Switching bullets at end of barrel life

[trental]

I did a search but didn't didn't use the right terms, or couldn't find anything specific to the subject. What is the opinion on switching bullets to extend the useable life of a barrel? Do you switch to a heavier bullet or lighter? Longer or shorter? Secant, VLD, or Hybrid?

Or, in your opinion, does it NOT make a difference?

I have two scenarios.

Gun #1) Factory Savage 6.5 Creedmoor with over 0.080" of throat growth (under 1400 rounds) and started keyholing at 1000yd using Lapua 139 Scenar. It shot incredible well and then... POOF, went sideways. Obvious answer (to me) is a new barrel. But could a different bullet stabilize?

Gun #2) 6mm Creedmoor with very little throat growth (0.109" freebore) (about 1400 rounds), lots of fire-cracking in first few inches. This gun still shoots VERY well but is slowing down. I'm almost out of the 107gr SMK and have 500 115gr JLKs, and 1000 Berger 108gr BTs. Which bullet would best extract what is left of this barrel's life? New barrel is on order.

Don't take the questions about my two rifles too seriously.

The main question is "what type of bullet can squeeze the most life out of a tired barrel?" I'm guessing a lighter bullet.

 

[AckleymanII]

Often, going to a "fat" bullet with a larger shank dia and pressure ring can help. Biggest help comes from a bullet with more bearing surface of the same weight you are shooting....less vld.

Chronograph the barrel when it is new and you have found the tune with a particular bullet. As the accuracy drops from use, so does the velocity. Sometimes, you can add more powder to bring the pressure(speed) up to where it was in "tune", and the accuracy will come back, To SOME DEGREE.

Chasing the lands to maintain the same bullet jump when the barrel was newer and in tune is a given...often turning your rifle into a single shot or a two shot.

If the barrel in front of the throat has become rough, often smoothing up that rough surface will save bullets from blowing up...deep subject here.

Blowing up those 139's is serious consequences of something very bad going on, considering rough throat, barrel, and excessive copper as a result of.

 

[MagnumManiac]

Going to a heavier LONGER bullet helps a lot to extend barrel life.
It is the throat that has elongated, so the longer bullet travels further before exiting the case, allowing less blow by past the bullet base. This blow by can cause erratic pressure causing poor accuracy.

Cheers.

 

[hambone1971]

I did a search but didn't didn't use the right terms, or couldn't find anything specific to the subject. What is the opinion on switching bullets to extend the useable life of a barrel? Do you switch to a heavier bullet or lighter? Longer or shorter? Secant, VLD, or Hybrid?

Or, in your opinion, does it NOT make a difference?

I have two scenarios.

Gun #1) Factory Savage 6.5 Creedmoor with over 0.080" of throat growth (under 1400 rounds) and started keyholing at 1000yd using Lapua 139 Scenar. It shot incredible well and then... POOF, went sideways. Obvious answer (to me) is a new barrel. But could a different bullet stabilize?

Gun #2) 6mm Creedmoor with very little throat growth (0.109" freebore) (about 1400 rounds), lots of fire-cracking in first few inches. This gun still shoots VERY well but is slowing down. I'm almost out of the 107gr SMK and have 500 115gr JLKs, and 1000 Berger 108gr BTs. Which bullet would best extract what is left of this barrel's life? New barrel is on order.

Don't take the questions about my two rifles too seriously.

The main question is "what type of bullet can squeeze the most life out of a tired barrel?" I'm guessing a lighter bullet.

Cheaper to try a different bullet and powder.
I have a Savage 12 approching 6000 rounds now. Still almost 1/2 moa and I shoot it long range now and then with no keyhole etc. I shoot 147 ELD m and RL-16 most of the time.
I've lost about 100 fps in speed since new but if I use RL26 I get it back. Never have chased the lands it shoots good right where bullet was set when new. I did back off the powder about .1grain to keep it in the node it seems....Barrel timing I guess. Good luck .. HB

 

[Nick Caprinolo]

If it were me, I would have the barrels rechambered. Your gunsmith can design the chamber to your exact specifications. Load three dummy rounds that shot great when you first got the rifle and have him fit them to the chamber. Probably cost about $300 per rifle, but now you two brand new rifles. Shooting at 1,000 yards requires exacting standards.

 

[std7mag]

I'll admit to switching to a heavier bullet when the throat of my 7mm-08AI wouldn't allow me to seat a 140gr VLD close to the lands.
Switched to 168s and RL19 for a while.
Then got tired of those and rebarreled to a different cartridge.

 

[johnfred1965]

A flat base bullet will seal the worn throat and reduce blowby for a little while, but you may not want to use a flat base bullet at 1K. In 6mm. the DTAC rebated rim is said to mimic a flat base bullet in this regard.

I have heard of and seen many examples of rough savage factory barrels that copper foul badly. Have you tried a good scrubbing with copper solvent in your 6.5? JB paste can help too, and can smooth out a rough throat to some degree.

My .02

 

[centerlineseal]

Going to a heavier LONGER bullet helps a lot to extend barrel life.

My experience in an older 700 in 7mm RM and a much older 721 in 300 H&H. Went to 168gr Berger VLD Hunts in both. New life in both.

Could just have been another variable, as we did powder and bullet seating tests to fine tune. I learned that here on this site. Old dogs CAN learn new tricks!

Your experience may vary.

 

[searcher]

I've gotten some of my older barrels to shoot some of their best groups long after I would have thought them incapable. Logic says substitute with longer bullet to make up for the lost throat, though I have found that even lighter bullets that like to jump can be very accurate. Because your Scenars are keyholing, they are running out of steam faster than before. You will likely find that what was your "max charge" for that load is no longer. You may be able to bump it up enough to get your bullets supersonic to the range you were getting before the wear. I'd first try that - do a new ladder test on up till you run signs of pressure - before backing down to whatever you found that worked. You want to find out what your existing bullet is capable of all over again. I'd do it over a chronograph if you can, so you can see whether the bullet will meet your objective in staying supersonic and can still shoot good groups with a nice, wide accuracy node once you bump the velocity back up. Second thing I'd do is try to find a longer, heavier bullet with higher BC and give it a try, running your ladder all the way up. I have done this with a few barrels that were really toasted in the throat with very good results. I buy good stuff - but am not quick to discard it when the shine wears off. I repurpose most target barrels into varmint barrels. If it only shoots a "lousy" 1/4" to 3/8" MOA - the squirrels have yet to complain. Ha.

 

[searcher]

Another thing I have found effective is to use moly or HBN coated bullets. You can usually get a tad higher velocity when using them when adding a bit more more powder. The moly also mildly minimizes bullet scratching going through the nasty throat which is not much at all at close range - but every bullet scratch at 1000 means more.

 

[xswanted]

I have a dasher with about 1500 rounds down the tube.

105 Bergers were the go to until about 1400. Sierra Matchkings in 107 are now shooting very well, seated .020 off the rifling, which is as close as I can get them with the throat growth.

So I’ll use these for a another 500 rounds hopefully. Then she’ll be toast is my guess.