Neck clearance ?

[MOShooter]

Got my new rifle a couple of days ago. My reamer print showes to have a .274 neck. The fired brass I have from it has necks of .272. My loaded rounds are .271 leaving me on .001 clearance. From what I've been reading that is cutting it too slim. I don't want to get into neck turning. So what are my options to fix my clearance?

Scott

 

[jcampbellsmith]

Redo your arithmetic. .274-.271 =0.003. My 6XC runs to very similar numbers and I just go shooting with it. Got two bucks yesterday morning.

Regards JCS

 

[XTR]

Got my new rifle a couple of days ago. My reamer print showes to have a .274 neck. The fired brass I have from it has necks of .272. My loaded rounds are .271 leaving me on .001 clearance. From what I've been reading that is cutting it too slim. I don't want to get into neck turning. So what are my options to fix my clearance?

Scott

You have some spring back from the necks. Mic the neck on your reamer, if it is .274 then the hole is .274 and you are fine, if it's smaller you may need to look into turning.

 

[Shynloco]

Redo your arithmetic. .274-.271 =0.003. My 6XC runs to very similar numbers and I just go shooting with it. Got two bucks yesterday morning.

Regards JCS

+1

 

[dixieppc]

Got my new rifle a couple of days ago. My reamer print showes to have a .274 neck. The fired brass I have from it has necks of .272. My loaded rounds are .271 leaving me on .001 clearance. From what I've been reading that is cutting it too slim. I don't want to get into neck turning. So what are my options to fix my clearance?

Scott

If I am reading you right you have .003 clearance not .001 clearance. Your chamber is .274 and your loaded round is .271 the difference being .003. The fired cases neck diameters of .272 is the point of where your cases spring back to after firing and has nothing to do with your clearance.

Regards

 

[dantiff2]

There is spring back but it should be what the reamer says. I had a BR with a tight neck (.270), after firing, my brass measured .270 on the nose. My current 6xc reamer is supposed to be a .273 neck and after firing, my necks are measuring .273. He might not have the right reamer print.

 

[idahoorion]

MOshooter,

check the math if your loaded round is 271 and your chamber neck is 274. you have 3 thou clearance. the neck when fired will expand to the chamber and then spring back. I know some f class shooters who run tighter than that but you have to keep stuff clean. my 6slr with win brass measures 271 to 272 loaded with a .2755 neck and when fired the spring back on the new brass makes the fired neck small enough a bullet will not slip in the case. I don't think your in a danger situation, but you'll want to have clean necks and chamber, but you would anyway. with minimal working on the neck those cases should last a while at least on the front end. Annealing the cases every few firings will keep the brass from work hardening, consult the smith for sure.

Idahoorion

 

[dantiff2]

One thing you didn't mention is: how old is the brass? Once fired?

 

[dantiff2]

Checking my current reamer print shows a .2734" neck deminsions. My necks measure .273 after firing. That is only a spring back of two tenthousandths on each side (.0002") or a total of .0004.


Dan

 

[MOShooter]

New brass. That was my math when I had the reamer made. I was unaware the brass would spring back. That was why I wanted to post the question to see if I was missing something. My first custom and a wildcat. Just making sure I don't blow myself up.

Thanks

Scott

 

[dcali]

In my view, 0.003" is cutting it too close with unturned brass, although just barely. Even good brass can vary in thickness by 0.001" within a lot. If you turn it, you'll KNOW you have 0.003", which is fine. But unturned, you might have 0.001" on some cases, and you might once in a while get one with no clearance. It sort of depends on which cases you measured to figure the 0.003". You might be fine, but you might be going to close.

I've found that .007" of clearance on a 6mm is plenty to give case neck life that will outlast the primer pockets without annealing, but I shoot for 0.005". I've done 0.001" before on a benchrest setup, but you really have to be careful, and turning is obviously required. I don't know if it helps accuracy any, but the cases last forever.

 

[CatShooter]

In my view, 0.003" is cutting it too close with unturned brass, although just barely. Even good brass can vary in thickness by 0.001" within a lot. If you turn it, you'll KNOW you have 0.003", which is fine. But unturned, you might have 0.001" on some cases, and you might once in a while get one with no clearance. It sort of depends on which cases you measured to figure the 0.003". You might be fine, but you might be going to close.

I've found that .007" of clearance on a 6mm is plenty to give case neck life that will outlast the primer pockets without annealing, but I shoot for 0.005". I've done 0.001" before on a benchrest setup, but you really have to be careful, and turning is obviously required. I don't know if it helps accuracy any, but the cases last forever.

If the case necks are not skim turned, and measure 3 thou smaller, then there is NO PROBLEM... what is the point of getting a "no-turrn" neck if you have to turn the necks (insert a big "DUH" here).

Using 7 thou clearance without annealing as a standard to compare - is a very low standard to set the bar at.

 

[dantiff2]

I have to agree with CATSHOOTER. I run a no turn neck and it gives me .002-.0025" clearance on a loaded round. I'm done turning necks. Saw no benefit. What I do is, when I get a batch of new brass is to confirm my loaded neck diameter. I would run .0015 on my tight neck gun with no problems but these were all turned.

Dan

 

[dcali]

You missed my point. My point is that .003" might actually be less than .001" for some cases. You have to measure a sample to find out. Without more information, that's cutting it close in my book. If it's really 0.003", then all is right with the world. But with unturned brass, that's a significant assumption. I wouldn't just assume that the one case that got measured is going to be representative of the largest case in the batch.

For example, I measured the necks on 50 new Lapua .308 cases. I found that the thinnest neck was 1.5 thous thinner than the thickest. That's a diametrical difference of roughly 0.003" (I say "roughly" since cases aren't uniform in their thickness). If the OP were to measure a case on the thinner side by chance and determine that he has .003" of clearance, then he'd be running a very tight clearance on the thickest case. And that was only 50 cases. It's not out of the realm of possibility that the 100th might provide zero clearance or less.

Is he probably fine? Yeah. But maybe not. Caution is good.

 

[dantiff2]

You missed my point. My point is that .003" might actually be less than .001" for some cases. You have to measure a sample to find out. Without more information, that's cutting it close in my book. If it's really 0.003", then all is right with the world. But with unturned brass, that's a significant assumption. I wouldn't just assume that the one case that got measured is going to be representative of the largest case in the batch.

For example, I measured the necks on 50 new Lapua .308 cases. I found that the thinnest neck was 1.5 thous thinner than the thickest. That's a diametrical difference of roughly 0.003" (since cases aren't uniform in their thickness). If the OP were to measure a case on the thinner side by chance and determine that he has .003" of clearance, then he'd be running a very tight clearance on the thickest case. And that was only 50 cases. It's not out of the realm of possibility that the 100th might provide zero clearance or less.

Your absolutely right. Below .004" neck clearance, I would not assume all the cases were the same. It only takes a minute to make sure all new brass has the correct od deminsion.

Dan

 

[CatShooter]

You missed my point. My point is that .003" might actually be less than .001" for some cases. You have to measure a sample to find out. Without more information, that's cutting it close in my book. If it's really 0.003", then all is right with the world. But with unturned brass, that's a significant assumption. I wouldn't just assume that the one case that got measured is going to be representative of the largest case in the batch.

I did not miss your point - your point is specious. If a shooter is using brass that varies 2 thou from case to case, then they have no business handloading.

Over many years, I have never found decent cases that varied as much as you are stating.

This is obviously a "theory" on your part... which has no validity.

 

[dantiff2]

We are steering this the wrong direction. The OP is not concerned with what clearance or neck wall thickness. He is questioning his reamer print. I can only report in my personal experience and that is I have never had more than half a thou spring back on neck od measurements. He is saying he would have to have .002. I could only see that with old work hardened brass. I think the reamer is slightly smaller than the print called for. Either open neck of chamber a couple thou or turn necks for a little more than .001 clearance

Dan

 

[dcali]

Call it theory if you like. I'm talking about actual measured data. 50 brand new cases that are considered to be of high quality from a single lot varied by 1.5 thous. I don't know how much more concrete I can make it.

 

[MOShooter]

Thanks for all the input. I forgot to say that I did inside neck ream them after I formed them to make sure there wasn't a doughnut. I've checked the 10 that I have loaded and all are right at .271. I'll just have to keep an eye on them.

Scott

 

[Keith Glasscock]

Scott,

Just an idea that I use sometimes. With loaded rounds, I take an appropriate sized neck bushing that is .001 bigger than the intended loaded diameter and just see if it will go over the loaded neck. You can feel if you have a case that is bigger than you intend, and it is faster than a micrometer or caliper.