Thoughts on this chamber (borescope)

[Ucsdryder]

I struggle a little to understand what I’m looking at through a bore scope. In the video it starts at the chamber then I pull it out toward the muzzle. I was surprised to see all the rings. I’m having issues with a bolt “click”. I’m trying To figure out what’s going on. Option 1…hot loads in a Saum are expanding the web. Option 2…a burr that’s causing this scratching on the case is causing the bolt click. In the picture you can see 2 rings. I have a thread going on LRH and got some awesome feedback, but wanted to put it in front of a few more people.

 

[WCB]

What do you mean by a bolt "click"?

 

[Ucsdryder]

What do you mean by a bolt "click"?

 

[QuackAttack]

Chamber was reamed incorrectly. Defective. That click is where primary extraction occurs as the bolt handle cams against the surface of the receiver, driving the bolt to the rear. Those grooves are allowing brass to obturate into them and trying to lock the case in place…all bad. Chamber should be smooth.

send it back.

 

[sndmn11]

send it back.

@Ucsdryder can we get another rifle maker thread?!?! #7SadlyAlmostUsuallyMalfunctions

 

[Shooter71]

Is it a new chamber? Is the brass new to that chamber, or fired in a different chamber? How are you sizing your brass? If the rings are deep enough they can cause a problem, but might be polished out. Usually the click comes from the head, web area not being sized enough by the die, either due to a bad fit between chamber and die, or by using brass that was formerly fired in a larger chamber. The sizing die won’t size enough to remove the brass’ memory.

 

[Ucsdryder]

Is it a new chamber? Is the brass new to that chamber, or fired in a different chamber? How are you sizing your brass? If the rings are deep enough they can cause a problem, but might be polished out. Usually the click comes from the head, web area not being sized enough by the die, either due to a bad fit between chamber and die, or by using brass that was formerly fired in a larger chamber. The sizing die won’t size enough to remove the brass’ memory.

Chamber has 150 rounds through it. Brass is 2-3 fired. I might have a couple that are 4x fired.

 

[Shooter71]

Has the brass only been fired in that chamber? Did the new brass click after the first firing? Full length sizing? I can’t tell from the picture but it looks like scuffing at the head end of the case. When rings are bad they’ll be shiny in a fired case.

 

[Ucsdryder]

Yes all from the same chamber. Full length sized and trimmed. Shoulder bump .002-.003. Clicking started at 3x I believe.

 

[Wrench]

Have you measured case head expansion in a fired case?

The chamber looks like it could be an issue, but you could also be up on pressure.

Are the rings on the brass something that you can feel, and are there signs of material flow and or scuff as the case moves back?

 

[Ucsdryder]

Have you measured case head expansion in a fired case?

The chamber looks like it could be an issue, but you could also be up on pressure.

Are the rings on the brass something that you can feel, and are there signs of material flow and or scuff as the case moves back?

 

[Wrench]

What are you getting right above the rim? .2" up the web is getting pretty thin.

 

[Ucsdryder]

What are you getting right above the rim? .2" up the web is getting pretty thin.

If I get the reflection right you can see the scuffing end. I THINK that’s where the die might be stopping sizing? That’s actually the thickest part of the case anywhere. It’s thicker there than at the web or .2 from the rim. On a fired 3x unsized it goes from .547 to .549 to .547. The second picture shows the measurement at each red mark.

 

[Str8shtr]

Many SAMMI reamers are made to minimum SAMMI spec. If you have a good setup and ream the chamber the same size as the min spec reamer, you end up with a pretty tight chamber. Chambers tight at the butt are very difficult to prevent bolt click. Some guys will spec their reamers fatter at the butt and order custom dies to prevent this. Basically I think your chamber is just tight at the butt. If the roughness of the chamber was a problem, it'd be a problem on the first couple firings.

 

[wind gypsy]

That chamber is pretty gross. Seems like pretty good clearance virgin brass to chamber dimensions. Maybe enough that a tighter based die would get it done but those chamber rings can’t be helping.

I’ll have to measure some 2 or 3x fired ADG when I get home.

 

[Ucsdryder]

That chamber is pretty gross. Seems like pretty good clearance virgin brass to chamber dimensions. Maybe enough that a tighter based die would get it done but those chamber rings can’t be helping.

I’ll have to measure some 2 or 3x fired ADG when I get home.

I think that might be the reason it took a couple firings. The case had to have time to expand to the full size of the chamber.

 

[gbflyer]

If I get the reflection right you can see the scuffing end. I THINK that’s where the die might be stopping sizing? That’s actually the thickest part of the case anywhere. It’s thicker there than at the web or .2 from the rim. On a fired 3x unsized it goes from .547 to .549 to .547. The second picture shows the measurement at each red mark.

Here’s some Internet advice, take it for what it’s worth:

That double ring on the case about 1/2” up is no bueno. The chamber might be polished out. If it is an accurate barrel I would try to salvage it. I wouldn’t worry too much about the borescope findings, a chamber needs to be a little rough to keep the bolt thrust within reason. Most of us shouldn’t be looking around with a borescope, we don’t know what we are looking at anyway. But when the case is showing rings it’s no good. It was chambered in a hurry, probably with a worn out reamer. I’d be in contact with whom ever produced it.

 

[QuackAttack]

Guys…the chamber has a blatant machining defect…it’s not brass. There are rings/grooves machined into the walls of the chamber. It will require a replacement barrel. That’s a factory defect and you can’t fix it. The part gets scrapped and a new barrel gets Installed.

 

[Ucsdryder]

Ok so I just dropped off the gun at the gunsmith. He looked at the brass and said that doesn’t look good. He shined a light down the chamber and said “oh crap”. Words you never want to hear from a gunsmith!!!

 

[Lawnboi]

Looks like sloppy work.

You didn’t take it back to the same guy did you?