just something to try, debunking a barrel life myth

[Ridge_Runner]

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

 

[SJB358]

Great info RR. How does the temp sensitivity work against you for LR shooting. I know you have talked about RL22 being a pain for your rifles. Scotty

 

[Ridge_Runner]

I work up my loads and practice in approx the same temps I hunt in, I start shooting in earnest around sept. with temps in the 35-50 degree range.
RR

 

[SJB358]

Got it. Makes sense in that aspect. Thanks for the tip's. I imagine it would keep the Alliant style powders more in check also? Scotty

 

[Ridge_Runner]

Got it. Makes sense in that aspect. Thanks for the tip's. I imagine it would keep the Alliant style powders more in check also? Scotty

yeah that would take care of the temp sensativity, the lot to lot varience is the killer, you can't adjust for that.
RR

 

[Desert Fox]

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

RR, with all due respect. Kerby's unscientific experiment is sadly unfounded and without merit. Lake City Ammunition Plant did an extensive testing long time ago to prove the validity of this claim. They found no significant difference in barrel life and accuracy between the extruded and ball powder. The amount of powder your cartridge burn is what determines the useful life of your barrel. Cartridge that burn less powder will last longer than the cartridge that burn more. There's no such thing as free lunch.

 

[Ridge_Runner]

didn't say anything was free, but I have done this test and found it to be so. here is what I did.
My pet load for my 7mm STW was 86 gr H-1000/140 BT/@3550 fps, I worked up a load with 95 gr WC872 and a 160 AccuBond (wc 872 is too slow for a 140 in the STW) which clocked 3340 fps (not a mild load by any means)
went to the bench and fired 3 H-1000/140 loads, barrel was too hot to touch for long, let the rifle cool completely, then shot 3 of the 160/872 loads, barrel was just warm, how could it not help?
I know guys who've shot the 277 Allen mag (338 LM imp. necked to 270) and got 900 rounds barrel life by using ball powders and not shooting it hot.I do not have the ability to prove this theory does help barrel life but common sense tells me it has to help. Not saying you will get zero throat erosion, but my belief is you can get more life from a barrel than most folks believe.
RR

 

[Desert Fox]

WC 872 is a surplus powder pulled from artillery shells. I haven't seen nor touch this powder. If my assumption is correct the granules are probably larger than a typical canister type ball powder that we're accustom to, therefor harder to ignite. Understand that the powder is intended to be use for artillery which has longer barrel length. Not sure how long is your 7STW barrel is but I suspect that not all of the powder were fully burned by the time the bullet exits the barrel. This explains why you can not get your velocity with the 140 when using the 872.

To give credence to the validity of the test, as in the case of the one conducted at the Lake City munition plant, the component make up should be the same or close to identical as possible. That means using the same brand of bullet, case, primer, and the amount of powder charge.

 

[wingnut]

Rational by Dr. Ken Howell on temp, pressure, powder selection & barrel life:

http://www.24hourcampfire.com/ubbthread ... cs/48608/1

 

[Ridge_Runner]

WC 872 is a surplus powder pulled from artillery shells. I haven't seen nor touch this powder. If my assumption is correct the granules are probably larger than a typical canister type ball powder that we're accustom to, therefor harder to ignite. Understand that the powder is intended to be use for artillery which has longer barrel length. Not sure how long is your 7STW barrel is but I suspect that not all of the powder were fully burned by the time the bullet exits the barrel. This explains why you can not get your velocity with the 140 when using the 872.

To give credence to the validity of the test, as in the case of the one conducted at the Lake City munition plant, the component make up should be the same or close to identical as possible. That means using the same brand of bullet, case, primer, and the amount of powder charge.

It is surplus, yes its designed for the 50 BMG and 20 mm vulcan cannon, its about the same consistancy as win. ball powders, and when trying to get a load for a 140 in the stw or the 7mmam, you can fill the case up and its not burning clean, so pressures are down. but 3340 is a top level load for the stw using any powder for the 160 in this rifle or any chambered in the stw.
read your tests and believe it, no matter to me, I just know what I know from hands on experience, and I'll always believe that ball powder is easier on throats due to a lower flame temp, cause we all know the erosion comes from hot gases, the hotter you load, the quicker you lose the throat.
RR

 

[glane5910]

I've been using H-380 in my 220 Swift for hundreds of rounds and it still shoots like the day I first sighted it in.

 

[efw]

This is great information and makes a lot of sense.

Anybody tried Ramshot Magnum and/or Hunter? I've heard that these provide better temp resistance than other ball powders.

Seems like those'd be great for a "best of both worlds" solution to this issue.

 

[Guest]

RR,
I have shot the IMR powders, Reloder powders and Ramshot Magnum ball powder in my 300 Ultra Mag over the years. I did experience a much cooler barrel using Ramshot Magnum Powder. I was then shooting Barnes 180 XLCBT Bullets with this powder. Very accurate powder, burns very clean too. Dropped that load to develop a 180 AccuBond load. Ramshot Magnum worked ok, but I had much better results with Retumbo and RL25. RL 25 is the powder for my gun with this load. I have close to 1,000 rounds through this gun. Although the theory may not be proven, I side with ya buddy. Just my experience with my gun. I do believe there are no free rides too, Overbore guns have a lot of horsepower, shortened barrel life comes with the territory.

Don

 

[RiverRider]

This is great information and makes a lot of sense.

Anybody tried Ramshot Magnum and/or Hunter? I've heard that these provide better temp resistance than other ball powders.

Seems like those'd be great for a "best of both worlds" solution to this issue.

The temperature tolerance promoted by Ramshot powders has nothing to do with combustion temperatures and barrel temperatures, it's all about consistency in varying environmental conditions.

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.

 

[JD338]

RR

That is good info, thanks for the heads up.

JD338

 

[Hegland]

Last time I checked, temperature and pressure are directly linked---at least this is the nonsense they taught me in my mechanical engineering classes.

Yeah, they always give IGL practice problems for some imaginary vessel of abstract size and shape; this would have been a much better illustration. 8)

 

[glane5910]

I'd think it would stand to reason then that the lower pressure/temps by "X" powder would cause less throat erosion? Throat erosion is basically the #1 enemy of bbl life/accuracy correct?

 

[FOTIS]

Absolutely! :wink:

 

[atmoshpere]

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?

 

[wingnut]

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?

Pic's via QuickLoad:

26 inch barrel, speed ~3060 fps: