.25 Cal Ammo Shootout, Part I: Ballistics through Polygon Barrel ,BC's, etc...

[SMH77]

Just as a PSA, I figured I’d share with you the results of my measurement today of 6 pellets in .25 caliber, as shot through my RAW HM1000x, polygon barrel: the JSB lites (25.39 grain), the JSB Heavy, Mk I (33.95 grn), the JSB Heavy, Mk II (33.95 grn), the H&N Baracudas (31.02 grn), the H&N Baracudas Hunter Extremes (28.40 grn), and the Predator Polymags (26 grn) pellets. Pellets were not measured and were taken straight out of the tin without sorting for weight. No sorting for head sizes was complete either.

Muzzle velocity, near was taken with the rear window of the chrony at 1 yard from the tip of the moderator
Distance to far measurement, was taken with the rear window of the chrony at 50 yard from the tip of the moderator
Delta (distance) between locations: 49 yards (measured with a Nikon laser rangefinder with angle compensation)

Setup​ @ 1 yard:

 

Setup at the target (@ 50 yards, a 49 yard delta):

I opened up Chairgun (Mac version) and adjusted the environmental conditions, altitude, etc. I then went to the BC calculator app, plugged in the data, and calculated the following results (below). The average temp today was 48.3F, with virtually no winds (1 mph out of the N), 40% Humidity, pressure at 30.44 in Hg.

My gun: RAW HM1000x, setup in .25 caliber, with a LW polygon barrel. Notes: the same chrony was used at both distances. Velocity data is shown below. I shot a full magazine at near and far, with each pellet (so 12 shots for each x 12 setups = 144+ shots).

A few comments: don't read too much into the standard deviations of the less accurate pellets (JSB Lites, H&N BHE, and PP) at 50 yards. I had several 'err1' or 'err2' messages as the pellets drifted slightly left or right, not centering over the optical windows. I feel this affected the reading slightly on certain pellets-thus I had to reshoot several of the JSB lites, and PP to get a full 12 shots of data. To be as accurate with the numbers as possible, I threw out the high and low (for calculating the averages) for both the 1 yard and 50 yard data. The standard deviation and spreads shown in the chart below represent all 12 data points for each pellet, at each distance-not the middle 10.

I hope this is helpful information for anyone looking for data from this gun / setup? If so, and you appreciate the time / effort, please take a minute and leave me a ‘+’ (it’s just a small way that makes me feel like I’m helping contribute useful content to the forums).

First up: JSB lites (25.39 grn):

12 shot group:

Next up: JSB Heavy, Mk I (33.95 grn):

12 shot group:

Next up: JSB Heavy, Mk II (33.95 grn):

12 shot group: (note the shots at the bottom are from the JSB Lites)

Next up: H&N Baracuda (31.02 grn):

12 shot group:

Next up: H&N Baracuda Hunter Extremes (28.40 grn):

12 shot group:

Last up: Predator Polymags (26 grn):

12 shot group:

And the RAW data, summarized in chart form (pun intended, LOL):

Overall comparison of the groups:

I will measure and post the 12 shot group sizes in a little bit. I have household things to tend to at the moment...

Sean 

 

[SMH77]

Updated chart with 12 shot group sizes added in inches and MOA.

Clear Winner: JSB Heavy, Mk I pellet. Close Runner Up (in my gun): JSB Heavy, Mk II pellet.

 

[Alejandroo]

"SMH77"Updated chart with 12 shot group sizes added in inches and MOA.

Clear Winner: JSB Heavy, Mk I pellet. Close Runner Up (in my gun): JSB Heavy, Mk II pellet.

WOOWWW !! are kidding ?? that's a lot of time and work put into this thread, of course you deserve more than a +1. Thanks for all the data, It should be great if this was some kind of sticky so everyone else can contribute to the .25 pellet performance database something similar that HAM has with the .22 caliber.
Thanks a lot SMH77.

What software did you use to calculate group size ??

Alejandro

 

[zx10wall]

Thank you Sean. Excellent!

 

[Saltlake58]

THANK YOU! that was a lot of work. I wanted to do some calculations on the JSB Mark 1's and 2's. This really helps me move forward.

Thanks again.

 

[Groundhog]

Thanks for the hard work and info . I found the MK1's at avg 824 fps has a bc of .0393 , did the calculation @ 107 yards . Velocity matters .

 

[SMH77]

"Groundhog"Thanks for the hard work and info . I found the MK1's at avg 824 fps has a bc of .0393 , did the calculation @ 77 yards . Velocity matters .

I think you're about to open up a bit of discussion: what gun / barrel did you test that on? Smooth twist / FX barrels seem to report lower BC's than LW or LW Polygon barrels do (hence why my numbers are higher than those in Ham's DB-he tested using a ST barrel on the Impact). The velocity alone probably isn't making that large of a difference (0.0556 vs. 0.0393 is a HUGE difference in BC).

Also, what was your close distance when you measured the BC?


Sean

 

[Groundhog]

Yes a smooth twist in Wildcat mk1 , and yes I'm sure twist rates and velocity will both affect bc . I used the poi calc in Chairgun , zero at 51 and then shot at 107 same poa input the drop in inches . This bc number is also spot on for me in shrelock pro from 35 out to 173 yards .

 

[SMH77]

I think there are too many differences in testing parameter to draw a straight comparison and conclude BC is affected by velocity (though I do agree it has an impact on BC). Also, comparing the BC's I came up with against the ones you're reporting (using totally different methods, different barrels, etc) is really apples to oranges and is going to make a direct comparison very difficult.

BC should honestly be tested out of each pellet / barrel combination with a specific method that is held constant. This is actually why I set out to test and report what I did for both .25 and .30 caliber pellets (the ones I had at my disposal): because the HAM's database didn't cover the pellets I was interested in between those two calibers, and becuase they were tested on a setup (and distances) that I knew would alter the BC's from what I shoot. Actually, when I first joined the forum, I was specifically looking for BC's from the gun (or barrel) /ammo combination I was going to be shooting a lot-and didn't get good answers, so I set out to document them, and share my finding (and document my method) for others to benefit from.

I hope I'm not coming across as negative or dismissing your BC's in a rude way-I don't intend to do that. I just don't think a comparison can be made directly between them because there are at least 5-6 different factors that I can think of that will affect the results directly, and only one of them is velocity.


Sean

 

[Groundhog]

Thanks for putting in the work , really . Wasn't trying to open a can of worms . Realy just posted to illustrate that as you said bc will vary by combo , methods used , etc . Encouragement for others to test and find out what their bc is rather than just useing the numbers they find on net .
And you have inspired me to delve deeper into this and find out for myself how much velocity aeffects the bc by experimenting , and try both methods of measurement . Thanks .

 

[Alejandroo]

Totally agree with your opinion, that's why I suggested that this thread would be like a .25 BC database where we all can post our findings with a decent methodology to measure results and that could be replicated by others.

As soon as I can shoot gain I'll prepare my test and post the findings, I have a condor SS and soon matador R5M in .25 to test.

Alejandro

 

[SMH77]

"Groundhog"Thanks for putting in the work , really . Wasn't trying to open a can of worms . Realy just posted to illustrate that as you said bc will vary by combo , methods used , etc . Encouragement for others to test and find out what their bc is rather than just useing the numbers they find on net .
And you have inspired me to delve deeper into this and find out for myself how much velocity aeffects the bc by experimenting , and try both methods of measurement . Thanks .

Totally agree with you, and thanks-I do appreciate the appreciation. Like you are pointing out, it really is important to test your own combination to understand exactly how it shoots, etc and to test your BC's over the most likely range to plan to shoot at.

I too plan to play with velocity by adjusting the hammer spring, but I think I'm going to leave the tension alone for right now, until I finish 'mapping' the changes in velocity over temperature as the weather changes (with a static setting). All sorts of good info to learn for this testing over time. I can't wait to plot BC vs. Temp for the same pellets, same setups as I gather the data. As noted, it will really only be good for my setup (and others shooting the same setup probably), but the general trends in velocity, BC, etc should generally apply for others.

Oh yeah, I'm at 890 feet above sea level too...


Sean

 

[SMH77]

"Alejandroo"Totally agree with your opinion, that's why I suggested that this thread would be like a .25 BC database where we all can post our findings with a decent methodology to measure results and that could be replicated by others.
As soon as I can shoot gain I'll prepare my test and post the findings, I have a condor SS and soon matador R5M in .25 to test.
Alejandro

That would be great! I'd love to see your results, following the same method and be sure to record the important parameters (elevation, temp, humidity, pressure). Try to find out who makes the barrel on that gun too (unless you already know, of course). I think the pellet-barrel-velocity combination will drive the BC (of course the other parameters will influence it also-hence the reason to record them), regardless of what action the barrel is mounted in.

I would like to see the same process followed with some of the FX barrels too.

I may repeat the same test with my LW (non-polygon) barrel setup, with the same pellets, next weekend if I get similar weather. I would be curious to see the direct comparison of group sizes as well as impact of barrel (only) on BC.


Sean

 

[Groundhog]

"I would like to see the same process followed with some of the FX barrels too. "

I might be up for that , plan to start the long process of learning everything I can about my crown in .25 as soon as I get this wildcat nailed down . Ill have see how close I can get to duplicating your process before committing . Buying a new chrograph next week to replace my 20 year old crony that has some issues .

 

[SMH77]

"Groundhog""I would like to see the same process followed with some of the FX barrels too. "
I might be up for that , plan to start the long process of learning everything I can about my crown in .25 as soon as I get this wildcat nailed down . Ill have see how close I can get to duplicating your process before committing . Buying a new chrograph next week to replace my 20 year old crony that has some issues .

That would be great. If I can help to be clear on the procedure, let me know. Perhaps I'll put together a diagram showing the details of the placement of the chronies, etc.

 

[Centercut]

That would be great. Since you started the project, I think if you set the standard for testing we could all follow it. I want to do the same for my .30 FX Bobcat MK2 (ST barrel) using JSB Lite and Heavy, and the new H&N. Might not be for a month or so, in process of moving (within San Diego) and have a lot of "honey do" projects at the new place to get done before I get to play again regularly... 
;(

 

[Groundhog]

 I reread your post and shouldn't have any issues doing this , will be a couple weeks though . I'm out of Baracudas and need to get another chrony . I will reshoot the standard smooth twist as well , I would like to see the differences I get between the two methods . I'm looking forward to this project . Guess I should stick with the 12 shot groups as well . Might throw a gen 1 Mrod and Condor in the mix while I'm at it , no shortage of .25's here lol .

 

[SMH77]

Sounds good guys. I can easily put together a small writeup on procedure, things I look for when setting up the chrony at the two locations, a diagram and photos. I think this is making the case of a forum-database / spreadsheet that could be saved as a sticky (like was suggested by Alejandroo). If we're going to open up the reporting to all types of guns/barrels, I could put together a form to fill in the critical information that is required, for anyone to download, fill out, and submit (or something like that). A spreadsheet where you could filter by gun / barrel and look at how the BC changes with altitude and temp would be very helpful for everyone, I'm sure...

I have no problem maintaining the database / updating the master file for everyone's use too, if needed.


Sean

 

[Alejandroo]

"SMH77"Sounds good guys. I can easily put together a small writeup on procedure, things I look for when setting up the chrony at the two locations, a diagram and photos. I think this is making the case of a forum-database / spreadsheet that could be saved as a sticky (like was suggested by Alejandroo). If we're going to open up the reporting to all types of guns/barrels, I could put together a form to fill in the critical information that is required, for anyone to download, fill out, and submit (or something like that). A spreadsheet where you could filter by gun / barrel and look at how the BC changes with altitude and temp would be very helpful for everyone, I'm sure...
I have no problem maintaining the database / updating the master file for everyone's use too, if needed.
Sean

Wow Sean great idea, maybe upload the spreadsheet in google drive or something so everyone can cooperate with it and of course you can have my full support and help that I can give since I just had surgery so I have a lot of time in front the PC reading airgun stuff of course and some other things but the only disadvantage right now is that I only have one hand to type (left shoulder surgery) so just have patience !!

Just let me know what to do or where to start and I'll do my best, BTW what's the software you used to calculate the group sizes in your post ?? bye bye and best regards to all.

Alejandro

 

[jking]

Nice work Sean, as soon as I get a good opportunity without distractions I'll check the BC on my Crown.
Jimmy