Was told by someone in the business, that throat erosion will increase chamber pressure....

rationale though tells me that erosion will decrease chamber pressure because that will let the gas escape more easily than a tight chamber...

kind of the same way freebore used in Weatherbys does...

anyone able to tell me my rationale is off? or what am I missing?

thanks!

quote:

Originally posted by seafire/B17G:

kind of the same way freebore used in Weatherbys does...

Erosion, like freebore, will let the bullet get a running start which will decrease pressure.

I'm guessing the guy believes the rougher surface of an eroded throat will impede the bullet, theoretically increasing pressure due to friction.

My guess is that the guy is FOS and by "in the buisness" you mean that he works in a gunshop.....

You have two things working here...one is the leade moving toward the muzzle and increasing in ID as the metal is "burned" off - reducing the pressure- and the other is the "roughening" of the metal grabbing and holding the bullet while tearing out little chunks of guilding metal - increasing the pressure-...so in effect "someone" is partially correct...and so are you...BUT...only to a certain extent each.

The only way to know for certain is to pressure test the new barrel and then pressure test at intervals(you pick the range)...chart it...then decide.

You might detect a pressure change through group size changes or chrono numbers...lower chrono number usually indicating lower pressures and visaversa...but in all actuality unless you are running in the red zone as far as pressure is concerned the question is more academic and reserved for esoterica than anything else, but it is still interesting to think about and something I would be interested in exploring had I the wherewithall to do it.

The question is like so many other question...we all jump to conclusions, but many of those conclusions, while fitting, seemingly, may not actually be anywhere near being correct or actual...our subjectiveness always gets in the way.

Otherwise the reality of it up for grabs while sucking on a barley pop and scarfing BBQ.

Luck

[QUOTE]Originally posted by FOOBAR:
Otherwise the reality of it up for grabs while sucking on a barley pop and scarfing BBQ.

Foobar, you left out the "Ho Humm" roger

quote:

My guess is that the guy is FOS and by "in the buisness" you mean that he works in a gunshop.....

No, actually a well noted gun writer....on another forum....

didn't make sense to me....

thanks to everyone for their inputs....

More than one 243 has blown due to a rough
throat.

Seafire
I did say "my guess"....

It just seems really odd that I have never seen anything about this in print. If it were a real issue I would think it would come up in some of the reloading manuals.

quote:

Originally posted by hawkins:
More than one 243 has blown due to a rough
throat.

Can you direct me to the source of your info? Thanks.

quote:

Originally posted by hawkins:
More than one 243 has blown due to a rough
throat.

If it was due to a rough throat, I'm guessing it must be the throat of the fool who pours liquor down it while loading his ammo.

The reason that the 243 pressure specs were
reduced was do to secondary pressure spikes.
The were associated with slow powders and
ROUGH THROATS.

quote:

Originally posted by hawkins:
The reason that the 243 pressure specs were
reduced was do to secondary pressure spikes.
The were associated with slow powders and
ROUGH THROATS.

Again... Can you direct me to the source of your info please? Thanks.

You "ho-hum" at one of my BBQ's and you're in for a rude shock...if you can't keep up you're end of the conversation, you end up being the main course...or at least an appetizer.

I'm thinking there is/was a whole lot more things going on wrong than is being owned up to when a 243 "blows"...

I also think MOST shooters never get this deep into ballistics, effects, rough throats, "erosion", etc., and the only way to come up with information is to do a ton of searching online...rough throats and what goes on is getting into areas that are very difficult to test or actually determing other than if you have a bore scope, are into very accurate rifles, competition and so forth...the average hunter could care less except for the "tough" cleaning end.

JHason...You might check on 6mmBR, Sabier, and some of the other small cal and long range forums...I've read some bits on those along with at least a modicum of "scientific" testing.

I had one of the first Rem 700 BDL 17 Rem in my area. Got it cheap because when you looked down the barrel you couldn't see any rifling and the first owner complained he was blowing primer pockets on factory ammo. I took it home and used 2 cans of Wipe-out on it over about 2 months to get it clean.

You could see rifling in front of the chamber but it felt like a rutted road when you ran a patch into it for about the first 6-7 inches. I shot it for another 2-3 years with a warm load of IMR 4320 and 25 gr Hornady's until I couldn't get it to shoot less than 1".

I sectioned the barrel and it DIDN'T have any rifling for the first 12" but the last 4" were still good and that was all that was needed to keep half way decent accuracy.

I won't say what I did to keep the velo up, but some can guess...

Whether or not a rough throat increases or decreases pressure falls into that absolutely/definitely not catagory. It's like gold...you find it where you find it. Rough throats cause pressure increases, but then again, by itself it doesn't.

Luck finding your answer.

Considering that the bullet can, will and does opturate in the throat (see Mann's "The bullets flight"), it does make some sense that having a throat that makes a 'gaters hide look smooth would tend to hang onto a jacketed bullet harder than a smooth throat would

Just because a "well known gun writer", an engineer, a shooting industry insider/manufacturer, or whoever writes something in a book, magazine, or on the net is far from "proof" that something is true. Especially a gun writer. In the past 2 decades gun writers have switched from being a person who experiments and writes about guns to someone who repeats manfacturers' ad copy oin article form. There are exceptions to this, of course, but they are few. Very few.

The most glaring example i have seen of a book being regarded as gospel by gun enthusiasts is H. R. Vaughn's "Rifle Accuracy Facts." Or as I like to call it, "H.R. Vaughn's Rifle Accuracy Opinions." He did an excellent job of writing the book in a convining manner where someone without extensive and advanced knowledge of the topic of each of his chapters would likely buy everything he said hook, line, and sinker.

Even the idea of barrel "erosion" is FAR from a settled matter. I and toehrs with my educational, research, and vocation experience can make an even better case that it is "corrosion." Others can argue that it really is erosion. An example of this sort of dicussion in action is why we have law suits - each side has a diametrically opposed opinion of some matter and each side provides "experts" that their opinion is correct and the pther party's opinion is wrong.

Does stress corrosion inn a barrel case an increase in pressure? Hell if know. Never thought about and really hav no intrest in studying it. Off the top of my head I think that the pressure reduction from "more freebore" is greater than the pressure increase from a rougher bore. I also think it is noise and washes out in the data.

One reference to pressure/barrel erosion is;
"Mechanism of interior ballistic peak phenomenon". It is online.
It think Vaughns "education, experience, vocation way over shadows that of the last poster. The book in question in my opinion is the best ever written on what happens to the
rifle when it is fired.
If you havent read it, do so.

Another ref; 24hour Campfire
Ask the gun writers
Re; Computer Ballistic Programs
John Barsness
Unlike Vaughn he is still alive, you can
insult him in person.

hwakins-

Are you saying i ionsulted Vaughn? If so then you relaly do need to work on yoiur reading comprehension.

I have said many times on this forum that his book is the best one i have ever read on the subjects he addressed. Does that mean that everything he said is 100% "true proven fact"? not no but hell no. If you think it is then that is just your ignorance showing.

As for published promoiting one side of the argument, big fucking deal. If you are saying that the article you mentioned "proves" something as indesputable fact, then once again that is your ignorance showing and proving that this stuff is over your head.

I have to tell you, that "insulting" comment really pisses me off. You are some spineless little mother fucker who does not even have the balls to post your real name and where you live. Dude, grow some balls. i would respect you a lot more if you said who you were and where you lived when you inulted me and twisted my words around. As i just wrote that i realized soemthing. Mabye even my simple post was over your head and you honestly do not understand that in no way, shape, or form insulted Vaughn and it was just your ignorance showing yet again.

Why would want to go to 24 hour camp fire? I have been on the site a few times. If I rememebr correctly i have zero posts on there. I may have made a few in the past, but do not rememebr doing it if i did. As for any gun writer, if they feel the need to challenge me in a public forum, they should feel free to do it here. I do not log onto this site every day, but they can alert me when they make a post. I respond to anything they throw my way. If you think the fact that a guy gets paid to write a magazine article means he knows something, then again, tha is your ignorance showing.

Things along these lines are not determiend to be 100% understood and known. That is the nature of the beast. if you have done graduate level and professional engineering research then you would know that.

We have some really thin skin here.

The story that was told claimed that the erosion issue was at the root of the pressures and velocities for the .243 being reduced about 8 or 10 years ago. I do believe that .243 factory ballistics have been reduced but I do not know the reason why.

On the other hand I have seen some badly eroded barrels that apparently were shot until the accuracy gave out with out pressures going out of site.

I rarely post on boards, but a friend directed me to this topic and I read the above posts with mild interest and increasing curiosity, especially concerning Mr. Stokeld's signature.

Marc: you are "a gunmaker who fixes American Custom Gunmakers' fuckups". I'd be interested to know what type and how many of these "repair" jobs you've done. As a strong supporter of the Guild, and also acquainted with a few of the craftsmen, I find it somewhat difficult to believe that ACGG gunmakers can't or won't fix their own mistakes. It sounds as though you are doing this on a continual basis; if so, you obviously have the talent to be a Guild member yourself and maybe should pursue that.

One other thing that is somewhat puzzling, Mr. Stokeld: the Spring issue of "Gunmaker" (ACGG publication) lists you as a director of the Guild's Education Foundation. Why would you bad-mouth the people in the very organization that you are an integral part of?

AT-

i used to regularly post on boards but almost never do these days like you. hell, i rarely read boards-just a couple or three days a week

anyway, yes, what you said about the past is correct. but that is the past and is not the case in the present. it is a very valid question and if i were you i would be like "wtf!?!" myself.

at any rate, i will not go into it in a public forum. i have not, and will not, identified a single gunmaker involved. hell, i have never and will never identify a single problem i have had to clean up in case soemone tries to get all csi and figure out who botched what job.

this is the very last thing i will say about it. when people ask me about why i say it i tell them that i have earned the right to say that by the hours standing in front of my bench, the sweat of my brow, callouses on my fingers, and carpel tunnel in my wrists. when i stop having to do it, i will stop writing it.

and that is all i am going to say about it

skunk out

eta:

btw- is "athiker" ap trail hiker? i was supposed to move to brasstown, nc last year but broke my back 2 months before the scheduled move. i am hoping to move to western nc this year, but it will probably be near brevard or waynesville, nc. love the at and brp. have spent many happy hours hiking the mountains of western nc. i have been around the world and seeen so many beautiful things, but if forced to pick just one "best" place i would have to say western nc in the fall when it was a good color year

skunk out again

eta number b:

thank you very much for being so professional in your post. you asked great questions and did not make any assumptions about my thoughtsor actions, nor did you misread or twist my words around to fit a poreconcieved narrative. your post is a model for how folks should ask soemting when things are heated. kudos athiker!

skunk out for the last time on this post

[btw- is "athiker" ap trail hiker?]

Yes, GA to PA in 2002; most incredible 10 weeks of my life.