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Some .25 cal BC numbers for the Masses

October 31 2010 at 10:17 PM
  (Login Chadd76)
YF

I finally got a bit of time to get out and measure some Velocities today to calculate some BC numbers for my .25 marauder.

Velocities were measured point blank and @50 yds. I averaged the BC of 10 shots to come up with these numbers.

Here are the numbers I came up with.

Benjamin Domed .25 average weight was 27.7 grn and I came up with a BC of .0317

JSB Kings .25 average weight was 25.4 grn and I came up with a BC of .0388

H&N Baracuda .25 average weight was 30.4 grn and I came up with a BC of .0409

H&N FTT .25 average weight was 19.6 grn and I came up with a BC of .0178

H&N Silver Point .25 average weight was 23.8 grn and I came up with a BC of .0159

I have to say that I have been pretty disappointed with both the consistency and accuracy of all the .25 H&N pellets I have. The weights are all over the place and none of them shoot very well out of my marauder. The baracuda's group at about 2" @50 yds mostly because of flyers, the FTT's and Silver Points don't even give what I would consider a group @50 yds more like a shotgun pattern.

Both the JSB's and Benjamins shoot well @ 50 yds and the odd thing about it is that I had some older H&N Baracudas with the orange label that shot as well as the JSB's and Benjamins but the newer blue label pellets suck.

The replacement barrel that I received from crosman seems to be shooting pretty well. I managed to hit a pepsi can Lasered @ 102 yds in a 10 mph cross wind 2 out of 5 times shooting benjamin domes, the three misses were in the ball park too. It is unbelievable how much hold over is required at 102yds and how much hold off is required for a 10mph cross wind at that distance.

Overall I am pretty happy with the Marauder .25. Accuracy wise it doesn't match any of my BSA's but what it lacks in accuracy it more than makes up for with retained energy. Even with the Benjamin domes it still retains ~30 Ftlbs of energy @50yds and ~20 @ 100 yards. My .22 superten only puts out 30 Ftlbs @ the muzzle.

I hope these numbers are useful to some of you guys.

Edit: I should have mentioned the numbers I came up with were at 470ft elevation and 70°f.




Thanks,

Chadd from Carlyle.

A Superten junkie


    
This message has been edited by Chadd76 on Nov 1, 2010 12:18 AM
This message has been edited by Chadd76 on Oct 31, 2010 10:21 PM


 
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(Login AirSmithCA)
YFOT

thanks for taking time to share Chadd

October 31 2010, 10:48 PM 

I've been working on improving the accuracy on a .25 BSA Lonestar . Interestingly enough I've found similar results with the pellets you mentioned as well.

Out of curiousity, what is the process for calculating BC? Sorry, of that sounds like a newbie question but I've never come across the info.


















"It doesn't get done til someone does it"

 
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(Login Chadd76)
YF

Re: thanks for taking time to share Chadd

October 31 2010, 11:02 PM 

Well I am sure if you look enough you can find the correct formulas either here on the yellow or somewhere on the net to calculate the BC. But I am lazy and just use the tool built into Chairgun.

There are two different ways you can do it. The first being measure pellet drop at two different distances for example you would shoot a target @10 yds then shoot the same target @50 yds while aiming at the same POI and measure the drop between 10 and 50 yds then plug the numbers in.

The other way is the way I did it. You need two chronographs that are pretty damn close to agreeing with each other on numbers. You place them at known distances in my case I had one at point blank and the other at 50 yds. You then will have two velocities for each shot, one from the near chrony and one from the far chrony. I took these two numbers for each shot plugged them into the Chairgun tool then averaged the BC numbers to come up with my final BC for each pellet.

Thanks,

Chadd from Carlyle.

A Superten junkie

 
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Yrrah
(Login Yrrah)
YFOT

Go to the top of the Forum page to the Forum Rules dropdown.

October 31 2010, 11:19 PM 

Scroll down to "Various Airgun Calculators" and you will find an excellent calculator for Ballistic Coefficient over on the right hand side courtesy of Steve NC. ........... Kind regards, Harry

 
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(Login AirSmithCA)
YFOT

Thanks Harry .. nt

October 31 2010, 11:36 PM 


 
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(Login Chadd76)
YF

I always forget about those. nt

October 31 2010, 11:37 PM 



Thanks,

Chadd from Carlyle.

A Superten junkie

 
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(Login smitty814)
YF

.25 cal BC numbers

October 31 2010, 11:04 PM 

Thanks for the great info. This is the first BC I've seen for the Benjamin Domed.

 
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Yrrah
(Login Yrrah)
YFOT

Chadd, You may like to read my research on BC with Kings

October 31 2010, 11:34 PM 

and the changes which occur as the pellet travels down range. The data was collected out to 200 yards.

http://www.network54.com/Forum/79537/thread/1265721221/Experiment-+BC+changes%2C++with+range+and-+or+time+of+flight+and-+or+velocity-+Long-

Note the altitude (which affects BC through reduced air friction) and the corrections to standard figures. The correction can be applied through Steve NC's calculator which is referenced above for Lonnie ..........

Best pellets for accuracy in my BSA .25 Hornet Special are JSB Kings. Old red tin Kodiaks or the original Barracudas and Benjamins are a close second out to 50 or 75 yards. Beyond that the Kings reign supreme.

http://www.network54.com/Forum/79537/thread/1255905232/%26quot%3BKings%26quot%3B++%28Edit%29+JSB+-25+cal+shoot+100+yd+sub+MOA+---++Quality+pellet-

Kind regards, Harry.

 
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(Login Chadd76)
YF

Re: Chadd, You may like to read my research on BC with Kings

October 31 2010, 11:41 PM 

I have read through that a few times now. It is pretty interesting how things change when you get way out there. I should have mentioned the numbers I came up with were at 470ft elevation and 70°f.

I was surprised how close our numbers were, I guess that goes to show you math doesn't lie :O)



Thanks,

Chadd from Carlyle.

A Superten junkie

 
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(Login Obturate)
YF

It amazes

November 1 2010, 7:38 AM 

me how much better the BC is for JSB pellets. Now I wish they would make a 30 grain .25 cal and a 20.5 grain .22 cal.
Dan

 
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(Login Chadd76)
YF

I thought the same thing. nt

November 1 2010, 9:25 AM 



Thanks,

Chadd from Carlyle.

A Superten junkie

 
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