Secant or tangent Ogive

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11 years 4 days ago - 11 years 3 days ago #30729 by Libertarian623
Secant or tangent Ogive was created by Libertarian623
I have been trying to find out why certain bullets do well out of my gun ( RRA LAR-8 ) and others do not rather than blindly buying bullets and testing at the range. I believe I found the paradox of semi-autos and bullets. The paradox has to do with the shape of the front of the bullet (Olgive) and COAL and magazine coal capacity. So semi-autos( AR or variant) have short magazines( they don't allow long bullets). Recent advances in bullet design have yielded bullets like the VLD Bergers and SMK, these have a secant Olgive ( means they need a long bullet to engage the lands and grooves of the barrel) But here's the paradox we cannot fully take benefit from a increased COAL because of our magazine dimensions, means that the bullet in a semi-autos will not be engaging the lands and grooves properly. By Contrast due to the tangent Olgive of a Nosler spritzer type bullet that can engage the lands and grooves more earlier at a shorter (COAL) that our magazines support because of its tangent olgive. IMHO this means that in general bullets with a secant Olgive will not fly as designed from my semi-autos until I get longer magazines or a redesign of the chamber(headspace). I think a very subtle change is all that's required, and as always I may be way over my head on the science here and be making bad assumptions. Anybody that cares to wade in is welcome.
Last edit: 11 years 3 days ago by Libertarian623. Reason: So it will add to the LAR-8 data here

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11 years 4 days ago #30731 by jtallen83
Replied by jtallen83 on topic Secant or tangent Ogive
That is a good summary of my understanding of the issue. The price we pay for having a 20 round mag is not being able to fully utilize the highest BC bullets available. The twist comes into play here as well. I think you can rule some bullets out from the start using this but nothing beats the actual testing in YOUR rifle.
I get lousy results with factory match ammo using the 175 gr. SMK but I got some nice tight groups with the same bullet in some lower power loads with the same COL I loaded myself. So many variables, so little time and money........... :usa:

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11 years 4 days ago #30763 by Libertarian623
Replied by Libertarian623 on topic Secant or tangent Ogive
Thanks for wading in JT. I was reading some stuff that is really making my head hurt. Also got me thinking about getting a 338 lapua, to play with. I seem to be gravitating towards making longer and longer shots. Also while I am posting ( have been working like crazy, not by choice SAR) I did intend on taking that 1-1.2K shot in the next couple of days it was just put off due to work getting in the way of fun.

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11 years 4 days ago #30765 by jtallen83
Replied by jtallen83 on topic Secant or tangent Ogive
Give this a look, got it on my dream list :pray: ;
www.armalite.com/ItemForm.aspx?item=50A1...4c-ae1f-d045b91324c3

Supersonic up to 2,500 yards! I'm sure the ammo would drain the pocket fast but 338 Lapua is is not exactly cheap either.

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11 years 4 days ago #30769 by Libertarian623
Replied by Libertarian623 on topic Secant or tangent Ogive
Thanks JT I had not seen that model. I had been hearing about the 416 but figured to wait awhile until someone else other than factory shooters wrote a review before passing judgement. BTW Ronnie should be classified a national treasure.

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11 years 4 days ago #30771 by MrMarty51
Replied by MrMarty51 on topic Secant or tangent Ogive

jtallen83 wrote: Give this a look, got it on my dream list :pray: ;
www.armalite.com/ItemForm.aspx?item=50A1...4c-ae1f-d045b91324c3

Supersonic up to 2,500 yards! I'm sure the ammo would drain the pocket fast but 338 Lapua is is not exactly cheap either.


That thing is incredible.
I wonder if they`ll ever bring it on in a semi auto, or at least a clip feed bolt action.

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11 years 4 days ago #30772 by jtallen83
Replied by jtallen83 on topic Secant or tangent Ogive
Barrett does, the semi-auto;
www.barrett.net/firearms/model82a1

I didn't see any clip fed bolt gun yet but that can't be far off if the cartridge gains popularity. Here are some interesting comparisons with the .50BMG round;
www.barrett.net/ammunition/416barrett

Ammo is about $6.50 a shot though, better make it count!

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11 years 4 days ago #30773 by 13fcolt
Replied by 13fcolt on topic Secant or tangent Ogive
That's the whole reason I want to try the Berger hybrid. It's benn making waves and sells out pretty quick.
bulletin.accurateshooter.com/2013/01/ber...at-you-need-to-know/

One of those simple "why didn't I think of that" solutions. I have yet to read a bad review.
The following user(s) said Thank You: jtallen83, Libertarian623

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11 years 4 days ago #30776 by jtallen83
Replied by jtallen83 on topic Secant or tangent Ogive
So all that work on the 175 SMK's could be out the window! I'm going to keep my eyes out for these "hybrids". I usually scan right past the Berger's due to price but they sound like the ticket for our AR-10's and the restrictive COL on them.
Great explanation on the chart and the video, Thanks, Colt!

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11 years 4 days ago #30789 by Libertarian623
Replied by Libertarian623 on topic Secant or tangent Ogive
:nicethread:
Colt thanks talk about good timing. This looks like the solution. This is what makes this site so good.

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