Bumping the shoulder back
- Thread starter igor
- Start date
venatic
Well-known member
If you adjust the dies per the RCBS instructions you should indeed already be bumping the shoulder back. If you are loading for a bolt gun you can adjust your dies to have a minimum "bump" just enough to have slight resistance upon closing the bolt. From memory I believe that too is covered by RCBS in the instructions.
Coyotejunki
Well-known member
By no means do I claim that this is the best way to measure, but it is IMO better than just blindly adjusting your dies. You can measure a datum this way and bump the shoulders back as far as you like or however far the dies will allow.
Coyotejunki
Well-known member
Neck sizing is what it says it is, neck sizing only. A full length sizing die sizes the full length, including the neck, it will move the shoulder.
You can also buy a body die if you already have a neck die and have been neck sizing only, you can use the body die to bump the shoulder.
Some people try to neck size only with a full length die, But I believe it partially sizes the body when you try this.
You can also buy a body die if you already have a neck die and have been neck sizing only, you can use the body die to bump the shoulder.
Some people try to neck size only with a full length die, But I believe it partially sizes the body when you try this.
Last edited:
Hidalgo
Well-known member
Perhaps this will help:
http://reloadingtips.com/how_to/sizing-die-adjustment.htm
The phrase "bump the shoulder" has traveled the circuit so much that it's almost become a process rather than a result. The main concern is to fit the cartridge to the chamber as accurately as possible. I'd recommend that you forget "bumping the shoulder" and instead concentrate on "fitting the brass". Several things can happen when you properly fit the brass to the gun, and shoulder movement is just one of them.
http://reloadingtips.com/how_to/sizing-die-adjustment.htm
The phrase "bump the shoulder" has traveled the circuit so much that it's almost become a process rather than a result. The main concern is to fit the cartridge to the chamber as accurately as possible. I'd recommend that you forget "bumping the shoulder" and instead concentrate on "fitting the brass". Several things can happen when you properly fit the brass to the gun, and shoulder movement is just one of them.
The phrase originated with custom made dies that did no other sizing - didn't size the body or the neck (well, actually, most of them do use bushing to size the neck at the same time, but it's optional...). Literal "shoulder bump" dies. Which, you won't find in the RCBS, Redding, Forster etc. catalogs. They are a custom made only proposition. I have a couple. They were custom made dies for custom chambers, used in bench rest matches. The idea was to do enough sizing to make bolt manipulation easy, so as to minimize disturbance of the bags, but no more. Just the absolute minimum sizing required to make it easy to machine gun a group before conditions changed without disturbing the bags.
The term has been bastardized to where now it relates more to shoulder set back measured during FL sizing. Which isn't really very closely related to a true shoulder bump die. But, whatever...
- DAA
The term has been bastardized to where now it relates more to shoulder set back measured during FL sizing. Which isn't really very closely related to a true shoulder bump die. But, whatever...
- DAA
NdIndy
New member
For the new loader, doing a full length size will give you more or less factory sized brass that should fit about any chamber. Just adjust the die per instructions and if you have to, trim. If you're loading for more than 1 rifle a full length size will work in both guns. After that if you want partial or neck only sizing you're limiting the brass to 1 gun, it will expand to that rifles chamber and likely won't fit the next rifle until you full length size it.
The process is pretty much identical once you get everything adjusted. Depending on the rifle you may not see any increase in accuracy or performance with a neck sized brass, but the brass itself tends to last a little longer. More of a consideration in that aspect if you have hard to find brass.
The process is pretty much identical once you get everything adjusted. Depending on the rifle you may not see any increase in accuracy or performance with a neck sized brass, but the brass itself tends to last a little longer. More of a consideration in that aspect if you have hard to find brass.
Originally Posted By: igorIs bumping the shoulder back something I am already and automaticly doing when I do a standard resize with my standard old Rockchucker and off the shelf rcbs die? Or is this some technique you experts are going to graciously explain to me?
Coyotejunki demonstrated a cheap and easy method to measure how far you are sitting back the shoulders.
Very few know it but Bonanza/Forester neck sizers have the shoulder angle bored to the correct angle and you can use this brand of die to bump shoulders.
Also, CH4D neck sizers will also bump shoulders.
It has always amazed me how bumping the shoulders back may allow a guy to shoot a case 12+ times without ever having to full length size the brass.
The key is to bump back the shoulder only as much as needed, not an excessive amount.
I have found this particularly useful when shooting max loads in 22/250's, 243's, and 25/06's. Since you are only bumping the shoulder back a few 0.001, then you eliminate a lot of case trimming also.
Crater'd primers may cause false readings when measuring the shoulder length to base. To knock the primers out, Lee and RCBS make a universal decapping die that does nothing other than deprime the case. Neil Jones makes a hand tool that you get a very good "feel" for how loose or tight the primer is when you deprime the fired case, and I consider this tool very valuable in my reloading outfit.
Some rifles will be very accurate at a very top end pressure load. I bump the necks on all these loads, and de prime with the Neil Jones tool checking for cases with loose primer pockets. I had a 25/06 that I bumped the shoulders on after every firing and continued to do so until the necks split, brass was cheap back then.
Good luck
Coyotejunki demonstrated a cheap and easy method to measure how far you are sitting back the shoulders.
Very few know it but Bonanza/Forester neck sizers have the shoulder angle bored to the correct angle and you can use this brand of die to bump shoulders.
Also, CH4D neck sizers will also bump shoulders.
It has always amazed me how bumping the shoulders back may allow a guy to shoot a case 12+ times without ever having to full length size the brass.
The key is to bump back the shoulder only as much as needed, not an excessive amount.
I have found this particularly useful when shooting max loads in 22/250's, 243's, and 25/06's. Since you are only bumping the shoulder back a few 0.001, then you eliminate a lot of case trimming also.
Crater'd primers may cause false readings when measuring the shoulder length to base. To knock the primers out, Lee and RCBS make a universal decapping die that does nothing other than deprime the case. Neil Jones makes a hand tool that you get a very good "feel" for how loose or tight the primer is when you deprime the fired case, and I consider this tool very valuable in my reloading outfit.
Some rifles will be very accurate at a very top end pressure load. I bump the necks on all these loads, and de prime with the Neil Jones tool checking for cases with loose primer pockets. I had a 25/06 that I bumped the shoulders on after every firing and continued to do so until the necks split, brass was cheap back then.
Good luck
I learned the hard way lol. When you full size a brass, afterwards check that it fits in the chamber. If it fits with a slight resistance when moving the bolt down then you have it right where you want. Obviously all chambers are slightly different and the factory fodders must be made to accomodate this. But you can create a better chamber/brass fit by setting up the shoulder of the brass a little better.
Originally Posted By: venaticIf you adjust the dies per the RCBS instructions you should indeed already be bumping the shoulder back. If you are loading for a bolt gun you can adjust your dies to have a minimum "bump" just enough to have slight resistance upon closing the bolt. From memory I believe that too is covered by RCBS in the instructions.
venatic,
I do not think this is listed in the RCBS instructions. This is something I learned from someone else and I wish RCBS would publish this. Of course maybe older instructions have this?
venatic,
I do not think this is listed in the RCBS instructions. This is something I learned from someone else and I wish RCBS would publish this. Of course maybe older instructions have this?
What the instructions do not tell you is as follows:
When you are full length sizing, you are sizing down two dimensions, the body(especially the web dia.) and the shoulder to base length.
More often than not, the dimension from the base to the shoulder is what needs bumping back, and usually only .002 will get the job done. However, when the dia at the base has to be resized, the shoulder is often pushed back .006-.012 to get the brass to the point to where the bolt will close easily.
There is a serious learning curve involved in learning how to measure which dimension is creating the problem with your bolt being "tight" when closing on a fired case. While this is only the basics in reloading, to the vast majority, this is very advanced reloading and not understood by most.
Tools needed are dial or electronic caliper, micrometer, and over size ogive gages or use of the shell holder as an over size ogive gage.
When you are full length sizing, you are sizing down two dimensions, the body(especially the web dia.) and the shoulder to base length.
More often than not, the dimension from the base to the shoulder is what needs bumping back, and usually only .002 will get the job done. However, when the dia at the base has to be resized, the shoulder is often pushed back .006-.012 to get the brass to the point to where the bolt will close easily.
There is a serious learning curve involved in learning how to measure which dimension is creating the problem with your bolt being "tight" when closing on a fired case. While this is only the basics in reloading, to the vast majority, this is very advanced reloading and not understood by most.
Tools needed are dial or electronic caliper, micrometer, and over size ogive gages or use of the shell holder as an over size ogive gage.
Originally Posted By: igorIs bumping the shoulder back something I am already and automaticly doing when I do a standard resize with my standard old Rockchucker and off the shelf rcbs die? Or is this some technique you experts are going to graciously explain to me?
If you are full length sizing then there is no need to worry about it...yes, you are currently setting the shoulder, as long as the die is adjusted correctly. The old term "bumping the shoulder back" is in reference to shooters that neck size only. After several times loading that batch of brass the cases get too stretched and eventually start to chamber a little harder than they should. Then you have to "bump the shoulder back" so they chamber easy again.
The term is generally not used when referencing full length sizing.
If you are full length sizing then there is no need to worry about it...yes, you are currently setting the shoulder, as long as the die is adjusted correctly. The old term "bumping the shoulder back" is in reference to shooters that neck size only. After several times loading that batch of brass the cases get too stretched and eventually start to chamber a little harder than they should. Then you have to "bump the shoulder back" so they chamber easy again.
The term is generally not used when referencing full length sizing.