I've always used standard full-length sizing dies but am starting to wonder about bushing dies. I will be starting to load for 7 saum in the next few days and want to get the most consistent brass i'm capable of. I have never used a bushing die of any kind, so not really sure where to start. How do you know which bushing to use for your brass, etc?
FL or bushing die?
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Measure the diameter of a loaded round at the neck. Say it's .320. Conventional wisdom is to use a .318 bushing. The difference being .002. I've settled on .003.
BTW, Redding (and others) sell the full length bushing die. That is the best of both worlds IMHO.
BTW, Redding (and others) sell the full length bushing die. That is the best of both worlds IMHO.
milboltnut
Well-Known Member
bushing dies work the brass less, however some sticklers don't like them due to more runout. Body die (only sets shoulder back and doesn't touch the neck) /neck bush die or a honed neck FL die from Forster. I like the idea of the first vs the latter.
vancewalker007
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There are bibles written on this issue and you can quickly go down a rabbit hole with it.
One of major error points new users don't realize is that brass from different manufactures have different thickness in the neck region. This effects the bushing sizes you need since we are talking about a few thousandths of an inch here. So, if you switch brass types say Hornady to Laupa your bushing will likely not give the same neck tension as Laupa brass is typically thicker than Hornady so you will have a higher tension with the Laupa. So, its a good idea to stick with a given manufacturer's brass once you lock down a load setup. Now you can circumvent this issue if you get into turning necks which gives you the power to control the neck wall thickness to your desired number. Turning necks can also be another rabbit hole.
On picking bushing, every chamber will be slightly different but likely your 7mm neck will be expanding to around .317-.321 depending on the reamer used. The SAAMI spec for the SAUM shows a max of .320 for the case and .321 for the chamber. You will not know the upper limit for sure until you have fired a round to measure. Most people using bushings use a 2 step (ie. 2 bushing) process to avoid stepping down the neck too much in one step. This is suppose to minimize the chance the case will get distorted damaging its neck alignment there by causing it to be misaligned to the bore of the rifle. The dogma is don't step down a neck more than 5 thousandths of an inch in one step. I'm sure some research would reveal where this rule of thumb came from but lets assume its correct. So, using this rule of thumb I will give you an example using my data from my 7mm LRM. My LRM cases expand to about .319 so my first pass bushing is a .315 then my final bushing to give the neck tension I desire to use is a .312. I had tried a .311 and a .313 along with the .312. I arrived at trying the .311, .312 and .313 final bushing by using a ball caliper to check the case mouth thickness then calculating the bushing sizes from there. So the cases measured 0.015 and the bullet is 0.284. So (2*0.015)+0.284 = 0.314. Take 0.314 and subtract .001-.003 and that gave me the bushing sizes try initially. Having a ball caliper is handy when messing with bushings. It will tell you what the thickness of the case necks are so you can do a rough calculation on possible bushings.
There is a ton of info online in videos this is an example.
www.bing.com
One of major error points new users don't realize is that brass from different manufactures have different thickness in the neck region. This effects the bushing sizes you need since we are talking about a few thousandths of an inch here. So, if you switch brass types say Hornady to Laupa your bushing will likely not give the same neck tension as Laupa brass is typically thicker than Hornady so you will have a higher tension with the Laupa. So, its a good idea to stick with a given manufacturer's brass once you lock down a load setup. Now you can circumvent this issue if you get into turning necks which gives you the power to control the neck wall thickness to your desired number. Turning necks can also be another rabbit hole.
On picking bushing, every chamber will be slightly different but likely your 7mm neck will be expanding to around .317-.321 depending on the reamer used. The SAAMI spec for the SAUM shows a max of .320 for the case and .321 for the chamber. You will not know the upper limit for sure until you have fired a round to measure. Most people using bushings use a 2 step (ie. 2 bushing) process to avoid stepping down the neck too much in one step. This is suppose to minimize the chance the case will get distorted damaging its neck alignment there by causing it to be misaligned to the bore of the rifle. The dogma is don't step down a neck more than 5 thousandths of an inch in one step. I'm sure some research would reveal where this rule of thumb came from but lets assume its correct. So, using this rule of thumb I will give you an example using my data from my 7mm LRM. My LRM cases expand to about .319 so my first pass bushing is a .315 then my final bushing to give the neck tension I desire to use is a .312. I had tried a .311 and a .313 along with the .312. I arrived at trying the .311, .312 and .313 final bushing by using a ball caliper to check the case mouth thickness then calculating the bushing sizes from there. So the cases measured 0.015 and the bullet is 0.284. So (2*0.015)+0.284 = 0.314. Take 0.314 and subtract .001-.003 and that gave me the bushing sizes try initially. Having a ball caliper is handy when messing with bushings. It will tell you what the thickness of the case necks are so you can do a rough calculation on possible bushings.
There is a ton of info online in videos this is an example.
using bushing dies - Search Videos
Orange Dust
Well-Known Member
I use a F/L die with the expander removed. I then run the cases through a mandrel die to expand the necks. I do this on all my LR rifles. Any rifle that gets used only in its point blank range just gets a F/L die or neck die.
milboltnut
Well-Known Member
Vancewalker
True !
Neck thickness may still change at that..... quote below form another member here.
On new brass which is .3116+- od, I push a standard 7mm expander ball (.282) thru it to open up the neck to .312+ just in case the neck is dinged, then I use a .311 neck bushing and the finished od is .3115/.3116. Fired brass neck od is .318 and I'm not sure what I'm gonna have to do to those.
.3115/.3116 shoots better than .3122 which is what I get with a standard fl sizer and expander ball.
.3115/.3116 shoots better than .3122 which is what I get with a standard fl sizer and expander ball.
What brass? Neck turned or no?
Wow, thanks Vance. This is exactly why I haven't gone down this rabbit hole yet. Every time I start to scratch the surface, I get somewhat overwhelmed with information and varying opinions so I stop there. I got a Sinclair mandrel die and figured I would remove the button in my Forster die and use the mandrel .002" undersized.There are bibles written on this issue and you can quickly go down a rabbit hole with it.
One of major error points new users don't realize is that brass from different manufactures have different thickness in the neck region. This effects the bushing sizes you need since we are talking about a few thousandths of an inch here. So, if you switch brass types say Hornady to Laupa your bushing will likely not give the same neck tension as Laupa brass is typically thicker than Hornady so you will have a higher tension with the Laupa. So, its a good idea to stick with a given manufacturer's brass once you lock down a load setup. Now you can circumvent this issue if you get into turning necks which gives you the power to control the neck wall thickness to your desired number. Turning necks can also be another rabbit hole.
On picking bushing, every chamber will be slightly different but likely your 7mm neck will be expanding to around .317-.321 depending on the reamer used. The SAAMI spec for the SAUM shows a max of .320 for the case and .321 for the chamber. You will not know the upper limit for sure until you have fired a round to measure. Most people using bushings use a 2 step (ie. 2 bushing) process to avoid stepping down the neck too much in one step. This is suppose to minimize the chance the case will get distorted damaging its neck alignment there by causing it to be misaligned to the bore of the rifle. The dogma is don't step down a neck more than 5 thousandths of an inch in one step. I'm sure some research would reveal where this rule of thumb came from but lets assume its correct. So, using this rule of thumb I will give you an example using my data from my 7mm LRM. My LRM cases expand to about .319 so my first pass bushing is a .315 then my final bushing to give the neck tension I desire to use is a .312. I had tried a .311 and a .313 along with the .312. I arrived at trying the .311, .312 and .313 final bushing by using a ball caliper to check the case mouth thickness then calculating the bushing sizes from there. So the cases measured 0.015 and the bullet is 0.284. So (2*0.015)+0.284 = 0.314. Take 0.314 and subtract .001-.003 and that gave me the bushing sizes try initially. Having a ball caliper is handy when messing with bushings. It will tell you what the thickness of the case necks are so you can do a rough calculation on possible bushings.
There is a ton of info online in videos this is an example.
using bushing dies - Search Videos
ADG, no turning
vancewalker007
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Mandrels work very good. My 79 year old father (been reloading over 50 years) has recently gotten into trying the mandrel way. Again you have to get that neck down safely to a diameter that can then be expanded. I am still using the 2 bushing approach no mandrel. Doing that has been more than accurate enough for long range hunting. We regularly take Coues deer at 400-700 yard region. Our longest shot on Coues being 934 yards that my son made with my father's old 7mm LRM a few years ago. My son made a 1092 yard shot on an Elk 3 years ago with ammo I loaded for his 7mm LRM using the 2 bushing setup. So, it works. I think even if were using a mandrel I'd still step down the necks in steps of 0.005 or less.
What is the best way to size down the neck before expanding if I don't have bushing dies?
vancewalker007
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- Joined
- Mar 30, 2013
- Messages
- 984
Well you need a sizer die to start the process. But remember if you use a standard SAAMI one step sizer you run a risk of causing runout numbers to go up. Which will effect accuracy.
Frankly if you want to use an expander mandrel I don't see a way around using a bushing die to allow you to control neck sizing as precisely as possible before applying the mandrel. From what I can glean the mandrel step is suppose to give better case to case accuracy on tension. On these steps anything you can do to improve the result will pay off in consistency.
If you decide to go the bushing route with the ADG brass 314-316 would be a good place to start.
