Guys who run tight neck chambers

[46and2]

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.

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?

 

[603Country]

I had similar problem a couple of years ago, when I had my 223 rebarreled. The gunsmith put in a tight chambering that I had not asked for. That, combined with thick Lapua case neck wall thickness forced me to turn case necks. Finally, I had him open up the chamber neck a bit.

 

[andrew l]

It's my opinion that whether you have a "turn" neck chamber or not, it's beneficial to have enough clearance so that you are able to pass the slip test you performed.

 

[rwj]

Chamber/neck clearance in my 6BRs is ~.003/.004” which exceeds the amount of interference fit being applied to the bullets. Knowing that there is enough radial neck clearance to allow free bullet release, I don’t worry about whether a bullet can pass thru the neck of a fired case (some do, some don’t). If the amount of bullet interference fit was greater than the chamber/neck clearance, I would think differently…

 

[mac86951]

+1 to cerrosafe the chamber. If you want to run Lapua brass you may need to open it up, or have it opened, the cerrosafe will tell you for sure; alternative is to use thinner neck brass, or turn necks which you already know about. Give your chamber a good cleaning, and scope it if you can; sounds like it's relatively new, could be something else is going on such as a too long neck; again cerrosafe will tell you.

 

[Walt Krafft]

Check for burrs on the inside and outside of the neck. They can give you false readings.

 

[46and2]

I didn't size the cases at all because I'm just fire forming them to my chamber, I wonder how much spring back there is on the virgin Lapua brass. I'm thinking about sizing and firing again to see if the spring back is less.

 

[Charlie-NY]

I had a similar problem (TWICE) with a gunsmith who said he used minimum spec reamers when I never specified anything and expected a SAMMI chamber. Loaded factory Nosler ammo was barely .001" under neck diameter. Totally unsafe for a hunting rifle IMO. I had to pull the bullets from the 30Nosler ammo, (I couldn't get brass at the time) and had to neck turn the brass before reassembling. What a PITA. The smith was sent the ammo in advance of rebarreling the rifle. There was no excuse for this to happen.

 

[PopCharlie]

I shoot a 6br with a tight neck chamber, .266. I started out turning neck to .010. This gave me loaded rounds at .264. I could not slide a bullet thru a fired neck. I then turned the necks to .009. At .009, I could slide a bullet in a fired case. Loaded rounds are at .262. This gives me .004 total clearance, .002 on each side. This is said to be ideal, but I can't shoot the difference.

PopCharlie

 

[rwj]

I had a similar problem (TWICE) with a gunsmith who said he used minimum spec reamers when I never specified anything and expected a SAMMI chamber.

Worn reamers produce smaller diameter chambers!

 

[jackieschmidt]

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.

 

[Nick Caprinolo]

Answer me one question. Why do you supposed die makers include an expander ball in their dies.

 

[Murray Brook]

Answer me one question. Why do you supposed die makers include an expander ball in their dies.

I would think that most die makers feel that the run-out induced by the expander ball doesn't make enough of a difference in accuracy when used in most hunting situations and saves the reloader one extra step in the process. JMO

 

[Old Navy]

I have run into that several times on new barrels. The second firing they would slide in.

 

[Charlie-NY]

Worn reamers produce smaller diameter chambers!

Maybe, but that's not what I expect when paying a professional gunsmith to do the work. It's his obligation to get things right. Making excuses about minimum spec reamers is just that - an excuse.

 

[Sandstorm]

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.

 

[jobhopper66]

Maybe but that's not what I expect when paying a professional gunsmith to do the work. It's his obligation to get things right. Making excuses about minimum spec reamers is just that - an excuse.

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.

 

[rwj]

Maybe, but that's not what I expect when paying a professional gunsmith to do the work. It's his obligation to get things right. Making excuses about minimum spec reamers is just that - an excuse.

Agreed… so that may well be a provider to avoid!

 

[Ledd Slinger]

No telling how many chambers a reamer cuts before it is replaced at a production rifle company like Christensen Arms. Each time a reamer cuts a chamber they get worn down a little bit. They eventually get dull and wear down then get sent off for re-sharpening. That reamer which started at .342” neck could be a lot smaller if it has cut a lot of chambers and been re-sharpened a few times. Could be really bad if the reamer started out of spec or is lesser quality like those produced by PTG.

That’s why I always like to spend the money and have my own reamers for custom barrels. May not use the reamers very often but at least I know how many chambers each one has cut and whether or not it’s still within spec of my print dimensions. I only purchase JGS reamers these days because they stay extremely sharp for a long time and the workmanship is first class.

For neck clearance I think .002” total diameter difference is a minimum (.001” on all sides) but I personally prefer .004” clearance (.002” clearance on all sides)

 

[46and2]

So, I shot a couple of pieces of Lapua brass for the 2nd firing. They go over a bullet much easier, maybe only .0005 interference.
I think I'll still cast the chamber and turn about. 001 after these are fire formed.

Thanks everyone.