Fire Cracking and Barrel Heat

[6.5 forever]

The target is why I pulled the barrel, it just was no longer competitive as tuned. So rather than using up more H4895 and primers, I swapped it out for a new barrel that shoots half the size.

Jim

The best thing to do for sure.

 

[Shooter13]

The target is why I pulled the barrel, it just was no longer competitive as tuned. So rather than using up more H4895 and primers, I swapped it out for a new barrel that shoots half the size.

Jim

That sir is exactly why you change barrels!! Good luck with the new one!

 

[DaveTooley]

We all have reasons for retiring a barrel, or not. On my 1K BR rifles I would retire them every two years. I didn't want one to lay down on me just before the Nationals. If it's a rifle you use a lot . Plan ahead

 

[Webster]

A follow up question > when a barrel fire cracks it is said to be hard on reamers to re chamber or set back, so without assuming can some one explain just what’s going on that increases the level of difficulty and is the barrel now hardened like heat treating a tool ?

Dumb question I know..

I wish I still had an article probably published by the military. It explained the chemical and phase changes that occur at a very shallow depth at the surface. The analysis was just on carbon steel barrels. Most of use have SS barrels. You cannot temper most types of stainless steel. I will look for the article. There's no reason to really be concerned, it always happens and it's normal. It's actually called hot gas erosion.

https://apps.dtic.mil/sti/pdfs/ADA440938.pdf

52 page miltary research article on erosion. I don't think it gets into sophiticated analysis of chemical and metallurgical changes at the surface, Will look for another article on metallurgical changes.

 

[JFrank]

I may be high jacking this thread or maybe it’s just evolving, nevertheless IMHO there’s no point in working a dog that just won’t hunt.
The competition is just too stiff to mess around, last weekend our 1000 yard HG two target, top ten agg was separated by 1.089.
Even the best barrel, bullets and tune won’t win if you make a mistake with a wind call.

Jim

 

[6.5 forever]

I wish I still had an article probably published by the military. It explained the chemical and phase changes that occur at a very shallow depth at the surface. The analysis was just on carbon steel barrels. Most of use have SS barrels. You cannot temper most types of stainless steel. I will look for the article. There's no reason to really be concerned, it always happens and it's normal. It's actually called hot gas erosion.

https://apps.dtic.mil/sti/pdfs/ADA440938.pdf

52 page miltary research article on erosion. I don't think it gets into sophiticated analysis of chemical and metallurgical changes at the surface, Will look for another article on metallurgical changes.

It's always good to understand what is happening when all you can see is the result.

 

[gunsandgunsmithing]

I've spoken with some pretty sharp people on this subject and most agree that temp is a big factor BUT not the only factor. Under extreme heat, the bbl is also expanding and contracting under pressure. They, and I agree, this expansion and contracting plays a role in what we see on the shallow surface of the bore. So, I think attributing it only to heat, is likely not completely the case, but certainly it factors largely into it.

I'm playing with a couple of reamers now that may help in regard to the heat and flame aspect. I'm simply laying the 45° angle at the chamber case mouth..end of chamber, from 45° to 15°. The whole idea is a much larger heat sink area as well as a far smoother step for the flame to flow over, as opposed to a very abrupt 45° step. Time will tell. I have seen no detriment to accuracy but still early. Way too early to see what affect it may have on bbl life, but that's the main objective behind it.

I've mentioned this a few times but will again... When S&W introduced their big 500 Mag revolvers, flame cutting of the top strap of the frame, above the cylinder gap, was a real issue. Their engineers cured it by simply polishing the inside of that area of the frame, allowing the flame to smoothly flow over and around without the rough eges that were there before, which started the cut and exacerbated it. Same principle with these reamers. Pretty much exactly but carrying it a little further.

 

[FrankG]

If you're doing the work then maybe. If you have to pay someone then I wouldn't do it.

^^^^^ this right here!

Dave your lucky! I told a customer that one time and he went off on me!

To add to Dave's post.... if you don't mind Dave?

If you don't cut the whole breech end off and you still have some threads left and you have to pick up the thread timing... again even more work and time added.

Also the wear/cracking goes up further into the barrel than most people think it does. O.K. so you cut 1" off the breech end, rethread it, recut the breech cone and rechamber it... yes it does put you into some cleaner rifling but if you only got a 1k rounds out of the barrel new (I'm just picking a number based on some calibers) don't expect to get another 1k rounds out of it the 2nd go around. You’re lucky if you even get 50%. It's usually less than that.

Don't forget being as your redoing the breech end to flip the barrel around and touch up the crown.

So..... It's not worth doing as Dave said, "if you have to pay someone to do the work."

If your doing it yourself... and the time doesn't mean anything to ya... knock yourself out.

If I have to pay someone to do the work... I'm putting a new stick on the gun.

 

[kapt]

This is a Bartlein 6BR with 1500+ rounds of "Balls To The Wall" loads. Still shoots low .200 groups.
Borescopes will cause you to have panic attacks....

 

[LVLAaron]

Heat checking is impregnated with carbon from powder residue. Carbon is hard and shortens the life span of the throat area.

That's more or less how you case harden steel. Add heat and carbon.

 

[Old Navy]

I sold a really good low round count 6mm CM to a guy a last year. 7.5 twist Shilen Select Match large shank. It shot the 115s really small. Abought six weeks later he came back to buy a Model 12 BR action. I asked him how it shot for him. He said he didn't install it because it was worn out. I printed him the last couple pages of the spread sheet for the groups I shot. Mostly .2 to low .3". Some people should not be aloud to own bore scopes.

 

[JFrank]

This is a Bartlein 6BR with 1500+ rounds of "Balls To The Wall" loads. Still shoots low .200 groups.
Borescopes will cause you to have panic attacks....

The target is King.. doesn’t matter what the barrel looks like or how many rounds down it.

 

[gunsandgunsmithing]

That's more or less how you case harden steel. Add heat and carbon.

Yes, but it's not. I've got a couple of reamers that cut absolutely beautiful chambers that have also done multiple setbacks of some pretty terrible looking bbls. Not sure how much time plays a role in case hardening but it's not even close to a bbl bore in terms of hardness. If it was, those reamers would be junk before finishing the very FIRST setback. Instead, one is possibly the best I've ever had and still makes winning and pretty chambers/ throats. Go figure is all I can say.

 

[chop house]

The target is why I pulled the barrel, it just was no longer competitive as tuned. So rather than using up more H4895 and primers, I swapped it out for a new barrel that shoots half the size.

Jim

I didn't know whether to give this a smiley or a frown. Barrels get cheaper when rounds are a buck each...

 

[centershot]

I've spoken with some pretty sharp people on this subject and most agree that temp is a big factor BUT not the only factor. Under extreme heat, the bbl is also expanding and contracting under pressure. They, and I agree, this expansion and contracting plays a role in what we see on the shallow surface of the bore. So, I think attributing it only to heat, is likely not completely the case, but certainly it factors largely into it.

I'm playing with a couple of reamers now that may help in regard to the heat and flame aspect. I'm simply laying the 45° angle at the chamber case mouth..end of chamber, from 45° to 15°. The whole idea is a much larger heat sink area as well as a far smoother step for the flame to flow over, as opposed to a very abrupt 45° step. Time will tell. I have seen no detriment to accuracy but still early. Way too early to see what affect it may have on bbl life, but that's the main objective behind it.

I've mentioned this a few times but will again... When S&W introduced their big 500 Mag revolvers, flame cutting of the top strap of the frame, above the cylinder gap, was a real issue. Their engineers cured it by simply polishing the inside of that area of the frame, allowing the flame to smoothly flow over and around without the rough eges that were there before, which started the cut and exacerbated it. Same principle with these reamers. Pretty much exactly but carrying it a little further.

This was also a problem with the .357 Maximum. The top strap was cut.

 

[JFrank]

I didn't know whether to give this a smiley or a frown. Barrels get cheaper when rounds are a buck each...

No doubt’ H4895 is like gold right now. I still have about 400 108 bergers for that barrel left, I’m not sending my new vapor trails down it. Although I have a jug of IMR 4064 I’ve been thinking about that might shoot great for some short range fun. WTH the brass for that barrel is already prepped and primed.

 

[DaveTooley]

Consider I was ignorant about many things early in my career. I have observed a lot the last 25 years . It easy to address the big things. The subtle things that are linked to other subtle things, some can do the math and some can't. I know once a barrel is fire cracked you can never get all the carbon fouling out of those cracks. I also know from cleaning my SR BR after every group that if I first push a wet patch down the barrel to remove the loose powder fouling my brass bore brush will last twice as long. Also we use abrasives, sometimes aggressively, to remove carbon. The math says the carbon is an abrasive. I want the throat, the most critical of the reamer/chamber to stay fresh as long as possible. I take reamers out of service when the freebore, lead angle and the junction with the cylinder section show the first signs of wear. YMMV

 

[gunsandgunsmithing]

This was also a problem with the .357 Maximum. The top strap was cut.

I've heard that as well. The info I posted on the 500 came from an engineer at S&W. He didn't mention the 357 Max but yes, I've heard the same more than once now. That's one I've never owned. My all time favorite big revolver caliber is probably the 41 Magnum. Now back to our regular programming.

 

[6.5 forever]

Consider I was ignorant about many things early in my career. I have observed a lot the last 25 years . It easy to address the big things. The subtle things that are linked to other subtle things, some can do the math and some can't. I know once a barrel is fire cracked you can never get all the carbon fouling out of those cracks. I also know from cleaning my SR BR after every group that if I first push a wet patch down the barrel to remove the loose powder fouling my brass bore brush will last twice as long. Also we use abrasives, sometimes aggressively, to remove carbon. The math says the carbon is an abrasive. I want the throat, the most critical of the reamer/chamber to stay fresh as long as

possible. I take reamers out of service when the freebore, lead angle and the junction with the cylinder section show the first signs of wear. YMMV

Dave good information. How many barrels can you turn with a reamer?

 

[6.5 forever]

I've heard that as well. The info I posted on the 500 came from an engineer at S&W. He didn't mention the 357 Max but yes, I've heard the same more than once now. That's one I've never owned. My all time favorite big revolver caliber is probably the 41 Magnum. Now back to our regular programming.

You must be too young to be influenced by Elmer Keith! Lol

I think he played with the 41 a little bit.