Neck Tension

[Bob3700]

Jlow,

If you truly turn your case necks to a consistent .0002" TIR, have you looked at the distribution of brass in your cases? That out of round that you turned off the necks exists all the way down to the base of the case to a lesser or greater extent. Get your tools out and measure the variation in brass thickness down at the head of the case.

Now think about this. Even with a perfect (and I would consider a neck wall thickness variation of .0002" perfect) is the bullet still starting straight into the throat when fired? Or, might that variation in case wall thickness turn your case into a banana when extreme pressure is applied? With a banana curve in your case might it be possible that the bullet no longer can enter the throat straight?

I would be working over a chronograph with a goal to get my SD down to a specific single digit number (average) and go shoot. Once you are in the realm of acceptable accuracy at 600 or 1000 yds (I'd say 1/2 MOA) then your shooting and wind reading skills are what will be holding you back, not the rifle or ammo.

Bob

 

[DanConzo]

I think you are probably right on Bob.

 

[jlow]

Jlow,

If you truly turn your case necks to a consistent .0002" TIR, have you looked at the distribution of brass in your cases? That out of round that you turned off the necks exists all the way down to the base of the case to a lesser or greater extent. Get your tools out and measure the variation in brass thickness down at the head of the case.

Now think about this. Even with a perfect (and I would consider a neck wall thickness variation of .0002" perfect) is the bullet still starting straight into the throat when fired? Or, might that variation in case wall thickness turn your case into a banana when extreme pressure is applied? With a banana curve in your case might it be possible that the bullet no longer can enter the throat straight?

I would be working over a chronograph with a goal to get my SD down to a specific single digit number (average) and go shoot. Once you are in the realm of acceptable accuracy at 600 or 1000 yds (I'd say 1/2 MOA) then your shooting and wind reading skills are what will be holding you back, not the rifle or ammo.

Bob

Thanks Bob3700 for your comment.

First, I selected my brass by culling anything that has more than 0.0015” variation in the neck thickness when they are new. This of course is because we know that neck variations also reflect case body variation and as you say when it is fired will banana. The cases I am working on are 4x fired and has good concentricity so this is not the problem.

Now the thing is as you know, before you turn any neck, you got to expand it first – this I did with the K&M expander. So after the necks are turned, they are of course too big to hold a bullet. To correct this, I size the neck down with a Lee Collet die. It is only after I size that I check for roundness because well that is when it really matters right?

The thing is if you start off with an expanded neck and you squeeze down, assuming that the mandrel in the Lee is not out of round (and it is not since I measured it), the neck will grow a little in thickness because the brass has to go somewhere but if the whole thing is concentric, then you should get a relatively even thickness but with a smaller OD/ID right?

This is where I am having problems i.e. the OD when measured at different spots are significantly different. This sounds odd but my question to those who is reading this, my question to you is have you ever measured the roundness of you necks after sizing or do you just assumed that they would be round?

 

[Bob3700]

Jlow,

I have to tell you that I am the odd duck out here because I do not outside neck turn my cases. My cases are in-line, inside neck reamed. With my lathe I have created FL sizing dies with a long upper section that guides an inside reamer down thru the neck of the case.

Once I have the cases reamed and they are fired, I full length resize them and then run them over a mandrel. This makes the ID of the case necks as consistent as possible. It is important to make sure that all of your necks are at the same state of hardness (annealed) so that they expand or spring back the same. As cases are fired more, the necks spring back more and you have to use a larger ID mandrel to expand the necks slightly more.

My focus is on keeping the ID of the necks the most consistent. That keeps my neck tension as close to the same as possible.

This helps me keep my SDs in single digits and groups at 600 and 1000 yds as small as possible.

Bob

 

[jlow]

Hi Bob,

You might be the odd duck but, the way you are doing it is IMHO the best way. The problem with outside neck turning is regardless of how well you neck turn (even “perfect” as someone called mine), the exact surface inside the neck may not be as smooth. This is because all one is during to “ensure” this is to either expand the neck from the inside (regular neck sizing) or push the outside in (Lee Collet). The fact is I KNOW for personal experience that neither one of those two methods are perfect, so in the end the “perfect” outside neck turn surface is NOT transferred to the inside neck surface which is what one wants and I think what you have.

Hardness I don’t think is my problem as I am annealing according to factory specs using a BenchSource.

Very nice! Thank you for sharing both your method and passion! I dig it!

 

[DanConzo]

I believe this is the best way possible for the best ids and no donuts.

 

[DanConzo]

Bob3700--Do you make the reamers or buy them, or buy them then grind them to size? I know RCBS sells them at a very high price $70 plus. They also make fl inline ream dies for about $100. I see you make your own dies, do you harden them? Do you ever get a donut w/ this system, if so do you just run reamer in to remove. I hope I didn't ask too many questions here, but the person who used this system that I knew has died and of course I want to know more about. Thanks

 

[lpreddick]

inside neck reaming got my attention. neck tension is not a static situation. please, no one start talking about "cold bonding". neck tension variation has given me fits. i approach handloading from a scientific perspective and am doing so with neck tension. i started turning necks as advised but noted the thickness of a neck increases as you approach the shoulder, even after turning and firing a few times. i neck size with reading bushings and can feel an increasing resistance as a flat based bullet is seated ...the pressure ring is the part of the bullet that stretches the brass the most...there is less contact between the bearing surface and neck. i use wilson inside neck reamers and note a more uniform seating after reaming. a boat tail bullet with no pressure ring seems to be even smoother. i am amazed at the difference when reaming what i thought was a uniform group of cases that were processed at the same time...all having the same external diameter after turning. the neck expander may not be pushing all the brass externally, equally. mine will not push an established donut out and reaming one is not nearly as easy as reaming neck brass. i'd like to hear more on reaming. thanks.

 

[Bob3700]

Dan,

You can purchase chucking reamers for most bore sizes and they can be ordered a half thousands smaller. So I have chucking reamers that are .2425" for my 6mm cases.

My dies are not hardened although there is no reason you cannot do that. I make the top of the die about 1.5 to 2 inches taller so that it is the section of the die that guides the chucking reamer.

The reamers are available from many different tool supply houses like KBC, McMaster-Carr. They are not that expensive, usually under $20 each.

Ideally, I like to chamber the die with a resizing reamer and then That way the case is held in perfect alignment when the reamer is run down thru the case.

The dies thread into my std. reloading press. Slide the case into the resizing die and run the reamer down thru the case neck. You can do this on a regular basis and make sure that donuts are not forming in your cases.

Once that is done, you can then adjust your neck tension by running the case over a specific OD mandrel.

I run very light neck tensions and soft seat my bullets long. That lets the throat of the bbl seat the bullets and I don't have to chase the throat as it wears.

I don't know how to adjust neck tension any better than that.

Bob

 

[DanConzo]

Bob--Are the chucking reamer shanks 3/8" and then do you bore out the hole on top of die for the shank to turn in w/ tight fit? I wonder if RCBS blank dies would have enough length for cases 2 to 2 7/8" long or maybe Newlon or someone else. I guess the reamer cutting end could be cut a little to help out some. I remember the old Lee Match Grade Loading Kit that had the off-set inside neck reamer for their hand die that worked pretty well. About how much length above the top of the case would a guy need to set this up? Thanks

 

[Luke_NL]

Am following this thread with interest. As of yet, I don't see myself chasing consistency to the umpteenth decimal (I would need some better measuring equipment, for starters) but I am in awe of the dedication of those that do. Hats off.

Hopefully you'll forgive me a "noob" question. When either turning necks or inside reaming (or both?) to make sure all is even to the (tens of) thousandths, do you do the same to your actual bullets?

LPreddicks comments about a "pressure ring" on bullets set me off in that sense, because -without measuring- do you know that said pressure ring is the same for each of the bullets in your lot? Weighing only does so much, and with the bullets being plated en masse, I could totally see the odd microns of plating being either more or less present on individual bullets. It would seem to me that, in order to achieve perfect alignment and consistency, you would have to ensure that (after neck turning and inside reaming) the surface contact between the "perfect case neck" and each bullet would be similar, i.e. that each bullet is just as painstakingly even in all aspects as said case. Would it not be best to "cancel out" (in whatever way) the mentioned pressure rings, to have the neck tension divided over the entire surface between neck and seated bullet?

That being said, I don't look forward to measuring each bullet and running them through a lathe to ensure they're all perfectly even :-X

 

[spclark]

No, it's not a usual practice to turn bullets.

There are some who'll do all kinds of sorting operations, the better to "uniform" bullets to be shot in order on a given target or yard line.

Some will choose bullet brands that give them greater confidence in product uniformity than they feel those provided by the major label manufacturers will give.

Some just buy, load & shoot.

You have to decide (after checking your wallet) what level of "anal" you're comfortable with....

 

[amlevin]

I'm just waiting for the post where someone picked up a good used SEM (scanning electron microscope) and has started analyzing their cases for uniform grain structure, just to take uniform neck tension to the next level of accuracy 8) 8) 8) 8)

Saw a used Hitachi S-3500N that's available for a mere $80k. It's supposed to be "Like New"

 

[SDDasher]

You have to decide (after checking your wallet) what level of "anal" you're comfortable with....

I am going to have to think that one over some........

 

[DanConzo]

I think the measurement stuff is over with, and the conclusion for neck wall thickness of a couple 10 thousandths is where a person wants to be. We may be making headway here on inline inside neck reaming as an alternative for outside neck turning for some who are interested. The one guy even brought the problems out about the wall thickness of the case body too, which would make a guy ponder what is the limit here for good accuracy. Donuts were even brought up. There may be a lot more to learn here even if it's in a future post but some good questions are now out. I figure this reloading post is for this stuff. I'd like to see more of this and pictures too. A manufacturer may make a new tool to satisfy some of this stuff or even better brass manufactured. Just mho.

 

[amlevin]

I think the measurement stuff is over with, and the conclusion for neck wall thickness of a couple 10 thousandths is where a person wants to be. We may be making headway here on inline inside neck reaming as an alternative for outside neck turning for some who are interested. The one guy even brought the problems out about the wall thickness of the case body too, which would make a guy ponder what is the limit here for good accuracy. Donuts were even brought up. There may be a lot more to learn here even if it's in a future post but some good questions are now out. I figure this reloading post is for this stuff. I'd like to see more of this and pictures too. A manufacturer may make a new tool to satisfy some of this stuff or even better brass manufactured. Just mho.

Your mention of case wall thickness and other variables may all become moot when "caseless" ammunition arrives fully on the scene.

From what I've been reading, it's not far away for the Military.

 

[DanConzo]

Amlevin--I didn't read or hear anything on it.

 

[Steve Blair]

Your mention of case wall thickness and other variables may all become moot when "caseless" ammunition arrives fully on the scene.

From what I've been reading, it's not far away for the Military.

[br]
Chamber sealing failures will likely never be resolved. I fired the G11 on HK's Aixheim range in the late eighties. It was an excellent handling weapon but suffered the necessity of extremely close tolerances to maintain breech sealing. Consequently, it was also very sensitive to contaminant ingress. Our heavy, expensive and inconvenient brass cases provide several very important functions that are difficult to replicate by mechanism or ammunition design. While it is possible that these technical barriers will be overcome, keep in mind that engineers have been working on caseless ammuntion since WW2 with varying success. Nonetheless, not a single weapon has been fielded despite the many potential benefits (reduced load, cheaper ammo, reduced strategic materials, etc.). The developments and technology demonstrators are always interesting but I would not hold my breath waiting.

 

[Bob3700]

Dan,

Actually, Hunington Dies (RCBS at one time) actually made these dies. You could order the die for the caliber you want and let them know the OD of the reamer.

The shank of the chucking reamers in the smaller sizes is larger than the cutting edges so the top of the dies are made to closely hold the shank of the reamer.

The leading edge of the reamers are beveled and will usually start in the case no problem. I will run the reamer down the case neck after 5-6 firings to remove any potential donuts. It really isn't that big of an issue for me as I seat my bullets above the shoulder/neck junction anyway. Nice to know that necks are cut uniform all the way thru.

Bob

 

[DanConzo]

Thanks Bob. In the past I had factory fl dies cut out on top for bushings, so possibly a standard fl die that is hardened could be bored or reamed on top for the reamer w/ carbide for the reamer shank taking threads out etc because there is a hole already there smaller than the reamer shank. What do you think?