Okay-

So here's the theory: Full length sizing is more accurate than neck sizing, because powder ignition invariably produces pressure spikes.

While a neck sized case already conforms to the chamber walls, and provides little space for case expansion, full length sized cases allow at least a little flexibility, and that little case expansion ameliorates--to some effective degree--the pressure spikes.

For various reasons, convenience among them (I like the ease of neck sizing), I've been neck sizing as much as possible.

Still, and this is an eye opener, I've shot my best groups with full length sized brass.

There are so many variables, including wind, temperature, and how many beers I had the night before, that I'm reluctant to subscribe to full length sizing.

Fact or opinion?

flaco

quote:

So here's the theory: Full length sizing is more accurate than neck sizing, because powder ignition invariably produces pressure spikes

I`ve heard of lots of reason for pressure spikes but this is the 1st time the way a case is sized has come up.
Don`t worry about pressure variation due to sizeing. Use the method you are most comfortable with and go shoot.............

quote:

Originally posted by flaco:

So here's the theory: Full length sizing is more accurate than neck sizing

Fact or opinion?

flaco

I've shot some good groups in new cases, but my best groups and more importantly, my most consistant groups, have been shot with Partial Full Length Resized brass. I really don't think that the pressure necessary to expand the brass to the chamber walls is significant at all and don't see how "flexibility" has anything to do with chamber pressure.

Some of the problem comes in from the varying definitions of Full Length, Partial Full Length and Neck Sizing.

So I will just continue to go from new cases to Neck Sizing for 3 or 4 loads to pushing the shoulder back .0015" for Partial Full Length Sizing for the remaining life of the case. Can't see how having a case that is smaller than your chamber and pushed to one side by the extractor button can be more beneficial than a case that fits your chamber and aligns your bullet with the bore.

I've also eventually gone to FLS'g , a friend was getting terrific results, and I was sick of having dozens of jars of cases to be checked, N.s'd, FLS'd, PFLS, maybe this and maybe that.

Now all cases get the same treatment, PFLS'ing seems to be the same as FLS'ing in what I load most for. IE. the case is too tight in the chamber one moment and the die hits bottom on the next slight adjustment.

quote:

Originally posted by just-a-hunter:

Once again flaco, I don't mean to be arguing or giving you the impression I'm calling you a dummy. I assure you this isn't my intention. After all, you seem to be a very knowledgable. I'm just trying to better understand the theory.

Todd

Hey Todd

You can disagree on this forum without anyone thinking you are insulting them. flaco is a good guy and won't take it wrong as long as you do it respectfully.

quote:

If your feeding your chamber a perfectly formed piece of brass, allowing no movement in the brass, how could this practice be less accurate.

The theory as to why a fire formed case would be less accurate is because factory chambers are not perfectly round and unless you insert your brass oriented the same way everytime, there would be alignment errors introduced. I don't think this would be the case but I was wrong once before in my life (what is my anniversary date anyway?).

To me a Full Length sized case would have space around it which means it could be on one side of the chamber or the other. Either by pushing on one edge of the case head with the extractor or just by gravity. In Partial Full Length the case is held in place because of contact with the bolt head and the shoulder with which it has a slight crush fit.

By measuring where the case shoulder is with the Stoney Point Head and Shoulders Gauge (an excellent tool, where are you HC?) I have taken the following measurements on 30-06 cases in a Steyr rifle:

New cases - 4.0400" (the actual measurement doesn't matter, just it's relationship to the other measurements)
Once fired - 4.0485" (expanded .0085")
Twice fired - 4.0500" (expanded .0015")
3 times fired - 4.0510" (expanded .0010")
4 times fired - 4.0515" (expanded .0005")

After the 4th firing the cases were too tight in the chamber and had to be Partial Full Length Resized (case body sized and shoulder moved back).

After the 3rd firing a slight crush fit could be felt after chambering the case in the gun.

The cases will have to be PFLR'ed from now on as they will have too tight a crush fit on every firing from now on.

The point is that if you just Neck Sized on the 2nd and 3rd firing then the case would not be held in position by contact with the case head and shoulder. You could induce a crush fit by PFLRing after the first firing because by sizing the case body the shoulder would be pushed forward enough to come in contact with the chamber shoulder and you could then push it back just far enough for a slight crush fit.

But, IMO, if you always push the shoulder back far enough so that no contact by the case between the case head/bolt face and the case shoulder/chamber shoulder, (Full Length Resizing) then accuracy would suffer.

Make sense?

I still neck size only if I'm using a die that fully supports the case. If not, runout can become an issue. I usually partial full length resize my hunting rounds. I always leave just enough of the neck unsized that the case will self center in the chamber. I feel that having the case perfectly aligned with the axis of the bore every time lends itself to better accuracy (better consistency) than full length resizing that allows for looser case-to-chamber fit.

When I'm setting up my die, I mark the shoulder of the brass to indicate any contact with the die shoulder and gradually screw down the die until I have sufficient bullet grip without bumping the shoulder. When I need to bump the shoulder, I'll use a body die or simply adjust my full length sizing die to bump the shoulder slightly. Using a headspace comparator helps greatly. I use a short piece of barrel stub that had the same reamer that made the chamber run in enough to allow me to use calipers to compare with my dummy round.

To me, "pressure spikes" implies inconsistent ignition. I'm not convinced that a looser fitting case in the chamber can possibly have a positive impact on accuracy. I believe in consistency in everything I can control.

Todd-

You must be new here... as it's not at all uncommon for threads to devolve into shouting matches.

For the most part, we all take it in stride.

In this case, the preference for FLS'd cases is the opinion of a well known target 'smith. He's been doing this for a long time, building rifles and shooting in competition, and while part of the FLS issue may for him be convenience--reloads can go in any rifle--I'm certain he also believes they're more accurate.

His approach is based on years of experience.

Right now I'm neck sizing, and partially for convenience too. I'm not fond of all that gooy lube.

LOL.

If you hang around long enough, you'll find it's hard not to come to the conclusion that, well, many very well informed folks have differing ways of approaching the same problems.

Sometimes, it's hard to say unequivocally that one approach is better than another: A "correct" solution.

And there's still, no matter how much rationalists hate it, a little of what I call the "incantation factor".

Black magic.

Problems that seem not to yield to a rational approach.

Mainly, I don't ask rhetorical questions.

I'm looking for different solutions, and the logic that supports them.

flaco

Thanks for your responses, Gents!

I like to use full length dies, but adjusted to not push the shoulder back.

I like:
1) Redding FL "S" dies with out the decapping stem
2) Forster full length dies without the decapping stem.

But I can get some great groups in some calibers with:
3) a cheap set of RCBS dies, with the decapping stem removed.

So why pay for Redding or Forster when cheap RCBS does a great job?

Becuase $50 more for dies is small potatoes compared to scopes, barrels, reamers, lathe tooling, stocks, and a day off from work.

quote:

Originally posted by woods:
... I was wrong once before in my life (what is my anniversary date anyway?).

I'd suggest it hasn't been very long and you are just about due for another one.

quote:

the Stoney Point Head and Shoulders Gauge (an excellent tool,

Well gooooood gosh, you didn't even make it a minute.

quote:

...You could induce a crush fit by PFLRing after the first firing because by sizing the case body the shoulder would be pushed forward enough to come in contact with the chamber shoulder and you could then push it back just far enough for a slight crush fit.

But, IMO, if you always push the shoulder back far enough so that no contact by the case between the case head/bolt face and the case shoulder/chamber shoulder, (Full Length Resizing) then accuracy would suffer.

As amazing as it is, Woods is absolutely 100% correct.

quote:

...what is my anniversary date anyway?...

Looks like 27Nov06 at 17:54.

quote:

Originally posted by flaco:
Todd-

You must be new here... as it's not at all uncommon for threads to devolve into shouting matches.

For the most part, we all take it in stride.

In this case, the preference for FLS'd cases is the opinion of a well known target 'smith. He's been doing this for a long time, building rifles and shooting in competition, and while part of the FLS issue may for him be convenience--reloads can go in any rifle--I'm certain he also believes they're more accurate.

His approach is based on years of experience.

Right now I'm neck sizing, and partially for convenience too. I'm not fond of all that gooy lube.

LOL.

If you hang around long enough, you'll find it's hard not to come to the conclusion that, well, many very well informed folks have differing ways of approaching the same problems.

Sometimes, it's hard to say unequivocally that one approach is better than another: A "correct" solution.

And there's still, no matter how much rationalists hate it, a little of what I call the "incantation factor".

Black magic.

Problems that seem not to yield to a rational approach.

Mainly, I don't ask rhetorical questions.

I'm looking for different solutions, and the logic that supports them.

flaco

Thanks for your responses, Gents!

There are many ways to load. Some are more complicated than others and one way is not the best way but may be the best way for the person using the process.
At the 200 yd match this weekend the oldest guy there with the least amount of equipment won the match. Each shooter had a slightly different process of loading between rounds. Sometimes we find that no matter what tools we have or how complicated our process is we still have to be able to shoot to get good groups.

quote:

we still have to be able to shoot good groups.

A big ... AMEN! ... to that wisdom. (Pay attention Woods! )

quote:

Originally posted by Hot Core:
As amazing as it is, Woods is absolutely 100% correct.

Can't hide anything from you HC! You are getting as sharp as last year's tomato stakes.

Truth is, you were right all along about PFLR, you just didn't know exactly why until I came along and used modern equipment to prove it.

SST has an alternate solution

quote:

I always leave just enough of the neck unsized that the case will self center in the chamber. I feel that having the case perfectly aligned with the axis of the bore every time lends itself to better accuracy (better consistency) than full length resizing that allows for looser case-to-chamber fit.

which would allow you to neck size for the first couple of reloadings until the shoulder moves forward enough for a slight crush fit. I have done this with a Lee Collet Neck Sizing Die by placing a washer around the case base on top of the shell holder. This leaves part of the case neck chamber size and keeps the case centered and the bullet aligned with the bore.

Then when the shoulder moves forward enough for a crush fit, start PRLR'ing.

I think I am going to start keeping track of the case body measurements just aft of the shoulder and see how much the case grows from new case to the 4th firing.

I never would have bought a neck sizer but I got a barrel from a friend at the range in 7mm08 and he sold me the Forster dies for 30 and I have grown very fond of the neck sizer. Makes life a lot easier.

quote:

I think I am going to start keeping track of the case body measurements just aft of the shoulder and see how much the case grows from new case to the 4th firing.

Hey Woods, I do like the analytical approach.

If you have one of those Run-Out measuring thingys, it would be easy enough to do, and in the exact same location as you rotate each Case.

Or, what did you have in mind?

Look forward to your results.