Has anyone else noticed that excellent groups happen more often with new brass in cases that headspace on a magnum belt?

Could it be that the belt is centering the case in the chamber by contact between the belt and the chamber? As opposed to an unbelted new case where the extractor or gravity would push one side of the case to the chamber wall.

After 3 or 4 firings I start headspacing even belted cases on the shoulder, but I have shot some excellent groups with new cases.

I have not noticed any excellent groups with new cases in an unbelted case.

Although I've seen some better groups from certain brands of brass I'm not sure I've seen better groups from new brass. Although, I think I've seen some posts that were made about it. ALSO--apparently some bench rest guys are using and liking the magnum collet sizing die that takes the body of the case back to factory dimensions from the belt up. (Gets rid of the slight bulge ahead of the belt).
Will be interesting to follow this post.

I wouldn`t think new brass would fit the chamber any better then fire formed, but then I don`t have any belted cartridges that I load for to really form an opinion from. I do feel that new brass in any form has a much more uniform consistancy and bullet release might benefit from it over older work hardened cases.
JMO........

quote:

Has anyone else noticed that excellent groups happen more often with new brass in cases that headspace on a magnum belt?

NO....I haven't and suspect it's unproven.

It may have happened to you but I'd be very reluctant to say it's a normal occurrance.

Well for example, this is the best my 338 Mato has ever shot about a year ago with new Norma brass



This is the 2nd best it has ever shot a couple of weeks ago with new WW brass


This is new Norma brass in a 300 win mag Mato about a year and a half ago (3 shots in black square on the right)




I was just going through old targets and my spreadsheet and wondering if it was a trend anyone else had noticed.

Plus, I thought maybe I could divert attention from that other thread (pressure and max charge) that is becoming too heated!!!

I've definitely seen some AWESOME groups with virign brass in several non-belted calibers. Most notably a brand new 6.5x284 I have, virgin Normas brass and a load that works well in another 6.5x284 I have, shot quarter minute! I have also had several .270's shoot great groups with virgin brass, of a couple of different brands, groups just as good as loads utilizing PFLRS brass giving a slight crush fit in the same rig.....

I have noticed the couple of belted rigs I have do shoot virgin brass well, but not better than fireformed, I do set them up off of the shoulder when reloading for them.....I didn't (and probably don't) keep as good of records as you Bob, but I think these rifles probably shoot about the same, virgin vs fireformed, both actually pretty darn good. I didn't need a lot of load development on my 300 Win Mag, 7 mag or 375 H&H, these rigs shot around an 1.25 to 1.5 right from the start, and this was good enough for their intended purpose, save the 7 mag, which I have just kind of sidelined--it's really just a spare barrel for one of my Sauer 202 takedowns--as are the other two belted rifles.

Sometimes it is a bit of mystery what works in one gun and not in another. I can't say all my belted magnums prefer new brass, but I do have one .257 Wby for which this is definitely the case.

To facilitate long case life, I always size belted brass to headspace on the shoulder, though.

- mike

I too have had surprisingly good results while fireforming brass, or using cases otherwise on their first firing, and not necessarily belted cases.

The prevailing wisdom is that the extra room around the new case allows the bullet to center itself in the throat more easily and it is often more noticeable if the rifle has a little wear on the ball seat area of the throat or if there is a concentricity problem with the round or the chamber. IOW, a banana-shaped cartridge loaded in unfired brass has room around the body, which allows the needed clearance for the bullet to get aligned with the bore.

Once a case has been fired several times, it has expanded to fit the chamber and there is none of the "wiggle room" left. The bullet is forced to face the direction imposed upon it by the case/chamber fit and alignment, which may not be exactly concentric with the throat/bore.

Hey Woods, If you decide to go to "one shot only in new cases", keep old Hot Core in mind before you Trash them. I can "dispose of them" for you and it won't cost you too much either.

I only have one belted case rifle, a 7 mm Rem Mag. I have shot a few hundered roumds through it, and the accuracy has not changed since starting with new brass. I found the best load, and that load always shoots three shots into 1/2" at 100 yards, since day one. It's a custom rifle, well bedded in a McMillan stock.

Don

One thing that may be related is some folks have posted that their rifle was most accurate using F/L resizing. I have never found this to be the case but perhaps reducing the size of the case to "factory specs" allows the cartridge to accomadate some chamber irregularity. I don't believe it would be an acrost the board thing tho.
I neck size, or as you folks say, partial full length resize all of my ammo, standard and belted, except, of course, my "take hunting" ammo.

It is not uncommon to experience better groups with new brass than with fired brass, however this has nothing to do with belted versus non-belted cases.

It usually has to do with cartridge concentricity. If your new cases are fairly consistently giving you better accuracy than fired cases, then your resizing die is likely leaving your necks cocked slightly out of alignmnent with the axis of the bore. This is often the case when one attempts to neck size-only with a conventional sizing die. You can correct neck misalignment and still have headspace-corrected fired brass by using a neck sizing die like the Lee Collet or the some of the bushing style neck dies.

Standard conventional RCBS sizing dies are rumored to be bad about neck misalignment, but I haven't done any comparisons to determine if there is any truth to this belief.

I have to agree. You are getting runout problems.

Don't tell Woods he has a concentricity problem........he is "crazy wild" about making straight ammo.

OK!

I had a rifle which only shot well with new cases.It was a factory Remington with a chamber cut to tight.Check and see if the bolt closes as easily with the ones that are not firing well.

CONCENTRICITY!!!

RUNOUT!!!

I size even new case necks with the Lee Factory Collet and seat with either a Redding Competition Seating Die (not cheap!!) or an RCBS Competition Seater (also not cheap!!). Runout even on new cases is always less than .0015".

THEN, I use the Bersin Tool to all but eliminate runout. I measure it on the bullet at the ogive and most times it does not even MOVE THE NEEDLE!!! The biggest problem is the quality of the bullet itself, by which I mean the only runout is created by the irregularities in the bullet which is uncorrectable.

RUNOUT

Runout and concentricity has nothing to do with my groups.

What I was wondering is if the belt accomplished the same purpose as PFLR in holding the case body in the center of the chamber rather than being canted like an unbelted new case.

With unbelted cases I have always achieved my best groups after several fireformings and PFLR with a slight crush fit. That is where the shoulder contact is centering the case body.

Hey shootaway, I didn't say that the fired and PFLR'ed cases were not shooting well, just not as good as new in some cases. Not flaming you, just correcting a possible misunderstanding.

And I guess that answers your question HC, I still use the brass. On second thought, what have you got to trade? Any gadgets you couldn't figure out how to work?

I made a 300 WM chamber .005" short, and then finished the belt relief cut in the barrel with a tiny lathe tool and cut .005" deeper and .002" wider.

This meats SAAMI specs on a chamber, but not the spirit, because the new brass is going to chamber on the shoulder.

Bart Bobbit tells me I went the wrong way on that deal. He says always headspace on the belt for accuracy. Size the brass accordingly.

But he is after the .4moa 20 shot worst group in his competition target rifle, and I am happy with my 1.5moa 5 shot average group in my 300WM hunting rifle.

I could put die chem on the shoulder cut in the barrel and put the reamer in there and twist my fingers and get .005" deeper at the shoulder, and be the way it was intended, but I am happy the way it is.

tnekkcc

If you only moved it back .005", you might not have moved it far enough to headspace on the shoulder. Since I started keeping records on shoulder measurements with the Head & Shoulders Gauge I have found that new brass is very far off the shoulder.

For example in a 338 win mag Mato new cases measured 4.097" to the shoulder and after firing the measurement expanded to 4.120". In a pre-64 264 win mag new cases measured 4.109" and once fired measured 4.136". That is an expansion of .023" in the 338 and .025" in the 264. In unbelted cases new brass is closer to the shoulder in most cases.

But that is the kind of stuff I'm looking for, someone who has at least thought of the effect the belt has on headspacing (not that I agree with Bart B on much of anything).

To see if thing are tight, I sometimes put a dab of Imperial sizing wax on the shoulder and see if chambering squishes it flat.

That rifle is in storage, and storage is closed right now, but I will do that experiment.

The advice of headspacing on the belt for accuracy is certainly an interesting one. Maybe it does work, not that all guns require this, but in the ones that present problems when sized to headspace on the shoulder...

However, other than in custom chambers where you have the advantage of (presuambly) knowing and controlling chamber dimensions, this could present a few problems. First, how far would you have to size the brass to be sure you headspace on the belt? I'm not aware of any tools which will allow you to measure this - like they are available to measure head-shoulder dimensions. So, what to do, size the brass to match new brass??

Secondly, if that is the apporach taken, as Woods noted above, factory chambers for belted magnums tend to be cut on the large side. I.e. you'll commonly observe "massive" case stretch from a case fired when headspacing on the belt. That is almost guaranteed to ensure you have to trim your cases after every firing/sizing. Worse, it is anybody's guess how long it will take before that brass experiences case separation. Not exactly an attractive prospect.

I guess if a (belted magnum) rifle does not shoot well with brass sized to headspace on the shoulder, but displays great accuracy with new brass, one could adopt an approach of trying to gradually size the cases more and more, and see it it helps. If one takes this path, I would suggest you keep track of how much headspace expansion you generate every time, and keep a VERY wary eye on your brass and any sign of impending case separations.

- mike

quote:

Originally posted by mho:


However, other than in custom chambers where you have the advantage of (presuambly) knowing and controlling chamber dimensions, this could present a few problems. First, how far would you have to size the brass to be sure you headspace on the belt? I'm not aware of any tools which will allow you to measure this - like they are available to measure head-shoulder dimensions. So, what to do, size the brass to match new brass??

Now we're talking! In order to headspace on the belt again, you would only have to push the shoulder back .005" (only about 20% of the distance back to new) or so and resize the case body. If you have a tight chamber and your die does not resize enough to prevent contact between case body and chamber body after resizing, then you might be negating any benefits from headspacing on the belt. But you are right, there are not any gadgets to measure the belt and figure out how much contact with your chamber it has.

Theoretically, resize the case body and push the shoulder back as above and the shell belt should control the headspace again. Would this cause excessive expansion and eventual case head separation earlier? Could be.

I will have to do tests. It will take a while since I've already once fired and loaded a batch of new brass in the 338.

quote:

Originally posted by woods:
...And I guess that answers your question HC, I still use the brass. On second thought, what have you got to trade? Any gadgets you couldn't figure out how to work?

Hey Woods, As luck would have it, you have caught me in the middle of getting a whole bunch of "new" things. But, so far I've got everything that has arrived figured out.

And part of it is a "trade" on a "new" 444Mar XLR.

quote:

But you are right, there are not any gadgets to measure the belt and figure out how much contact with your chamber it has.

If you had a Chamber Cast, would it then be possible to measure the Belt Dimensions and compare them to it? Of course it would require the use of an "old fashioned" 0.0001" capable Micrometer. But surely everyone already has one of them to measure CHE/PRE.

quote:

Originally posted by woods:
In order to headspace on the belt again, you would only have to push the shoulder back .005" (only about 20% of the distance back to new) or so and resize the case body.

Hey Woods, I have come to appreciate you as a thoughtful and knowledgedable reloader who likes to verify things for yourself. So tell me, what am I overlooking when I don't see the logic that a reduction of head-shoulder dimension of .005" will guarantee the sized case will now headspace on the belt?? This in a chamber that allows the brass to grow in head-shoulder dimension .02-.03" on the initial firing. I'm sure you have thought this through, I just can't seem to get my head around it...

- mike

P.S. I have been discussing a similar issue on another board of late. One thing one could also attempt to verify, is whether the rather ample magnum chambers might cause your brass to workharden beyond expectation. That has caused inconsistencies in seating force (neck tension) and screwed up groups for me in the past.

mike

My logic is that if the case is sized small enough so that there is clearance around the case body and clearance between the case shoulder and chamber shoulder (which could be accomplished by as little as .003" or slightly more at .005") then the case would contact at the belt only. Essentially it would headspace off the belt again. That is assuming that the chamber is large enough so that the sizing die actually contacts and resizes the case body (I have one chamber where the Redding Body Die does not size the case body).

The reference to the 20% is comparing the .005" shoulder push back to the .02"+ that these case normally grow.

In your question regarding the large growth of some of the cases from new to chamber size and the work hardening, I would say that is not as much a problem as you might think. The reason is because 85% of the shoulder growth occurs on the 1st firing when the case is new and soft. Once the brass starts to become harder around the 4th or 5th firing, it is as close to chamber size as any other kind of case.

If belts were uniform enough to headspace on, then that could lead to better alignment as long as the chamber belt rim and the bore were also in perfect alignment. A crush fit at the shoulder could possibly alter that alignment. The question is in what way.

The belt area has much less expansion or maybe none and I'm going to start measuring it. Especially from the case head to the front edge of the belt to see if it moves and is uniform all the way around.

quote:

Originally posted by woods:
What I was wondering is if the belt accomplished the same purpose as PFLR in holding the case body in the center of the chamber rather than being canted like an unbelted new case.

That's doubtful. With most chambers the belt fits rather loosely to begin with. I can't see that it would help in any way in supporting or centering the case.

quote:

Originally posted by Stonecreek:

quote:

Originally posted by woods:
What I was wondering is if the belt accomplished the same purpose as PFLR in holding the case body in the center of the chamber rather than being canted like an unbelted new case.

That's doubtful. With most chambers the belt fits rather loosely to begin with. I can't see that it would help in any way in supporting or centering the case.

again.....dead on here!

When the firing pin pushes the cartridge forward, something has to stop the cartridge:
1) The shoulder
2) The rim
3) Bullet jammed in the lands hard
4) Combination of the above

So even if the chamber is loose, something has to stop the forward motion.

I liked the idea of the shoulder in the chamber and the shoulder on the case acting like a collet in a the arbor of a mill or lathe.
The firing pin is like a draw bar, er push bar.

If the chamber and the die were made with rotary motion of a reamer, they should be round and concentric.

I knew that the shoulder relief in the chamber would be concentric, but I did not see how the brass belt was going to be all that accurate, especially when the long cartridge and small belt amplify the belt error when measured at the bullet.

Good post tnekkcc, I always thought along those lines also with the case body sized and slight crush fit on shoulder should be the best and most accurate sizing.

Question, does the belt and case head also expand (although significantly less than the rest of the case) until it fits the chamber or is the brass too thick in that area?

Here's another question. If new brass typically expands forward over .02" in the shoulder area, does the firing pin push the case forward enough to jam the bullet in the lands if you are seating at .02" or less? Or does the rim stop it first? Or if it is a CRF then does the case head holder on the bolt face stop it first?

I mean if you seat a bullet .005" off the lands with new cases, doesn't the firing pin then jam the bullet into the lands?

quote:

Originally posted by woods:
Has anyone else noticed that excellent groups happen more often with new brass in cases that headspace on a magnum belt?

Could it be that the belt is centering the case in the chamber by contact between the belt and the chamber? As opposed to an unbelted new case where the extractor or gravity would push one side of the case to the chamber wall.

After 3 or 4 firings I start headspacing even belted cases on the shoulder, but I have shot some excellent groups with new cases.

I have not noticed any excellent groups with new cases in an unbelted case.

The brass above the belt will expand and move the case off center.There are custom sizing dies made to just size this part of belted cases, to bring the brass back to factory diameters. Another area is the case neck diameter. New brass (only a very few lots) will be the correct wall thickness. Most are undersized as far as what the loaded rounds neck diameter should measure.The case in point, 243win with a max. neck dia. of .276". If a loaded round with new brass measures this dia. when FL resized it will shoot well. As the brass is worked, using standard RCBS FL dies with expander button, the neck dia. of a loaded round will get smaller as it reloaded. This gives more slop in the neck chamber area and accurace will drop off. When the round is not centered in the chamber accuracy fall off. There are a few ways to center the round in the chamber. PFLRS, or jaming the bullet into the rifling, or a tight neck chambered rifle with neck turned brass.Die info

quote:

As the brass is worked, using standard RCBS FL dies with expander button, the neck dia. of a loaded round will get smaller as it reloaded. This gives more slop in the neck chamber area and accurace will drop off. When the round is not centered in the chamber accuracy fall off. There are a few ways to center the round in the chamber. PFLRS, or jaming the bullet into the rifling, or a tight neck chambered rifle with neck turned brass.

I agree. This is the reason I try to PFLS my brass or not bump the shoulder unless needed. I believe the angled shoulder of the case when making contact with the mateing angled chamber shoulder area will, if at a lenght to datum that insures contact, force the case axis in line with the bore. This of course is assuming the chamber is concentric as is the ammo shoulder/base itself. Neck sizeing, if one doesn`t move the neck out of line will accomplish the same result as it leaves the shoulder alone. I find though when neck sizeing I sometimes get necks pulled off center. A off center neck even if the body axis is in alinement will place the bullet out of line. I am not sure if it is technic or a adjustment problem with the die, but it is just as easy to Part size and have things straight for me.

It seems to me that the round will be centered better after the case has been fire formed to your chamber than before. So it sounds to me like your theory is just backwards from reality.

quote:

Originally posted by El Deguello:
It seems to me that the round will be centered better after the case has been fire formed to your chamber than before. So it sounds to me like your theory is just backwards from reality.

I agree. I am into PFLR everytime also.

It's not really a theory, just an observation in search of a theory.

Sounds like there is not really any way to measure the belt's effect in the chamber and the consensus of opinion is that most chambers and cases are too sloppy for it to have a defining effect anyway. Perhaps with a chamber cast then the amount of contact at the forward edge of the belt could be measured.

Yes, I only partially FL resize cases that I've already fired in one of my rifles, and so far, I've gotten some pretty decent accuracy perfornmance out of ammo so treated......

same topic at benchrest central More info here

Woods,

I think it has alot to do with the chamber dimensions. Alot of unbelted cartridges will shoot great with new brass as well. If the unbelted cart chamber is alittle large I can see a definite advantage to the belt in a similarly oversized chamber.

Most of my Magnum rifles shoot great groups whether the brass is new or not. I also have several unbelted cart rifles that shoot well with new brass.

Reloader

quote:

Originally posted by woods:
...I am into PFLR everytime also.

...most chambers and cases are too sloppy for it to have a defining effect anyway. ...

Hey Woods, About the only way I can think of for this to be practical, and it would still take a lot of effort, is to buy a large quantity of Belted Cases. Then cut all the Belts on a lathe so they are the same exact size. (That in itself should be enough to kill the project.)

Then purchase a special-cut Reamer to put that exact Belt dimension into the Chamber. But there are problems with that. If it is an exact fit, then chambering and extracting will be very slow, difficult and require arms like King Kong(aka like mine ). Especially if you shoot some "warm Loads".

Or cut the Chamber Belt Recess slightly oversize for the Special Cut Belts. And of course that gets you back to the sloppiness of how much oversize.

Each SAFE MAX Load will alter the Casehead and Belt dimension slightly if there is room for it to actually Expand just a bit.
---

Seems to me it is still better to have the Bolt Face cut exactly perpendicular to the Bore CenterLine, the Chanber cut dead on the Bore CenterLine and then contine with the (never improved upon) P-FLR.

Don't let my negative thoughts keep you from the quest though. Try it and see how it works.
-----

Huuuum, perhaps a slightly Cone shaped Belt, like an extra Shoulder.

Best of luck to you.

Yeah, it seems that there is no exact specific knowledge about what effect the belt has on orientation of the case in the chamber and no practical way of finding out or measuring it.

Give me time, I'll think of some way. I guess the initial step would be a chamber cast to measure chamber dimensions and compare the measurements to case measurements.

Hey HC, maybe I can invent a "thingy" to measure it all. I'll send you one for free.

quote:

Originally posted by woods:
...no practical way of finding out or measuring it. ... maybe I can invent a "thingy" to measure it all. I'll send you one for free.

Well...., it could easily be done on a Coordinate Measuring Machine(CMM) for the Cases. And it would do the Chamber with the barrel out of the Action.

I really don't have the space available for a CMM at the moment, but I do appreciate the offer for a FREE one.