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rsterne
Acting on the advice of UK Ballistician Miles Morris, I have redesigned my Bob’s Boattails…. The new designs have less taper to the boattail, and a smaller step at the rebate…. These changes are to encourage reattachment of the flow behind the rebate, to increase stability and reduce drag…. It results in a larger base diameter, which should also allow them to utilize a slower twist rate…. The drawings are dimensioned for a .257 cal bullet, but alternate calibers are shown in blue, to show what the results would be if the bullet was scaled up or down…. I have made Al aware of these changes, and the plan is to use the new designs for any future tooling to produce BBT’s…. Here are the drawings….
https://hosting.photobucket.com/images/oo221/rsterne/New_257_cal_BBT_90_gr(2).jpg?width=1920&height=1080&fit=bounds[/img]
https://hosting.photobucket.com/images/oo221/rsterne/New_257_cal_BBT_78_gr(1).jpg?width=1920&height=1080&fit=bounds[/img]
https://hosting.photobucket.com/images/oo221/rsterne/New_257_cal_BBT_65_gr(1).jpg?width=1920&height=1080&fit=bounds[/img]
Twist rates are proportional to caliber, and the weights shown for other calibers are for the HP and FN versions…. It is intended to utilize the RG style moulds to allow Flat Nose, Cup Point, and Hollow Point bullets to be made from the same mould by changing pins…. The longer BBT’s have a red line showing the front of the HP version, shortened to produce a 50% Meplat, to give a larger HP…. The tooling would be made long enough to allow the smaller Meplat if the mould is made for solids only….
Production of any of these will depend on interest, and NOE’s production capability at the time….
Bob
rsterne-
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Mike B.
The design on the one existing Group Buy has been updated….
http://noebulletmolds.com/smf/index.php?topic=1628.0
Anyone interested in that .257 cal 78 gr. BBT should add their name there….
Bob
phwilbur1
Jonathan Flammer
I don’t think Al would be much interested in .177 cal slugs, for production reasons…. However, if you want to start a thread asking for it, you may drum up enough interest to have him look at it…. A lot of PCPs should be able to handle a 15-16 gr. slug in .177 cal…. and twist rates should not be a problem, a 15-16″ twist would be great!….
Bob
Anonymous
The .177 cal slug is a scaled down version of the 1.5 caliber long BBT shown above and will weigh 16 gr. as a FN and 15 gr. as a HP…. The .20 cal version uses the same tooling and is “interpolated out” to the larger diameter required, but will be the same length as the .177 cal…. It will be about 4 gr. heavier (19-20 gr.)….
Al has done the drawing required for the tooling, I saw it today….
Bob
You might wish to put in an a firm I want on the forum … for the specific mould design size, plus the number & type (HP or non HP) cavities on the forum website…
The group buy link tends to specify the minimum requirements…
https://noebulletmolds.com/site/about-us-2/group-buy-rules/
That will tend to help your endeavor on requests for a specific mould design … etc.
Your call on how you wish to proceed…
Take Care, & Stay Safe…
Mike B.,
I would like a 4-cavity aluminum mold with HP pins in both .177 and .20 caliber.
Is there someplace else I should post this info?
I would gladly pay for them in advance if that’s how it is done.
I just don’t want to miss out!
A little guidance for a newbie would be greatly appreciated..
Thanks!
Annie
Mike B.
phwilbur1
Jonathan Flammer
larrynufer
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