shooting a 308 light loads to max on barrel life

[dataforce1@gmail.com]

Hi,

Yesterday range session shot 168 Sierra Matchking and Varget. Loads were 42 grains to 46 grains max in Sierra manual. Barrel is Bartlein bull sporter. Action is 788. I pier bedded the old Remington 788 stock.

Brass is remington, remington large rifle primers, Seated .018 off lands. BTW the sierra manual says 43.5 max for 168 bullet. The IMR Data site says 46gr. for same bullet.

Best 100 yd. 3 shot groups: .33 w/ 42 gr, .44 w/42.5, .42 w/ 43gr, .25 w/ 44gr, .21w/ 46. 3 shots sessions with 45gr, and 45. 5 were both .60. (shooter not gun)

Here is my question: does it make a significant difference on barrel life to shoot lighter loads? This case would be 42 to 44 vs. max load of 46 gr. varget. I would shoot lighter for practice, and range work. I would go w/ max to hunt hogs.

This is my first custom barrel and I have not been able to find the very, very best load. (altho the .21 is pretty good.) the rifle seems to have a broad sweet spot. Other rifles loved a specific load, this one shoots well with several loads.

And or, is the .21 OK, and experiment w/ seating depth, brass, primers?

And for load testing I shoot 2, 3 round groups. Should I use a larger sample, say 3, 3 shot groups and take average?

 

[bigedp51]

At 43,000 cup the peak flame temperature is reaching the melting point of modern barrel steel.

Keep your loads in the 30-30 range of 38,000 to 40,000 cup and you will have longer barrel life.

 

[amlevin]

When anyone mentions the "peak flame temperatures" and their "approaching the melting point" I always wonder just how hot these flame temperatures are.

I do know that 416 SS Steel allow has a melting point of 2700+ degrees. Just what are some of these "peak flame temperatures"????

 

[bigedp51]

When anyone mentions the "peak flame temperatures" and their "approaching the melting point" I always wonder just how hot these flame temperatures are.

I do know that 416 SS Steel allow has a melting point of 2700+ degrees. Just what are some of these "peak flame temperatures"????

That would depend on the type powder being used, normally a double base powder will burn hotter depending on the nitroglycerin percentage and what deterrents are added. If you want to burn a barrel out quickly just load some early cordite powder with 45% nitroglycerin.

 

[amlevin]

When anyone mentions the "peak flame temperatures" and their "approaching the melting point" I always wonder just how hot these flame temperatures are.

I do know that 416 SS Steel allow has a melting point of 2700+ degrees. Just what are some of these "peak flame temperatures"????

That would depend on the type powder being used, normally a double base powder will burn hotter depending on the nitroglycerin percentage and what deterrents are added. If you want to burn a barrel out quickly just load some early cordite powder with 45% nitroglycerin.

True, it would also depend on the material the barrel is made of and if it's chrome lined or not.

Still interested in just exactly what "temperatures" are involved rather than "Hot", "Hotter", "Hottest", and "Holy S---". Certainly someone out there has access to the heat of combustion for any of the commonly used powders presented in "numbers" not adjectives.

 

[bigedp51]

When anyone mentions the "peak flame temperatures" and their "approaching the melting point" I always wonder just how hot these flame temperatures are.

I do know that 416 SS Steel allow has a melting point of 2700+ degrees. Just what are some of these "peak flame temperatures"????

That would depend on the type powder being used, normally a double base powder will burn hotter depending on the nitroglycerin percentage and what deterrents are added. If you want to burn a barrel out quickly just load some early cordite powder with 45% nitroglycerin.

True, it would also depend on the material the barrel is made of and if it's chrome lined or not.

Still interested in just exactly what "temperatures" are involved rather than "Hot", "Hotter", "Hottest", and "Holy S---". Certainly someone out there has access to the heat of combustion for any of the commonly used powders presented in "numbers" not adjectives.

From Understanding Firearm Ballistics 6th edition, by Robert A Rinker
Pg 29 second paragraph

"Pressures of 55,000 psi are common at the peak but may drop to 6,000 psi by the time the bullet reaches the muzzle. With most powder, the flame temperature will reach about 5,550 degrees F at the peak pressure. Most barrel steel will melt at half that temp or about 2,500 F."

 

[dataforce1@gmail.com]

Hi thanks for replies.

I now believe my post to be silly. I got a 308 not a 30-30 and will load the sucker to fullest capabilities of the caliber. Barrel burns out in 6 months
or 6 years, so be it.

 

[amlevin]

"Pressures of 55,000 psi are common at the peak but may drop to 6,000 psi by the time the bullet reaches the muzzle. With most powder, the flame temperature will reach about 5,550 degrees F at the peak pressure. Most barrel steel will melt at half that temp or about 2,500 F."

Thank you for that. Now, consider how much time the steel is subjected to that temperature.

I maintain that the mechanical stresses of a bullet hitting the throat are a far greater factor than the millisecond or so the temp reaches or exceeds the melting point. Have you ever cast bullets and put a reject back in the pot? Does it melt instantly? Or does it take time, more than a millisecond or two?

 

[nastynatesfish]

It doesn't make much sense to shoot to practice what your not gonna be shooting at normal times? If your shooting any distance your trajectory will be different as to drift. I think unless your trying to teach someone who is recoil sensitive I'd shoot regular charge loads. Fwiw

 

[Dgd6mm]

Shooting Sports = Expendables... With that being said I shoot Nitrated barrels and 6CM's with H-1000 for extended barrel life. Then on some other cartridges not so easy on barrels. I know this going into the build. I played with some #'s on QL this AM looking at a lower accuracy node for my .308 and all pressure ran between 38,000 - 44,000 PSI. So from what biged said you have an option. Hope I did not get to far off topic.

 

[jo191145]

Hi thanks for replies.

I now believe my post to be silly. I got a 308 not a 30-30 and will load the sucker to fullest capabilities of the caliber. Barrel burns out in 6 months
or 6 years, so be it.

JMO's
There you go, your on the right track although the question was not silly.
My original smart a$$ response might have been Hang it on the wall it will last forever ;D

The easiest way to shorten barrel life is to expend enourmous amounts of ammo in a short amount of time.
Keep the barrel from running red hot and you'll never notice the difference between a few grains of powder.
The 308W is not a barrel burner.

Your accuracy seems to be spot on. A few more five shot groups to verify consistency and I'd say your just about done tweaking.
Thats assuming this guns main use is hog whacking.
Might want to move out a little further for testing. See what it really does.
How much practice, tweaking you decide to do is entirely up to you of course.

Still JMO. If it were me I'd think twice about using the SMK on hogs. I realize they're vermin but if Hogzilla comes charging out of the bush I'd want something designed to penetrate bone and flesh with controlled expansion. Match bullets just aren't designed for that.

Happy hunting, sounds like fun.