Home Forums Reloading Big Game Rifles False shoulder

I have a Mato 300 win mag that has a lot of shoulder space in front of new cases. With the Hornady Head & Shoulders Gauge I have the following measurements:

new cases - 2.251"
fully expanded after 3 firings - 2.2725"

that make a shoulder gap (can't call it headspace since it is a belted case) of .0215". A little more than I like because of thinning at the pressure ring and possible future case head separations. Previously I have always just tossed the brass after about 6 firings.

So I got some new Nosler 300 win mag cases and set out to expand the neck to 338 caliber so I could create a false shoulder. It didn't take long to figure out that my normal dies, the Lee Collet will not work. I did find some old FL dies in 300 win mag and 338 win mag and the well lubed expander ball on the 338 win mag did expand the neck with a moderate amount of effort and then I set the 300 win mag to neck size only and adjusted it in until I got a severe crush fit



The ones on the left were trying the Lee Collet and the one on the right is with the FL dies. FL dies with expander balls may have a use afterall.

Uncharted territory for me, anyone see any problems?

Just a comment or two.

I've seen that gap between shoulder and chamber be even more significant than your .021". Forget the max I've seen but it was around .030", maybe a tad more. Around .015" seems quite common and the very least I've ever seen. I have found that regardless what you do that you'll still get a stretch in the body down near the web where you'll get your incipient case separation. Not much you can do to prevent it and that includes blowing out the cases with COW, no bullet and chambered with the false shoulder. You should be able to get about 10 reloads out of them before they start separating providing you anneal necks at about the fourth reload.

I'm uncertain about the cases with which you are working but if you can find a case whose body is longer than the 300 Win Mag, you can make cases out of them. I've never tried. For 338 Win Mag of which I've had several, I've been using 358 Norma Mag cases where the body is .040" longer than the 338. I size them initially to provide about .001" clearance at the shoulder and thereby eliminate that initial stretch. I've got cases that have gone well over 20 reloads and still going strong. I neck size with bushing dies and anneal every fourth reload at which point I anneal and push the shoulder back a tad.

I'd be calling Berreta and seeing if they'll fix it or trade you up to a Sako.

Spot

Try some lapua brass if you can still find it. I use it in my win mag and do not get the typical ring ahead of the belt. Its slightly longer than Remington or Win brass. Or you could have a good smith set the barrel back with a more precise reamer. Another option is to have a smith cut the belt portion of the chamber slightly deeper.

Load long, drive the bullet in the rifleings. Maker sure you use a reduced load though. Then you can just neck size after that..

It seems to work better for me any how, less shortening of the necks when done.

Or like they have said above...

Right now I reload for about 40 rifles and I am still building my database but some of the gaps are:

Belted cases
Mato 338 win mag - .0270"
Sako 338 win mag - .0220"
Sako 300 win mag - .017"
Win 264 win mag pre 64 - .0310"
Custom 6.5 rem mag - .017"
Custom 6.5 rem mag - .015"

Unbelted cases
Rem 30-06 - .015"
Custom 280AI (Hart) - .017"
Rem 22-250 - .0105"

I would suspect the measurement would depend upon what stage of use the reamer was in when used and how worn out it was. However, it does depend as much on the brass manufacturers as the rifle manufacturers.

I did get one case head separation on that 338 win mag on the 6th reloading


The thinning was undetectable on the other cases with the same number of reloadings, by feeling with a paper clip or even with splitting the case.



Why do you say that? Do you have any evidence? You may be right but it seems that putting the case in a crush fit so that the firing pin can not push it forward on the initial firing would alleviate some of it.



I thought about getting some 300 Weatherby cases, sizing down and trimming the excess length. Wouldn't really look forward to a headstamp that was not correct.



I've done that. I'm just not sure the firing pin will not force the bullet deeper into the lands and there would be case travel anyway.



IMO, that would be trading down and there would be no guarantee that the initial shoulder gap would be much less anyway.

I have not experienced a case head separation....yet. Does it happen when firing or when extracting the brass? How dangerous is it? How does one go about removing the brass? The only belted magnum that I load for is my .350 mag. It is relatively new, so as of right now, the oldest brass I have has only been loaded 3 times. When I get home, I will have to look at my records to see how much stretch I have from new brass to fired brass.

HAVE evidence? No, didn't expect to have to prove it to anyone for any reason, just to myself.

I checked it in two ways while trying every way imaginable to get the bend at the body/shoulder junction to bend and unbend up into the shoulder to prevent the initial stretch. I painted cases with Dychem around the body up to the bend, nothing on the shoulder. Did the same on the shoulder, nothing on the body and tried to get the shoulder to bend at a different location. Never could do it with ANY method. The bend moved forward and stopped at the bend in the chamber. It stretched the body regardless of what I did. That included COW with no bullets, false shoulders, jamming bullets in the lands, etc.

On the old Shooters' board about 10 years ago there was a long thread on this and I was in the middle of it. After a long discussion one guy came on that had done similarly to what I had done and had the same results. He claimed that he had tried one other method that DID work. That was to compress a load with ultra slow powder for the cartridge, THEN jam a bullet in the lands. He opined that the slow powder filling the case created a slower and more even distribution of the pressure in the case, enabling that bend to straighten and cause a new one. With COW that fast pistol powder is at the base of the case with only the inert COW bearing on the shoulder. While the pressure of the load may exert equal pressure in the interior of the powder chamber, it was possible that the compressablility of the COW aborbed some of the pressure. I never tried it for two reasons; I had discovered the use of the Norma Mag cases for the several 338's I had, and I was also concerned with the SEE problems that were quite prominent at the time. Those secondary explosions had been more or less isolated to the very slow powders with somewhat reduced loads. I just didn't want to go there and never tried it, but the guy sounded like he knew what he was talking about. I split many a case after one firing in order to measure the thinning of the body down near the base with all those painted cases and I still have the jig which enables me to do it quickly on a bandsaw.



I never found it to be a problem. Without exception ALL my 338 Win Mag cases for several guns are marked "358 Norma Mag". I track my brass closely and have lots identified and kept separately for each rifle. I use both 404 Jeffery cases and 338 RUM cases in 338 Jamison and there is no way to have a headstamp marked for the latter.

Incidentally, for the 7mm Rem Mag shooters, they can use the 300 Norma Mag cases for that application. It is cost effective if you anneal, headspace on the shoulder and minimally size the brass.

First, incipient case separation isn't particularly dangerous in a modern gun with good venting. It can flame cut your chamber, which isn't good.

It usually happens slowly but can happen after only one or two reloads depending on method of sizing and the softness of the brass in the body which is affected by the annealing during the manufacturing process.

If you carefully inspect your cases, the first sign is a bump on the inside of the case near the base. It starts on one side of the case so that it is important to run your paper clip or dental pick the entire 360� on the inside. On the exterior the first signs are what appears to be a frosty line right near the pressure ring of the case and it can be confusing to identify what you are seeing. That little frosty line also usually appears on one side of the case and the inside of the brass will have a noticeable bump at that point when checking the interior.

There is ample warning if you inspect and watch carefully. If you get careless, what happens is that the entire case can be separated and on extraction you are left with the forward part of the case stuck in the chamber. That usually comes out very easily with a bronze bore brush run in there and reversed at the neck. Fire cutting of the chamber is the major risk, that and the escaping gases.

Not questioning your conclusions here at all bobski, just trying to figure it out. Seems to me from your explanation that you are trying to stop the case brass from expanding forward. Perhaps you are saying that you feel that if the body/shoulder bend does not change location during firing that the case must be thinning at the web.

What I am trying to do is to keep the case head hard against the bolt. Correct me if I am wrong but my understanding of the way thinning at the pressure ring occurs is that the firing pin slams the case forward, the case body expands out to the chamber walls, the case body grips the chamber, the pressure then forces the case head back to the bolt face causing thinning at the pressure ring where the case body no longer is in contact with the chamber. If you keep the case head hard against the bolt face it would be perfectly fine for the brass to flow forward to fill the chamber. Just thinking out loud here not stating facts.

Have you ever tried a hydraulic form die?

Woods,

What you have observed happens with most all belted bottlenecked chambers. Its in the design as tolerances to clear the shoulder must exist if its going to headspace somewhere else and thats the belt.

Where most of the problems happen in handloading is the over sizing of the shoulder, pushing it back too much each time.

Be very careful to set each belted FL die just right so as to size the case and its shoulder to the minimum. Besides that you must use a feeler wire on the inside of each case every time its inspected before loading it and make sure to turn it and check it again in other places as the failure is not uniform.

Since some thinning will occur you might establish whats tolerable as almost all belted rounds have this defect in terms of handloading.

My case head separation sounded funny when it fired, ejected fine and fell apart in my hand. That happens most of the time. Had a buddy that it did minor damage to his rifle and stock but I'm not sure if it was a case head separation or an overpressure situation.

Notice the dent at the case/shoulder bend. On another thread a poster showed the exact same thing on his case head separation. That was discussed and bobski's buddy Hot Core said it was from the gases escaping out the separation near the case head and traveling forward to get out the bore.

But in any case belted magnums are most known for CHS and I suspect that the reason is because the brass manufacturers do not produce brass closer to chamber dimensions because they know the case is supposed to headspace on the belt. The most common cause of CHS is full length resizing every time and pushing the shoulder back too far. That will greatly accelerate thinning at the pressure ring since it happens every firing and not just on the first.

We were posting at the same time here Savage_99, didn't mean to ignore you or repost what you just said.

Gotta go to work, but I figured out a way to measure how far the belt allows these cases to travel forward and will measure it tonight.

Exactly what I'm saying!



Not sure that you're wrong, just that your conclusion is based on having some headspace tolerance on the belt at the time of the firing pin strike. I don't believe there is any evidence to say you are right or wrong, however I question it. I think expansion and contraction is pretty uniform forward of the web, none to speak of at the web so you could be correct.



If brass has zero headspace on both belt and shoulder there should be NO brass "flow". I find no evidence of any thinning in the Norma cases that headspace on the shoulder with minimal headspace clearance. As mentioned, I have one lot that has over 20 reloads and still going strong.

One thing you may be overlooking in regards the initial firing, when the case goes forward to try to fill that big gap at the shoulder, the belt stops the forward thrust. The inertia and ensuing pressure from the discharge pushes the front part of the case forward and with the immediate stop of the back part at the belt, the forward part is still having a long way to go. Much like a dog running and hitting the end of the tether. What happens? Stretch at the weakest point which is the arced plane of the body near the web. The rounded and bent part at the shoulder certainly isn't as weak and it doesn't straighten out and re-bend further down the shoulder where we want it to.



No, but I think that might do it, albeit a very expensive approach and not at all cost effective. I'd still question you can straighten out that bend at the shoulder without stretching the body. I'd like to experiment with an Ackley, or improved, shoulder to try to determine exactly what happens there, and why. Likely the fact the shoulder is minimally in contact with the chamber in the middle of it, has much to do with it.

Bobski....depending on the smith doing the work, I`ve formed AI cases in two fashions...the first, acording to PO Ackley, is a slight crush fit in the improved chamber, of the case being formed. The case is head spaced at the neck/shoulded junction. Now, saying that, we also know virgin brass is not uniform in size, and your numbers suggested in your first posts are close to what I`ve found in virgin brass, compaired to the chamber in which they are to be fired. This done by compairing brass before and after firing.
So, I have come to form AI brass by jaming bullets into the lands for the first firing. The shoulder is blown out to fit the improved chamber. I then adjust my dies to bump the case back 3 thous. in resizing.

Thanks, I was aware of how they are formed; my question is, where does the brass at the shoulder come from, is it from a stretch in the body or is it from the shoulder beyond the bend at the shoulder/body juncture? Is that bend straightened out and re-formed further into the shoulder, or does the body of the case stretch forward of the web? It's difficult with the experience I've had with the belted cases, to believe that formed bend at the body/shoulder straigtens out, but if it does you'd have to attribute it to the headspacing on the shoulder because I know a jammed bullet or a false shoulder doesn't do it. The latter usually has a gentle slope to the caliber to which it's expanded and it doesn't seem to hold the case well under the high pressure of discharge.

While I've helped friends with their improved forming, I've never looked into it as I did for the belted mags to determine what happens with the brass. Never owned an Ackley and likely never will.

This is a way to measure how much headspace these new 300 win mag cases have. Yes, I did say headspace because I am going to measure how far forward the case will travel from contact with the bolt face till it is stopped by contact between the front of the belt and the chamber.

I seated a bullet deep in one of the new cases so it would not contact the lands


I use a R-P tool that is a long rod with a couple of collets on it


you insert it down the muzzle till it contacts the bolt face and lock the rear collet


then I inserted the case in the chamber and pushed it hard forward with a dowel rod


which would take all the headspace out. Then I pushed the R-P tool in until it htis the bullet, lock the rear collet


and measure between the collets


then I reinserted the bolt and chambered the round. I then reinserted the tool and set the rear collet after pushing the round against the bolt face with it. It measured
[img]http://img.photobucket.com/albums/v663/bwestfall/RELOADING/DSCN0764.jpg[/img]

.008" difference.

To me that means that the case can travel .008" until the belt stops forward movement. Now that is only part of the .0215" that the case expands forward from fire forming in this rifle.

Hey bobski, I have a 280AI and was planning on fireforming some new 280 rem cases. What is the best method to mark the case/shoulder junction to see if it changes locations?

I used Dychem, as I stated earlier, and marked the "corner". It's pretty well rounded in a new case, which is the reason I marked several. Were I doing it today it would be with a fine point permanent marker putting a real fine line on the apex of the curve at that juncture. A scratch with an Xacto knife might be even better. After forming you could certainly tell if that point was flattened and the sharpened bend of the shoulder moved forward.

I ran a 30 Gibbs for about 8-10 years. This case design as I'm sure you all know has an extremely short neck (appprox .25"),which requires blowing the shoulder way forward. When I first started playing with it I used the jam bullets into the lands method to fireform and was not able to get good case life. I had several cases that I caught prior to separating and a couple of partials and one complete separation. These were all with somewhere around 4-6 reloads. Once I started using 35 Whelen brass and a false shoulder to fireform I stopped having case separation issues and case life improved to 10 or more firings. I think that with the shallow angle on an 06 case atleast the shoulder angle will flatten out. I am currently working with a 257 AI I'll have to mark the shoulder junction
and see if it moves or flattens out. If I knew how to post pictures I'd go do it right now and take some before and after shots.

Hey dodgefan

Take your pics and download to your computer

Open up an account at photobucket http://photobucket.com

Click on "Choose Files" under Upload Images & Video

Browse to your picture and either double click or open, it will upload your pic

When it's finished you can add a title if you want and then click the blue button "Save and Continue"

Your pic will show up with 4 addresses below it, click on the bottom one and it will highlight blue meaning it has been copied

Go to your post here and right click, go down and click paste



done deal.