7 Degree Leade?

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TexasMac
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Re: 7 Degree Leade?

Post by TexasMac » Fri Apr 16, 2021 4:24 pm

bruce m wrote:
Fri Apr 16, 2021 4:08 pm
alfajim wrote:
Fri Apr 16, 2021 12:22 am
Bruce
The chamber print in Spence's trapdoor book shows a 45' by .075" transition. It;s from the armory print.
Jim O
the more i think about this, the more i think 45 degrees is incorrect in spence's book.
the numbers as presented do not add up.
bruce.
Either the 45 degree angle is incorrect or the 0.075" transition step length is too long. The 45 degree step in my Sharps is only 0.013" long.
Wayne
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J.B.
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Re: 7 Degree Leade?

Post by J.B. » Fri Apr 16, 2021 4:27 pm

Wow :shock: :!: ...This is reading like an advanced science class now :lol: .. Too much choice... too many decisions. It seems that, within reason at least, regardless of the chamber, transition and lead one has in their rifle...if they load to those parameters, the chances are one will have a respectable result. I've had a 45/110 Shiloh with their standard chamber...which is typically nice and tight anyway ..and shot bore diameter paper patch bullets without issue. Initially I had a few paper rings but once I had longer brass and had done a little more homework those went away and yes, accuracy was fine. When I ordered my 44 x 2 1/4" I was seriously considering opting for the traditional paper patch only chamber but I just couldnt make myself commit to it. Around that time I believe, Shiloh had ordered a tight spec reamer with the 7 degree transition and after some discussion.. decided to go with that option. As previously stated, it has performed flawlessly with both paper patch and grease groove and as a result is my 'go to' rifle. This was all before I started with the dual diameter paper patch route which I'm trying now. This has the added benefit of not needing to overwork the brass to get
a snug slip fit. I had been running dual diameter grease groove beforehand ..also with good results. While I acknowledge Jims reference to the taper coming from the outside of the case possibly being an issue, I've not seen it manifest itself as a problem in either of the two rifles I have so chambered. I'm also quite sure if I went with the standard Shiloh chamber with the more abrupt chamber end/ transition, when loaded to suit, I'd have no problems either. So you have the original spec Sharps chamber for pp only, the 7 degree transition ..still in a tight chamber and the 'standard' possibly 45 degree chamber stop...to a 2-3 degree leade. Seems like a win, win or win scenario. They all work...its just that one of the three means bore diameter pp only.
rgds
J.B.
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bruce m
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Re: 7 Degree Leade?

Post by bruce m » Fri Apr 16, 2021 4:32 pm

good post j.b.
bruce.
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bruce m
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Re: 7 Degree Leade?

Post by bruce m » Fri Apr 16, 2021 4:34 pm

wayne,
just goes to show, don't believe everything you read until you ask the questions.
roughly how long would the step be with a 12 degree transition?
bruce.
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semtav
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Re: 7 Degree Leade?

Post by semtav » Fri Apr 16, 2021 5:34 pm

Google is your friend !! everything is just plug and play now. 45* was the easiest before.

TexasMac
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Re: 7 Degree Leade?

Post by TexasMac » Fri Apr 16, 2021 6:00 pm

bruce m wrote:
Fri Apr 16, 2021 4:34 pm
wayne,
just goes to show, don't believe everything you read until you ask the questions.
roughly how long would the step be with a 12 degree transition?
bruce.
Bruce,

Here’s the trig formula & calculation for a 12 degree transition step. For a different angle go to an online tangent calculator such as https://www.rapidtables.com/calc/math/T ... lator.html and plug in the angle. BTW, for a 45 degree angle the tangent is equal to 1.0. Therefore the step would be 0.0125" wide

Wayne

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mdeland
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Re: 7 Degree Leade?

Post by mdeland » Fri Apr 16, 2021 6:04 pm

Give me a day or two guys and I'll turn a 12 degree angle on a piece of steel in my lathe from end of neck (45-70 reamer diameter) to bore diameter and post a picture of it.

TexasMac
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Re: 7 Degree Leade?

Post by TexasMac » Fri Apr 16, 2021 6:35 pm

BTW, it's spelled tangent not tanget. I'm reasonably good at math. or trig. but a poor speller. :lol:
So following is a corrected illustration.

Wayne

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Re: 7 Degree Leade?

Post by TexasMac » Fri Apr 16, 2021 7:23 pm

So, referring to the previously listed trapdoor transition step length of 0.075", would mean the step angle is approximately 9.5 degrees, give or take .5 degrees or so depending on the difference between the chamber and groove diameters.

Wayne
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alfajim
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Re: 7 Degree Leade?

Post by alfajim » Fri Apr 16, 2021 7:33 pm

Here are all the dimensions of the trapdoor chamber. From print.

Dia. at opening .508"-.512"

Dia. at transition .482"-.486"

Chamber length to transition 2.035 from front of rim ledge.

Transition 45' by .075" chamber total 2.100"

Cartridge case length 2.100 to front of crimp.

Jim O

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Re: 7 Degree Leade?

Post by Kenny Wasserburger » Fri Apr 16, 2021 7:51 pm

So, I guess with all this theory about the superiority of the 7°leade, I only have a few questions.



How Many National Championships has this super chamber won? :roll:


A standard Shiloh Chamber can win National Scope titles, with a grease groove bullet, the same chamber can win Scope Titles with a PP bullet in Creedmoor and Midrange. It can win Winter National scope titles, same gun did that in 2013 at Phoenix and at Raton.

A standard Chamber can set a PP world Record group and won a 5@200 trophy in 2008. The same chamber in 2006 won a 5@200 with a grease Groove bullet. Can a 7°leade do that?


Kenny Wasserburger
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alfajim
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Re: 7 Degree Leade?

Post by alfajim » Fri Apr 16, 2021 7:57 pm

alfajim wrote:
Fri Apr 16, 2021 7:33 pm
Here are all the dimensions of the trapdoor chamber. From print.

Dia. at opening .508"-.512"

Dia. at transition .482"-.486"

Chamber length to transition 2.035 from front of rim ledge.

Transition 45' by .075" chamber total 2.100"

Cartridge case length 2.100 to front of crimp.

Jim O
Forgot to add the bore dia.'s bore .450"-.452" groove dia. .460"-.465"

bruce m
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Re: 7 Degree Leade?

Post by bruce m » Fri Apr 16, 2021 10:43 pm

TexasMac wrote:
Fri Apr 16, 2021 7:23 pm
So, referring to the previously listed trapdoor transition step length of 0.075", would mean the step angle is approximately 9.5 degrees, give or take .5 degrees or so depending on the difference between the chamber and groove diameters.

Wayne
the plot thickens.
maybe 12ish degrees is max spec and a bit lower is acceptable.
or trapdoor chambers were more generous, giving an opposite of greater than 0.0125".
bruce.
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Re: 7 Degree Leade?

Post by TexasMac » Sun Apr 18, 2021 12:42 pm

Let’s go back a bit to the trapdoor discussion. After doing some research the transition step angle is 12 degrees 45 minutes (12.75 degrees), not 45 degrees or 12 degrees, and the 0.075” transition step length is correct if the measurement is made using the chamber diameter and the bore diameter. Although it’s well known that the groove diameters of trapdoors can vary a significant amount and the bore diameter to a smaller amount, my earlier illustration used 12 degrees to determine the transition step length to an average groove diameter, not the bore diameter. So, the following revised chart is based on a step angle of 12.75 degrees, chamber diameter of 0.484” and bore diameter of 0.450”.

Wayne

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Re: 7 Degree Leade?

Post by TexasMac » Sun Apr 18, 2021 12:48 pm

BTW, my earlier comment that the transition step angle in Browning BPCRs is 12.5 degrees is a typo. It's actually 12.75 degrees, the same as in the Springfield trapdoors.

Wayne
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