Guys who run tight neck chambers

[Charlie-NY]

I have opened up several barrels for more neck clearance to be on the safe side..
Have your smith fix them...and I know its a big hassle after the fact.
He should have got it right the first time.

I don't think member rwj was making an excuse for your situation merely a possible explanation. I personally had a situation where a possible worn reamer worked to my advantage. I had a factory heavy barrel Savage in 223 that shot way better than I ever had seen before. After we cast the chamber and took measurements we found the dimensions to be on the minimum side rather than on the generous side. My gunsmith chalked it up to a worn reamer. I realize my experience does nothing to help your situation and I hope you get your problem sorted out.

I agree that a worn reamer could have caused this but not twice on two different rifles with different chambers. I doubt that a chamber neck that is merely .001" over the neck diameter of the provided factory ammo is still within SAMMI specs but I'm not a gunsmith. I also think that a neck that tight should have the neck diameter stamped right on the barrel under the chamber designation. Not doing so seems dangerous because if I sold the rifle and someone used ammo that was only .001" larger in neck diameter it sure wouldn't be good.

For now, it's just a matter of neck turning off .001" all the way around to get to the .003" of release that seems safe and reasonable for a hunting rifle but I specifically indicated that I did not want to turn brass and provided the Nosler factory ammo. You live & you learn.

 

[jackieschmidt]

From a machinist point of view, If a reamer is worn enough, (ie, dull enough), to produce a noticeable undersize situation, it is time to retire it.

 

[mac86951]

From a machinist point of view, If a reamer is worn enough, (ie, dull enough), to produce a noticeable undersize situation, it is time to retire it.

Hmmm... That or regrind to 20-practical? I'm curious where does a reamer wear out the most, body, neck, shoulder? I'd guess neck/shoulder first... The transition from shoulder to body most?

 

[shortgrass]

I just fired some Lapua 300win mag brass and I cant slip a bullet into a fired neck.
All of my other 300wm brass can easily fit. My ABM loaded neck is .336, my Lapua load neck is .338, the necks are .015 thick. SAAMI is supposed to be .3421 to .3407.View attachment 1338218

My chamber is supposed to be SAAMI, I called Christiansen Arms to verify. I'm thinking about Cerro safe/ casting my chamber to find out for sure. I have no pressure signs but have only fired 20 rounds so far. I might have to turn my necks.

Can you guys who run tight necks fit a bullet in your fired case necks ? After spring back?

The top drawing is max ammunition, the bottom drawing is minimum chamber. @ .338 dia neck of your loaded rounds, neck dia is in tolerance. You have some other perceived problem, which may not be a problem at all!

 

[shortgrass]

I agree that a worn reamer could have caused this but not twice on two different rifles with different chambers. I doubt that a chamber neck that is merely .001" over the neck diameter of the provided factory ammo is still within SAMMI specs but I'm not a gunsmith. I also think that a neck that tight should have the neck diameter stamped right on the barrel under the chamber designation. Not doing so seems dangerous because if I sold the rifle and someone used ammo that was only .001" larger in neck diameter it sure wouldn't be good.

For now, it's just a matter of neck turning off .001" all the way around to get to the .003" of release that seems safe and reasonable for a hunting rifle but I specifically indicated that I did not want to turn brass and provided the Nosler factory ammo. You live & you learn.

I don't have a SAAMI print I can post here, but you can see one at www.saami.org. The difference between max neck dia of factory loaded ammo and min neck dia of a SAAMI chamber for the .30 Nosler is .002". According to SAAMI your chamber is to spec. SAAMI isn't worried about .001" clearance per side (safety), why are you?

 

[Charlie-NY]

SAAMI isn't worried about .001" clearance per side (safety), why are you?

I find it hard to believe that a SAMMI spec chamber can have only .001" neck clearance and still be in spec. Not all factory ammo has the exact same loaded neck diameter. What if a different brand ammo was only .001" larger in neck diameter? Is zero neck clearance within SAMMI specs and shouldn't a reasonable person be worried about things like that?

Don't forget, this was a hunting rifle using factory ammo. Your comment seems off base to me.

 

[Drop Port]

Hmmm... That or regrind to 20-practical? I'm curious where does a reamer wear out the most, body, neck, shoulder? I'd guess neck/shoulder first... The transition from shoulder to body most?

Throat

 

[shortgrass]

I find it hard to believe that a SAMMI spec chamber can have only .001" neck clearance and still be in spec. Not all factory ammo has the exact same loaded neck diameter. What if a different brand ammo was only .001" larger in neck diameter? Is zero neck clearance within SAMMI specs and shouldn't a reasonable person be worried about things like that?

Don't forget, this was a hunting rifle using factory ammo. Your comment seems odd off base to me.

Not off base at all! Go to the SAAMI web site and see for yourself! www.saami.org The chamber and cartridge drawings are there for all to view. Top drawing is max cartridge, bottom drawing is min chamber. Diameter and length tolerances are listed on the print. "What if a different brand ammo was only .001" larger in neck diameter?". Then that ammo would not be in tolerance to the SAAMI specifications....

 

[Drop Port]

As a Benchrest Shooter, we use tight necks on everything. That being defined as a chamber neck reamed to a dimension that requires turning the necks to achieve the proper clearance over a loaded round.

in years past, many shooters thought that extremely tight necks, with only .0005 clearance over the loaded round, were the way to go. Much of this line of thinking originated in that Houston warehouse crap. In the past-years, the trends have definetally been toward more clearance. To quote NBRSA Shooter Jack Neary…….”turn thin to win”.

And your assumption is correct, you should at least be able to slip a bullet into a fired case. Also, the “soot line” left on the case neck after firing should resemble a sine wave.

If the barrel was not on the rifle, you could simply reach in with a small hole gage and get the actual neck dimension. Short of that, as was said, cerrosafe would be the best bet.
here is a picture of what most of us want to see on a fired neck. This is my 6PPC with right at .002 clearance for a loaded round.
I give my 30BR cases closer to .003. It’s on the right.View attachment 1338831
View attachment 1338830

I wish I had this info when I built my first 6.5x284 chases my tail then gave the necks some generous neck clearance and it was a whole new rifle

 

[Charlie-NY]

"What if a different brand ammo was only .001" larger in neck diameter?". Then that ammo would not be in tolerance to the SAAMI specifications....

You are making the assumption that the Nosler ammo that I have is at the maximum SAAMI spec in neck diameter and that anything larger would not conform with SAAMI specs. I don't make that assumption.

All-in-all, its not reasonable for a gunsmith to cut a chamber with such tight tolerances in a hunting rifle without informing the customer. I've had many custom rifles built, some tight neck and others not, but I always knew exactly what I was getting. And regardless of all the technical mumbo-jumbo, .001" of total neck clearance on a hunting rifle isn't even close to the norm. If you don't specifically request a neck that tight it simply shouldn't be.

Not looking to beat a dead horse and I see that you disagree with me and that's OK. Thanks for the SAAMI link. I think it will prove most helpful in the future.

Have a good one.

 

[shortgrass]

You are making the assumption that the Nosler ammo that I have is at the maximum SAAMI spec in neck diameter and that anything larger would not conform with SAAMI specs. I don't make that assumption.

All-in-all, its not reasonable for a gunsmith to cut a chamber with such tight tolerances in a hunting rifle without informing the customer. I've had many custom rifles built, some tight neck and others not, but I always knew exactly what I was getting. And regardless of all the technical mumbo-jumbo, .001" of total neck clearance on a hunting rifle isn't even close to the norm. If you don't specifically request a neck that tight it simply shouldn't be.

Not looking to beat a dead horse and I see that you disagree with me and that's OK. Thanks for the SAAMI link. I think it will prove most helpful in the future.

Have a good one.

If you didn't bother to mic the necks of the loaded ammo, and you don't know what neck diameter is in the chamber, how do you know it is "tight"? You asked the gunsmith to cut a SAAMI spec chamber, he did. Now you complain about it. According to the print, SAAMI sees no problem with the numbers they provide, neck between min and ammo at max diameters. Personally, I like .003-.0035 neck clearance, but you didn't ask for that,,,,, you asked for SAAMI spec and that is what you got. A minimum SAAMI spec reamer is still within SAAMI specs with the tolerance given. If you want the neck in the chamber to be a specific number, that is what you should ask for, give a number, don't make him guess what it is you want.

 

[Charlie-NY]

In a nutshell - my initial post stated that this happened TWICE. On the first rebarrel of a custom hunting rifle I got to the range only to find out that my ammo would NOT chamber at all. When I called the smith I was advised that it was a "minimum spec chamber". Call it whatever you want but ammo should fit in the chamber with room to spare. I ended up neck turning all the brass which I did not want to do.
I chalked it up to a misunderstanding and bit the bullet.

In an effort to AVOID any misunderstanding when I had another custom hunting rifle rebarreled, I provided 3 boxes of Nosler factory ammo. It was made clear that I wanted the ammo to fit without turning. I fired one round and noticed nearly no expansion. In my concern, I asked the smith why this happened. I was told that it's a minimum spec chamber. After looking at the specs I could see that there was only about .001" of total clearance. It was even slightly less depending on exactly where you measured the neck.

You can continue to defend the work done but I think you would feel differently if they were your rifles and didn't meet your expectations. And by the way - I still don't believe that .001" of neck clearance meets SAAMI expectations or that of any reasonable person. Maybe the reamer was worn a bit but that's not for a customer to figure out.

I'm done on this one, and like I said, have a good one.