just something to try, debunking a barrel life myth

[wingnut]

Here is an example of what Dr. Ken Howell was talking about (see several posts above):

Use a larger case to get lower pressures thus less erosion and be satisfied with the same or only slightly better speeds.

Max load with 30-06 (24 inch barrel, 60K psi, 2677 fps):

24 inch barrel, 50K psi, 2750 fps:

Will the game know the difference?
Which barrel will last longer?
Which will have longer case life?

 

[boolit]

Kirby Allen of APS, ft. shaw montana turned me on to this, those of you who have barrel burners try this experiment, take your pet load of extruded powder and fire 3 rounds, feel the barrel.
then work up an equivelent load with a ball powder, then shoot a 3 shot group, feel the barrel, you will notice the barrel is much cooler, nitroglycerine makes ball powder more temp sensative, but it has a lower flame temp, it has to help barrel life.
My big 7mm, likes the 160 accubonds jammed .006", I would on occasion pull a bullet while unloading, at roundcount 450, I still on occasion pull a bullet, so my throat erosion is minmal, I'm guessing around .004 or less. I fully expect to get 900+ rounds before I set the barrel back. right now its shooting as well as it ever has, 800 yard groups run 4-5 inches with hunting bullets.
RR

ball powder...lower flame temp...help barrel life?

I was told it burns out throats.... guess I was told wrong.

 

[Ridge_Runner]

Here is an example of what Dr. Ken Howell was talking about (see several posts above):

Use a larger case to get lower pressures thus less erosion and be satisfied with the same or only slightly better speeds.

Max load with 30-06 (24 inch barrel, 60K psi, 2677 fps):

24 inch barrel, 50K psi, 2750 fps:

Will the game know the difference?
Which barrel will last longer?
Which will have longer case life?

ok, you take a 280 and a 7 RM, both using IMR 4350, even at the same pressures, the 7 RM will use more powder to get the same MV, and it will take longer to burn that excess powder, the throat will be subjected to the flame temps longer so in my mind will have more erosion.
BTW I read the link several posts above and my thoughts were Ken Howell was just trying to sell his chambering more than stating facts.
RR

 

[Desert Fox]

BTW I read the link several posts above and my thoughts were Ken Howell was just trying to sell his chambering more than stating facts.

RR, This is where you and me can agree!

The illustration above proved nothing and has no relevance to what the OP was discussing here on this thread. The thread is about ball powder burns cooler than extruded powder. What was shown however was basic handloading 101. Every handloader knows that a magnum caliber can be downloaded to match non magnum cartridge performance, especially when using slow burning powder at a much lower pressure. It's a case of Ken Howell just reinventing the wheel. DF

 

[wingnut]

RR-

"ok, you take a 280 and a 7 RM, both using IMR 4350, even at the same pressures, the 7 RM will use more powder to get the same MV, and it will take longer to burn that excess powder, the throat will be subjected to the flame temps longer so in my mind will have more erosion."

QuickLoad-

160g AB, IMR 4350, 24 inch barrel
280 Rem vs 7mm RM

Same MV (2858 fps):
51.6g vs 57.2g
100.5% fill 89.6% fill
60K psi 53.8K psi

Same psi:
51.6g vs 59.5g
100.5% fill 93.2% fill
60K psi 60K psi
2858 fps 2956 fps

If temp and pressure are directly related shouldn't the temp be near the same when the pressure is the same? Remember to account for the ~20% increase in volume of the RM case over the 280 case.

Get yourself a copy of QuickLoad and play with the modeling. The calculus has already been done.

"... my thoughts were Ken Howell was just trying to sell his chambering more than stating facts."

KH is a broke old man that lived and learned from the cartridge pioneers. He does not make a dime from his chamberings. However, you may want to beg, borrow or steal a copy of his books starting with "Designing and Forming Custom Cartridges"

 

[Desert Fox]

BTW I read the link several posts above and my thoughts were Ken Howell was just trying to sell his chambering more than stating facts.
RR

Wrong choice of word here by RR. I think he meant promoting. Everyone knows that applying patent for chamber design is useless proposition. Ask Rick Jamison with his SM.

 

[Ridge_Runner]

ok, if nothing effects barrel life except the amount of powder and the pressure applied with it, why will a 338 win mag have twice the barrel life of a 220 swift? isn't it a fact that if you load two cartridges of the same basic case to the same pressures that the one with the larger bullet diameter will always have a longer barrel life given the same treatment?
and DF is correct, poor choice of words, but if enough people talk about the howell cartridges, then more folks go scrounge up his books, he can get an increase in speaking fees due to the notorieity, personaly I study to the level that I can comprehend, and learn from what I actualy see, would I have known just how temp sensative WC872 was by using quickload, would I be able to figure out that 105 gr at 90 degrees will shoot the same speed as 110 gr at 50?
would a computer program tell me about the difference in barrel temps between H-1000 and WC872 when loaded to top end levels?
RR

 

[Antelope_Sniper]

I'd think ... Throat erosion is basically the #1 enemy of bbl life/accuracy correct?

That is correct. When a bench rest shooter "shoots out" his barrel, he doesn't toss it in the garbage. The smith will "bring it in a turn", cutting off or two threads, setting the barrel back a 1/16 to 1/8 of an inch, and cut a new throat, new threads, screw it back on, and the shooter will be ready for another season. You can also do this with factory barrels, but alot of guys use the shot out throat as an excuse to go custom.

 

[boolit]

Throat erosion?

Hot loads over time.... I read an artical where the powder doesn't completely burn and acts as a abrasion to the throat....

 

[Ridge_Runner]

Throat erosion?

Hot loads over time.... I read an artical where the powder doesn't completely burn and acts as a abrasion to the throat....

and ball powder being round in shape is not as abrasive as the extruded, plus the lower flame temps.
RR

 

[RiverRider]

As far as any powder being easier on a bore than another just because of its chemical makeup...I have my doubts. Velocity is a product of pressure and time. Last time I checked, temperature and pressure are directly linked---at least this is the nonsense they taught me in my mechanical engineering classes. Could it be that there's something I am not taking into consideration? Sure. Lay it on me in rational terms and I will accept it. Weak explanations need not apply.

RiverRider,

Question: does a load that produces a peak pressure of say 65,000 psi and an avg pressure of say 40,000 psi (hypothetical numbers) produce the same velocity given all other things to be constant as a load with a peak of 60,000psi and the same avg of 40,000 psi? It would seem that by playing with burn rates/pressure curves, you could possibly acheive the same velocity in two identical guns, with significantly different peak pressure/temp levels, which could in turn affect bbl erosion rate. I confess to not being very knowledgable in this area, so i'm operating under various assumptions, mainly that it is higher PEAK pressure/temp, that causes the most erosion and not total BTUs produced.

Thoughts?

I have no pat answers, just a few clues. A few of the factoids I've managed to retrieve from my aging memory:

1. All propellants contain roughly the same amount of energy per unit of weight, it's just the burn rate that makes them different.

2. Propellants do what they do because they turn from a solid to a gas almost instantaneously.

3. It's the volume of gas (and by extension the volume or quantity of powder) that follows a bullet down the bore that produces erosion.

I say these are "factoids" with a certain amount of reservation. I wish I had a nickel for every commonly accepted "fact" related to reloading that's gone down in flames (I love the one about faster powders in rifles with shorter barrels).

I would think that a lower peak pressure means lower erosion effect, but to get lower peak pressures AND the same velocity you have to burn MORE of a slower burning powder---as in the Re25 vs. IMR4350 example. So maybe not.

The older I get the less confident I am in what I think I know. Certainly an interesting subject, though.

 

[RiverRider]

A thought just occurred to me (yeah, I know---everyone duck! :shock: ).

Pressure is nothing more than a static measurement. An air tank that's pressurized to 1000 psi is deteriorating no faster than one that is pressurized to 100 psi. The "pressure" is not doing a thing to harm the steel of which the tanks are made, unless the pressure is high enough to cause a tank to rupture.

I think it's just a commonly accepted myth that pressure is what causes erosion. It may seem to be true because there is always pressure behind a bullet and we relate that pressure to the bullet's movement. We talk about pressure all the time because it's the thing that can destroy our firearms.

I think the bottom line is that erosion is more or less proportional to the amount of gas that follows the bullet down the bore. The gas IS in motion and can therefore erode the bore surface.

Yeah, that's the ticket...my final answer!
:roll:

 

[atmoshpere]

Sounds logical to me. I've yet to shoot the barrel out of any of my guns, so from a practical standpoint I can't say it's of huge concern to me...yet :grin: Still fun to consider though!

 

[wingnut]

Just FYI...

Much has been made about ball powders being cooler burning than extruded powders, but the fact of the matter is that there really isn't much difference. Flame temperature is very close to the same for all smokeless powders and runs about 3300 degrees F. Ball type powders tend to be from 3200 to 3300 degrees F and extruded powders tend to run 3300 to 3400 degrees F but there is wide variation.

http://www.frfrogspad.com/intballi.htm

Table:

http://www.stardestroyer.net/Armour/She ... llants.htm

gas- temp, pressure, volume:

http://wps.pearsoned.com.au/cd1/49/1262 ... index.html

 

[RiverRider]

This discussion has raised a few questions in my mind.

I know I can pass my finger through the flame of a candle quite slowly and never even feel the heat. I wonder just how much heat can transfer to a barrel during the time ignited propellant is confined within the chamber and the barrel.

Which leads to the next question: if that amount of heat transfer in minute, then what is the mechanism that heats up a barrel? Seems to me that the friction of the bullet passing down the bore would account for a significant portion of it. But, there's more...

How about when you bend a piece of coathanger back and forth to break it when you have nothing to cut it with? Any metal I know of gets hot where it is flexed repeatedly, but these kinds of everyday experiences deal with straining metal far beyond the modulus of elasticity. I wonder if repeated and continuous stress within the limits of the MoE can cause heat build up. If so, then mere presence of chamber pressure could account for some of the heat build-up in a rifle barrel.

And then I get to wondering---could there be erosion in the absence of noticeable heat? I am always having to repair certain faucets around the house because they are not being shut off tightly enough. A tiny bit of leakage of water causes erosion of the seat area of the valve and ruins it so I have to replace it. The gases that push bullets down the bore are indeed fluid in nature.

I think we take certain things for granted and don't really understand what we see happening on an everyday basis.

My head hurts!

 

[wingnut]

RR-

Google or Bing are your friends:

http://www.loadammo.com/whatisballistics.htm

 

[Desert Fox]

The thing is, it's been proven that heat of the expanding gas (Average 5,500 degrees Fahrenheit) does very little to erode the bore. It is the small amount of gas escaping around around the bullet as it travel down the barrel is what cause throat erosion. This is the reason why you see a lot of erosion around the throat area because the bullet was just starting to move and haven't fully sealed the bore yet.

The bottom line, barrel life is influenced by peak pressure and gas volume. Double your powder charge, and it will reduce your barrel life by 75% whereas, if you lower your charge by 10%, you'll increase your barrel life by 20%. It doesn't matter whether you use ball or extruded powder. The no free lunch analogy still hold true! DF

 

[RiverRider]

Wingnut, the internet is a wonderful thing. Everything that is true can be found there. The problem is, everything else can be found there too. I am not knocking your link, I am saying I like to know more about the author of any article before I invest the time to read it. Ferreting out the truth can be tricky business and a lot of hard work in itself.

I will now go forth and investigate this link! :arrow:

Ahhh...good link there. Looks like it should be pretty good information. I still wonder about strain and flexing and whether it translates to heat. I'd like to know how Hatcher reached these conclusions also.

 

[wingnut]

The bottom line, barrel life is influenced by peak pressure and gas volume. Double your powder charge, and it will reduce your barrel life by 75% whereas, if you lower your charge by 10%, you'll increase your barrel life by 20%. It doesn't matter whether you use ball or extruded powder. The no free lunch analogy still hold true! DF

Exactly the point. Barrels and cases are consumable items just like bullets, powder & primers. If you want them to last longer, keep the pressure moderate. Your choice, pay now or pay later.

You can double your powder charge, I'll watch from afar. :shock: :wink:

 

[Ridge_Runner]

RR-

Google or Bing are your friends:

http://www.loadammo.com/whatisballistics.htm

yep if its on the net it must be so, specialy if it comes from fr.frogspad.
the information I post is from one of 2 sources
somebody whom I trust, that has burnt up more barrels than 99.9% of the so called experts, who believe everything that they google and bing, or what I have saw from my own experience.
I agree, there is no free lunch but there are things you can do to help barrel life that are measureable. things that I have noted. burn up a few barrels and tell me how it goes.
RR