Does the angle of the case shoulder have any bearing on throat erosion?

speedygonzalez

speedygonzalez

Member
Throat sandblasting theory

Speedy: I've followed your writings for a number of years, and respect your opinions ( I also do not "like" or use moly: tried it/ more disadvantages than advantages), and would look forward to your thoughts concerning shoulder angle. Does the angle of the case shoulder have any bearing on throat erosion? I'm thinking of the 243 Win. with the 20 degree shoulder, and a proven barrel burner, as opposed to a similar round with a 30 degree angle, for example. Some believe the sharper angle keeps the "turbulence point" closer to the confines of the case neck, and "short" of the throat area. Thanking you in advance. Frank D. Shuster at: fdshuster@hotmail.com
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Dear Frank,

The fundamental principal of exchanging stored chemical energy of a propellant into the kinetic energy of a projectile is through the generation of gas and it's accompanying pressure rise. These gas laws then lead us back into the standard principles of fluid dynamics and laminar flow and turbulent flow but forward flow non the less.
The theory that the individual grains of powder are focused in a specific area because of the shoulder angle or length of the neck thus causing increased throat erosion are quite humorous. If you think if the case neck as a length of barrel the powders are forced forward just as the bullet leaves the barrel of the firearm itself. the turbulent flow inside the case itself would be theoretically increased as the shoulder angle became greater as in an improved case....food for thought their boss!
Now lets open up the forum for greater discussion.

Good Shooting,
Speedy Gonzalez

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Not this again!

Hi Speedy:

From what I have been taught over the years about gas flow, I must say NO to your question!

Perhaps there are some people out there who have been trained in basic physics can chime in with some facts!

Zeke
 
I agree with you! That is not my question, the question is Frank Shuster's. this was my reply to him and I did the cad drawing up for him. I just thought it would be a good post for shooters about this urban legend that keeps cropping up all of the time. I had plenty of physics and hydraulic classes for my M.E. Degree boss. I'll change up the title so people won't think I am asking the question.

Good Shooting,
Speedy
 
I had asked

the question some weeks ago, " would a longer neck aid in the limiting of throat erosion". The only answer I received from someone who had actually experimented was that the test was inconclusive. What do you think Speedy? Is there an optimal neck length that is in relation to the case configuration and would necks a bit longer than what we are currently using help reduce throat erosion?

I was thinking specifically of the Aardvark case at the time I asked the question.

Thanks, Pete
 
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I do not feel the neck length or shoulder angle will have any effect on throat erosion. We documented two 458 Win. Mag.s which are basically straight walled cases and while we were not looking for throat erosion we noticed that although the powder exits these cases almost striaght out the mouth of the case both barrels exhibited the same heat checking at around 450 rounds as does any other barrel. The heat & pressure plus introduction of cool air as we extract the case is just hard on barrels. The only process that I ever saw that kept this checking process at bay for 1000 to 1500 rounds before it began to manifest itsef was the J-TEX Catalytic Conversion Process which is an electro-chemical procedure the closes the grain structure of the steel at a molecular level. I do not know if they are still around in Gladewater, Texas.
If you had a hummer barrel it would stay that way for two to three times as long...if it sucked, well it would suck forever.

Speedy
 
WHEEEEE What A Great Time to be alive!!!

:D

good old TPT again.

I've got a question for the True Believers in Turbulence Point Theory....

HOW FAR down the bore has the bullet traveled by the time 95% of the powder is fully involved and is no longer granular?

IMO those little logs of powder jostling at the door AREN'T THERE once the door opens! Nor is there a "plug of powder being crammed into the hole......

Thank you Speedy!

BTW, ain't it GREAT to work with young and fresh minds??? Holy CRAP are these kids SMART eh?? My rule with my own kids is simple (and I've got a passel :) ) "Just DON'T SCREW 'EM UP Al...... God gave 'em a real brain. Watch, guide, Love and learn!..)

Good On Ya Speedster....

al
 
alinwa said:
...

IMO those little logs of powder jostling at the door AREN'T THERE once the door opens! Nor is there a "plug of powder being crammed into the hole......

....

al
Click to expand...

I heard one of the major bullet manufacturers had a fire in their shooting tunnel because of a build up of unburned powder in the front of their tunnel. If that is actually true, then not all the powder is being burned inside the case or in the barrel for that matter and is going out the end of the barrel. A simple way to check that would be to put a white sheet in front of your muzzle on the ground and see what kind of residue winds up on the sheet. Of course, it would have to be done on a calm day. So means that it would need to be done somewhere other than Texas as calm days here are few and far between.

I'm of the opinion that case capacity-bullet diameter relationship has more to do with the rate of throat erosion than shoulder angle or length of neck. But, that's just opinion from what I've seen with how many rounds that have been fired through barrels that have come in for rebarreling. Even at that, you have to take the number of rounds through the barrel with a grain of salt unless actual records have been kept. Most times "it has 2000 to 3000 rounds through it.", means I have no real idea how many rounds I've shot through it.

Mike
 
Just some thoughts on this barrel burning business. We all know that some powders cause more throat erosion than others, this is a minor factor for this conversation.
BUT, we all know some cartridge chamberings burn barrels out much quicker than others. Now, reason out these "overbores" and their shoulder angle and neck length relationships.

Something to do on a 35F rainy Saturday morning.
 
Jerry, the rate of erosion is most likely due to multiple factors. I've seen some good arguments that the problems with the SAAMI .243 Winchester has to do with the freebore/leade specs, as opposed to the neck length & shoulder angle. But who knows?

Discovering of the various elements & the roles they play would be time consuming & costly.

Cold & rainy here, too. Fortunately, I gotta work.
 
If

the powder was bouncing off the neck, then hitting the throat causing erosion, why wouldn't the neck be melting instead of the throat? Brass melts at a lower temperasture than 416 stainless.

Later
Dave
 
Does the angle of the case shoulder have any bearing on throat erosion.

The flame duration is the culprit. I agree with speedy.
Slow powder will really hurry up the process. This has been written about several time that i know of and printed in several books.
 
Erosion.........and Benchrest

Since this is Centerfire Benchrest, the big question is, how does this affect the number of rounds that a good barrel will have down it before accuracy is compromised to an extent that you can measure.

Considering the success of the 6PPC in the Competitive Arena, is it a barrel eater, or not. I darned sure would not change anything about it to gain a few hundred extra rounds if it meant compromising the basic concept........jackie
 
Let's consider this.

The base of the bullet has departed the case. Now, the expanding gas mass is leaving the constraints of the case, and impinging on the base of the bullet, and the surrounding countryside (barrel). The velocity of these gases is, of course, very high. The base of the bullet is receiving a constant bombardment of molecules of hot (abrasive?) particulate matter, which immediately change direction (through impulse or reactionary force).

This redirected gas now impinges on whatever is in it's path, the barrel, and other molecules of gas. Perhaps even the expanding gas following out of the case pick up these particles that have lost energy, and again catapult them into the mix, down the barrel, or sideways, causing additional wear.

Whether it be flamethrower effect, or particulate matter abrasion, perhaps the area nearest the chamber will be most affected.

Does the shape and length of the shoulder/neck area of the case play a part on erosion in front of the chamber? I would have to think so, as some of the forces are not necessarily linear to the bullet axis, acting tangentially, or redirecting, off the case neck.

This is just my way of looking at it, and it probably doesn't add up to two beans, as far as being an accurate portrayal of effects. But, it is the way my derelict mind works. You fellas, or anyone in the know, can probably tear this half-baked theory apart. Nonetheless, I thought I'd throw it out there anyway.

(Fellas, I wrote this post before I noticed post one had pictures with it. Post one was much expanded on my screen, at bottom of page [oldest posts last], and I didn't notice them until I went to submit this.) Post one is very well presented.

Thank you,
Longshooter
 
longshooter said:
Let's consider this.

The base of the bullet has departed the case. Now, the expanding gas mass is leaving the constraints of the case, and impinging on the base of the bullet, and the surrounding countryside (barrel). The velocity of these gases is, of course, very high. The base of the bullet is receiving a constant bombardment of molecules of hot (abrasive?)
Thank you,
Longshooter
Click to expand...
I wonder, if this is the case. Remember, the powder burns from the bottom of the column not the top.

Coots-get your sh*t in the truck. Dublin is next week!!
 
Another question:

I have noticed in several barrels that I have owned, one groove will get black and seems to stay that way with normal cleaning. JB or the like will take the black out. Does this mean the black groove is deeper than the others or is there something else going on?
 
There are some things that need to be tested to be verified or disproven. It seems to me that this is one of them. Testing requires significant expenditure of money and time. Theorizing is much less expensive, but when all is said and done, without actual test data do we really "know" anything? Where's the beef?
 
Yes Sir

JerrySharrett said:
I wonder, if this is the case. Remember, the powder burns from the bottom of the column not the top.

Coots-get your sh*t in the truck. Dublin is next week!!
Click to expand...

Jerry

I sold my wife's old trailer(her Valentines Day Present a few years back)and I will finish packing her new trailer tomorrow or Monday. See you next week.

Later
Dave
 
Dave Coots said:
Jerry

I sold my wife's old trailer(her Valentines Day Present a few years back)and I will finish packing her new trailer tomorrow or Monday. See you next week.

Later
Dave
Click to expand...

Gosh, you are really a nice guy. Buying her a new trailer.

We'll be there Tuesday, God willing.
 
My guess there is no vortex affect created by the shoulder angle, just look at some of those great spark photography PS primer detonation photographs that were presented in the mid-90's, showing all the various different manufactured primers and their varied flame patterns, as shot from a PPC case in a stub chamber with 1/4 inch long bore.

None of the photographs ever showed any signs of an angular vortesy affect, only billowing plumes of various different sizes, ranging from the smallest produced by Federal and CCI primers to the largest produced by, I believe, Remington primers that also contained alot of flaming particulate said to be aluminum oxide or some variant................Don
 
good to hear from you mr speedy,well one question

is it possible there is a center to the heat of explosion? a wild guess would be about 4 inches out from the bolt face,no matter what kind of cal ,if that is true can a longer case put the throat closer to this heat of explosion?for instance h4350 in a 7mm mag eats the throat fast and hard but h4350 in a 6.5-284 is half to two thirds less.just a theory so the reason i asked was it seems by certain changes in patterns within my barrels indicate there was a change in temp or something happened in the burn at a given point in my particular barrels that indicate this theory. tim in tx
 
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