When is a 6.5 CM chamber too large?

[SuperBruce]

Core question: for a 6.5 creedmoor, is a 0.006" oversized chamber diameter about a 1/3 inch from the case head too much? What should I expect from a barrel spun up by a smith wrt diameter tolerance?

Backstory
I recently had a 6.5 CM barrel spun up and took it out for the first time, shooting 140 ELDM and 143 ELDX Hornady factory ammo. The velocities were normal and the rifle grouped okay (not awful nor spectacular, about 1 MOA which isn't great but not a concern, yet) but the brass came out with a slight shinny ring (looked like slight roughness) but more concerning was bulged at 0.33" above the case base. Taking some calipers to it at the bulge shows a diameter of 0.478", and then it tapers back down to the case head (you can see this bulge by eye). Fired brass (also from the same box of Hornady factory ammo) from the old factory barrel measures [0.470 - 0.471"] at the same spot and doesn't have a "taper back down" property. The oversized brass requires significantly more force at the latter half of the stroke to resize (full length sizing die), consistent with the bulge. Btween headspace go/no-go gauges and using a comparator the headspace seems about 0.002" shorter on the new barrel but that seems totally fine, and maybe even a plus.
If I'm readying the SAAMI spec right, the chamber should have a diameter between [0.4714 - 0.4734] based on the 0.002" tolerance (please tell me I'm wrong if this isn't the right way to read the spec). If brass is coming out greater than 0.004" larger than the max then it's probably around 0.006" oversized after accounting for spring-back.

Thanks in advance.

 

[Evintos]

I don't know where you got 0.4734, chamber spec below for the section I think you're concerned about.

Couple questions, is the bulge just a single bulge like a single ring above the case head like in Fig. 1 or is it more like fig 2 the bulge starts about half an inch above the case head and extends down to the web of the case? Take a pic of your brass.

Fig 1.

Fig 2.

 

[Rob01]

Pictures?

 

[SuperBruce]

@Evintos, I got the upper bound of 0.4734 from adding the diameter tollerance of 0.002" found in the bottom right of the first image you posted to the diameter you highlighted by the breach end of the chamber. Wrt whether it looks like fig 1 or fig 2, I'd say it's closer to fig 2 but after measuring the base to the bulge is at 0.33" so that may be more in the spirit of fig 1.

@Rob01, @Evintos, of course you're right, a picture is worth a thousand words (other than the measurements ). The brass on the left is fired from the old barrel, the brass on the right is fired from the new barrel. Otherwise everything is the same, even the same box of Hornady 143 ELDx factory ammo. Key features that jumped out (to me, a non-expert) from the brass on the right is the shinny ring at 0.33" where the diameter maxes out at 0.478" and then (visibly) tapers back down the the case head diameter.

Thanks again for the help.

 

[KnowNothing256]

Yah that's a chamber problem. I'd reach out to whoever sold/chambered the barrel.

 

[Evintos]

Barrel screwed up for sure. Contact the smith and let them know.

 

[Rob01]

Yup get with the smith. Definitely an issue.

 

[spamassassin]

Yo dawg, we heard you like ruining brass. I'd be pretty pissed about that. That's a pretty obvious screw up that someone almost certainly knew about and let it ship anyway. If they didn't know about it then they're cutting chambers with an inexcusable lack of due care and attention and should not be trusted.

 

[SuperBruce]

Thanks everyone, I'll get in contact with the smith who I know will get this squared away.

For my own knowledge, what is the likely issue? I took a couple more measurements and the case body closest to the shoulder is essentially the same diameter between new and old barrel and the middle (by eyeballed) of the case body has a 0.003" greater diameter for the new barrel. Based on this excess slope of the case diameter I speculate that the reamer wasn't completely parallel to the axis of the barrel rotation but I've zero experience here so I'm mostly guessing.

 

[BuildingConceptsllc]

I've never seen anything like that. I would just try to get my money back and not want anything else from whoever chambered that.

How would a chamber with that shape get made that way? Anyone? I mean, that would be a lot of wobble going on or a reamer malfunction or something?

 

[Evintos]

Barrel not indicated properly in the chuck, reamer not indicated in the holder properly, tailstock center not indicated properly, reamer holder not secured in the tailstock, carelessness, combo of a bunch of things.

 

[UpSideDown]

Out of curiosity does a Go/No-Go gauge set check out in this barrel?

 

[gunsnjeeps]

BTW, smash the brass from that chamber. It'll be too stretched to reload. It almost looks like brass from a long chamber. Also, is there a ring on the neck of the brass or is that just in the picture.

 

[KnowNothing256]

Out of curiosity does a Go/No-Go gauge set check out in this barrel?

He mentioned go/no-gauges in the original post, and a chamber could show "good" using those gauges and still exhibit the problem OP describes. Those gauges aren't designed to check for a too-large chamber body, and they won't indicate it if it's there. They'd indicate a way-too-small chamber body, but not too-large.

 

[458win]

That’s some incredibly shoddy work. Is it safe yes. Will your brass last more then 2-3 firings? Probably not. To many people these days using that term gunsmith…

 

[SuperBruce]

I've never seen anything like that. I would just try to get my money back and not want anything else from whoever chambered that.

Maybe I'm just a sucker, we'll see, but I'm not hurting to get the rifle back soon so if it doesn't require more $ from me I don't see the harm in giving him the chance to fix things. He makes a lot of really good rifles for folks I know and as far as I've heard he is known to be a real honest guy.

Out of curiosity does a Go/No-Go gauge set check out in this barrel?

Yes, checked with a pair of go/no-go gauges and the headspace is fine. Based on comparing brass it's actually 0.002" tighter than the factory barrel (a Bergara HMR).

BTW, smash the brass from that chamber. It'll be to stretched to reload. It almost looks like brass from a long chamber. Also, is there a ring on the neck of the brass or is that just in the picture.

The necks are normal. It must be the picture which was intended to showcase the bases so it's a pretty poor angle for looking at the necks.

 

[UpSideDown]

Yeah it looks like @Evintos said, the cut looks like it was done with the reamer tail off-center and the chamber in the barrel has a steeper taper than it's supposed to, which shows in the case by blowing the whole case out until it gets to the thicker web at the base of the case where it tapers back down to near-original diameter. Barrel might be able to be set back and rechambered but it needs new machining, and the gunsmith needs to know what happened.

 

[SuperBruce]

Barrel might be able to be set back and rechambered but it needs new machining, and the gunsmith needs to know what happened.

Yeah, I'm a bit worried about that. The barrel is a sendero profile which only had 2" of shank to start with so there isn't a lot of meat left to keep cutting deeper.

 

[Barelstroker]

Maybe I'm just a sucker, we'll see, but I'm not hurting to get the rifle back soon so if it doesn't require more $ from me I don't see the harm in giving him the chance to fix things. He makes a lot of really good rifles for folks I know and as far as I've heard he is known to be a real honest guy.


Yes, checked with a pair of go/no-go gauges and the headspace is fine. Based on comparing brass it's actually 0.002" tighter than the factory barrel (a Bergara HMR).


The necks are normal. It must be the picture which was intended to showcase the bases so it's a pretty poor angle for looking at the necks.

I wouldn't get all Vanessa about the Gun Smith just yet.
I've seen that exact same issue in two rifles, one of which I still own & the other I sold a while back.
In both cases, one of the bolt lugs was barely making contact with it's lug abutment.
Lapping the the bolt lugs to even things up eliminated the case bulge issue for both rifles.
Now I'm not saying that the chamber definitely doesn't have issues but, there can definitely be other reasons.

 

[SuperBruce]

I wouldn't get all Vanessa about the Gun Smith just yet.
I've seen that exact same issue in two rifles, one of which I still own & the other I sold a while back.
In both cases, one of the bolt lugs was barely making contact with it's lug abutment.
Lapping the the bolt lugs to even things up eliminated the case bulge issue for both rifles.
Now I'm not saying that the chamber definitely doesn't have issues but, there can definitely be other reasons.

The chamber is definitely larger. The bulged cases can be reinserted fine into the new barrel but stick out ~3/4 inch (I've forgotten exactly how much) when trying to insert them into the old barrel. That, and the action worked fine before.

 

[Wannashootit]

Fucked up fo sho...
Not enough taper (bulged as you say)- but sure looks to me like that barrel might be short chambered.
The case just above the extractor groove in the brass also looks like it's expanded, from too much of the casehead being exposed beyond the chamber walls.

Was this a "typical" shouldered barrel where the smith had the action in-hand?

 

[rothgyr]

I wouldn't get all Vanessa about the Gun Smith just yet.
I've seen that exact same issue in two rifles, one of which I still own & the other I sold a while back.
In both cases, one of the bolt lugs was barely making contact with it's lug abutment.
Lapping the the bolt lugs to even things up eliminated the case bulge issue for both rifles.
Now I'm not saying that the chamber definitely doesn't have issues but, there can definitely be other reasons.

This. OP, what receiver are you using? Any chance you could mark the lugs with a sharpie and see if they're both making contact?

I wouldn't fire your smith just yet. I had a rifle built by GA Precision and it had some pretty big QC issues, and they're the most renowned gunsmith I've ever heard of. Just because I got a lemon doesn't mean everything they produce is just crap. I let them get me taken care of, and their CS was great, so I'm good with GA Precision and won't discourage people from using them.

 

[SuperBruce]

This. OP, what receiver are you using? Any chance you could mark the lugs with a sharpie and see if they're both making contact?

I wouldn't fire your smith just yet. I had a rifle built by GA Precision and it had some pretty big QC issues, and they're the most renowned gunsmith I've ever heard of. Just because I got a lemon doesn't mean everything they produce is just crap. I let them get me taken care of, and their CS was great, so I'm good with GA Precision and won't discourage people from using them.

Bergara B-14 HMR. I can't inspect it now, the rifles back with the smith. Would you expect this to change after a re-barrel? It worked fine with the factory barrel. I'm definitely not firing him yet. If a smith went out of business the first time something wasn't right they'd be almost no smiths. I'm confident he'll make things right one way or another.

Fucked up fo sho...
Not enough taper (bulged as you say)- but sure looks to me like that barrel might be short chambered.
The case just above the extractor groove in the brass also looks like it's expanded, from too much of the casehead being exposed beyond the chamber walls.

Was this a "typical" shouldered barrel where the smith had the action in-hand?

Fired brass stick out of the new chamber almost exactly the same amount as from the old chamber so if it's short its on the order of a hundredth inch (it was hard to get a perfectly accurate measurement with the new barrel in the action but it was within the accuracy to which I could measure from the old depth).

Yes, it was a shouldered barrel and smith had the action in hand and did all disassembly and reassembly.

 

[rothgyr]

With the throughput on Bergara in recent years, It's entirely possible for it to be out of center. 8541 Tactical had a T1x that was crazy accurate, but when rebarreled, it was found that the receiver was actually out of round, but the manufacturer had made it work by making the factory barrel fit anyways.

Not saying that it's likely that Bergara did something similar, but it's not uncommon for a factory worker to work around problems instead of fixing them. I'm interested to see what your smith says after looking at it.

 

[KnowNothing256]

Having a REAL hard time understanding how asymmetric lug contact (that was fine with the factory barrel) could cause symmetric excessive case expansion forward of the case head. If it was a lug issue leading to insufficient case insertion into the chamber, you'd see a bulge in the portion that was unsupported by the chamber, sharply tapering back to the first supported portion, which would be larger than it should be (cause it's located at a portion further down the chamber body taper than it should be). What you wouldn't see, at least based on what I'm imagining in my mind, would be a barrel that won't chamber a no-go gauge, exhibits similar case head protrusion as the factory barrel (which didn't have an issue), and symmetrically blows out the case body with a steady taper all the way back down to the correct shoulder diameter.

I cannot imagine that this is anything but a bad chamber.

Some pics below (pistol cases, sorry, the pics were better for these than what I could find for rifle cases) showing what I'd expect to see if a lug issue was causing inadequate case insertion into the chamber.

 

[Wannashootit]

Fired brass stick out of the new chamber almost exactly the same amount as from the old chamber

Gotcha.
My guess then is that even though that upper section of the casehead was inside the chamber, the much thicker case in that area didn't blow out completely to conform to the end of the chamber. I can see in the picture at the top that it's angled "upwards" and clearly expanded.
Bet one more firing of that brass would do it, though

Let us know what the smith says... but I don't see that chamber being able to be "cleaned up" with any amount of setback.

 

[Barelstroker]

Have you heard anything from the Smith yet?

 

[SuperBruce]

Have you heard anything from the Smith yet?

Not yet. I'll be sure to update here when I do.

 

[Maxduty]

Had a rifle built years ago by a guy on the east coast that had the same issue. He said it was fine, but I'd split about every tenth case at that line. After it happened the second time, I took it to someone else and he knew what it was immediately. I didn't know much about smithing terms then so the explanation was something about a reamer with a floating pilot from what I can recall. He chopped two inches off the tenon and redid the work and it shot great for years until the barrel finally shot out.

 

[SuperBruce]

Okay, got results back from the smith. It wasn't possible to definitively determine what happened but the likely culprit(s) are the reamer and/or (my bet) a problem with the reamer alignment caused by the floating reamer holder. He re-cut the chamber and it's now spitting out brass with diameter 0.473 close to the case head. Still a little on the large side (0.003 more than I'd gotten from the original barrel), but not near as bad as before.

With regard to the 0.473 brass barrel he gave me two options:

1. Full refund.
2. Take the barrel and a $100 discount for the hassle and slightly large chamber.

I opted for #2. With standard fl-sizing dies I expect brass life could be a bit shorter. I figure if that bugs me I can get a forster shoulder-bump die.

 

[DJL2]

Okay, got results back from the smith. It wasn't possible to definitively determine what happened but the likely culprit(s) are the reamer and/or (my bet) a problem with the reamer alignment caused by the floating reamer holder. He re-cut the chamber and it's now spitting out brass with diameter 0.473 close to the case head. Still a little on the large side (0.003 more than I'd gotten from the original barrel), but not near as bad as before.

With regard to the 0.473 brass barrel he gave me two options:

1. Full refund.
2. Take the barrel and a $100 discount for the hassle and slightly large chamber.

I opted for #2. With standard fl-sizing dies I expect brass life could be a bit shorter. I figure if that bugs me I can get a forster shoulder-bump die.

A craftsman NEVER blames his tools. I don’t know what you’d consider the guy you‘re using, but I can tell you what he’s not. ;-)

 

[spife7980]

With regard to the 0.473 brass barrel he gave me two options:

1. Full refund.
2. Take the barrel and a $100 discount for the hassle and slightly large chamber.

I opted for #2. With standard fl-sizing dies I expect brass life could be a bit shorter. I figure if that bugs me I can get a forster shoulder-bump die.

Why not lop it off and chamber it correctly? .473 is still on the fine line IMO. Your dies are going to be sizing that base a bunch.

 

[Evintos]

Okay, got results back from the smith. It wasn't possible to definitively determine what happened but the likely culprit(s) are the reamer and/or (my bet) a problem with the reamer alignment caused by the floating reamer holder. He re-cut the chamber and it's now spitting out brass with diameter 0.473 close to the case head. Still a little on the large side (0.003 more than I'd gotten from the original barrel), but not near as bad as before.

With regard to the 0.473 brass barrel he gave me two options:

1. Full refund.
2. Take the barrel and a $100 discount for the hassle and slightly large chamber.

I opted for #2. With standard fl-sizing dies I expect brass life could be a bit shorter. I figure if that bugs me I can get a forster shoulder-bump die.

You can also use the $100 to partially pay for a custom die. Send several fired pieces of brass, wait a while, get custom full length sizing die. Whidden is one such company that offers the service, Redding is another.

 

[SuperBruce]

Why not lop it off and chamber it correctly? .473 is still on the fine line IMO. Your dies are going to be sizing that base a bunch.
View attachment 7873494

Good question. Only speculation but I suspect there isn't a lot of shank left, the barrel profile was a sendero so it was on the short side to start with so there may not be much shank left for the chamber.

 

[SuperBruce]

You can also use the $100 to partially pay for a custom die. Send several fired pieces of brass, wait a while, get custom full length sizing die. Whidden is one such company that offers the service.

Good point. Clearly a die specific to my chamber would be the best, but would the advantages of that over a shoulder bump die be significant? I've only used FL sizing dies historically so I'm not in the position to know either way.

I'm also curious on what people would expect the brass life decrease to be for a 0.003" oversized (from the mean) chamber. The smith suggested it would likely be on the order of 20% reduction in brass life but it was couched in phrasing that suggested a very high degree of uncertainty.

 

[Evintos]

You can get inconsistent chambering when the brass around the web is near max size as well as this weird click (bolt click) when trying to extract (slightly more force needed for extraction) with using shoulder bump dies. This happens with multiple firings and sizing. FLS dies tend not to have this issue.

The brass life decrease is really based off two things, how much smaller is your die squeezing the body of the brass to how much it is expanding. When the extreme range is unnecessarily large, you reach case head separation failures much earlier.

 

[SuperBruce]

You can get inconsistent chambering when the brass around the web is near max size as well as this weird click (bolt click) when trying to extract (slightly more force needed for extraction) with using shoulder bump dies. This happens with multiple firings and sizing. FLS dies tend not to have this issue.

The brass life decrease is really based off two things, how much smaller is your die squeezing the body of the brass to how much it is expanding. When the extreme range is unnecessarily large, you reach case head separation failures much earlier.

My current 6.5 creed die (RCBS match master FL) appears to take brass down to 0.469-0.470 depending on the sample. That means a change of 0.003 to 0.004 per-sizing op. That's significantly less work than the necks see on any cycle but that is probably an apples-to-oranges comparison at best.

 

[spife7980]

My current 6.5 creed die (RCBS match master FL) appears to take brass down to 0.469-0.470 depending on the sample. That means a change of 0.003 to 0.004 per-sizing op. That's significantly less work than the necks see on any cycle but that is probably an apples-to-oranges comparison at best.

Neck brass is soft and meant to change easily so it can seal off the chamber.
Base brass is hard and difficult to move so that it is capable of withholding the pressure and not shitting its pants in your face.

 

[Evintos]

My current 6.5 creed die (RCBS match master FL) appears to take brass down to 0.469-0.470 depending on the sample. That means a change of 0.003 to 0.004 per-sizing op. That's significantly less work than the necks see on any cycle but that is probably an apples-to-oranges comparison at best.

That's actually not bad at all since the die isn't sizing to SAAMI cartridge min (0.4623"). I would not worry about significant case life decreases.

 

[4O6shootist]

My current 6.5 creed die (RCBS match master FL) appears to take brass down to 0.469-0.470 depending on the sample. That means a change of 0.003 to 0.004 per-sizing op. That's significantly less work than the necks see on any cycle but that is probably an apples-to-oranges comparison at best.

I had similar issues. Fired cases were giving bolt lift and clickers on my 25cm using redding type S, before and after sizing was only resulting in 0005 sizing of the bottom half inch of the case. Switched to a matchmaster and started getting it down to 468 from 4705 fired. All my issues went away. I've got 4 reloads on the peterson brass since the die switch and no problems observed yet. If you talk to short action customs, they designs their custom dies to size 002 at shoulder and at base from fired dimension.

 

[SuperBruce]

The saga continues.

I got the rifle back and fired a few more hornady factory cartridges this morning (140 ELDM and 143 ELDX). Groups seem to be better, but I don't know if that's because I didn't mount the muzzle brake this time or not, but groups are not my primary concern. As it shakes out, the brass are still coming out with a diameter of 0.476" about 0.3 inches from the base. I was told by the smith that he measured the case width at the "0.200" line (he says it's a standard measurement on prints?) and it was 0.473". My best guess is that is 0.200 forward of the base, where it is pretty close to 0.473 (it's flaring out at that point, see the image in post 4).

So, I'm markedly less happy about brass coming out with a diameter of 0.476 than I was about the idea of 0.473 but I don't know if I should be. If it is an issue, there are plenty of ways to work around this, custom dies, and I even thought about using a bump+neck sizing only die and then sending the case only part of the way up my FL sizer to see if I can keep it closer to the fireformed size (will this work? My guess is "kinda"). On the other hand, unless it's "fine" I'm kind of going back toward refund and not having a wonky-chambered rifle.

 

[KnowNothing256]

The saga continues.

I got the rifle back and fired a few more hornady factory cartridges this morning (140 ELDM and 143 ELDX). Groups seem to be better, but I don't know if that's because I didn't mount the muzzle brake this time or not, but groups are not my primary concern. As it shakes out, the brass are still coming out with a diameter of 0.476" about 0.3 inches from the base. I was told by the smith that he measured the case width at the "0.200" line (he says it's a standard measurement on prints?) and it was 0.473". My best guess is that is 0.200 forward of the base, where it is pretty close to 0.473 (it's flaring out at that point, see the image in post 4).

So, I'm markedly less happy about brass coming out with a diameter of 0.476 than I was about the idea of 0.473 but I don't know if I should be. If it is an issue, there are plenty of ways to work around this, custom dies, and I even thought about using a bump+neck sizing only die and then sending the case only part of the way up my FL sizer to see if I can keep it closer to the fireformed size (will this work? My guess is "kinda"). On the other hand, unless it's "fine" I'm kind of going back toward refund and not having a wonky-chambered rifle.

No offense intended, but I was surprised you didn’t go the refund route the first time.

This chamber was a hot mess from the beginning, and I’d sooner go to someone who could cut a good chamber, and catch a bad one before it left the shop, than let the guy that messed it up once try to fix it. Fixing a problem like this sounded like a more complex situation than just chambering a blank, which he already failed to do correctly.

I’d take the refund and get a new tube from elsewhere.

 

[SuperBruce]

No offense intended, but I was surprised you didn’t go the refund route the first time.

This chamber was a hot mess from the beginning, and I’d sooner go to someone who could cut a good chamber, and catch a bad one before it left the shop, than let the guy that messed it up once try to fix it. Fixing a problem like this sounded like a more complex situation than just chambering a blank, which he already failed to do correctly.

I’d take the refund and get a new tube from elsewhere.

No offense taken, that would have been the right choice to maximize the probability for success. I wanted to give the guy another crack at it since it does shoot well, I just expect it's going to wreck brass and be a general pain.

 

[AllenOne1]

If you can get a refund out of him I would take it. If you try to live with it you are going to think about it every time you pull the trigger and you are going to end up with a custom set of dies trying to deal with this barrel that will never work on another barrel. This ends up being a pretty expensive barrel. When you rebarrel you will toss the barrel, the brass and the dies. Take the money and move on.