[CD Cash]

Hello to the list,

Quick question for all of you knowledgable folks out there. I have read in Brian Pearce's Articles(Cast Bullets in 44 Magnum in "Rifle's Handloader"?) that large doses of slow burning powders accelerate throat erosion and barrel wear in these 44 Mag. handguns. I hope I am not misquoting his article. My question regards us lever rifle shooters. Does this also apply to Lever Guns with similar or bottlenecked cartridges? Does a large dose of Slow Burning rifle powder such as IMR 4350, SR 4759 or IMR 4320 accelerate the wear in barrels as opposed to quicker burning powders? If so, why? In my 356 Win., 42.0 grains of IMR 4350 comes nearly to the top where the case neck begins, but the load seems to be very low pressure......with only 1700-1800 fps with a 200 gr. cast bullet, whereas Jacketed bullets of the same weight are pushed above 2400 fps with faster burning powders. I am also thinking of using the IMR 4350 in my dad's Swedish Mauser in 6.5X 55. Just wondering if anyone has ideas about powder burn rate and barrel wear as I had not thought about it much. I am a bit on the poor side and want to keep my guns shooting for as long as possible! I doubt I could wear them out but want to keep wear and tear to a minimum. Thanks for any ideas here.

 

[Jack Monteith]

Hi, CD:
This is my guess, since I'm not Homer Powley. A heavy load in a .44 Magnum means 20+ grains of 2400, H110 or W296, so the burn is in the barrel as well as the chamber. On the other hand, a hot load of say, Unique, uses half as much powder and pretty well burns in the cylinder. So the throat doesn't get as much abuse. The hot .357 Magnum 125 gr. loads with 20 grains of powder are noted for chewing up revolvers.

Rifles burn their powder in the barrel, so it comes down to more heat and pressure on the throat with a fast powder versus some sandblasting down the bore with a slower powder. The benchresters know that when accuracy's gone and the throat's burnt out, the muzzle end rifling still looks like new. So I'm inclined to think that the slower powder would save the barrel. Since neither the .358 or the 6.5 Swede are really high intensity rounds, I'd expect barrel life would be 5000 rounds for hunting accuracy. Sierra expects 3000+ rounds out of their .308 Winchester test barrels and they don't wait between shots to let the barrel cool off. Hornady #3 discusses a 7mm Remington that was worn out after 2000 rounds. So I'd worry more about accuracy, terminal performance and availably and cost of componets.

Bye
Jack

 

[CD Cash]

Thanks Jack!

I very much appreciate your expertise on the matter and you taking the time to explain it. Sounds about right and makes sense. I'll guess I'll stick to what is working.....the slow burners from here on out and not worry about the rest....except the factors you mentioned. I want to try the SR 4759 next and see if it improves accuracy with these RCBS 200 gr. FNGC's. I just added a Williams Reciever site which I can't wait to try out also. Many thanks again for your help. I have learned so much on this site.

 

[IDShooter]

CD,
I have tried to research this topic as well. The two main things that cause throat erosion are high pressure and a large case size-to-bore ratio, with the worst situation being a combination of both. It seems high pressure is an important component in rapid wear. With your .356 at the velocities you mention I don't think wear should be major concern. The jacketed loads will obviously create more pressure and wear but the .356 isn't a high case-to-bore ratio cartridge so I think you'd be fine.
If I remember right, the 44 Brian Pearce talked about had MANY rounds through it, like 10's of thousands. Maybe I'm remembering parts of more than one article. Anyway, I think if you mostly shoot light cast loads and save the high power stuff for it's intended usage a good revolver should last a long long time.

Happy shooting!! ID

 

[MikeG]

4350 works great in the Swede. Don't worry about it, it's not like you are shooting a Swift.

 

[Jack Monteith]

Hi, Gents:
The target rifle boys figure there's another factor affecting barrel life, or why a .243 Winchester won't hold target accuracy for a 1000 rounds, but a 6mm Remington does much better. Basically, the shoulder of the case forms part of a cone. If the peak of the whole cone is beyond the case mouth, you've got a barrel burner. If it's inside, the cartridge is easy on barrels. The theory is that the peak of turbulence happens here, and it's better to let the disposable case take the abuse than the barrel. Hope this makes sense.

Bye
Jack

 

[IDShooter]

Jack,
I've heard that before and it makes sense. What I would like to see are controlled experiments that actually test just one of these variables at a time. If anyone has conducted them I have not been able to find the data. I imagine that it is prohibitively expensive work with very little opportunity for recuping your investment.
ID

 

[alyeska338]

ID,
I think that would make great term project for your algebra class. I'm sure you could work in the use of some quadratic formulas to explain the results!!!

 

[Jack Monteith]

Hi, Gents:
Sounds like basic trig to me, but one gent got his sines and tangents mixed up in an article he wrote.

That's the kind of experiment P.O. Ackley would do at the drop of a hat. I'm no Ackley, but if you took a 6mm Remington barrel and another with a short necked chamber, but otherwise identical, and shot them, you should know in 500 rounds. Some of those target shooters measure their throats after every match.

Bye
Jack

 

[CD Cash]

Thanks to all you fellers. I so much appreciate the responses. I have definitely been enlightened on the subject here......pretty interesting what goes on inside a barrel. I had just never thought it about it much. Like IDShooter.....I don't have the time to shoot a whole lot now.....just time to think about these little mysteries! Many Thanks again.

 

[IDShooter]

Jack,
The 26 degree shoulder on a 6mm would require a VERY short neck. I think you'd have to alter the shoulder angle to match the 243, but still maintain equivalent case capacity to the 6mm. Of course, you'd have to use identical powder loaded to the same pressure. And your test barrels would need to be from the same manufacturer and to the same specs. Rate of fire would have to be the same. Temperature as well. Then I think it would be worthwhile to repeat the experiment with a powder of a different burning rate loaded to the same pressures. Then repeat the experiment with ball powder vs stick powder in the same burning rate range. Maybe single base vs. double base. Repeat all these trials at various pressure levels. Determine if chrome-moly erodes in the same way as stainless... Oh, the fun I could have!!!

Alyeska, do you suppose I could get a grant through the college??

ID

 

[alyeska338]

You could give Ruger, Brownchester, Remington, etal a call have them donate the firearms for the published findings, same with powder, primer, brass and bullet manufacturers. Shoot, you talk Dillon into donating a new free top o' line progressive press. Of course you call your test, xxxx steel corrosion/wear resistance when subjected to high velocity, intense heat environments and probably get some Democrat dollars. They would think you were testing bridge spans in the Mojave desert.... I would think the actions would have to be mapped and after every one hundred rounds or so, remapped to study the wear. This could be done with some type of CAD or GIS program. Of course you would need both raster and vector capabilities and I'm sure you could Autodesk and ESRI to donate the software for that. I don't think regular trig would handle it, may have to get into some integral calculus to figure the area or volume of wear induced (I doubt it would be geometric). But the CAD or GIS software would give the capability to push button calculate all that is needed. Easy, see...