doing this all along as well but again some feel this offers nothing of value in comapring one bullet to another.

Personally, I think you only have to test for yourself and whatever system you use that allows you to develope accurate predictable drop charts is the system you should use.

Good SHooting!!

Kirby Allen(50)

 

[Mikecr]

Re: Come on out - It\'s safe now

[ QUOTE ]
What qaulifying information are we after and what can be a consensus on how to go about getting B.C. figures that all can understand and agree upon?

Are we talking about having 2 chronographs?

Are there any programs out there that can convert to sea level from the conditions of where we(tester) are at at the time of testing?

[/ QUOTE ]

The information needed depends on what is missing.
If the observation is drop or clicks/MOA of compensation, then example qualifiers would be scope height(exact), MV, Atmos data, Scope type("/100yds, 1/8moa, etc), base angle, zero, shot angle, wind compensation, bearing, lattitude.

Many of these are eliminated with 2 chronographs. So this would be the preferred/more accurate method provided you aren't introducing even more error. Cheap chronos, narrow screen spacing, #of shots in avg, etc, would need to be taken into account if all is based on this data alone.

Then with software, trial & error to get a local match and again from hypothetical SL Std BCs. This would need to be derived and validated with more than one program because they all have strength and weakness in different areas.

This is why some of the best bullet makers don't advertise BC. They don't know, and don't have the resources or motivation to find out. Their bullets sell based on other attributes.
Some tolerances and assumptions would always have to be accepted. But there are plenty of resources here to pinpoint and convert observations into truly usable information -across the board. Just takes patience, and a culture which allows for open -polite- questions.

But why is this important to do? Like Fifty suggests, all that matters to you is what you need to enter in your software, right? If you hunt locally only, and have a particular caliber/cartridge/twist already, then it probably doesn't matter for you. Buy it, try it.
But for those who hunt abroad, or those considering a new rifle chambering and shooting system, it all starts with a bullet. And comparisons in choice can only occur within the same standards.

 

[Jon A]

Re: Come on out - It\'s safe now

Maybe I should post the raw data from the test I did recently so people can see how I went about it. Not as an example of "the only way" or "the best way" but just the way I did it with the equipment I had.

 

[Matt27]

Re: Come on out - It\'s safe now

If one was to take a 4x8 piece of plywood(i believe like kirby does) and start at 100yards and get your zero(aiming point would be the top of the plywood) and move the plywood to 200 still maitaining aiming point of the top of the plywood and fire a group and then circling or marking the group and then move it to 300 and so on while still maintaining aiming point of the top of the plywood.
NOTE--- One would not adjust the elevation turret---

One will be able to get drop in inches out to 500-600 yards. Can one then go back to the ballistic programs and match up the drop figures while recording all the necessary data like temp, humidity, baro, bearing, lattitude, MV, scope height, base angle???

 

[royinidaho]

Re: Come on out - It\'s safe now

[ QUOTE ]
If one was to take a 4x8 piece of plywood(i believe like kirby does) and start at 100yards and get your zero(aiming point would be the top of the plywood) and move the plywood to 200 still maitaining aiming point of the top of the plywood and fire a group and then circling or marking the group and then move it to 300 and so on while still maintaining aiming point of the top of the plywood.
NOTE--- One would not adjust the elevation turret---


[/ QUOTE ]

Matt27, that's exactly what I did last fall. Took all most all day. Using a tape measure marked out to 500 yds in 100yd increments. Used cardboard box of sufficient height (I hoped based on factory bc). Was across a dry lake bed.

Let me tell ya, that was a lot of walking, the lake was dry, but when you broke through the crust you could sink up to your knee. Thus no driving.

Time of day was a factor as too much time was taken. After I was done I made some SWAGs (scientific as I was holding a calculator in my hand when I made 'em but mostly WAGs).

After much more shooting an playing I came up with a drop chart. After all that work, my first shot # 650 was spot on.

Why, not this. Set up a regular paper target target at say 100 or 200 yds. Align it so that the 4X8 large target is lined up properly at say 500 yds. Line up the near target exactly at the top edge of the far target (if that can be done) then shoot.

Will the "paper" mess up the bullet profile?
If I'm successful w/getting accurate drop measurements using this method and develop a usuable drop chart out to 800 yds does it make any difference what the velocity or bc is? (Just thinking very basically)

Am shooting .338 252gr bullet w/o published bc. They're so purdy I kinda hate to shoot 'em. Have 'em all lined up on the shelf in the shop in itty bitty grass skirts so they wiggle when I close the door hard. /ubbthreads/images/graemlins/wink.gif

 

[Mikecr]

Re: Come on out - It\'s safe now

[ QUOTE ]
Can one then go back to the ballistic programs and match up the drop figures while recording all the necessary data like temp, humidity, baro, bearing, lattitude, MV, scope height, base angle???

[/ QUOTE ]

Yes, with as much of that info as you can get loaded into your ballistic program, you can trial & error BC input till drop(not path) matches. A real good program will allow a drag curve such as G7 to be used for this. With high BC bullets that would be more accurate. But for hunting bullets at reasonable distances, G1 works well enough.

 

[ricka0]

Re: Come on out - It\'s safe now

[ QUOTE ]
<font color="purple"> Maybe I should post the raw data from the test I did recently so people can see how I went about it. Not as an example of "the only way" or "the best way" but just the way I did it with the equipment I had. </font>

[/ QUOTE ]

Using two accurate/repeatable chronys and calibrating them as you mentioned earlier is the best way short of radar. It wouldn't be hard for me to show the error bounds of the other approaches are an order of magnitude greater.

I'm not condeming the drop data approach - but if you want to know the BC with an error bound (%) in the low single digits - use dopplar radar or two chronys.