redding neck bushings

[mattkarstetter]

ive got a 7mm wsm. the necks of some of my loaded ammo meausre .313 to .315. i think i need a point .312 and .311. i got those numbers by averaging to .314 and subtracting .002. I have not neck turned these yet. It is all winchester brass. Am i on the right track. Ive also got a post in the WTB thread if anyone has any of these bushings that they are not using anymore and want to clean them out.

thanks

matt

 

[oldgrayone]

Re: redding neck bushings

From Reddings web site.
http://www.redding-reloading.com/tech-line-a-tips
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. (These dummy cartridges can be loaded with your old set of dies or a borrowed set.) Then, simply subtract 0.001" from the cartridge that had the smallest average measurement. This will allow for a slight amount of spring back and create a proper press fit for the bullet.

Another method of determining bushing size, is to measure the neck wall thickness of the cartridge cases with a ball type or tubing micrometer. Double this measurement and add the bullet diameter to calculate the neck diameter of a loaded cartridge. As above, subtract 0.001" from this figure to determine bushing size. This method is the least desirable of the two, as a ball micrometer is fairly expensive and more difficult to read consistently than a conventional micrometer

 

[WARDOG]

Re: redding neck bushings

I am in the process of loading some 7 WSM right now, necking down .300 Norma to 7mm and sizing 7mm WSM Winchester brass. I am <span style="font-style: italic">also</span> using the Redding Neck Bushing dies.
I have learned a lot in the last few days, with a lot of help from others here.
As I was advised, it is not <span style="font-style: italic">all</span> cut and dry to get the measurements for the bushings. In my case necking down the Norma brass is adding another dimension to getting to the final bushing size. A .320 bushing gets me a .2835 ID (Internal Dimension) on the neck. That is exactly what the Berger 180 O.D. measures. So I am going to try a .318 bushing next to try to get the ID tension right, and neck turn the O.D. just enough to get it to fire a light 150 gr the first time to fireform the case. I have to blow the shoulder forward since the angle of the shoulder and dimensions are different between the 7mm and the .300 WSM. So I can't neck trim too much right off.
I have also realized that ultimately you will have to have <span style="font-style: italic">two</span> bushing dimensions. The first larger bushing to size the neck when preparing the virgin brass, then a smaller bushing to neck size the case after neck turning it and firing it. That smaller bushing will be used over and over to resize the neck for the proper tension.
In my search for answers I have found that your question is a popular one. I happen to have the chamber reamer dimensions from my builder, so I know the play I have in the neck diameter, and neck thickness.
I can run a WSM Winchester brass tomorrow to give you the bushing diameter for the I.D. neck that you want for your desired tension. What neck thickness do you want after neck turning?
I will post the result here tomorrow.
<span style="font-weight: bold">FYI:</span> I do plan on writing up a topic here for my successful procedures for necking down the popular <span style="font-style: italic">Norma</span> brass from .300 to 7mm. I should be able to write it up by the beginning of March.
Other Reloaders here: If I gave poor advice please advise us. I won't be offended.

<span style="font-weight: bold"><span style="color: #993300">WARDOG</span></span>

 

[WARDOG]

Re: redding neck bushings

OK. I tried to size the Winchester brass this morning to answer your question.
The virgin Winchester brass measures <span style="font-style: italic">all over the place</span>.
Out of 10 cases, the I.D. of the necks measured .275 - .278"
The O.D. of the necks measured .309 - .312.
So... using virgin Win. brass if you loaded the case, you would have <span style="font-style: italic">a lot</span> of neck tension, and it would be inconsistent, unless you neck turned.
In order for me to help you, I would need to know what you ultimatley want your neck thickness to be, and what the I.D. to be for your desired neck tension.
I have the following bushings .311, .312, .313, .314, .316, .318, .320 so I should be able to figure it out for you.

 

[mattkarstetter]

Re: redding neck bushings

i have some once fired brass. the way i understand it is that the brass in now formed to the chamber. so the outside measurement of the brass should be the same. i will check that out when i have some time. if this is true it should show some variations on the inside neck diameter of a few thousandths.

at that point i should then measure a berger 180 vld because that is the only bullet i am using in this gun and have purchased 800 from the same lot.

if i then measure the thickness of the neck and multiply it by two i should have the total number for the material my bushing will be sizing. of course i will have to clean these cases in the ultrasonic cleaner and use a nylon brush to clean the inside of the necks to ensure that i am not including any carbon in my measurements.

if all that is true then im not sure how far to turn the necks down.

i am in the process of getting the guage for measuring neck thickness but am not sure which one to buy. any advice would be greatly appreciated. i am looking at sinclair but do not know which one to get. any expecrience would be appreciated.


i also have the rcbs neck trimming tool. im sure their are better ones available but for now that is what i have. if anyone has advice on these, please let me know.

i apologize for the run on post, so thanks for bearing with me. any help you guys can impart would be greatly appreciated.

so far this site has forced me to sell 2 cars and a snowmobile to keep up my new found "crack" habit. This as well as numerous glares and comments about my time spent here, and i cant thank you guys enough because 5 little holes really close together on a piece of paper far far away are the best therapy i have found in years.

until tomorow

thanks

matt

 

[EWP]

Re: redding neck bushings

I use the Redding neck thickness gauge, it's much easier to read, faster, and gives much more consistent measurements/results than my expensive ball mic.

The most useful tools I have for case prep
Concentricity gauge http://www.sinclairintl.com/.aspx/sid=70547/pid=37479/Product/SINCLAIR_CONCENTRICITY_GAGE_WITH_DIAL

&

Redding case neck indicator