Barrel life and shoulder taper.

[8shots]

This week-end at a shoot some guy was stating that barrel life was a function of the angle of the case shoulder. I found a supporting article on the net.
The theory is this:
The tapered shoulder directs the hot gasses to a point as it exits the case. This point is where the axis meet if a line is drawn following the taper of the shoulder. So for a case with a gradual sloping shoulder this point would be further down the barrel then for a sharp slope, which could be right at the lands. They argue barrel burn takes place at this "hot spot".
Now here is the kicker: If a cartidge is designed so that the point actually falls inside the case neck, then less barrel burn and therefore damage will occur, resulting in longer barrel life. This is because the shell neck takes the punishment of the hot spot.
Bullshit or true?
I always thought barrel life was a function of powder capacity to bore size. So-called under or over bore?
Any comments on this?

 

[Advokaten]

Re: Barrel life and shoulder taper.

Perhaps one of many factors,

I for one think of the mass of gun powder ejected in the barrel along with the bullet is responsible for most of the throat wear.

I thought all men knew that all powder is not bured within the case, rather that it´s burned in the first 2-3 inches of barrel.

ergo the thoughts about shoulder taper could rather be described as the angle of the ejected burning powder given by the case shoulder.

But in real life I have no idea and I belive that few others have as well.

/Chris

 

[8shots]

Re: Barrel life and shoulder taper.

Thanks for reply, but to clarify a bit, the argument made is that at this converging point the gas is the hottest, so most damage occurs at this point. It is acknowledged that the heated gas burns all the way down the barrel.
But does this gas actually converge to such a point? I personally think not and that the bullet would act as a "stop" effectively craeting new dynamics irrespective of case taper.

 

[Jeffvn]

Re: Barrel life and shoulder taper.

I have heard similar statements, and recently had a chance to speak on the phone at length with the developer of the 338 Norma mag., who agreed in part with the theory, but also noted that teh length of the neck is part of equation too. If you look at the .338 Norma Mag., you'll see a decent shoulder angle combined with a neck that is longer than one caliber in length (.403 for a .338 caliber). The expected throat life (the portion of the barrel that is erroded by the gases comeing out of the case), is significantly higher than standard magnum chamberings of similar capacity. It will be interesting to find out the results when folks start to burn out throats/barrels for this fairly new chambering.

I too would be interested in seeing objective barrel life data on various chamberings with various shoulder angles and neck length.

JeffVN

 

[RTH1800]

Re: Barrel life and shoulder taper.

We may all end up shooting the 300 H&H again! Smile

 

[GRIM]

Re: Barrel life and shoulder taper.

Sort of like a shape charge focusing the blast at a particular location?

I've always wondered about how technology that is used in setting up speakers and how sound bounces around inside a speaker cabinet could be utilized to design a cartridge that would reduce throat erosion...

However I think that it's all simply how much powder you use and the heat it's creating and transferring to the throat along with under/over bore size issues.

 

[Wheres-Waldo]

Re: Barrel life and shoulder taper.

If what your asking/saying were true, we would see a miriad of cartridges with the same barrel life, which isnt the case.
40* shoulders are very common, but the cases that use them vary quite a bit in barrel life.

 

[raptor99]

Re: Barrel life and shoulder taper.

I have also read about this theory and have heard that the 30 degree shoulder is in the "Sweet spot" range with a long neck. Supposedly this is one of the reasons the standard 243 is hard on throats but the wild cats off of this case do better.

Now take a look at the 6.5x284. It has either a 30 degree or close to it and its damn hard on barrels. I believe it all boils down to the powder we use and how hot we get the barrel when were shooting.

Its a proven fact that powders like N165 and H1000 burn cooler and therefore are easier on barrels.

 

[oneshot onekill]

Re: Barrel life and shoulder taper.

It's an interesting thought but doesn't really hold water to me. Since ignition begins at the back of the round, everything is getting pushed out of the shell before a good portion of the powder is even burned (probably most of it). It doesn't stand to reason that the convergence point in the neck would be any hotter than anywhere else. Even if it was, that point is in the center of the bore.

 

[jbell]

Re: Barrel life and shoulder taper.

I have had conversations about the neck length / shoulder angle having an effict on throat life , however I think it may be more of theory. I think it is very difficult to scientificly prove these factors have a actual effect on accuracy , b/c it is so difficult to have 2 barrels with slight chamber modifications as described above and then subject them to the exact same "punnishment" or shooting/cleaning routine. There are just too many variables. But in the end who realy gives a damn , whial its intresting to talk about there is nothing you can do about it w/ everything else being equal. Just my 2 cents.

 

[sniperaviator]

Re: Barrel life and shoulder taper.

Anyone ever heard of science? You know, the idea that you have theory, develop an experiment to proove or disprove it and reach a conclusion? Or is all just "sweet spots" and conjecture?

Military could do it.

 

[8shots]

Re: Barrel life and shoulder taper.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: oneshot onekill</div><div class="ubbcode-body">It's an interesting thought but doesn't really hold water to me. Since ignition begins at the back of the round, everything is getting pushed out of the shell before a good portion of the powder is even burned (probably most of it). It doesn't stand to reason that the convergence point in the neck would be any hotter than anywhere else. Even if it was, that point is in the center of the bore. </div></div>

This is the view I hold as well.