Help me figure out Chamber Size

[Endyo]

I was given a reamer print so it should be simple right?

0.313" is what the print shows if I'm reading correctly.


Here's what's been bothering me. I have been using Norma brass without any apparent issues.
Finished round OD at the neck is 0.316" I haven't noticed any catching or excessive force seating loaded catridges. I have to figure that the neck is being squeezed down to 0.313" adding 0.003" further neck tension to the bullet from the "crush fit". The rifle shoots great...

I'd be ok with that, but I am working on turning necks. What's really stumping me is this:

Fired brass from this chamber is coming out at 0.319"-0.320"...it's my understanding that brass fits to the chamber's dimensions and shrinks (springs) back about 0.001". So if my chamber is 0.313" and fired brass is coming out 0.320" something isn't adding up.

Please help. I'm not sure if I'm missing something. I've been spending all day testing different neck turning thicknesses and it's driving me crazy. If my chamber is in fact 0.320" than I have no need to neck turn and it may be better NOT to.

I was told this is a No turn chamber, but the rifle was set up for Lapua. I'm wondering if this is the correct reamer print.

 

[DanSavage]

You would not be OK if your loaded round neck is getting squeezed down even more by the chamber when you chamber the round,, the rifle would more than likely blow up.

You simply have a .320 neck cut out in the chamber. The fired brass can't lie,,I'm wondering if the reamer print may be screwed up between a 6.5-284?

I wouldn't turn the neck's much,, just touch them up if needed.

I would try Lapua brass.

 

[Northridge]

Lapua is good brass but considering his .320 chamber neck it's going to be on the looser side for clearance as necked up lapua brass measures about .313 loaded round on average. Norma brass is measuring about .003th larger loaded round about.316

 

[Brians356]

I would think it would be quite obvious closing the bolt if it were squeezing a loaded neck down several thousandths. I'm quite surprised you haven't chambered, then ejected the unfired round and simply re-measured the neck OD, if there remains any doubt.

 

[DanSavage]

You are right,, the reamer print show's the neck should be cut to .313,,which would make it a tight neck and one you would have to turn the necks down gaining consistancy. If that is what your smith gave you and what you wanted I would take it back and have him figure out how he is going to make it right.

 

[Endyo]

I would think it would be quite obvious closing the bolt if it were squeezing a loaded neck down several thousandths. I'm quite surprised you haven't chambered, then ejected the unfired round and simply re-measured the neck OD, if there remains any doubt.

Thank you. All common sense responses.

The neck OD of a fired round comes out to roughly 0.3185-0.320". Which is close to what the chamber has to actually be.

I never had problems with the brass chambering I wasn't sure if this was the same as a crush fit with an oversized shoulder...from above posts obviously not.

I have zero experience chambering rifles. All I knew is that things weren't adding up and it was driving me crazy.

 

[dkhunt14]

.313 would be too big for 6.5. I would measure the reamer or do a chamber cast. Matt

 

[Endyo]

.313 would be too big for 6.5. I would measure the reamer or do a chamber cast. Matt

I'll have a chance to meet the riflesmith at the Berger Southwest shoot. I'll ask if he can bring the reamer for me to measure.

I didn't buy the rifle direct from him so it's not his fault on the specs of the rifle. He actually reached out to me when he heard I bought his rifle. He's done a lot to help me without having ever made a buck off of me.

If I'm feeling really squirrelly I may try my hand at a chamber casting.

 

[dkhunt14]

Maybe the previous owner had it opened up because he didn't want to turn brass. Matt

 

[Patch700]

Incorrect reamer print... One more reason why I do not have dies cut based off reamer prints.

If this is a reamer you yourself purchased from dave then i would call them.. If this is a print your smith provided from his tool selection then I would call him to let him know.

Someone who specs a certian reamer and gets the wrong one may not be as willing to deal with it as yourself.

Good luck

 

[Patch700]

I should add to this that even tho the print is off , you made mention the rifle shoots great...

That may very well be because you have a good amount of clearance in the neck area.

If brass life doesn't appear to suffer and you anneal , I would shoot it and enjoy.. But still advise who sent you the print that it is not a match to what you have.

 

[fguffey]

Maybe the previous owner had it opened up because he didn't want to turn brass. Matt

Where would he find brass that would require neck turning for a chamber neck that was +/- .001” of .318”?

There are case formers as in reloaders with the ability to form cases. Necking a case neck up and or down should be part of the skills that would be required to qualify as a ‘case former’.

Chamber casting; I am an unorthodoxy chamber caster.


F. Guffey

 

[dkhunt14]

Where would he find brass that would require neck turning for a chamber neck that was +/- .001” of .318”?
F. Guffey

It was supposed to be a .313 and that would need turned. Maybe the original owner of the gun had somebody open up the neck because they didn't want to turn. He says it measures closer to .320 now. Fired brass at .319 to .320. Read the first post. Matt

 

[fguffey]

I was given a reamer print so it should be simple right?

I was given a reamer print so it should be simple right?

He also said he had a reamer print. It should be obvious the print of the reamer is not a print of the chamber. Then I said it is not impossible to form cases for a few. Then there was that part about jump back, snap back or spring back.

I do not find it difficult to fit a case neck to a chamber. The limiting factor is the availability of cases. It is easy to turn a neck it is easy to ream a neck, adding metal as putting brass on the neck to make it thicker is the difficult part.

He says it measures closer to .320 now.

Close? What happens when spring back is added or subtracted? He has a print and a fired case.


F. Guffey

 

[savagedasher]

I was given a reamer print so it should be simple right?

He also said he had a reamer print. It should be obvious the print of the reamer is not a print of the chamber. Then I said it is not impossible to form cases for a few. Then there was that part about jump back, snap back or spring back.

I do not find it difficult to fit a case neck to a chamber. The limiting factor is the availability of cases. It is easy to turn a neck it is easy to ream a neck, adding metal as putting brass on the neck to make it thicker is the difficult part.



Close? What happens when spring back is added or subtracted? He has a print and a fired case.


F. Guffey

The reamer looks it is not a bushing reamer.
Not saying the chamber job is bad but it could be . Have you checked the the rest of the case comparing it with reamer print.
If not it must be a .320 neck. Larry

 

[Steve Blair]

As others noted, it is not possible for your chamber to match the reamer print specs, given the dimensions you cited. Just to make certain, I measured the reamer originally made from that print. My .284 chambers used Lapua brass turned to .012" neck wall for a loaded diameter of ~Ø.3085". Fired brass measures ~Ø.312". You can see what the reamer neck portion measures in the third image. Used correctly, it should cut very close to Ø.313".

 

[dkhunt14]

It is possible it is not the right print. It is also possible the previous owner had the neck opened up. My buddy hated turning necks and the first thing he did when buying a tight necked gun was have the neck opened up. Matt

 

[Endyo]

I apologize to Steve. I should have blacked out his name. He has no association with the mix up I experienced. Want to clarify any confusion.

 

[Steve Blair]

No apology necessary. I've posted that print and others here several times.

 

[Endyo]

No apology necessary. I've posted that print and others here several times.

I'm wondering if that's how this particular print was mistakenly sent to me.

I figure my loaded rounds measure 0.316" OD and my chamber is likely 0.320".
My ES went down with a very high amount of seating force ~100lbs.
(That force reading was on New Norma brass)
I don't guess I'll be neck turning say maybe to hit high spots.