BC of Parker 275BE

[153]

Anyone know the BC of a Parker 275BE?

[wilmsmeyer]

> .20 & < .30. Nothing great....just like the rest of our bullets.

[doohan]

Approx. .214 or so

[Dave W]

I came up with about .220 going by the drops I got shooting sabotless. As Wilms said, nothing special.

[Harley]

I asked SW for his opinion and he suggested .275 as a conservative guess. I plugged that number in my ballistics program and based my scope settings on the results. It was dead accurate way past 300 yards.

BTW, I asked Parker for the B.C., but they failed to reply.

Harley

[sw]

Jan 14, 2009 22:48:36 GMT -5 Harley said:

I asked SW for his opinion and he suggested .275 as a conservative guess. I plugged that number in my ballistics program and based my scope settings on the results. It was dead accurate way past 300 yards.

BTW, I asked Parker for the B.C., but they failed to reply.

Harley

I won't go into details, but the velocity loss method of obtaining a BC won't give a # that will work in the most commonly used formulas. This is because the G-1 drag coefficient is incorrect for what we shoot. I shoot out thru 300 or 350 yds, triangulate the centers of groups, plot them on a graph, use the least squares method of caculating the points and then back it into the equation and calculate a BC that works in the formula. The published BCs given(for our commonly used bullets) will not work in ballistic programs, especially past 200 yds. The sleeker the bullet is the more it will be off, as opposed to the natural reasoning that would make a person to think it would be closer.

[ewc]

sw-

What b.c. did you come up with for the Barnes 195 and 200 SST in the .40?

Thanks-

Judd

[deadeye]

Jan 15, 2009 8:07:09 GMT -5 sw said:

Jan 14, 2009 22:48:36 GMT -5 Harley said:

I asked SW for his opinion and he suggested .275 as a conservative guess. I plugged that number in my ballistics program and based my scope settings on the results. It was dead accurate way past 300 yards.

BTW, I asked Parker for the B.C., but they failed to reply.

Harley

I won't go into details, but the velocity loss method of obtaining a BC won't give a # that will work in the most commonly used formulas. This is because the G-1 drag coefficient is incorrect for what we shoot. I shoot out thru 300 or 350 yds, triangulate the centers of groups, plot them on a graph, use the least squares method of caculating the points and then back it into the equation and calculate a BC that works in the formula. The published BCs given(for our commonly used bullets) will not work in ballistic programs, especially past 200 yds. The sleeker the bullet is the more it will be off, as opposed to the natural reasoning that would make a person to think it would be closer.

curious,have you tried-g-2,g-5,g-6,g-7,g-8,g-I or g-L drag functions for closer traj results past 300yds ?l

[lc]

Judd according to their sites expander MZ .176 SST .265

[ewc]

Thanks lc-

[sw]

Jan 15, 2009 11:21:58 GMT -5 lc said:

Judd according to their sites expander MZ .176 SST .265

I actually use 0.265 as a BC in the stock formula/G-1 coef. The 40 cal(195g) Barnes expander has a much more closed nose than the pictures show or like the 45cal bullets have. I think it will be closer to .23-.24.

[sw]

Concerning BCs and their usage: they are velocity dependent. Example: Sierra gives 5 BCs for some of it's match bullets - a different BC for the bullet for specific bullet ranges such as 0.585 for 2700-3100'/sec, 0.605 for 2400-2700'/sec, etc. I do not know at what speed ranges the BCs were obtained for the different bullets we use; but do expect that the speeds are significantly less than what we normally shoot. This is a major source of error. Also, the shape of the projectiles differ enough from the "norm" , that the commonly used G-1 coef is fairly well off. The question Deadeye asked is an excellent question. I just haven't done that as I have the "luxury" to shoot as far as I want in agricultural fields and only have to drive less than 2 miles to do so. NOTHING equals shooting at the ranges and seeing the actual groups and having the ability to obtain the actual drops. Hunting recently cut soybean fields where the shots could be >600yds, and having seen the differences of trajectory between the 250,275,and 300g 45 cal bullets out of 50 cal Sav/SMI and then shooting 40 cal bullets out of 45 cal PacNors at 2700+'/sec pushed me deeply into the 40 and 45 cal camp. In normal wt MLers, the 40 and 45 have significant trajectory advantages, IMO. Out to 200 yds there is not major advantage but over 250 yds, the differences are dramatic. All this said though, a long range heavy rifle shooting 45 bullets sabotless(45 cal) or 45 bullets saboted(50 cal) is likely the ultimate long range smokeless MLer(that uses deer hunting legal calibers). Example: The Bad Bull. I suspect RB,Richard, Edge,DD, others could build a rifle in 45 or 50 that could even surpass the Bad Bull. It would not be a "sporter" .