Gunsmithing Simple Freebore / Throat question

[jrsandiego12]

Is the bullet supposed to touch the sides of the freebore / throat portion of the chamber??

My understanding was "no" - hence the name FREEbore. But I have multiple barrels now where the bullet diameter touches the freebore before the bullet touches the lands.

 

[Supersubes]

No, there should be clearance.

 

[Hateca]

Is the bullet supposed to touch the sides of the freebore / throat portion of the chamber??

My understanding was "no" - hence the name FREEbore. But I have multiple barrels now where the bullet diameter touches the freebore before the bullet touches the lands.

How do yo know that and where is the bullet making contact?

 

[Aftermath]

Is the bullet supposed to touch the sides of the freebore / throat portion of the chamber??

My understanding was "no" - hence the name FREEbore. But I have multiple barrels now where the bullet diameter touches the freebore before the bullet touches the lands.

What are you using to measure freebore?

 

[jrsandiego12]

How do yo know that and where is the bullet making contact?

I am using the Hornady OAL gauge (I know, I'm not using the action and bolt method because that method wasn't working for exactly this reason - I can feel the friction of the bullet in the freebore). With the OAL gauge I can sink the bullet down into the brass case so just the tip is coming out. When I see the case in the chamber I move the bullet forward with the rod and the circumference of the bullet is making contact with the freebore and causing friction all the way forward until the bullet achieves a hard stop at the lands. The bullet very clearly has nearly uniform rub marks around the circumference of the bullet down the body of the bullet.

I have used Hornady ELD Match bullets and measured them for uniformity at .264 inches. And it happens - slightly less - with Berger Hybrid Target bullets that measure uniform at .2635 inches.

I wish there was a way to simply "lap" the freebore section to be sure any roughness is removed. I checked with the manufacturer and they said the freebore should not be touching the bullet.

 

[Aftermath]

You can have that area honed but try this before you take it to a gunsmith...
Using your OAL gauge, set it so the bullet will be 0.004" off the lands. Push it all the way into the chamber and extract...are there any marks on the bullet?

 

[Wannashootit]

I can feel the friction of the bullet in the freebore).

How are you able to differentiate between the neck tension on the bullet (yeah, it's light in a modified case, but it's still there) and the bullet ogive contacting the groove diameter of the barrel?

 

[jrsandiego12]

The neck tension is slight - I can move the bullet through the neck easily with barely any pressure - I have prepped the modified case to make it smooth on the bullet too. When the bullet circumference makes contact with the freebore the resistance goes up significantly and lasts for about the approximate length of the freebore section - it is NOT the short length of the bullet pressing into the lands - and then the bullet has more resistance at and into the lands over a very short distance.

Secondly, the scrapes, friction marks left on the bullet are around the large circumference .264 area of the bullet - not near an Ogive point where the lands touch.

 

[Ecureuil]

If this is not a new barrel, you might be running into carbon. I've had similar issues on an AR trying to find the lands with the Hornady tool. Maybe run a boresnake or brush through there and try again if you haven't already.

 

[wil_pt]

Do they look like these?

 

[Hateca]

Well if these are custom chambered barrels what reamer was used was it a custom reamer or a spec reamer? tightening up reamer specs are done all the time. Custom made for throat, lead, no turn neck, turn neck, you name it. If custom chambered ask to see the reamer print or the reamer specs.

if these are factory barrels I can almost guarantee you are experiencing something else. Factory chambers are loose as a goose and in no way are that tight at the throat.

 

[Shooter71]

How does it shoot?

 

[Edds]

Is the bullet supposed to touch the sides of the freebore / throat portion of the chamber??

My understanding was "no" - hence the name FREEbore. But I have multiple barrels now where the bullet diameter touches the freebore before the bullet touches the lands.

As long as the bullet isn't getting stuck, touching is good.