Lapua Once Fired Cracks

[Old Navy]

I decided I wanted to get back to shooting my 6.5X284. Had a Savage large shank barrel in the closet I took off my Model 12 Benchrest a couple years ago. I installed it with .002" headspace. I opened a new box of Lapua that just came in today. Loaded some 142 SMK up with three different powders and seated them right at the lands. First two three shots groups were my original best shooter when I took the barrel off. 51.5 H4831 SC. All was well. Primers looked good and easy lift. Third group was 48 grains of H4350. Also looked good. While the barrel was cooling I put my reading glasses on for a better look. That is when I noticed the cracks in the photo. They are deep enough to catch them with my fingernail. They run about 3/4 around the neck. I have never seen or read anything here like this. I know the first thing you guys will ask is if I scoped the barrel. Got the note pad out. Bad battery. Charged battery and hooked up Tslong. Must have a broken wire. Kept cutting on and off but I finally got a few good photos. What a day. Hope you guys can help me decide whether it is the barrel or brass.

 

[ebb]

That is not a crack, that looks to be a flaw in the chamber making that imprint in the neck.

 

[AlNyhus]

Get a look at the neck area of the chamber. -Al

 

[Hoot]

Per QuickLoad, that's not a terribly hot load. Looks too identical to be cracks. They're rarely that identical a manifestation. You didn't say what you saw in the neck of the chamber, with the Teslong. Sure looks like a precise scoring that might occur from some sharpie.

Hoot

 

[tac284]

Is it just me or does the top half of the neck look smaller than the bottom half?

 

[Old Navy]

That is not a crack, that looks to be a flaw in the chamber making that imprint in the neck.

That was my first impression to. This barrel had several hundred rounds through it before I took it off. It is a Savage and they look rough inside. I had a high spot right at the datum line on a 6 BR. I di d get after the neck with JB on a patch on a bronze brush for a few minutes and fired another round. No change. Right while I was typing this a light bulb went off between my ears. I got reading on the fired case necks of .303" with a mic. That didn't sound right. I just measured the cases below and above the cuts with my vernier caliper . .3025 to .303' below and .2945 to .295" above. What the hell kind of mess do I have?

 

[Hammer101st]

Would a carbon ring do that? I have seen alot of srewed up chambers but that looks like the neck was never finished or bad reamer

 

[Webster]

I decided I wanted to get back to shooting my 6.5X284. Had a Savage large shank barrel in the closet I took off my Model 12 Benchrest a couple years ago. I installed it with .002" headspace. I opened a new box of Lapua that just came in today. Loaded some 142 SMK up with three different powders and seated them right at the lands. First two three shots groups were my original best shooter when I took the barrel off. 51.5 H4831 SC. All was well. Primers looked good and easy lift. Third group was 48 grains of H4350. Also looked good. While the barrel was cooling I put my reading glasses on for a better look. That is when I noticed the cracks in the photo. They are deep enough to catch them with my fingernail. They run about 3/4 around the neck. I have never seen or read anything here like this. I know the first thing you guys will ask is if I scoped the barrel. Got the note pad out. Bad battery. Charged battery and hooked up Tslong. Must have a broken wire. Kept cutting on and off but I finally got a few good photos. What a day. Hope you guys can help me decide whether it is the barrel or brass.

Cracks are not uniform straight lines. They must be scratches or you might call them gouges. Cannot image how they formed in a straight line uniform in depth. Cannot image a high point in the chamber. If there is one it should be easy to see. Do you get the lines if you chamber a round and extract without firing it?

 

[mac86951]

What's the chance there's a piece of neck or some such stuck in the chamber? Almost looks like a 284 reamer run into a 6.5 barrel, which might leave a generous neck; but if it was a chamber issue, I'd have thought you'd notice by now.

Got a bore scope?

-Mac

 

[Old Navy]

Is it just me or does the top half of the neck look smaller than the bottom half?

It is. Looks like I have a .008" step in the neck. The worst thing about this is I shot it several hundred times and didn't catch it before. I am goin to let this topic run a little more to get more input but it looks like I need to call James at Northland and buy a real barrel. I have several from him and they are all good shooters.

 

[Dusty Stevens]

Id like to know what you saw in the neck part of the chamber with the borescope.

 

[Old Navy]

Id like to know what you saw in the neck part of the chamber with the borescope.

Been wondering where you were. Did you catch the part about the step? I am going to cast the chamber tomorrow if I can find the directions for my Cerrosafe. Haven't made a cast in 20 years. The photos aren't very good. The lines are in the neck area.

 

[joshb]

Cerrosafe: Put a thin coat of oil on your chamber. I block the barrel with a cleaning rod and a small wad of steel wool. Pour in the cerrosafe to fill only the chamber. Count to 100 and push it out with the cleaning rod. Wait exactly an hour and measure away.

 

[Hoot]

i must say, this is one of the more interesting threads that I've seen around here recently. Makes me wonder how those other 3-shot groups managed to escape unfazed. Not to get off into the weeds but I'm curious how the three groups performed? IE, was the 4350 group a lot different than it's predecessors? Inquiring minds want to know...

Hoot

 

[Old Navy]

Cerrosafe: Put a thin coat of oil on your chamber. I block the barrel with a cleaning rod and a small wad of steel wool. Pour in the cerrosafe to fill only the chamber. Count to 100 and push it out with the cleaning rod. Wait exactly an hour and measure away.

Thanks. This cast should be something to see.

 

[243winxb]

Stepped chamber, like some pistols have. Size neck with bushing. Stop at line. May be the new hot setup.

 

[SKWERLZ]

Special 45% neck tension 6.5x284 reamer??

Lol
Sorry
Couldn’t resist.

Roughing reamer then bad finish reamer with short neck?

 

[HandgunHTR]

If I read your OP correctly this is a barrel you have shot before, correct? Or was it just on a gun that you had that got a new barrel and this one has just been sitting for a couple years untouched?
If it is the first (you have shot it before), I am at a loss as to why it didn’t show before and is now. An 0.008” step is significant.

 

[762willdo]

Can you take a paper clip and scrape the inside of the neck and feel the crack? If you can’t it’s a machining problem, if you can its a whole nother can of worms, my money says you can’t.

 

[Old Navy]

I made two chamber cast this morning. The cast shows a .007 to .0075" sharp step down. I let it cool an hour and got .3045" at the bottom and .2975" at the top. These are + - .0005" of course. I still can't believe I put 300 + rounds through this barrel the first time and never saw this. I have always cleaned my brass after every firing just to catch little problems before they turn into big problems. I did check some of the things you guys mentioned. Thanks for all the help. James at Northland Shooters is shipping me a new barrel today.