Lost 100 fps after 550 rounds

[Longtine88]

Plus he could have reduced the friction of the bore and dropped the pressure and speed.

 

[L.Sherm]

It is well know when barrels start approaching the end of there life they slow down alot, simple reason friction from firecracking

 

[L.Sherm]

Plus he could have reduced the friction of the bore and dropped the pressure and speed.

Why does firecracking strip off copper

 

[Longtine88]

Why does firecracking strip off copper

I was replying to Kimber's post. But for some reason the reply didn't pop in there. Confusion sorry

 

[jjmp]

It's ruff ,uneven

 

[Mc Fraser]

Have you measured the distance to the lands of your rifling now with the same bullets you are using? As the rifling in the lands erodes, the bullet has more "jump" before it contacts the lands which decreases the pressure of your loads and therefore decreases the velocity of your load. If you measure the lands and seat the bullets further out where it's back to however far off the lands you were to begin with, it should bring your pressure and velocity back to where you were originally.

I'll do that, thanks for the idea.

If I had to guess I'd say the difference in fps is due to the difference in powder lots. I always try to buy powder in the biggest quantity that I can of the same lot number. It seems every time I change lot numbers I need to re-visit the load to change something to get velocity or accuracy back to what it was with the first lot. I just bought H-4895, I couldn't find it in bigger than 1# containers, but all 4 containers that I got were the same lot number.

If throat erosion was the culprit, wouldn't the OP see a gradual change over time, not a huge difference from one shooting session to another? Throat erosion is also a function of how hot you get the barrel during your shooting sessions. Since I am not a target shooter where I have to get all my shots in during a certain time limit if the barrel is too hot to rest my hand on it as close to the chamber as possible, I stop shooting until the barrel cools back down.

When I bought the 7mm Allen Magnum, I bought enough powder and primers of the same lot number to last for at least 1,500 shots.

I never had issues with temp stable powders and different lots.

OP, 600 rounds of 570 and expect your bore to look like a sewer pipe, flyers are the first sign that the barrel is approaching the end. If you are running a hot rod and love running a hot rod, then just ante up the pot by having several barrels chambered at the same time.

I learned a hard lesson on 570, 560, and 550...$2000 later, I figured it out!

Having multiple barrels chambered with the same reamer, and same barrel maker, the first is a sacrificial lamb on load development, the second is for hunting and verifying zero from year to year with long barrel life.

I have never seen the downside in ordering 3 barrel blanks at a time in the caliber I like to shoot along with the reamer design I prefer.

I don't mind burning a barrel, I just didn't know what was wrong with it.

 

[VinceMule]

Teslong bore scope, measuring to the lands now vs new will both be an eye opener. Excessive fouling can crop up it's ugly head also.

 

[DDB TX]

How about the brass? Different makers? New vs. 3x used? Full length vs. neck sized?

 

[QuietTexan]

I agree with what's been said - CF Barrel + N570 = throat is toasty, barrel is done pending accuracy loss IMO.

Two points:
1 - if it groups then a 100FPS loss isn't anything to worry about. Negligible ballistic change to me, if the 100 FPS is super critical then the easier answer is next time step up cartridge size, 30 Sherman, 300 RUM, something like that, so that as the barrel dies you keep what you need. Can also run slower out of the gate or use a different powder and maybe it lasts longer.

2- Great chance to bore scope the barrel (I take videos via my Teslong camera), and clean in ways you would never have thought to before. There's no risk since it's almost dead right? So try the red Iosso, try a steel brush, try Tubbs lapping bullets, something you've heard about but never wanted to risk in a good barrel. I was surprised how none of the bad things I read about on the internet happened (ie nylon brushes carving grooves in the rifling) and how much easier some of the things I learned made my life.

 

[Idaho Lefty]

bout' NOW, some of you guys might start to realize, WHY,.. the 6.5 CreedMOOR is SO,.. freakin' Popular !
Loo'ong, long,.. Barrel Life,.

 

[Phil Rizzo]

The reason the barrel lasts longer on a CM is because it is so lackluster in performance. nothing new, look at .308 Win
Dude has a .300 PRC here…

Would his choice of bore paste do anything to polish the fire cracks? The one he is already using.

 

[L.Sherm]

Would his choice of bore paste do anything to polish the fire cracks?

It could help the copper stripping if done properly but its not gonna help get 100fps back possible a little.

 

[Idaho Lefty]

@ Phil,..
For Deer, Antelope, coyotes and LOW Recoil Practice, on Steel,.. way out there,.. I use the 6.5 Creed.
For Elk Moose,.. the .270 WSM, 6.5 PRC, 7 Magnums etc.,.. ARE Plenty !
I've skipped over, the .308 as IT's,.. NOT,. really necessary for,.. My uses

 

[Phil Rizzo]

@ Phil,..
For Deer, Antelope, coyotes and LOW Recoil Practice, on Steel,.. way out there,.. I use the 6.5 Creed.
For Elk Moose,.. the .270 WSM, 6.5 PRC, 7 Magnums etc.,.. ARE Plenty !
I've skipped over, the .308 as IT's,.. NOT,. really necessary for,.. My uses

I'm happy for you, bare minimum speed isn't my first choice though. For anything in life.
It would however be my last choice.
You and I are talking about the 6.5 CM that you brought up, not the excellent choices you list under it.
Recoil, barrel wear and extra expense go along with the performance I desire.
and I'm happy with it also.
Im thankful we have options.