Indicating Barrel thats chambered

[Blair Mason]

Any tips on indicating a barrel that already has a chamber cut?

I ran into an issue where I cut a 280 Ackley for a guy, and he decided after I finished that he wanted a SAMMI 280 Ackley so Im having to run a different reamer a little deeper. I usually use a PTG rod and indicate it that way. Now my rod is only sticking out about 2 inches instead of the normal 5 or 6. I wish I had a long reach indicator and I would just not use a rod at all.

Thanks for the help!

 

[Dusty Stevens]

Ptg makes range rods and indicator rods. Indicator rods are made for prechambered barrels and will do what you need to do. Or if you trust your work indicate off your chamber front and back

 

[boltman223]

Can you use the original chamber to indicate off of?

 

[boltfluter]

Just thinking out loud. I wonder if you could dial it in with the original reamer in the chamber, and dial in the shank of the reamer. Have no clue if it would work, but would be easy enough to check once dialed in. Just a thought. Good luck.

Paul

 

[carlsbad]

Grizzly rod works well for indicating in just behond the throat.

 

[Stan Taylor]

How much deeper do you have to chamber instead of indicator I would set up in a steadyrest an run the chamber in the reamer should follow the existing chamber.

 

[rgc54]

Stan has it correct let the reamer be the center if the chamber is true

 

[gunsandgunsmithing]

Get a saami and a std go gauge first. Put them both in the chamber and measure the difference. Start there and let us know what you find.

 

[gunsandgunsmithing]

As for indicating it in...no amount of indicating will stop it from following the existing hole if you're anywhere in the ballpark

 

[swd]

You know your work, if it's normally only got a couple tenths or less of run out just dial it in off the back or the chamber and your GTG. In the future get a long reach indicator, they're a great tool to have. I use it more than any of my other indicators.

 

[Walt Krafft]

There are three possibilities here. One, you didn't indicate it worth a crap when you originally chambered it so there is no guarantee how concentric the chamber is to the bore. Two, you screwed it up when you originally chambered it, and know it is messed up. Three, you did a good job on the original chamber so it is concentric to the bore. If number three, indicate the chamber and proceed. If one or two it don't make rat difference what you do, its gonna be junk.

 

[Blair Mason]

Thanks for all the replys. I have to cut .049 deeper. I guess I was worried that I could have one end of the chamber dialed in, say the back of the chamber and be off in the front. Just like how you can have the close end of the range rod dialed and the front in a few thou off at the end, or vice versa. I agree that the reamer should follow the original chamber but 50 thou seemed like a long ways to push the reamer if it was off.

I think a grizzly rod and/or a long reach indicator are in my future but hopefully i can get this rifle built right and out the door sooner than that.

 

[swd]

If I recall there’s only about .013” difference between Saami and most wild cat 280AI’s

 

[Dusty Stevens]

Sounds like you need an indicator rod. Dial in the 2 points and keep moving

 

[Shawnba67]

If I recall there’s only about .013” difference between Saami and most wild cat 280AI’s

That difference is between the old and new datum lines. The new 280 used a wider datum line which moved it .014 from old line. The chambers are the same just measuring a different spot on the shoulder. I do not remember what the datum is but its like going from .375 to .400. Stil measuring same thing just in a diffetent spot.
If OP has to go 49 thousanths deeper I dont know what chamber he cut originally. But it will take some work to get a reamer to not to follow that hole!

 

[gunsandgunsmithing]

E

That difference is between the old and new datum lines. The new 280 used a wider datum line which moved it .014 from old line. The chambers are the same just measuring a different spot on the shoulder. I do not remember what the datum is but its like going from .375 to .400. Stil measuring same thing just in a diffetent spot.
If OP has to go 49 thousanths deeper I dont know what chamber he cut originally. But it will take some work to get a reamer to not to follow that hole!

Exactly right!
Oh, and same reamer too!

 

[Blair Mason]

That difference is between the old and new datum lines. The new 280 used a wider datum line which moved it .014 from old line. The chambers are the same just measuring a different spot on the shoulder. I do not remember what the datum is but its like going from .375 to .400. Stil measuring same thing just in a diffetent spot.
If OP has to go 49 thousanths deeper I dont know what chamber he cut originally. But it will take some work to get a reamer to not to follow that hole!

I used a 30-06 Ackley headspace gauge with a 280 ackley 40 degree reamer. This may not have been the correct combination. I have a Sammi reamer and Sammi headspace gauge now. The chamber should be cut straight i think i just got my reamer/headspace gauge combo wrong the first go round.

Im learning...obviously. this is my 3rd barrel. My other two shoot absolutely great.

 

[eww1350]

Anytime I am working on a barrel that has an existing chamber, (making an Ackley out of a standard chamber) I indicate both the front and back of the existing chamber, if you don't the probability of getting an egg shaped chamber is very high..!!

Eddie in Texas

 

[Shawnba67]

I used a 30-06 Ackley headspace gauge with a 280 ackley 40 degree reamer. This may not have been the correct combination. I have a Sammi reamer and Sammi headspace gauge now. The chamber should be cut straight i think i just got my reamer/headspace gauge combo wrong the first go round.

Im learning...obviously. this is my 3rd barrel. My other two shoot absolutely great.

7mm06Ackley! If you didnt need factory ammo it might even be a better choice!
Glad you got it sorted

 

[tobnpr]

The reamer is going to follow the existing hole.
I'd also stick it between centers (dead center will accurately locate center of the chamber), put the steady on the tenon, back off the tailstock; use a micrometer stop on the reamer holder and do the last few hundredths by hand.
No reason to overthink this when you're using the same reamer used to originally cut the chamber.