Fired case neck size vs loaded neck size

[adamsgt]

Took my Ruger precision Rifle to the range last week to get the scope dialed in. I used Federal GM .308 w/168 gr Sierra MK bullet ammunition. Shot about 20 rounds at 100 yards. Groups were unremarkable. At home I measured the neck size of the fired cases and they ran .346. I seated a Sierra 168 MK in a Lapua .308 case and the neck diameter measured .339 That's a .007 difference. Both the Federal and Lapua neck thickness was about .015.

Is this cause for concern? It's not what we expect with BR calibers. Don't know if that could be the reason for the lackluster groups I saw. I called Ruger to ask about the chamber neck diameter but the rep said he could only discuss the land and groove measurements in the barrel. Instead he recommended that I shoot Black Hills .308 ammo. The rep seemed pissed that I dared to ask him something he couldn't read off a script.

In the Sinclair catalog, on page 37, there is a discussion on appropriate bushing size from Redding. In the case where the fired case neck size is considerably larger(.006 to .010), tests have shown that a bushing .001 larger (than the loaded round) may give you the desired bullet grip. Since this seems to fit my situation, it implies that I should use a .340 neck bushing. I'm not sure I understand this. Help Please.

 

[CMaier]

Actually about normal...340 is "normal" i think on commercial 30 cal chambers.

My recent 300 win mag is a 340 neck and the brass cones out at 339. but 346 is a bit large..missed that

Not br fun, but typical commercial...now see if you can reach the lands
under mag length.
One of my 308's went to 2.96 to reach the lands.

 

[jackie schmidt]

Took my Ruger precision Rifle to the range last week to get the scope dialed in. I used Federal GM .308 w/168 gr Sierra MK bullet ammunition. Shot about 20 rounds at 100 yards. Groups were unremarkable. At home I measured the neck size of the fired cases and they ran .346. I seated a Sierra 168 MK in a Lapua .308 case and the neck diameter measured .339 That's a .007 difference. Both the Federal and Lapua neck thickness was about .015.

Is this cause for concern? It's not what we expect with BR calibers. Don't know if that could be the reason for the lackluster groups I saw. I called Ruger to ask about the chamber neck diameter but the rep said he could only discuss the land and groove measurements in the barrel. Instead he recommended that I shoot Black Hills .308 ammo. The rep seemed pissed that I dared to ask him something he couldn't read off a script.

In the Sinclair catalog, on page 37, there is a discussion on appropriate bushing size from Redding. In the case where the fired case neck size is considerably larger(.006 to .010), tests have shown that a bushing .001 larger (than the loaded round) may give you the desired bullet grip. Since this seems to fit my situation, it implies that I should use a .340 neck bushing. I'm not sure I understand this. Help Please.

All Factory Rifles have what we would call generous neck clearances when compared to what we use in accuracy minded rifles.

Remember, it has to be able to safely fire a standard 308 round anywhere on the planet, made by any manufacturer.

 

[adamsgt]

All Factory Rifles have what we would call generous neck clearances when compared to what we use in accuracy minded rifles.

Remember, it has to be able to safely fire a standard 308 round anywhere on the planet, made by any manufacturer.

I understand that Jackie, but this rifle is being hyped by Ruger as a "Precision Rifle". In all fairness to Ruger, I haven't given this rifle a good wring out yet so off to Quickload and some load development.

Still, no one has yet addressed the question of why I should use a bushing die .001 larger than the neck diameter with a bullet loaded. That sounds like some really soft seating. I hope someone comes back with a reply that results in me doing a dumb polack forehead slap.

 

[Boyd Allen]

I think that you may want to take another look at the advice on bushing selection. The bushing needs to be smaller than the neck diameter of a loaded round, not larger.

 

[CMaier]

another monday morning brain phart typo.
i use 1,2 and 3 thou depending on the rifle

 

[jackie schmidt]

I understand that Jackie, but this rifle is being hyped by Ruger as a "Precision Rifle". In all fairness to Ruger, I haven't given this rifle a good wring out yet so off to Quickload and some load development.

Still, no one has yet addressed the question of why I should use a bushing die .001 larger than the neck diameter with a bullet loaded. That sounds like some really soft seating. I hope someone comes back with a reply that results in me doing a dumb polack forehead slap.

Looks like you need about a .337 bushing.

The term "Precision Rifle" is a misnomer as far as things like chamber size and throat length are concerned. It is still a mass produced rifle sold to the general public, and has to be manufactured to SAAMI specs so it can chamber and shoot standard mass produced ammunition.

 

[adamsgt]

I think that you may want to take another look at the advice on bushing selection. The bushing needs to be smaller than the neck diameter of a loaded round, not larger.

Boyd, I was quoting out of the Sinclair catalog. I've also got the printed 2015 Redding catalog which stated for fired cases with case necks (.006 to 010)" larger than loaded cartridges, "under these circumstances our tests have shown that a bushing .001 larger may give the desired results".

The Sinclair catalog paraphrased the Redding catalog by saying "Redding's tests have shown that a bushing .001" larger (than the loaded round) may give you the desired bullet grip".

I've noted that the Redding statement does not state "larger than what. whereas the Sinclair statement adds (than the loaded round).

At this point I remembered that I downloaded the 2016 Redding catalog as a pdf last night. I went to the page that had the note about this situation and it was gone. In it's place was this:

"Final note: If you are not sorting case neck wall thickness
for uniformity, we do not recommend the use of any
bushing style die without a sizing button."

So, if I use a .337 or .338 bushing to size a .346 neck I'll be alright if it goes? Or I go with a die that uses an expander button and forgo tweaking neck tension.

So, I guess if Sinclair issues a new catalog that statement should be gone. Just for grins I'm going to call Sinclair today and tweak them about it as it makes no sense.

 

[Boyd Allen]

From the current Redding catalog, part of a tech. tip relating to bushing selection:
"The easiest way to determine the proper diameter bushing, is to measure the neck diameter of several loaded or dummy cartridges with an accurate micrometer. Subtract .001”–.002” from the average neck diameter and this diameter bushing will generally size

case necks to create the proper press fit for the bullet."

My own experience with bushing FL dies has been that I one picks a bushing that sizes un-turned necks so that a very light drag from the expander ball is felt, that neck ID are more uniform, and concentricity is not adversely affected. The problems that are widely associated with the use of expander balls are caused their being part of one piece dies that size necks excessively, wich results in excessive pull as the expander passes through the neck. This causes the case shoulder to yield slightly, asymmetrically, cocking the neck. Any time that I expand necks, whether with expander ball or mandrel, I lube their IDs and then remove the lube after sizing. The rate at which the press handle is manipulated during expanding operations affects the total force exerted on the case.

 

[adamsgt]

I guess the remaining question is can I run a .346 neck into a .337 bushing? I have .337 and .338 bushings along with a Type S full length sizing die en route but won't get here till Friday or so.

 

[alinwa]

I guess the remaining question is can I run a .346 neck into a .337 bushing? I have .337 and .338 bushings along with a Type S full length sizing die en route but won't get here till Friday or so.

yes

 

[adamsgt]

yes

Short and sweet always fits the bill, thanks Al.

 

[WSnyder]

In the Sinclair catalog, on page 37, there is a discussion on appropriate bushing size from Redding. In the case where the fired case neck size is considerably larger(.006 to .010), tests have shown that a bushing .001 larger (than the loaded round) may give you the desired bullet grip. Since this seems to fit my situation, it implies that I should use a .340 neck bushing. I'm not sure I understand this. Help Please.

Still, no one has yet addressed the question of why I should use a bushing die .001 larger than the neck diameter with a bullet loaded. That sounds like some really soft seating. I hope someone comes back with a reply that results in me doing a dumb polack forehead slap.

The reasoning behind this was at some point someone noticed that when you ran large OD necks into a much smaller bushing the neck would roll in on the leading edge of the bushing to a smaller diameter than desired and what the bushing ID would normally give resulting in a neck ID/OD smaller than desired. So what seems counter intuitive can actually work to get the neck tension desired with a larger bushing than seems correct. When/if this happens is why at one time they recommended what they did or maybe still do. Many people experienced the phenomena. I have sized necks in two steps with two different bushings for this reason with a SAAMI chamber. One step in a full length S die and a second step in a Comp neck die.

 

[adamsgt]

The reasoning behind this was at some point someone noticed that when you ran large OD necks into a much smaller bushing the neck would roll in on the leading edge of the bushing to a smaller diameter than desired and what the bushing ID would normally give resulting in a neck ID/OD smaller than desired. So what seems counter intuitive can actually work to get the neck tension desired with a larger bushing than seems correct. When/if this happens is why at one time they recommended what they did or maybe still do. Many people experienced the phenomena. I have sized necks in two steps with two different bushings for this reason with a SAAMI chamber. One step in a full length S die and a second step in a Comp neck die.

Thanks for the explanation. Makes sense. I hadn't thought of the rollover of the lip of the case. I'll bring my pin gauges home to check the cases when I put that .346 case into the .337 bushing. I had considered that I might have to use a two step process to get the neck sized right. Well, the bushings and die are scheduled to arrive Friday so I'll get to check this out over the weekend.

 

[XBBR Shooter]

I think that you may want to take another look at the advice on bushing selection. The bushing needs to be smaller than the neck diameter of a loaded round, not larger.

 

[Boyd Allen]

Larger than what? I would say larger than what was arrived at by the previously stated method. Evidently you think that they meant larger than the average loaded round diameter. I will give them a call Monday and ask which it is, and get back to you. If you try a bushing that is one OVER average loaded neck diameter, I would be interested in hearing if the ammo passes their bullet security test.

 

[XBBR Shooter]

Larger than what? I would say larger than what was arrived at by the previously stated method. Evidently you think that they meant larger than the average loaded round diameter. I will give them a call Monday and ask which it is, and get back to you. If you try a bushing that is one OVER average loaded neck diameter, I would be interested in hearing if the ammo passes their bullet security test.

Well, actually, I am the one that discovered the problem around 2002-ish, and contacted Redding about - One year later, the "Tip" poster appeared in their catalogue, and has been there ever since... I still have the rifle that "discovered" the problem.

It came about when I had a 300 Winchester Magnum, 1,200 meter match rifle built by one of the better known Camp Perry gun builders. The reamer cut a minimum body, but the neck was quite large (~ 8 thou over loaded neck).

When I used a bushing "S" die, the sized neck was SMALLER than the bushing (and please don't say the bushing was not the dia that it was marked - it was the first thing checked with a cerosafe cast). After neck sizing, the bushing was actually a very loose fit on the sized neck, and would fall off if tilted over.

Here is an email I still have in my files with Patrick Ryan, at Redding.

"From: xxxxx@xxx.net [mailto:xxxxx@xxx.net]
Sent: Thursday, July 10, 2008 5:43 PM
To: Techline@redding-reloading.com
Subject: Re: Comp bushing sizers... and bushings.


Good afternoon Patrick T. Ryan.

Two things today...

About 5 or 6 years ago, I had Moe Defino build a 300 Win Mag 1,200 meter target rifle, built on a Rem 40-XB Stainless single shot action. The chamber was standard SAAMI, not a tight neck or a no turn neck.

For loading cases, I used a Bushing "S" neck die, and the sized necks were not coming out the diameter they were supposed to have, they were coming out smaller...

After much confusion and frustration, I found that "if" sizing down of the neck was a lot (~8 or 9 thou), then the neck would over shoot the bore diameter of the bushing wind up smaller than the bushing... and of course, they had a little ridge on the neck where the neck stopped in the bushing (just cosmetic, but dog ugly, none the less).

I called you about it, and at that time, you hadn't heard of this undersizing problem, and I don't think you believed me that it was happening.

In your next catalogue, I read something in your information about this problem happening, and warning customers that they might need a larger bushing that the normal recommendations suggested. That was good.

I still get into arguments about it with people that say it can't happen.

Since then, I have become a "Bushing watcher" At that time, the bushings had a rounded edge that the neck encountered entering the bushing. I thought that was not the best design, but I understand the necessities of manufacturing.

About 3 years ago (I think), I received a bushing that has a 45 degree angle at the entrance to the bushing bore - that made really ugly necks with scratches - I spoke to someone up there (not you), and they said they were doing that to cut costs. Not good!

I thought that a long, tapered, conical edge, something like 25 degrees would be better, allowing a more gentle entrance into the bushing, and little or no overshoot in sizing necks that were 8 to 10 thou over the bushing size. Kinda like the current trend in case mouth chamfering tools that are 20 and 14 degrees.

I have thought of contacting you and recommending it, but I know how much you just love to get 800 e-mails a day telling you how to run your business and make your dies .

But I just had Remington Custom Shop put new 6mm Remington barrel put on a 40-XB rifle, and they used a reamer with a SAAMI neck - fired cases come out at ~.278-ish, so that's 8 to 9 thou over a loaded neck.

To make what is becoming a long story a little shorter... I just bought a new Bushing for the new 6mm Rem Comp Sizer. It is a .269... I checked the OD of the finished sized neck, and it was .2685"... 0.0005 over shoot on a neck that was 9 thou over the bushing size - so I looked at the bushing with a jeweler's loup, and there is a long conical taper going into the bore - well, I'll be damned. Also, the little ridge on the case neck at the end of the sized section is gone - it is a gentle tapered ramp.

So... if you have changed the way you are making the bushings, BRAVO - it is a success - if it is an accident, keep doing it, because it is a success.

Now to the other part of this.

Most of my neck sizers are Bushing "S" dies. I have one Comp Sizer for a 6mmBR. But I decided to get a comp sizer for this 6mm Rem.

I have two problems with it - one is yours and one is, mine (kinda - I guess).

First, the the case chamber is too long - a new case goes into the chamber so far that there is only 0.121" sticking out - the shell holder is 0.125, so the shell holder is raising the chamber, not the case shoulder - so all the advantages of the centering of the case before sizing the neck are lost

The second part is that fired cases won't go all the way into the chamber, because they are a few thou larger at the base, so the chamber, (with a fired case) is raised by friction of the lower body, not the shoulder... also not a good thing.

Now... I know that these dies were originally designed for benchrest guys with minimum chambers, but there is a growing bunch of match shooters that are buying these dies that do NOT have minimum chambers - probably the larger portion of the market these days.
Many of these folks do not have the technical savvy to solve these problems, or even to detect these things.

I would think that it might be worthwhile to make the body diameter a little larger to accommodate standard SAAMI chamber body sizes.

Now, I will have to find someone with a lath to cut the chamber 10 thou shorter, and then polish out the inner walls to take my cases - a real pain, but doable - but I think there are many customers that would just send the dies back to the dealer, and buy something else.

So now you have had e-mail #801 on how to run your business, and make your dies

Keep up the good work.

Paul"

 

[Boyd Allen]

Interesting. Thanks for sharing. I learned something. For large necked chambers, I try to go with good brass, not turn, and use a combined sizing process with a Lee collet die, and a body die. I believe that this can actually give superior results in that situation.

Some time back, I suggested a couple of modifications of the Redding competition seater to a friend. He cut the sleeve off so that the shoulder of the case pushed it up, and because the fit of the body of the case was somewhat loose, he used some tape carefully applied to the inside of the sleeve near its bottom opening, to reduce that clearance.

Another thing that I suggested was to set the body of the die so that there was LIGHT toggling at the top of his Rockchucker's ram stroke,. this to improve cosistency of ogive to head measurements of loaded ammo.

I had also mentioned that modifying shell holders to allow more lateral movement on the press ram, and switching from the stock spring clip to an O ring might allow cases to center better in both sizing and seating dies might work. After determining that the stock setup was holding cases slightly off center, he made those modifications as well as "keyholing" the ram slot (chucked the ram in his lathe) to allow more movement of the shell holder to the rear. The net result was a measurable improvement of the concentricity of sized brass.

 

[XBBR Shooter]

[...] He cut the sleeve off so that the shoulder of the case pushed it up, and because the fit of the body of the case was somewhat loose, he used some tape carefully applied to the inside of the sleeve near its bottom opening, to reduce that clearance.

Great minds think alike...

I have bought a bunch of Comp neck sizers, and about half of them have chambers that are too long. I called about it two years ago, and the new customer service people that replaced Pat Ryan don't know doodley squat about loading. I had to explain it 4 different ways before he understood what I was talking about - then he says, "That's the way they're supposed to be."

The sleeve MUST be lifted by the case shoulder, or you might as well save a bunch of money and by the bushing "S" neck die.