Opinions wanted, or facts...About 6.5x284 or 260 barrel life

[Mikecr]

I agree with Grayfox.
But to clarify a mis-notion elsewhere, the 6.5x284 is capable of way more MV than a 260.
3000+fps is NOT hot for it at all.

I shoot a 6.5wssm imp holding same capacity as a 260AI. My accuracy load with a 28" barrel is 3040fps with 140gr bullets, and I do not FL size -ever. My max, the point where FL sizing would be needed, is over 3200fps. Some would call this hot, some would just FL size and go onward.
The 6.5x284 holds 11gr more H20 capacity, so it can leave me in the dust easily.

Nothing is free.
Yet the melonite coating seems potential for gain in barrel life.
So what is it's real cost?
Hopefully, whatever it is, won't matter to us..

 

[Trickymissfit]

I had the opportunity to meet John Hoover the other day at his shop. He is a very knowledge on the 6.5x284. From my understanding, one of the best. After reading this thread, it made me remember the interview he did. If you haven't read this article it is a pretty good read on the 6.5x284.

6.5-284s of the Hoover Clan

If you don't want to read the entire article, this question was related to barrel life.

Q: Barrel wear is an issue with the 6.5-284. What can be done to extend useful barrel life?

"If you slack off one place you're going to pay elsewhere. If you reduce your velocity you will suffer downrange. Most top competitors are willing to replace barrels after 800 rounds or so--that's just part of the game. I will say, however, that I've had good results with setting back barrels. We used to do that part-way through a season. Recently we've gone a full season before setting back the barrel about 1". I've seen no significant loss in velocity or accuracy from setting back the barrel from 30" to 29" or so. In fact, I'd say pretty much every time we've set back a barrel it shot as well or better than before. And it continues to shoot accurately for many hundreds of rounds. Depending on how much shooting you do between matches, you may be able to extend your barrel's life from one season to nearly two."

After speaking with Mr. Hoover about the 6.5x284 and discussing velocity, he indicated the magic number they strive for when shooting is 2950 FPS.

the problem with both the .260 and the 6.5/284 is too short of a neck length. Although the .284 case has a better shoulder angle. Thenyou add into fact that the 6.5/284 is pretty much overbore, but not to the extreme like a.264 mag. Even the 6.5-06 is a little overbore as well. But it has a much longer neck length to help with the barrell life. The 6.5-06AI should have a much longer barrel life than either of the other two, but will also require a long action. The 6.5x55 will fit in a short action, and is not in an overbore condition. The 6.5x57AI would be even better but you'll run into about .04 case shrinkage when fire forming. This puts you right back into the short neck syndrome. But a 6.5x55AI reamed with a .33" neck length would be easilly better than any round discussed here (that's why I said to use the 57mm case as a parent case). I think it could well be the best 6.5 round period. Just ream the chamber short with a 6.5-06AI reamer for a 6.5x55AI headspace. (all Ackley cases have the same taper per inch and the same shoulder angle)
gary

 

[Bart B]

The rate that a barrel burns out is largely a function of the amount of powder burned in relation to the bore size.

Over four decades of high power competition, I noted how long barrels lasted for the top competitors. Their barrels started out with 1/4 MOA accuracy at 200 yards. Calibers ranged from 30 down to 24. Did some research on what the benchrester's 22 and 24 caliber barrels did for barrel life as well. Then I took the data and came up with a formula that uses powder charge weight in grains and the bore's cross sectional area in square millimeters. One thing stood out among all others; when 1 grain of powder was used for each square millimeter of the bore area, accuracy at this level lasted for about 3000 rounds. Some of the top competitors would notice that after about 1500 rounds, the accuracy had degraded about 20 to 30 percent; 'twas about 5/16 MOA accuracy at that point. Good enough for all but the top level matches such as the Nationals and Regional ones. Sierra Bullets' tech agreed with my calculations; their .308 Win. test barrels got replaced at about 3000 rounds and holding about 1/4 MOA accuracy burning one grain of powde for each of its bore area of 46 square millimeters.

A 6.5mm bore has about 33 square millimeters of area. Cartridges burning 33 grains of powder shooting 1/4 MOA will get about 3000 rounds of barrel life. Increase the powder charge 41% and barrel life gets cut in half. Double it and life is now one fourth as much.

No wonder the .243 Win. case got about 1500 rounds of best accuracy when it was first used. The top barrel makers agreed with this when I asked them what the .,243 was getting in their barrels. Its "bore capacity (area)" is 28 grains. But the 6PPC round in benchrest gets about 3000 rounds of good accuracy burning 28 grains of powder.

The 6.5x.284 has a bore area of 33 square millimeters. Burning 47 or so grains of powder's been producing about 1500 rounds of best accuracy in competition. And benchresters using this round sometimes rebarrel at 700 to 800 rounds when they see it's accuracy drop off a bit. My own 6.5mm barrel, a .264 Win. Mag., lasted 640 rounds of best accuracy burning 72 grains of powder for each shot.

For rifles getting around 1/2 MOA accuracy, barrel life will be about twice as much. A 1 MOA rifle and ammo may well get three to four times as many rounds of barrel life before loss of accuracy's noticed.

 

[TOM H]

Well since this post was started last year it seem the OP had a 6.5x284 build.

Old 02-14-2012, 03:56 PM
Michael Eichele Michael Eichele is offline
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Re: MORE SPECIFICS on 6.5x284 and different powders
Derek,

Keep us posted. I am in the exact same boat as you are. Mine will finish to 27". Like you, I am looking for a hunting length rifle but would also like to maximize my velocity potential. We want our cake and to be able to eat it as well right? Right!
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[Greyfox]

Over four decades of high power competition, I noted how long barrels lasted for the top competitors.................... A 1 MOA rifle and ammo may well get three to four times as many rounds of barrel life before loss of accuracy's noticed.

I didn't realize that you are "that" Bart. I ran across your formula years back when I was doing a lot of 308 target shooting. I think it's the only comprehensive study that's been conducted on barrel life, and your formula tied very closely to what I have experienced with barrel life. Nice work!

 

[TOM H]

I didn't realize that you are "that" Bart. I ran across your formula years back when I was doing a lot of 308 target shooting. I think it's the only comprehensive study that's been conducted on barrel life, and your formula tied very closely to what I have experienced with barrel life. Nice work!

You mean Bart Bobbitt if he is he should admit it

Barrel life (Bart Bobbitt)

 

[Bart B]

You mean Bart Bobbitt if he is he should admit it

OK, I have no problem admitting I'm me. I did that thread years ago when I did engineering and documentation work at Hewlett-Packard.

One thing I should comment on is that rapid firing problably doesn't cause as much acceleration in barrel wear as excessive peak pressure does. Boots Obermeyer (barrel maker par excellence!) gave me some interesting data that backs that up. He claimed that all those hot-rodders loading ammo to pressures far above the 55,000 CUP range do far more damage fire cracking the rifling's leade such that bullets really get unbalanced in their first inch of travel down the bore.

My formula doesn't work for .22 rimfire cartridges. Before the mid 1980's when all the factories changed their priming mixture formula, folks shooting the best scores in competition got 50,000 to 60,000 rounds of 1/2 MOA accuracy at 100 yards with their standard velocity .22 long rifle match ammo. A deadly explosion at Eley's plant in Great Britian caused priming mixtures to change and have more glass frit as the filler. The new mixture caused more throat erosion (and less accuracy) and barrel life's been about 30,000 rounds since. And virtually all the records set before then still stand as it's virtually impossible nowadays go get ammo that'll shoot under 3/4 MOA at a hunderd.

 

[Trickymissfit]

Over four decades of high power competition, I noted how long barrels lasted for the top competitors. Their barrels started out with 1/4 MOA accuracy at 200 yards. Calibers ranged from 30 down to 24. Did some research on what the benchrester's 22 and 24 caliber barrels did for barrel life as well. Then I took the data and came up with a formula that uses powder charge weight in grains and the bore's cross sectional area in square millimeters. One thing stood out among all others; when 1 grain of powder was used for each square millimeter of the bore area, accuracy at this level lasted for about 3000 rounds. Some of the top competitors would notice that after about 1500 rounds, the accuracy had degraded about 20 to 30 percent; 'twas about 5/16 MOA accuracy at that point. Good enough for all but the top level matches such as the Nationals and Regional ones. Sierra Bullets' tech agreed with my calculations; their .308 Win. test barrels got replaced at about 3000 rounds and holding about 1/4 MOA accuracy burning one grain of powde for each of its bore area of 46 square millimeters.

A 6.5mm bore has about 33 square millimeters of area. Cartridges burning 33 grains of powder shooting 1/4 MOA will get about 3000 rounds of barrel life. Increase the powder charge 41% and barrel life gets cut in half. Double it and life is now one fourth as much.

No wonder the .243 Win. case got about 1500 rounds of best accuracy when it was first used. The top barrel makers agreed with this when I asked them what the .,243 was getting in their barrels. Its "bore capacity (area)" is 28 grains. But the 6PPC round in benchrest gets about 3000 rounds of good accuracy burning 28 grains of powder.

The 6.5x.284 has a bore area of 33 square millimeters. Burning 47 or so grains of powder's been producing about 1500 rounds of best accuracy in competition. And benchresters using this round sometimes rebarrel at 700 to 800 rounds when they see it's accuracy drop off a bit. My own 6.5mm barrel, a .264 Win. Mag., lasted 640 rounds of best accuracy burning 72 grains of powder for each shot.

For rifles getting around 1/2 MOA accuracy, barrel life will be about twice as much. A 1 MOA rifle and ammo may well get three to four times as many rounds of barrel life before loss of accuracy's noticed.

agree with your thoughts, but you also must have a way to factor in the shoulder angle and neck length in there too. How I am not sure. Still basicly your ideas are sound. But also assuming that all shoulders and neck lengths are generic. We all know that the 35 and 40 degree angled shoulder produces a longer throat life in the chamber, and add a minimum of 1.25 cailbers for a neck length you will see a certain increase in barrel life. One other thing that may become an issue here is that some powders just seem to burn hotter than others do. Probably need to take a few minutes and read what Ackley published a few years back on bore capacity. I imagine it parallels your thoughts
gary

 

[Bart B]

agree with your thoughts, but you also must have a way to factor in the shoulder angle and neck length in there too. How I am not sure. Still basicly your ideas are sound. But also assuming that all shoulders and neck lengths are generic. We all know that the 35 and 40 degree angled shoulder produces a longer throat life in the chamber, and add a minimum of 1.25 cailbers for a neck length you will see a certain increase in barrel life.

The shape and size of the shoulder and neck will determint the temperature, shape and size of the flame's jet effect going out of the case mouth. Same thing's used in military jet engines to change the shape of the exhaust for different speeds in flight. Check out:

Propelling nozzle - Wikipedia, the free encyclopedia

for details. I'm reasonably sure that would effect bore erosion in the leade.

There's other factors, too, including the details of how one tests for and determines barrel life. And I really don't think "we all" know that. Surely, there's a few (a lot?) that don't know that.

 

[Trickymissfit]

OK, I have no problem admitting I'm me. I did that thread years ago when I did engineering and documentation work at Hewlett-Packard.

One thing I should comment on is that rapid firing problably doesn't cause as much acceleration in barrel wear as excessive peak pressure does. Boots Obermeyer (barrel maker par excellence!) gave me some interesting data that backs that up. He claimed that all those hot-rodders loading ammo to pressures far above the 55,000 CUP range do far more damage fire cracking the rifling's leade such that bullets really get unbalanced in their first inch of travel down the bore.

My formula doesn't work for .22 rimfire cartridges. Before the mid 1980's when all the factories changed their priming mixture formula, folks shooting the best scores in competition got 50,000 to 60,000 rounds of 1/2 MOA accuracy at 100 yards with their standard velocity .22 long rifle match ammo. A deadly explosion at Eley's plant in Great Britian caused priming mixtures to change and have more glass frit as the filler. The new mixture caused more throat erosion (and less accuracy) and barrel life's been about 30,000 rounds since. And virtually all the records set before then still stand as it's virtually impossible nowadays go get ammo that'll shoot under 3/4 MOA at a hunderd.

last time I was down at Borden everybody (well almost everbody) was using Federal Olympic Gold Medal Match ammo from certain lot numbers. Barrel life I don't know, but these guys were shooting well over 10K rounds a year on their barrels. Old Bill turned us onto the Federal stuff the first trip down there, and we never looked back. But even then we never seriously ran with those big dogs! (we did get a couple top five finishes) Shooting 100BR in rimfire is harder than most folks can imagine! I played with it for years, but the best groups were always in the very low eights for me, and that was with a certain lot of RWS. I ran into several constant nagging problems doing this, and the lead ring liked to drove me nuts! The bullets were cast (or swedged) out of an alloy that was just a little too soft for me. With a tuner (they call them "tunas") Tony was shooting a constant mid twos at fifty yards, and would often dip into the very high ones. Great groups, but second class down there! You know it's stiff when the guys with a 40XBR finish #20 in a field of twenty!

I gave it up when I could no longer afford the ammo. At $13 dollars for fifty rounds it just got out of my budgit. Have not talked with Tony in several years now (close to six), so I don't now what he's doing now. If I could buy ammo for four dollars a box of fifty, I might get back into it again. You spend $2500 on a good bare rifle build (no sights), and another $1200 on optics (some guys have close to $5K in them); you suddenly find that you can't afford a couple bricks of ammo.
gary