TMI, L
L!
With all the discussion about the relative over bore cartridges
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L!
Nah, if I'd said it resembled that coyote...that would be TMI.TMI, L
Rich Coyle
Well-Known Member
Lonie at Hornady proved longer necks produce longer throat life. Maybe the shoulder angle has something to do with it also.
J E Custom
Well-Known Member
Anything that will keep the powder in the case longer allowing more powder to be burnt inside the case will improve throat life.
There are many ways to accomplish this. Faster burn rate powder, A shorter more efficient case design that holds the same amount and type of powder, A steeper shoulder angle that holds the powder in the case longer changing the flame front allowing more to be burnt in the case, (This is why the 40o shoulder works so well). We hear the term, More efficient cartridge all the time, But in truth, A short fat case design that holds 70 grains of powder has a shorter powder column (More burn surface)than a standard magnum case that holds the same amount of powder, pushing more un burnt powder out of the case. The velocities will be almost identical, but the erosion will be greater with the longer case design. Powder shape is also a contributor to throat erosion. (Ball or spherical compared to tubular shaped powder. Even the length of the tubular powder granular size can have an impact on erosion.
The principals are still the same though and the longer you can keep the powder in the cartridge case by any means, the slower the throat will erode. The reason velocity is normally though of as the culprit is because it takes lots of powder and pressure in the large cartridges and they are the ones with the reputation for poor throat life. But when you look at the combination of all the factors mentioned, The throat burners have most if not all of these conditions present in them.
So throat life depends on many different conditions to manifest it self.
J E CUSTOM
Capt RB
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I've always wondered how much help the Roy shoulder helps in a like sized case with a conventional. It would seem in theory that the longer surface turning the expanding gasses away from the throat would help more than the conventional angle. I do feel that it helps in feeding and wish it was incorporated into the ex wife looking cases ie short fat no neck
I would think it is true. Plus, most Weatherby cases have very long necks too.
Rich Coyle
Well-Known Member
I used Weatherby shoulders on a couple of my wildcats 'cause I like the look. Soon, I hope, one will be in my hands that matches a .264 Win Mag with a neck about .300". Don't know how long they would last if I used a different shape. The 'smith told me I would get it in December. We are running out of December.
This is one of those times when precision is more important than speed.
This is one of those times when precision is more important than speed.
J E Custom
Well-Known Member
He attempted to redirect the pressure wave by using the double radius to do this, But in truth, by the time the flame front reaches the shoulder, the problem already exist. His shoulder design did help contain the powder longer and allow for more powder along with other chamber design innovations. More shoulder angle and the elimination of the double radius seams to negate any advantages of his design, and with his free bore philosophy the 40o shoulder and his free bore recommendations appear to be more efficient and able to produce even more velocity with the same pressures.
Like many, I experimented with the primer tube to move primary ignition to the front of the case for a "Reverse Burn" to see if there was any accuracy advantage. But I did not shoot this system enough to see if there was any throat erosion benefits.
The short fat cartridge design with 30 to 40o shoulder angles seem to be the best compromise for efficiency and consistency. Throat erosion rate is yet to be determined in my opinion. The 7mm STW is one of my favorite cartridges but so far it has consumed the barrel the fastest of any of my rifles. (250 rounds down the barrel) But I must admit I pushed it to the limit of its velocity. I also shot a 7mm Remington mag to its limit and beyond for 1000 yard matches (Some brand of Cases lasted 2 firings, others blew the primers the first shot) The rifle loved velocity and the hotter I loaded it, the better it shot. but it has faired better and now has 400 to 500 rounds down the tube and still shoots great with reduced loads, some throat erosion is present but not bad enough to re barrel it.
There are plusses and minuses to many design features and to get the best performances for the need/job, some compromises must be made.
Just my opinion
J E CUSTOM
I find it very informative and just sharing for what is it worth for others to decipher, http://precisionrifleblog.com/2012/07/09/practical-tips-to-extend-barrel-life/
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