what are the benefits of FL sizing or bumping the shoulder back?

[panzer075]

So thru the course of struggling with my Oby barrel to arrive at a load I have seen posts that neck bushing sizing isn't enough and you must fl size or bump the shoulder back?

I always thought neck sizing was the way to go...can anyone give their thought why it is more beneficial to go FL or bump?

Loading for F class single shot...

 

[Erik Cortina]

Neck sizing only takes care of the neck. However, the rest of the brass body, especially the base, gets not resized so it keeps growing and hardening. Once it work hardens you will get a click in your bolt and F/L sizing alone will not fix it anymore.

F/L sizing every time allows your brass to have a perfect fit to your chamber every time. It is consistent.
If you neck size only, at some point you will have to F/L size, so it is not consistent.

 

[7stubby]

I went from Neck sizing only to FL sizing because I wanted to know each and every round that I put in the chamber will 1: chamber when I close the bolt and not have a hard time closing it causing the rifle to move in the bag. 2: that every case is as close to being the same dimensionally, reducing another variable and making my cases/load more constant.

You will get answers both ways. But if you set your FL die correctly, you shouldn't have any problems with reducing case life. I also shoot F Class and its not a good feeling have people standing around you as you are trying to close the bolt on a round that has only been neck sized and is a little too big to fit.

 

[watercam]

You can neck size if you like but you will have to bump your shoulder back and probably size the body of your case at some point to get it to chamber. Every long range competitor that I know full-length sizes their cases and use bushings without expander balls. You want to bump your shoulder back about .001" and keep your neck tension to about .001" as well. Since you will no doubt have a match chamber cut your headspace will be at or close to minimum in any event. Choose a bushing that is .001" less than the diameter of the neck of a loaded round AFTER you have outside trimmed (or not) your brass. This can be calculated by measuring the thickness of both sides of your neck wall and add the diameter or your bullet. Then subtract .001". This all assumes that your are single loading. If loading from a magazine, go to .003" neck tension.

 

[pacificman]

All of the above are exactly right and is what I have found to to be the most consistent way to size all of my brass in all of my rifles. Once you get the die set up for a perfect fit for your chamber then you will know that your ammo is the most consistent it can be every time you reload. I have neck sized only in the past and I no longer neck size only. I have not found any better accuracy by neck sizing only compared to a perfect partial full length sized case.

 

[amamnn]

If you have a FL die made to match the dimensions of your chamber, and you have done your fire forming right and etc, then the bad effects of FL sizing (working the brass too much) are minimized and that procedure can be done a lot before trimming is required. However, if you have an off the shelf die and a chamber that is pretty generous dimension-wise then Neck sizing can be useful.

Apparently Forster is saving big bucks on advertising since I continue to see hordes of handloaders who still do not know that they make a very useful neck die that uses bushings to reset the neck--and--also resets the shoulder!!!!!! I have a couple and they work fine--you must use Forster bushings in them.

 

[amlevin]

To eliminate this dillema, to FL or neck size/shoulder bump, just get a sizing die that's made to match fired cases from your rifle.

One die that could eliminate up to two others. (Neck Size and Body die)

 

[243winxb]

consistently of case volume by full length sizing- 5.56 mm cartridge.

Assuming the brass case does not relax after firing, the case volume increases
by about 4%.

Page 29 http://www.dtic.mil/dtic/tr/fulltext/u2/a456635.pdf As we all know, soon or later, you have to full length size/bump the brass. This changes case volume. But does it matter? Is not the chamber the true volume?? There for, its only the weight variation of the brass in the chamber that matters ?

 

[stool]

Re: consistently of case volume by full length sizing- 5.56 mm cartridge.

no...
because you expend energy expanding the brass to the chamber size..that energy is lost and never seen by the bullet.
there are no free lunches.

Assuming the brass case does not relax after firing, the case volume increases
by about 4%.

Page 29 http://www.dtic.mil/dtic/tr/fulltext/u2/a456635.pdf As we all know, soon or later, you have to full length size/bump the brass. This changes case volume. But does it matter? Is not the chamber the true volume?? There for, its only the weight variation of the brass in the chamber that matters ?

 

[wedgy]

I had this conversation with a technician at Sinclair and he said their engineers were split 50/50 neck vs full.

 

[MildBill]

If you have a FL die made to match the dimensions of your chamber, and you have done your fire forming right and etc, then the bad effects of FL sizing (working the brass too much) are minimized and that procedure can be done a lot before trimming is required. However, if you have an off the shelf die and a chamber that is pretty generous dimension-wise then Neck sizing can be useful.

Apparently Forster is saving big bucks on advertising since I continue to see hordes of handloaders who still do not know that they make a very useful neck die that uses bushings to reset the neck--and--also resets the shoulder!!!!!! I have a couple and they work fine--you must use Forster bushings in them.

forster only makes the bushing bump dies for a limited number of cartridges. I have some for a few of mine too and really like them.

 

[Shynloco]

....If you neck size only, at some point you will have to F/L size, so it is not consistent.

Therein lies one of the key ingredients to attain accuracy (in terms of case prep)...CONSISTENCY! That no matter what the discipline you are shooting.

Alex

 

[WyleWD]

I had this conversation with a technician at Sinclair and he said their engineers were split 50/50 neck vs full.

+1. I agree with them. It is definately a toss of the coin. As long as you are doing it right either way, and it works for ya.... good deal. WD

 

[Erik Cortina]

I had this conversation with a technician at Sinclair and he said their engineers were split 50/50 neck vs full.

I can't remember the last time I saw one of them on the firing line.

 

[LHSmith]

Sinclair has engineers on board? The degreed Professional Engineer kind?
If you load in the upper end NS is not an option.

 

[Travelor]

A Full length sizing die over sizes the necks and they are them brought back up in size when they are fulled over the expanding portion of the decapping pin assembly. This stretches the case every time it is sized. I.E. decreases the case life and requires frequent trimming.

By using a collet neck die you DO NOT oversize the neck and then stretch it by pulling it over an expander. Thus no stretched cases. When it is time to either push back the shoulder or size the case body dimensions, the body die sizes the case body and bumps the solder back to a desired size. These dies do not overwork the brass or stretch the cases.

IIRC, there was a test the NRA conducted using a factory standard chambered rifle and comparing accuracy with FL sizing vs the conventional neck only sizing dies (over sized necks and pulled over and expander). The test resulted in the Fl dies resulting on more accurate reloaded ammo. The reasoning was that a case expands not uniformly in a "large" factory chamber (one side of the case expands more than the other side) resulting in ammo that was not parallel with the bore when neck sized only.

 

[Erik Cortina]

Travelor, they make F/L bushing dies.

 

[Coolhand]

There was a test done by Chuck Hawks I think from memory regarding case resizing options , neck only , conventional FL sizing with dies adjusted as suggested by the manufacturer and FL sizing with minimal shoulder bump. Test was conducted using a rifle which was a known performer , all three methods produced more than acceptable results down range but the conclusion was that FL sizing with minimal shoulder bump produced the best results. I use a Warner Custom FL Die , no dragging of necks over expanders and quite the best money I ever spent. Personally in both my Palma rifle and in my .260 hunting rifle , I FL resize with minimal bump.

regards
Mike.

 

[RHux]

I have a Forster FL die with the neck honed to .336 for Lapua brass . I also have a Lee Collet die and a Forster Bushing / Shoulder bump die . I use the Lee Die to size the necks and then use the Bump Die without the bushing to bump the shoulder. Why ? No lube needed . Both ways shoot the same MOA.

 

[BoydAllen]

A lot of people's reservations about FL sizing come from their experiences with one piece dies that are way too small in their necks, and as a result, the drag on the expander ball is so much that shoulders of cases are asymmetrically pulled out of shape, necks cocked relative to bodies, and concentricity suffers. None of this is true of a die that is properly designed for the chamber being used. In the most accurate rifles that I know of, those used for short range benchrest, pressures that are commonly loaded to, and the need for rapid single shot loading and firing, without rifles being disturbed on their bags, has dictated virtual universal use of FL sizing, using dies that are very closely matched to chambers. When I see reports of tests of accuracy, I want to know all of the specifics as to how the test was done. Many such "tests" involve shooting with rifles that are difficult to get consistent (as opposed to wallet group) results from, shot from rests that have the same problem, off of benches that have their own issues, without the benefit of wind flags, using a trigger pull weight and scope magnification that would never pass muster for serious competition. On the other hand, if a procedure gives you the results that you are looking for, then there is no reason to change it.