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Author Topic: Question about case bulging from different powders for you reloading experts  (Read 1405 times)

Offline Bushcraft

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Drills don't make perfectly centered holes, particularly the longer the hole and longer the drill bit. Barrels are deep hole drilled before the rifling is cut in them. Accordingly, and most people don't realize this, that drilled hole down the center of your barrel isn't actually perfectly centered throughout the length of the barrel regardless of how much money you spend on one. Reamers  don't always make perfectly centered holes either depending on how they are setup. There could have been different hardnesses in the steel being chambered.  The lathe could be old and have excessive runout. The chamber could have been cut without being perfectly aligned with the bore (as it should be!). Reamers can cut out of round chambers if they aren't set up correctly. The reamer could have been used a lot and had asymmetric wear. Lot's of variables at play.  Really serious shooters will oftentimes buy a reamer cut to their exact specifications and it is ONLY used on their new barrels.


While most of those details are technically accurate on their own, it's misleading in the context of this thread and sounds like you know just enough to confuse the issue. For example - it doesn't matter if the barrel blank wasn't drilled perfectly centered, because the barrel's exterior dimensions are machined concentric to the hole afterwards, not concentric to the OD before drilling and rifling. While it's possible for a chamber to be off-center relative to the bolt, the things you list are not the causes, nor do we have any real reason to think the OP's chamber is off-center.

What the OP described is a simple and common phenomenon with generous factory rifle chambers. It's not unusual, it happens more than most people notice, and it's not a problem. No need to make a big deal out of something that doesn't matter.


Well, if you want to get technical, there's nothing I stated that's misleading.  Perhaps not perfectly descriptive and on point, but not misleading.

The OP originally wanted to know why there is a bulge in his brass.

You provided a reasonable guess as to why (which I don't necessarily disagree with BTW), but the commonality of the "phenomenon with generous factory rifle chambers" problem doesn't necessarily answer his question...particularly since he doesn't have a factory production barrel that's been speed cut with a dubious production reamer who's seen who knows how many chamberings.

Conversely, I provided some information that he may not have known about (which admittedly may not have been perfectly descriptive and on point).  And, I provided a very simple method that he could do at home that would allow him to see for himself if his chamber is out-of-round (which would more definitively address why his brass is bulged).  Who knows what technique his gunsmith used to ream the chamber? Some use different approaches than others.

Meanwhile, if the barrel shoots well enough to suit him...it's all moot anyway.

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For anyone reading this thread that may not know and wants to learn, a barrel's bore axis is almost never perfectly concentric to the outside of the barrel. Almost all rifle barrels, no matter how good they are, have a bore that looks like a snake as it travels through the steel (albeit very small amounts of curve). This means that while the very ends of a finished barrel exterior may be concentric to the centerline of the bore openings, but not necessarily be concentric to the bore axis.  Again, this is due to the fact that drills don't bore holes perfectly down a centered axis, the centerline of the bore is not always perfectly concentric to the exterior of the barrel. Any good smith knows this, a lot of precision rifle shooters know this, but 99% of firearm owners don't.  One can easily observe this by chopping a barrel up in short 2' sections sometime and chalk them up them in a lathe. The results might surprise some folks.

Here's a video that pretty clearly illustrates the non-too-subtle difference between a cheap factory barrel and the much tighter tolerances of a custom barrel.



 
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Offline gadwall

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Try a few loads with a powder that has a slower burn rate and with once or twice fired brass. :twocents:
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Offline Yondering

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Well, if you want to get technical, there's nothing I stated that's misleading. 

Your comments are misleading because they're irrelevant to the OP. Most of what you talked about has no impact on whether a barrel ends up with the chamber centered or not. Like the drilling thing - it doesn't matter because that happens before the outside of the barrel is machined.

As someone who turns my own barrels, it's clear that you do not, and are not even very familiar with the process other than watching some youtube videos. Like I said, you seem to know just enough to be dangerous.

Offline Bushcraft

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Well, if you want to get technical, there's nothing I stated that's misleading. 

Your comments are misleading because they're irrelevant to the OP. Most of what you talked about has no impact on whether a barrel ends up with the chamber centered or not. Like the drilling thing - it doesn't matter because that happens before the outside of the barrel is machined.

As someone who turns my own barrels, it's clear that you do not, and are not even very familiar with the process other than watching some youtube videos. Like I said, you seem to know just enough to be dangerous.

Dangerous?  Haha! Dude...I haven't recommended a single thing to the OP that is dangerous.

Not that I'm saying it's dangerous at all, but even though it's unlikely isn't it true that his chamber could very well be out of round?

Answer...Yes.

And if yes, wouldn't that explain why he has reoccurring bulges in his brass?

Answer...Yes.

And if yes, wouldn't that make your "it's no big deal it's just extractor pressure" answer absolutely misleading, particularly since this isn't a factory production barrel?

Answer...Also yes.

You're right about one thing though, even though it's been some time since I was formally trained on how to use big lathes and mills and could easily do the simple job on my own, I don't turn my own barrels.  I just let the pro's do it since I don't have the time, desire or room in my garage.

It's not at all hard so don't act like it's rocket science.

At least I offered to help the guy out with more information than what amounts to a dismissive shoulder shrug from you.

So whatever...carry on.
Liberalism is the philosophy of Western suicide. 

Work hard. Hunt hard. Lift other hunters up.

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