Neck turning...min neck thickness

[Bob Wright]

Chamber casting is the ticket to determine actual neck size in chamber. Check with a local Smith to do it if you don't want to mess with it.

 

[ButterBean]

I don't know....dropped group size 0.15" in the original barrel...that seems like something. Your thoughts? I could have become a better shooter....

Don't let him get under your skin, He has the answer for everything, You have found that annealing helped the problem so stick with that regiment and if it were me i would take a little less off and don't worry if it just cleans up one side as it will still help

 

[corsteve]

have a 7/mm 300prc turn necks 1000 no problems

 

[DUSTY NOGGIN]

annealing was your fix ..

 

[J E Custom]

Normal case neck expansion should be between .003 and .006 depending on your chamber. If you have a tight neck chamber you will want a fired case to be a minimum of .003 thousandths larger than the neck chamber in order to get consistent bullet releases. Any more only over works your brass, My personal preference is .004 (.002 per side). on dangerous game rifles you will want .006 to .008 (You don't worry about brass if hunting something that can/will kill you).

Fire formed cases are normally the most dependable for measuring the neck chamber diameter if you don't/can't make a chamber cast. The fired case dimension, plus the bullet diameter, plus the clearance you want, (.003 minimum) will tell you what your case neck wall should be for your chamber. Example: fired case neck measures= .335, minus bullet diameter of .308 = .027 minus .003 expansion =.024 divided by 2 = .014 is the neck wall thickness you should use as the maximum. less than that will cause no ill effects except shorter brass life. If your brass is work hardened annealing will give you a better/more accurate dimension.

I have seen neck wall thicknesses as thin as .010 that shot great but they were used in very tight neck chambers that cases had to be turned just to get the necessary expansion of the neck.

It really doesn't matter how thick or thin the neck wall is as long as it is uniform and within the .003 to .006 expansion range for your chamber. To tight = pressure, to loose = shorter case life and possibly accuracy if over sized.

Find out what your neck chamber size is and uniformly trim to have ,003 to ,006 clearance between a loaded round and your neck chamber dimension and all will be well.

J E CUSTOM

 

[redleg1013]

Firstly, I've yet to get a bag of Winchester 300 WSM brass that didn't have at least five that were unusable, so there's that...
Secondly, you're getting a whole lot of release, as was mentioned above, which could be exacerbating the issue. Not to sound insulting, but are you fire forming and resizing before turning?Personally I've found a great deal of neck wall variation goes away just resizing and using an expander mandrel. It sounds like you found a workaround with annealing. If you're planning on getting a new barrel you MIGHT be better off not working a bunch of brass up that you're likely going to have to replace anyway.

 

[corsteve]

i have a 7mm/300prc that we built we anneal brass an use a bushing die bu t have since went with a ptg die blank an a reamer no problems

 

[Mikecr]

I'll add something here,,, not trying to annoy anyone, but:
Needing more neck clearance than bullet release requires is nothing more than a mob notion.
We don't actually NEED more clearance than you can well manage.

What holds your bullets is the gripping hoop force of neck springback against .XXX area of seated bearing.
What releases your bullets is neck expansion due to pressure.
How much does a neck have to expand to release bullet bearing?
This would be hard to measure, but as long as the brass and jacket molecules are not in chemical bind, then a millionth of an inch separation might as well be a mile. A bullet is freely swingin in the wind by then.
How much pressure does it take to expand a neck a millionth of an inch?
Well, it's little relative to peak chamber pressure.

The only way to delay this release is to establish an interference fit (negative clearance) so that a neck could not expand AT ALL. Of course that's a VERY dangerous condition.
And since your management of field clearances includes +/- relative miles, it is prudent to provide plenty enough clearance.

I can & do manage 0.0005"(1/2thou) of neck clearance (fitted neck) for one of my guns. No problem.
For others, not MY chambers, 1-3thou is reasonable.
This does not affect pressures, and I'm confident that no human will ever prove it can.
There is no basis for more neck clearance resulting in lower pressure.
What I'm trying to relay here is that you do not HAVE TO produce more clearance, and that you're not really hurting anything (pressure-wise) with less. It's not really anything to be terrified of.

Now it is bad to results if your loaded runout exceeds clearances, as this causes chambered pressure points.
But keep in mind, the tighter your clearances, the straighter your ammo. This is How I easily manage 1/2thou of clearances. The case runout from that chamber is too low to measure without abnormal procedure and tools.
This is as self-perpetuating as large clearances are to large runout.
So again, nothing to be worried about really.

 

[ButterBean]

I'll add something here,,, not trying to annoy anyone, but:
Needing more neck clearance than bullet release requires is nothing more than a mob notion.
We don't actually NEED more clearance than you can well manage.

What holds your bullets is the gripping hoop force of neck springback against .XXX area of seated bearing.
What releases your bullets is neck expansion due to pressure.
How much does a neck have to expand to release bullet bearing?
This would be hard to measure, but as long as the brass and jacket molecules are not in chemical bind, then a millionth of an inch separation might as well be a mile. A bullet is freely swingin in the wind by then.
How much pressure does it take to expand a neck a millionth of an inch?
Well, it's little relative to peak chamber pressure.

The only way to delay this release is to establish an interference fit (negative clearance) so that a neck could not expand AT ALL. Of course that's a VERY dangerous condition.
And since your management of field clearances includes +/- relative miles, it is prudent to provide plenty enough clearance.

I can & do manage 0.0005"(1/2thou) of neck clearance (fitted neck) for one of my guns. No problem.
For others, not MY chambers, 1-3thou is reasonable.
This does not affect pressures, and I'm confident that no human will ever prove it can.
There is no basis for more neck clearance resulting in lower pressure.
What I'm trying to relay here is that you do not HAVE TO produce more clearance, and that you're not really hurting anything (pressure-wise) with less. It's not really anything to be terrified of.

Now it is bad to results if your loaded runout exceeds clearances, as this causes chambered pressure points.
But keep in mind, the tighter your clearances, the straighter your ammo. This is How I easily manage 1/2thou of clearances. The case runout from that chamber is too low to measure without abnormal procedure and tools.
This is as self-perpetuating as large clearances are to large runout.
So again, nothing to be worried about really.

And once again we're in the ditch, and completely sidetracked from the OP's question of " Neck turning...min neck thickness "

 

[DUSTY NOGGIN]

IMO you dont turn for neck clearance . you turn for neck thickness consistency and concentricity of future firings

i preffer 100 percent turn cutter contact

... if you anneal it will seal

 

[ButterBean]

IMO you dont turn for neck clearance . you turn for neck thickness consistency and concentricity of future firings

i preffer 100 percent turn cutter contact

... if you anneal it will seal

^^^^^^^^^^^^^^^^^^^^^
I agree percent, I would guess that why te majority of us neck turn

 

[J E Custom]

Sometimes we, as experienced re loaders forget that many people don't turn the necks and just load cases as is. The differences in neck clearance becomes crucial when firing cases with different case neck thicknesses because if you get a case that has "No" room to expand, high pressure normally follows. Unless you turn every neck to allow for some expansion in that chamber, you can definitely
experience this condition. So .003+ will normally take care of this issue on unturned case necks.

If you can turn every neck to the exact thickness for your chamber you wouldn't need over .001 thousandths to release the bullet cleanly, But there are many other considerations that need to be addressed when going with such close tolerances in my opinion and the decision is yours on how much clearance you want.

The main reason for turning is uniform neck wall thickness, and as long as you have some clearance,
you will be ok. If you have a special neck diameter, my recommendation is to turn every neck until they all clean up. as far as the actual neck wall thickness, I an not sure that there is a minimum thickness as long as you have enough to apply bullet grip. I have always stopped at .010 thousandths neck wall as my minimum.

Standards are there for safety reasons and as long as you know the risk, you can do what you want but you are own your own.

J E CUSTOM

 

[nksmfamjp]

Sometimes we, as experienced re loaders forget that many people don't turn the necks and just load cases as is. The differences in neck clearance becomes crucial when firing cases with different case neck thicknesses because if you get a case that has "No" room to expand, high pressure normally follows. Unless you turn every neck to allow for some expansion in that chamber, you can definitely
experience this condition. So .003+ will normally take care of this issue on unturned case necks.

If you can turn every neck to the exact thickness for your chamber you wouldn't need over .001 thousandths to release the bullet cleanly, But there are many other considerations that need to be addressed when going with such close tolerances in my opinion and the decision is yours on how much clearance you want.

The main reason for turning is uniform neck wall thickness, and as long as you have some clearance,
you will be ok. If you have a special neck diameter, my recommendation is to turn every neck until they all clean up. as far as the actual neck wall thickness, I an not sure that there is a minimum thickness as long as you have enough to apply bullet grip. I have always stopped at .010 thousandths neck wall as my minimum.

Standards are there for safety reasons and as long as you know the risk, you can do what you want but you are own your own.

J E CUSTOM

Thanks. I'm at 0.014", but I think I will drop to 0.0136 or 0.0134 to see if I can get a bit more clean up.