Cast Bullet Database - A Work In Progress

[rsterne]

I have updated the Database at the bottom of the first post to Version 10.... This adds data on .30 cal pellets and slugs, and corrects some previous errors.... When actual BC testing is done, I put the Drag Model used in the "Est. BC" column.... If I am questioning the measured BC for some reason (eg. spiralling, which can add drag) I show it in red instead of blue....

Bob

[Greg_E]

I noticed that you didn't have any 9mm listed and was wondering about things like the Lee 356-125-2R which I've been casting at .357 (+0.0002 to +0.0004). I'm still just starting testing with these to see how well they might work. I also finally acquired a Lyman 356637 that will hopefully get here soon. This is the design that they used to make the 9mm Devastator hollow point and I may machine this mould to be able to make hollow points. I'm hoping that the 356637 doesn't have too much contact with the barrel and produce really slow speeds from friction.

I've also been powder coating and sizing, my Bulldog seems to squeeze them down to .357 so I'll probably go with that size for most of my testing. But I should probably do a little polish in my .357 die, it seems to undersize just a bit, need to look at it in more detail and run more rounds through. My .358 die seems to be right on size.

[rsterne]

9mm and .357 are pretty much interchangeable.... If the .357 is too tight in your 9mm barrel you can size it a bit....

Bob

[tjhepler]

I own three air rifles, a .177 cal; .30 cal Hatsan Blitz and a .50 cal Airforce Texan. I have been looking for pellet molds so I can cast my own pellets for the 30 & 50 calibers. I found molds for sale from a African manufacture that are very expensive and another from NOE who never has them in stock. I am hoping that on this site someone will be able to direct me to other dealers. Thank you in advance

[rsterne]

I suggest you post this question in the Cast Pellet and Boolit Gate....

https://www.gatewaytoairguns.org/GTA/index.php?board=229.0

NOE only make pellet molds up to .357 cal / 9mm.... Quite a few moldmakers do slugs in .30 and .50 cal, but if you are looking for Diabolo pellets, there is little choice....

Bob

[rsterne]

I have had a request to make up a chart on my new version of Bob's Boattails, with the specifications such as weight, length, SD and Twist.... I included a couple of Flat Base offspring as well.... Obviously only a small number of these are available, but it shows what could be made, if the desire is there.... I built it in Excel, but the Forum would not let me attach that, so I had to rearrange it and print it as a .pdf file.... It is attached below.... If you have any questions, please post them in this thread....

Bob

[Back_Roads]

 In general nice layout, makes it easy to see if any of my hairbrain ideas have a glimmer of hope, and also confirmation as why things I tried do work.
 Thanks for the cookies Bob

[rsterne]

I have updated the Database in the first post to Version 11.... I am still using G1 for the BC's because that is the most popular, however, for most airgun slugs, using the RA4 drag model.... along with the BC(RA4) of course.... will give more accurate trajectories....

Bob

[rsterne]

I have updated the Database in the first post to Version 12.... Ballistic Coefficients for many .257 and .224 cal slugs have been added.... I am still using the G1 drag model because is is the most commonly used, but in every slug I test now, the RA4 drag model is a better "fit".... The BC changes less over a wider range of velocities using RA4 instead of G1.... Fortunately, there is an easy to use converter you can find here.... https://www.jbmballistics.com/cgi-bin/jbmgf-5.1.cgi

Input the "BC" from my Database, selecting "G1" for the input.... Input the "Calibre" and "Bulet Weight", and the "Velocity", and then select "RA4" as the "New Drag Function".... When you hit "Calculate" you will see a table, and the left lower number is the one you want, the "New Ballistic Coefficient: 0.XXX RA4".... Use that in your Ballistics Calculator after selecting RA4 as the drag model....

Bob

[rsterne]

I realized that I was using the average velocity as measured at the site conditions in the "Avg. Vel." column.... The BC is corrected to ICAO standard atmospheric conditions, and the velocity should have been as well.... I have gone back over all my data and made this change to the Database.... and yes, it was a LOT of work.... The previously stated velocity for most of the data has decreased about 15-20 fps, and the column is now labelled "ICAO Vel.".... The BC stated now corresponds to that velocity, as it should, from Version 13 onwards.... This change should allow a more accurate conversion from G1 to other drag models, such as RA4....

Sorry for the ongoing small error, but you won't need to worry about it in future, as I have updated my spreadsheet to report the ICAO velocity, along with the BC....

Bob

[rsterne]

I have updated the Database in the first post to Version 14.... I have added data on 6mm /.243 slugs, and the heavier/longer slugs in .257 cal in a 10" Twist barrel....

Bob

[rsterne]

Version 15 is now in the first post for download.... I have added .25 cal NOE cast pellets, and a few other things....

Bob

[Scotchmo]

Looking at the airgun bullet database, my initial tests of projectiles from a NOE 154gr BT mold have the G1 Act. BC as a higher value than any other listed projectile. G1 BC = 0.350 at 1050fps in a 1:10 twist. Nothing else even close.

[ballisticboy]

It will be partly because G1 is totally the wrong reference drag law for that type of projectile at those speeds, giving an artificially high BC value. Use RA4 or even G7.

[Scotchmo]

It will be partly because G1 is totally the wrong reference drag law for that type of projectile at those speeds, giving an artificially high BC value. Use RA4 or even G7.

That’s a great point to emphasize. I actually use RA4 for these 2+ caliber long BT slugs. For the 3+ caliber long slugs, G7 might be even better. The three models (G1, G7, RA4) have three different scale factors, so we can’t compare the values directly. Bob gave a link to a drag model conversion calculator. Knowing that G1 was inappropriate for this slug, I still used the converter to get a G1 number for comparison, since G1 is what Bob’s chart uses. RA4 is definitely a better match in this instance, especially when shot at velocities over 1000fps. The RA4 value for this slug came out to 0.270.

When I started my magnum slug journey, I was using G1 and needed to use the multi BC function in Strelok in order to get a good trajectory match for my .257 as I got close to 1000fps. The multi BC function is a work around for a poor drag model match.

I think the G1 model is only appropriate for “bragging rights” when shooting these long slugs at near sonic velocities. For actual trajectory calculation, we should use a more appropriate drag model.

[rsterne]

Interesting point, Scott.... When I started my database, we weren't pushing velocities much over 900 fps, and it was pretty much the only drag model used.... As you and others have proven, the G1 is a poor match for airgun slugs when shot at over 1000 fps.... I don't have the time right now to convert all this data from G1 to RA4, but it would probably be a much better match....

Being able to have a BC (G1) of 0.350 definitely gives you (us) bragging rights, though!.... 

Bob