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Question: Body die vs modified full length die

 
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  #1  
Old 04-03-2006, 05:08 AM
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Question: Body die vs modified full length die

I recently bought a Redding bushing die and it works great. However, after resizing the cases (Lapua)about 7 times, I'm feeling more resistance on the bolt handle when I'm closing the bolt.I've been told to get a body die that will resize the body of the case, without interfering with the neck.
My questions:
1) Is the dimension of a body die(bump die??)the same as a full length die if you ignore the neck dimension of the full length die? In other words, could one in theory make a body die from a FL die by reaming out the neck portion of the die and removing the depriming rod?
2)with such a die (body die)- are you just setting the shoulder back slightly, or are you also sizing the base of the case?
I could use a Fl die after annealing, but then I'd have to fireform the cases again to get them to spec and this seems like a waste of powder and bullets.
I await your answers with bated breath! [img]/ubbthreads/images/graemlins/grin.gif[/img]
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  #2  
Old 04-03-2006, 06:14 AM
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Re: Question: Body die vs modified full length die

What you've described is probably the best way to modify a standard full-length sizing die to full-length size cases, set the shoulder back a couple thousandths, size all of the neck and keep it very straight and end up with a case that'll probably shoot more accurate than anything else.

I'd lap out (or have someone else do it using a lathe to turn the die) the full-length sizing die's neck to about two or three thousandths smaller than loaded round neck diameter. That should hold bullets tight enough so they won't move from recoil while in the magazine. Start by lapping it to four thousandths smaller, then try some loads. That should be fine for box magazine use or it may be a bit too tight. It depends on the elasticity of the brass in the neck. You may end up with two dies; one with a smaller neck for magazine use and one with a larger one for single loading.

Full-length sizing with such a die typically produces better accuracy than neck-only or partial-neck sizing. And case life with such a die as mentioned above will be very long providing the fired case body diameters are not reduced more than about three thousandths of an inch. I've said it before, but Sierra Bullets has always used full-lenght sizing dies to test their bullets for accuracy and I don't think anybody shoots them as accurate as they do.

There is no such thing as perfectly round chambers and fired cases and fired case headspace varies a tiny bit. So the idea many folks have that a fired case perfectly fits the chamber is a myth. Non-believers should measure both for roundness (not diameter) and headspace to learn.
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  #3  
Old 04-05-2006, 08:08 PM
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Re: Question: Body die vs modified full length die


[ QUOTE ]
Full-length sizing with such a die typically produces better accuracy than neck-only or partial-neck sizing.

[/ QUOTE ]

This is not necessarily so. While FL sizing can be as accurate as anything, a hard fast rule stating this is always the case is by nature incorrect. The reason why is because a FL sizer has as much of a possibility of being "off" as a neck sizer does. Your reloaded brass can only be as good as the die that sizes it.

So, a beginner reading this thread might FL size his brass to make it more accurate but he might be using a low grade die or even a basic RCBS die that isn't running true and now he thinks that his Neck sizer is not to be used and it might actually be a good die.

There have been swings proceedings in benchrest for the last 20 years. FOr awhile, neck sizing was thought to be best. THen partial neck sizing. Then it was FL sizing. THen it went back to neck. Now it is just barely pushing the shoulder back and necksizing the whole neck with the proper bushing. THIS IS NOT BECAUSE IT'S MORE ACCURATE. It is because of speed. That's right. Speed of operating the action. With the shoulder bumped back just a touch, it ensures that the bolt will close easily and no surprises during the relay will occur.

A simple look back at the match results for the last 10 years will show that the group sizes have stayed pretty close to the same throughout the different methods of sizing while the 6ppc has been used with N133. FL sizing didn't make them more accurate, it just made them easier to operate.

[ QUOTE ]
There is no such thing as perfectly round chambers and fired cases and fired case headspace varies a tiny bit. So the idea many folks have that a fired case perfectly fits the chamber is a myth. Non-believers should measure both for roundness (not diameter) and headspace to learn.

[/ QUOTE ]


With this being said, then how would FL sizing make things more accurate since it is making the brass rest farther away from the chamber walls?

Another point I might make:
Concentricity is the name of this game. It tells you how accurately the dies are making your brass. And IT IS EASIER (with standard dies) TO MAKE BRASS MORE CONCENTRIC WITH NECK SIZERS SIMPLY BECAUSE A BAD NECK SIZER MOVES LESS OF THE BRASS THAN A BAD FL SIZER.

I run neck sizers only until I have to FL size on three of my 1k rifles because I have experimented with neckers and full sizers and the neckers gave better accuracy. That being said, I have two rifles that shoot better FL sized at and over 1000 yards. Bottom line: experiment with your own dies, and then make a decision as to what is more accurate with that particular rifle and don't get caught up in the Neck/FL sizing debate because it is not a hard, fast rule. [img]/ubbthreads/images/graemlins/wink.gif[/img]
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  #4  
Old 04-06-2006, 02:13 AM
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Re: Question: Body die vs modified full length die

[ QUOTE ]
(Full-length sizing with such a die typically produces better accuracy than neck-only or partial-neck sizing.) ....a hard fast rule stating this is always the case is by nature incorrect.

(There is no such thing as perfectly round chambers and fired cases and fired case headspace varies a tiny bit.) With this being said, then how would FL sizing make things more accurate since it is making the brass rest farther away from the chamber walls?

[/ QUOTE ]The key word in the first part is "typical." Typical means usually, most of the time, more often than not, the majority of instances and other similar definitions. Typical does not mean always. So, what I said is not a "hard fast rule."

For the second part, the brass typically rests zero distance from the chamber walls at one point. That's the point where the extractor presses the back part of the loaded case body against the chamber wall There will typically be some clearance oppostite that contact point. I really don't know why the mechanics of a smaller case body on a full-length sized case shoots more accurate. It may be because the non-round nature of both case and chamber end up causing less unwanted barrel movement during firing. Ask Sierra Bullets why they get better accuracy using properly full-length sized cases over any neck-sizing method. They've been doing it for over 50 years and I don't think anybody shoots their bullets as accurate as they do.

The smallest 15+ shot groups at 600, 800 and 1000 yards I know of have all been done with full-length sized or new non-concentric cases in non-concentric chambers. While there have been smaller 5- or 10-shot groups, they are not "typical" because they're at the small end of the group sizes attained. Benchrest single-group records nestle in this area but the many-group aggregates are larger and more closely related to what one can typically expect on average. Note that a rifle rarely shoots a group equal to or smaller than the tiniest one in its barrel's history. But it almost always shoots smaller groups than the largest one ever fired.

You don't need to 'shout' at me by typing in all capital letters. I can read what you're telling me much easier when you're using initial capitals only.
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Old 04-06-2006, 08:49 AM
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Re: Question: Body die vs modified full length die

[ QUOTE ]
With this being said, then how would FL sizing make things more accurate since it is making the brass rest farther away from the chamber walls?

[/ QUOTE ]

Wisdom from David Tubb...and affirms my FL sizing routine

Chamber...NOT completely round/true
fired case...NOT completely round true

You wont get the same case position with neck sizing without indexing cases.

FL cases...sit the same place in the chamber each time...same impulse/harmonics on firing...

Alsosome cases will fireform more fully than others, but with a FL size and 0.001-0.002" shoulder bump, you have a better chance at identical cases.

as always, YMMV,
JB
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  #6  
Old 04-06-2006, 05:34 PM
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Re: Question: Body die vs modified full length die

[ QUOTE ]
The key word in the first part is "typical." Typical means usually, most of the time, more often than not, the majority of instances and other similar definitions. Typical does not mean always. So, what I said is not a "hard fast rule."



[/ QUOTE ]

Agreed. Would not have piped up about it except you made it sound like that was a undeniable fact that was set in stone.




[ QUOTE ]
It may be because the non-round nature of both case and chamber

[/ QUOTE ]

And remember, there is also no perfect die whether it be a neck sizer or FL die!




[ QUOTE ]
Ask Sierra Bullets why they get better accuracy using properly full-length sized cases over any neck-sizing method. They've been doing it for over 50 years

[/ QUOTE ]

The reason they do it probably the same reason why Barnes next door does it. Because they have to have ammo that will fit in every test barrel they clamp into the vise. It may or may not be the most accurate way of sizing that particular brass, but it has to be done to make it fit.


[ QUOTE ]
I really don't know why the mechanics of a smaller case body on a full-length sized case shoots more accurate.

[/ QUOTE ]

So what you're saying is that you have no facts to back up your claim that that FL sizing is always more accurate?




[ QUOTE ]
They've been doing it for over 50 years and I don't think anybody shoots their bullets as accurate as they do.


[/ QUOTE ]


Well if that were the case, I don't think they would sell very many bullets!



[ QUOTE ]
The smallest 15+ shot groups at 600, 800 and 1000 yards I know of have all been done with full-length sized or new non-concentric cases in non-concentric chambers. While there have been smaller 5- or 10-shot groups, they are not "typical" because they're at the small end of the group sizes attained. Benchrest single-group records nestle in this area but the many-group aggregates are larger and more closely related to what one can typically expect on average. Note that a rifle rarely shoots a group equal to or smaller than the tiniest one in its barrel's history. But it almost always shoots smaller groups than the largest one ever fired.


[/ QUOTE ]


Not sure what the point is here or how it relates to my point that the best groups come from experimenting with neck and fl sizing and picking the best one for the individual rifle.



[ QUOTE ]
You don't need to 'shout' at me by typing in all capital letters. I can read what you're telling me much easier when you're using initial capitals only.

[/ QUOTE ]


Not shouting at you. Just making sure the point stood out and was read because you seem to not counterpoint with any real evidence or references. It is always either "change the subject" or pull out a long lost opinion which you try and pass as a fact from the Bart B's book of revelations that no one knows anything about. Not trying to flame you here, just saying it as I see it and anyone who knows me knows I state my mind and I wave the bs flag when I hear it. It is my nature.
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  #7  
Old 04-06-2006, 05:58 PM
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Re: Question: Body die vs modified full length die

[ QUOTE ]
You wont get the same case position with neck sizing without indexing cases.


[/ QUOTE ]

Well that is true, and it is also true for FL sizing. REmember, there is no perfect die so if consistency is required, indexing for both methods would be viable. However, that being said, I have fired numerous 6" groups at 1000 yards with both methods and no indexing was used.



[ QUOTE ]
FL cases...sit the same place in the chamber each time...same impulse/harmonics on firing...



[/ QUOTE ]

That would only be true IF the sizing die used was true, and the springback on the case was consistent, and your case heads were square, and if the ejector plunger was removed. Granted, the difference would be small but it would be small for the neck sizer too.



[ QUOTE ]
Alsosome cases will fireform more fully than others, but with a FL size and 0.001-0.002" shoulder bump, you have a better chance at identical cases.


[/ QUOTE ]

This is correct. But, cases that have been fired many times and are as long as they can possibly be and still fit in the chamber will be pretty darn close to the same headspace length. It is obviously would help to fire similiar pressures in each case throughout it's life to keep them as close to the same shape as possible. Cases that have been shot at super high pressure can be FL sized .001" back but may not squeeze back as well as another case that has not been fired so hot because of the nature of spring back after sizing.

I'll give you an example of this. In my 338 thunder, I have fired one case with a way over the top load of RL22 that stuck my bolt shut pretty well. Now when I size that case, the setting on the die will not push the shoulder back .001" like it will all the other cases. It goes down then comes right back out. I have to screw the die down a touch more to get it to FL size that piece back the .001".


<font color="blue"> Again, bottom line:
Try both Neck and FL sizing and see which works best for your individual rifle. Both can be accurate just as easy as both can cause problems because there is no perfect die but some are better than others. </font>
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