Enough Neck Clearance Between Case Neck and Chamber?

[cdeiglmeier]

Alright, guys I need help from some of you gunsmith/reloading guru's because I'm trying to slowly eliminate theories as to why I am having such high ES/SD numbers. One of those theories is my neck clearance between the loaded case and the chamber. I'm running a custom 7mm rem mag, with Nosler brass, 180 grain Berger hybrids over 69.9 grains of Retumbo. My neck diameter of a loaded round measures 0.3110" (+/- .0005), My smith says the reamer they used for my chamber has a neck diameter of 0.3130". So my main question: is 0.002" enough neck clearance to allow good bullet release?

I've measured the neck of several fired cases and they all measure the same as a loaded round, 0.3110"; which means I cannot push a bullet into the neck of a fired case as I've seen some people say you should be able to do with your fired cases. I don't know if this is because the neck clearance is on the tighter side and/or the Nosler brass I'm using is really thick and returns to pre-firing shape, resisting the deformation of expansion after firing.

On a side note just so you have all the information you need, I anneal all my brass on a benchsource annealer after every firing, I body size bumping the shoulders 0.001-0.002" and then I neck size with a Redding bushing neck die and then use an expander mandrel to achieve 0.282 ID which should give me 0.002" neck tension consistently. I do not use any neck lube for the bullet while seating for shooting, just bare cleaned brass (this could maybe contribute as well and is another theory I need to test).

 

[Milo 2.5]

Not enough clearance. I'd say the reamer used is a neck turn one. Figure .003" clearance on 6mm and most smaller 6.5 stuff, I'd want .004" minimum on a 7mag, maybe even 5 thou.

 

[cdeiglmeier]

Not enough clearance. I'd say the reamer used is a neck turn one. Figure .003" clearance on 6mm and most smaller 6.5 stuff, I'd want .004" minimum on a 7mag, maybe even 5 thou.

Thanks Milo! I have been finding similar conclusions across the interwebs. I'm contemplating getting a neck turning setup to turn down the necks I already have or if I should buy some new brand of brass and test again. In the 7mm mag, WSM, SAUM thread in the reloading depot I found that most other brands of 7mm brass are around 0.309 with a loaded round. That right there tells me Nosler is a much thicker brass.

 

[Milo 2.5]

Thanks Milo! I have been finding similar conclusions across the interwebs. I'm contemplating getting a neck turning setup to turn down the necks I already have or if I should buy some new brand of brass and test again. In the 7mm mag, WSM, SAUM thread in the reloading depot I found that most other brands of 7mm brass are around 0.309 with a loaded round. That right there tells me Nosler is a much thicker brass.

I've never had a 7 mag, but shoot a 7 saum, with Rem brass, and a 180 hybrid, my loaded rds measure .3145". I use a 312 bushing for the most part. Fired brass measure .3205", mine probably excessive on the clearance given springback, 3 firings on this brass w/o issue, glad you posted, I need to monitor this brass for donuts with a bushing die. My first chamber with this reamer.

 

[cdeiglmeier]

I've never had a 7 mag, but shoot a 7 saum, with Rem brass, and a 180 hybrid, my loaded rds measure .3145". I use a 312 bushing for the most part. Fired brass measure .3205", mine probably excessive on the clearance given springback, 3 firings on this brass w/o issue, glad you posted, I need to monitor this brass for donuts with a bushing die. My first chamber with this reamer.

Oh ok, you're running 6 thou neck clearance. Good to know. Do you think I should turn my necks down ~2 thou or should I see if the smith can open up the neck of the chamber?

 

[Milo 2.5]

Oh ok, you're running 6 thou neck clearance. Good to know. Do you think I should turn my necks down ~2 thou or should I see if the smith can open up the neck of the chamber?

I've never been in this situation, not going to say. I have turning equipment, it sucks.

 

[arm017]

Oh ok, you're running 6 thou neck clearance. Good to know. Do you think I should turn my necks down ~2 thou or should I see if the smith can open up the neck of the chamber?

If the smith did not inform you prior that it was a no turn neck, then I would approach him on the situation to see if he can rectify it. Definitely need more neck clearance. Maybe try different brand of brass that would happen to have less brass thickness- I haven't worked with much nosler brass to recall how they tend to run in terms of their brass thickness.

Turning necks isn't the end of the world though? lol

 

[lightman]

Oh ok, you're running 6 thou neck clearance. Good to know. Do you think I should turn my necks down ~2 thou or should I see if the smith can open up the neck of the chamber?

Thats a tough question. I have 2 rifles that I have to turn the necks on that were planned to be no turn necks. But, they shoot so well that I'm hesitant to touch the chambers. I choose to turn the necks. My 6.5-284 on the other hand was planned to be a tight neck and I run .002 clearance with no problems. A .290 neck and I turn the cases to .288.

 

[Milo 2.5]

Turning necks isn't the end of the world though? lol

Ripping your nuts off on a barbwire fence wouldn't be the end of the world either, just saying

 

[arm017]

Ripping your nuts off on a barbwire fence wouldn't be the end of the world either, just saying

Oh then you just gotta buy my 5 part modular system with caliber specific parts that I'll make you spend incrementally so you don't realize that you've dropped 800 on my system on a painstaking, questionably valuable procedure... lol

OP - throwing more money at the problem is usually not the solution. neck turning especially already fired brass is difficult to get consistent.

 

[arm017]

Also for the sake of the thread - Just spoke w/ good friend and mentor Eric Cortina last night who is planning on running a no turn 284 shehane F class cartridge with a no turn neck. As he was mentioning how he thought it was one of those sacred cows that F class guys obsessed over himself included, and was wanting to try a no turn neck to prove to himself one way or another.

 

[Milo 2.5]

I'd consult a qualified smith about just enlarging the neck, but this a way cheaper and easier option.

 

[cdeiglmeier]

I'd consult a qualified smith about just enlarging the neck, but this a way cheaper and easier option.

Yea I'm gonna consult a qualified gunsmith! and see what they say. I don't want to buy all the shit for turning necks and then that's another process I'm gonna obsess over and try to get "perfect" every time. and as someone who's never turned necks before, I'm questionable on it since someone in this thread has already said that it's pretty hard to get right on already fired brass.

 

[Supersubes]

I typically like more clearance for a field gun, but your .002 clearance should be enough. There’s no requirement to be able to push a bullet into the fired case. That’s typically the situation since neck clearances are typically two to three times what you have now. When you only have .001 per side, the neck is going to spring back. As long as the neck isn’t pinched between the chamber neck and your bullet, your good. On that note though, you don’t have much extra, so your ammo needs to be perfect since it won’t take much to bind it up. Do you know what the loaded round runout is? You’re sizing in three steps, that could certainly hurt concentricity. Just a little bit of runout is going to cause one side of the case neck to press against the chamber neck. Have you ever tried segregating the cases which are screwing up the averages? It’s possible those may have a thick neck on one side. Or maybe those cases have varying capacity? Any chance your trim length is a little long and bumping the end of the chamber? Maybe you have some carbon build-up at the end of the chamber, and your cases are bumping that? Then there’s just the normal load stuff. Maybe it doesn’t like the powder, or perhaps your bullet is too close to the lands, etc.

 

[cdeiglmeier]

I typically like more clearance for a field gun, but your .002 clearance should be enough. There’s no requirement to be able to push a bullet into the fired case. That’s typically the situation since neck clearances are typically two to three times what you have now. When you only have .001 per side, the neck is going to spring back. As long as the neck isn’t pinched between the chamber neck and your bullet, your good. On that note though, you don’t have much extra, so your ammo needs to be perfect since it won’t take much to bind it up. Do you know what the loaded round runout is? You’re sizing in three steps, that could certainly hurt concentricity. Just a little bit of runout is going to cause one side of the case neck to press against the chamber neck. Have you ever tried segregating the cases which are screwing up the averages? It’s possible those may have a thick neck on one side. Or maybe those cases have varying capacity? Any chance your trim length is a little long and bumping the end of the chamber? Maybe you have some carbon build-up at the end of the chamber, and your cases are bumping that? Then there’s just the normal load stuff. Maybe it doesn’t like the powder, or perhaps your bullet is too close to the lands, etc.

My loaded rounds runout has been coming to <0.0002" on my 21st century runout gauge. I have not separated cases that were screwing up the averages, but I do weight sort my brass to within 0.5 of a grain of each other. So I don't think its a capacity thing. My chamber is cut to 2.49" in length for the brass and I trim to 2.48 after every firing. But, virgin brass takes roughly 3 firings before it even gets to the point of needing a trim. I've looked in the chamber and can't see any carbon ring build-up, but I do not have a bore scope to 100% make sure but I'm gonna see if someone I know has one that I can borrow and check out my chamber. I don't think the bullet is too close to the lands, I've seated my bullets 20 thou off the lands from my measurements with my Hornady OAL gauge. But I spoke with a local gunsmith, who thinks its most likely neck clearance issue; he recommended I neck turn 20 cases 0.002" under what I currently have, giving me 0.004 neck clearance and see if that fixes the issue. If it does then we found the issue. If it doesn't then we are going back to the drawing board, where we will look more into the other aspects.

 

[TripleBull]

But I spoke with a local gunsmith, who thinks its most likely neck clearance issue; he recommended I neck turn 20 cases 0.002" under what I currently have, giving me 0.004 neck clearance and see if that fixes the issue.

It's worth a try to collect more info. If turning works, you can then decide if you want to expand the chamber, look at other brass, etc. In other words, you don't have to turn all your brass. I've seen enough neck-turning success stories that I'm not as cautious about it as some folks here, but I do think you need to do the minimum and pay attention to the details. Have you put a tube mic on your necks to assess neck thickness consistency?

 

[Milo 2.5]

My loaded rounds runout has been coming to <0.0002" on my 21st century runout gauge. I have not separated cases that were screwing up the averages, but I do weight sort my brass to within 0.5 of a grain of each other. So I don't think its a capacity thing. My chamber is cut to 2.49" in length for the brass and I trim to 2.48 after every firing. But, virgin brass takes roughly 3 firings before it even gets to the point of needing a trim. I've looked in the chamber and can't see any carbon ring build-up, but I do not have a bore scope to 100% make sure but I'm gonna see if someone I know has one that I can borrow and check out my chamber. I don't think the bullet is too close to the lands, I've seated my bullets 20 thou off the lands from my measurements with my Hornady OAL gauge. But I spoke with a local gunsmith, who thinks its most likely neck clearance issue; he recommended I neck turn 20 cases 0.002" under what I currently have, giving me 0.004 neck clearance and see if that fixes the issue. If it does then we found the issue. If it doesn't then we are going back to the drawing board, where we will look more into the other aspects.

Are you 100% sure what you are loading is a low ES-SD load upfront? I recommended more clearance as more of a buffer zone than to improve numbers. Are you going to turn your exiting brass or buy some new, if new, you've lost your baseline, I'd probably just do 10, plus the first 2 you ruin, lol, enough to gather any data you need.

 

[Milo 2.5]

It's worth a try to collect more info. If turning works, you can then decide if you want to expand the chamber, look at other brass, etc. In other words, you don't have to turn all your brass. I've seen enough neck-turning success stories that I'm not as cautious about it as some folks here, but I do think you need to do the minimum and pay attention to the details. Have you put a tube mic on your necks to assess neck thickness consistency?

No question neck that turning works, to me it's, does what you're trying to accomplish necessitate it? I'd bet I've had over 30 new barrels spun up in the last 9 yrs, not once have I sat back and asked myself if neck turning would make any one of those shoot better. I have the equipment to do it, I choose not to.

 

[cdeiglmeier]

Are you 100% sure what you are loading is a low ES-SD load upfront? I recommended more clearance as more of a buffer zone than to improve numbers. Are you going to turn your exiting brass or buy some new, if new, you've lost your baseline, I'd probably just do 10, plus the first 2 you ruin, lol, enough to gather any data you need.

I'm definitely going to turn existing brass that I have, to maintain as much variables as possible! Definitely going to be brass I have that has been fired in my chamber. You're right! I'll try 10 cases neck turned and see what happens. If that does work and solves the problem, then I will cross the bridge of what I want to do when I come to it haha either I neck turn all my cases for the rifle, or I see if the gunsmith can open up the neck of the chamber. The smith I talked to said there's a lot more that goes into open up the neck of a chamber so he said he'd be hesitant to pick that option, but he said we can discuss that further once we figure out for sure its a neck clearance issue.

My previous load for this rifle was 71.1 grains of Retumbo, 180 Berger Hybrids, seated at the same depth, same CCI 250 primers, and same brass prep and I was getting ES of 12-15 and SD of 8-9. Not the lowest of numbers but it worked. Only reason I dropped is that my barrel sped up, within the last 25 rounds by about 50 fps, the increased temp, pushed this load well into the over-pressure zone. So subsequently I dropped my powder charge back down to a previous node I found during initial load development which was 69.8-70.0 grains, which is why I'm loading 69.9 grains now. I talked with the gunsmith about why this previous load seemed to work and the current load of 69.9 is not performing like we expect when we were talking about neck clearance and neck clearance issues. He said that it still leads us to the same 2 theories we already had, either you don't have enough neck clearance or the barrel doesn't like this powder/powder charge. But he (being very mechanically inclined as an engineer) said it's possible that since you were pushing extreme pressures, the pressures created by your powder charge (71.1 grains), were enough to "force" the neck to expand as much as it could with the small chamber and forcing the bullet out with enough force that the neck clearance issue didn't have a great effect on it but as you dropped the powder charge, that excess pressure that was previously there helping mask the clearance issue is now more visible and effecting the release of the bullet that you've dropped the powder charge back within normal limits. He used some physics analogy to explain how it's possible for this to work with excessive pressures, but basically it was the fact that excessive pressures can mask the real problem. The only way to eliminate either of these theories though is to change one of the variables and test again, and he said the the most telling sign is that I can't push a bullet into the neck of a fired case, that coupled with the fact that my velocities are all over the place is a tell-tale sign that it's a neck clearance issue.

 

[cdeiglmeier]

It's worth a try to collect more info. If turning works, you can then decide if you want to expand the chamber, look at other brass, etc. In other words, you don't have to turn all your brass. I've seen enough neck-turning success stories that I'm not as cautious about it as some folks here, but I do think you need to do the minimum and pay attention to the details. Have you put a tube mic on your necks to assess neck thickness consistency?

Unfortunately, I do not have a set of tube mics to check this. Right now just using a Mitutoyo digital caliper. Hopefully, finding a local friend who has some to check this as well.

 

[Milo 2.5]

I'm definitely going to turn existing brass that I have, to maintain as much variables as possible! Definitely going to be brass I have that has been fired in my chamber. You're right! I'll try 10 cases neck turned and see what happens. If that does work and solves the problem, then I will cross the bridge of what I want to do when I come to it haha either I neck turn all my cases for the rifle, or I see if the gunsmith can open up the neck of the chamber. The smith I talked to said there's a lot more that goes into open up the neck of a chamber so he said he'd be hesitant to pick that option, but he said we can discuss that further once we figure out for sure its a neck clearance issue.

My previous load for this rifle was 71.1 grains of Retumbo, 180 Berger Hybrids, seated at the same depth, same CCI 250 primers, and same brass prep and I was getting ES of 12-15 and SD of 8-9. Not the lowest of numbers but it worked. Only reason I dropped is that my barrel sped up, within the last 25 rounds by about 50 fps, the increased temp, pushed this load well into the over-pressure zone. So subsequently I dropped my powder charge back down to a previous node I found during initial load development which was 69.8-70.0 grains, which is why I'm loading 69.9 grains now. I talked with the gunsmith about why this previous load seemed to work and the current load of 69.9 is not performing like we expect when we were talking about neck clearance and neck clearance issues. He said that it still leads us to the same 2 theories we already had, either you don't have enough neck clearance or the barrel doesn't like this powder/powder charge. But he (being very mechanically inclined as an engineer) said it's possible that since you were pushing extreme pressures, the pressures created by your powder charge (71.1 grains), were enough to "force" the neck to expand as much as it could with the small chamber and forcing the bullet out with enough force that the neck clearance issue didn't have a great effect on it but as you dropped the powder charge, that excess pressure that was previously there helping mask the clearance issue is now more visible and effecting the release of the bullet that you've dropped the powder charge back within normal limits. He used some physics analogy to explain how it's possible for this to work with excessive pressures, but basically it was the fact that excessive pressures can mask the real problem. The only way to eliminate either of these theories though is to change one of the variables and test again, and he said the the most telling sign is that I can't push a bullet into the neck of a fired case, that coupled with the fact that my velocities are all over the place is a tell-tale sign that it's a neck clearance issue.

Follow your smiths advice on re-reaming neck, I have it in my head it could be done by hand and am probably way off base. If you must buy turning gear, K&M has a decent setup you can get into under a hundred I think, with case holder, it's been awhile though.

 

[cdeiglmeier]

Follow your smiths advice on re-reaming neck, I have it in my head it could be done by hand and am probably way off base. If you must buy turning gear, K&M has a decent setup you can get into under a hundred I think, with case holder, it's been awhile though.

Yea as I've never turned necks before this will be a new endeavor for me. I'm doing lots of research and watching videos on all the different setup's out on the market. Just like a lot of us on this forum, I'm super picky in the reloading room but also super impatient when it comes to reloading hahaha. I want things to be as consistent as possible but take the least amount of time possible which is how I ended up with a Giraud trimmer and A&D FX120i autothrower/autotrickler..... the addiction is real lol

 

[M_R_Woodard]

You could try some Winchester brass, it has thinner necks than others. It doesn't hold up as well as the Nosler though.

 

[kabarNC]

I ended up having to turn necks for my .284, had exactly what you describe in the OP. I didnt want to invest in neck turning equipment, the time to do it, or any other calibers that needed it for that matter. I went with PMA tool, a turning setup configured exactly how you specify, dedicated to that one chamber/cartridge. I really am impressed with it, SDs went down to 3 or 4, and is extremely easy to use. Think it was 70.00. Very helpful and knowledgable on the phone also, good folks.

http://www.pmatool.com/pma-neck-turning-tool-model-b/