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17tbs 01-11-2016 08:03 PM

Super heavy .172" bore rider.
Has anyone tinkered with the idea of a super heavy .172"?

I copied one from a military ball ammunition example, in 4.6mm (.1815" ) using the Hornady 40gr fmj by turning it down to 4.3mm, or .172 with the front half of the bearing surface at .170".

It looks weird and I don't know if it will stabilize in a 1 in 9 at an estimated 2450fps from the original parent case converted to a .172"x30mm.

I just did it for grins. My 1 in 12 16".25" TC barrel in 223 is supposed to be incapable of stabilization of 69gr hpbt Sierras but it does it anyhow and ignored the calculation putting it at about .83 stab fact.

rickiesrevenge 01-11-2016 08:04 PM

How long is it?


17tbs 01-11-2016 08:12 PM

Compared to the 30 grain Kindler gold its still a fair bit bigger in length. 17.9mm

Holy smoke, I just ran the jbm calculator for stability and it came out 1.087.... wheels are spinning... H-4198.... I ran 30grain Kindlers up to 2980fps on a very compressed load out of my longer barrel... and without any severe pressure indications.

EDIT: This bullet weighes in at 36.4gr, still giving a 1.036 stability factor according to the JBM stability calculator.

Chickenthief 01-12-2016 09:26 AM

I'm by far an expert but is'nt the bore .168"?

The Berger 37gr (BC .331) was ,855" long and needs a 1:6.5 barrel to stabilise

trotterlg 01-12-2016 03:30 PM

There must be some way to design an aero stabilized bullet. I am sure there must be some shape that will fly straight without spin. Larry

reed1911 01-12-2016 04:49 PM

Depends on what you call straight.

trotterlg 01-12-2016 06:46 PM

What I was referring to is a design that will keep the bullet flying one end forward without spin, an aerodynamically stable bullet. Then impart some spin to keep it straight, any spin rate would do. Larry

Mr Jacket 01-12-2016 09:31 PM

I make a 37gr .172 bullet for my 1:71/4 twist 17-222.shoots very well.

rickiesrevenge 01-12-2016 11:19 PM

Whats the BC on your 37gr? Could you post a picture of it?


17tbs 01-13-2016 02:41 AM


Yes, the lands are typically 0.168" I don't know what mine is, I do know that my chamber throat was rather odd shaped with an incline from a .1730" to 0.1724" for the first 0.03" then a 1.5 leade angle from there onward. The effect is that I can seat the GSC banded 17 and 19 grain solids that mic at 0.1730 on the tops of the bands with groves cut at 0.1695" is right into the case and right into this tapered throat and therefore it's practically ensured of a straight start. At 0.170" the front half of my heavily modified 4.6 now floats way up into the area about half way between the 0.1724" end of the throat and where the tops of the lands are encountered, it pretty much kisses this whole transition area for about 0.05" .

It sort of just eases in on the lands since there is only 0.001" difference in each side, maybe even less since the calipers are not precise enough for a 0.00001" measurement.

Larry, yes there is a way to get it to fly straight, put some feletching on it.

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