Here is what the shortmags website posts:
We get many posts from folks loading the short mags for the first time who are puzzled when their handloads will not chamber easily. Though there are a number of possible causes, in nearly every case the problem is caused by the sizing die not being set up properly.

Short answer - Here are two quotes from previous threads that will point you in the right direction:

"Many of us find we have to get all the sizing the die can provide. That means not only bumping the shell holder, but making sure all spring is removed from the press linkage. That means there should be resistance at the end of the stroke as the press cams over. - Moderator"

"This is a problem we solved here almost 3 years ago with the ShortMags. You need to 'bump' the brass case shoulder back about 2 to 3 thou. Get yourself the Stoney Point Head & Shoulder Gauge. Take measurements of the case and then set your FL sizing die to move the shoulder back about 0.002" to start and they should slip right in to your chamber. I wouldn't move the shoulder more than 4 or 5 thou though, you then get into working the brass too much. - Hunt-Nut"

Long answer - First, full-length re-size. Neck sizing does not work well with the short mags for most reloaders.

Second, you can NOT setup your sizing die in the same manner you are used to with standard cartridges. You will need to get virtually all the sizing your dies can provide. To do that, you will need to adjust your die down further than you are used to - down past contact with the shellholder. You will need to have it require extra force to get the press handle to "cam over" at the end of its stroke. This extra effort removes all the 'play' in your linkage and gives you the little extra bit of sizing the short mags need.

To do this right, getting enough sizing for easy chambering but without overworking the brass (if that's even possible with your press/die combo), you need to be setting the shoulder back approximately .002". One of the easiest and least expensive ways to check this is to use the Stoney Point device made for this purpose. It's called the Head 'n Shoulders Cartridge Headspace Gauge. Read about it at the Stoney Point site. It is not expensive - here's one good place to get it.

Once you have the gauge on hand, you can measure the shoulder position on your fired, unsized cases. After res-sizing, measuring again should show the shoulder moved back aboout .002". You may be surprised to find that if you have not turned your sizing die in further than normal, the shoulder may not be moved back at all. Turn the sizer die in in small increments, just a small fraction of a turn, until you get the target amount of shoulder set back. If your dies allow for more than .002" of set back, going further will shorten brass life so if .002" solves your chambering problem, stop there.

If you have followed these instructions and still have problems with difficult chambering of handloads (even though factory loads chamber fine) - then start a new thread in the reloading procedures section and note that you have already tried the procedure in the FAQ section. We will help you figure what else may be causing the problem.

Here are my questions to the post above...

I have read all of the info that I can find in the FAQ section and I have some additional questions that I am searching for answers...

1) I tried to neck size my 270WSM brass and did encounter some chambering problems so that is when I started looking for an explanation. I understand how bumping the shoulder back would allow for easier chambering if the brass was being expanded in that manner however, I have no trouble chambering my fired brass and I would suspect if that was indeed the problem then I would have the same difficulty in chambering fired brass and neck-sized brass.

This was not the case as during the process of neck sizing I was not able to chamber my handloads? I noticed what appeared to be a bulge running around the case about 1/4 of the way up from the bottom of the case (primer end). Then once I tried full-length resizing my brass the bulge was no longer apparent and I was able to chamber rounds effectively without any problems? If this was in fact what was happening it seems as though it was not a problem with the shoulder of the brass...

2) "Cam over". I have read the cam over portion of the thread and it seems that the dies are not machined to the proper spec as if you were to shave 0.002" off the bottom of the die or the shell holder there would be no need to put the extra strain on equipment? Maybe I am missing something but as you can tell I am slightly puzzled...

Any further explanations would be greatly appreciated!

Thanks

I can't comment on the chambering problems but I do have something to say about cam-over:

Cam-over is necessary to get the full amount of resizing out of a given die. Whether or not you want this amount of resizing is another story, but anyway...

If you adjust a die to just kiss the shell holder during set up you will be able to see that when actually pushing a case up into the die that the shell holder no longer contacts the die. This is due to the extra force needed to push the case into the die causing the press to flex a little. This will happen even in a very rigid press. Adjusting for cam-over removes this variable and makes sure that the shell holder hits the die each time. It actually takes quite a bit of cam-over with larger cases to make sure the shell holder contacts the die.

For the same reason, the act of adjusting the die in small increments until .002 set back is achieved will not be consistant either if the shell holder does not contact the die. Its just a waste of time. Slightly different resizing force needed for each individual case will cause different amounts of flex.
This is why ( I guess) Redding makes a set of shell holders that are of different heights. It allows you to use the one that gives the right amount of setback while touching the base of the die.

If the shell holder isn't touching the die at the end of the press stroke then there is no way of knowing exactly how much resizing will occur, everything is 'floating' so to speak until that shell holder hits the die.

Of course some presses flex a lot and some only a little. I don't think cam-over is a big concern regarding wear on the press. I think they are designed for it.

Having said all of this, most of the time for hunting ammo I doubt that camover is an issue, but trying to set an exact resize length with no removal of the variable flex is an exercise in futility.

This is actually covered in most reloading manuals but I've noticed that we tend to forget the basic principles when we start trying to fiddle and fine tune. Fine tuning is great but you have to have a solid base to rest the fine tuning on first, sort of like trying to make quarter inch scope adjustments on a rifle that shoots 3" groups...or adjusting the air pressure by half a psi in the left rear tire of an '76 Impala.

I see???
you stated you could chamber your fired brass but after neck sizing they would not chamber, That after neck sizing you found a buldge near the base of the case???
what type of neck die are you using?
if you have to use that much pressure and cam over to neck size, you are pushing the brass to the base where it is not supported by the die?
you do not need to set the shoulder back on fire formed brass when you neck size.
Set your neck die to only partial resize the neck. and if your die has a ball expander lube the inside so the expander does not pull the neck and lengthen the sholder.
Dave

Hivelosity hit the nail on the head with the neck dies. I have been reloading for my 270 WSM a couple years now and do not neck size. I have found FL sizing to work much better and the brass lasts just as long.

I lube my expander ball every 10 or so rounds with a small amount of case lube. I found that if you don't, at least in my redding dies, it will in fact stretch the neck. At your next reloading, you get a bulge at the base because you stretched the case out.

One of the best things I ever did was grind about .020" off a shellholder to keep around for "tough sizing" brass like the 7wsm my friend has. No need to "cam over" and leverage the die against the shellholder real hard just "hoping" to get that last .005" of spring back out!!
A stoney point headspace kit is a wonderful thing to have for all cases.....and especially these buggers.

I am not actually using a neck sizing die... I just back my RCBS full-length resizing die off so it only sizes the neck. Could this be somehow causing my problem?

quote:

if you have to use that much pressure and cam over to neck size, you are pushing the brass to the base where it is not supported by the die?

yes. If it takes that much pressure to size the neck and since it is a FL die backed off you are probably still setting the shoulder back some.
Adjust the die so you only size about 1/2 ot2/3
of the neck and use a little lube inside each case neck

quote:

Originally posted by Swarovski:
I am not actually using a neck sizing die... I just back my RCBS full-length resizing die off so it only sizes the neck. Could this be somehow causing my problem?

Yes.

As your FL Die Resizes the Neck, the portion of the Die that Resizes the Case Wall is in fact doing just that - pushing the Case Wall back into a pre-fired diameter. As this happens, it causes the Case Shoulder to be pushed farther from the Case Head, thus effectively lengthening the Case Shoulder-to-Case Head dimension.

So, you have a couple of easy options to resolve the problem:
1. Try to Resize "less" of the Case Neck using the FL Die. Try to Neck Size only the first 1/3 of the Case Neck and see if the empty Case will easily chamber. If it does, the problem is resolved.
2. Buy a Neck Sizer. This will absolutely fix the problem you are experiencing.
3. Switch to Partial-Full Length Resizing(P-FLR) and you can use your same FL Die, the problem will be resolved and as a nice side bonus, your groups are typically better than with Neck Sizing.

The only negative thing is you will have to Lube the Cases and remove the Lube after P-FLRing, which is a small bit of effort for enhanced accuracy.
---

To P-FLR you:

Adjusting a FLR Die to P-FLR in your situation is done by "slightly lowering" the FLR Die in the press than you have it set right now. Since you are having trouble closing the Bolt on you Case right now, you are very close to where you want to be to P-FLR, so only screw the FL Die into the press 1/16th of a turn at a time as you do this.

Lube a case, Resize it, wipe off the Lube and try it in the Chamber. If it closes with a slight bit of resistance STOP because you are right where you want to be - Zero Headspace.

If it still won't close on the case, screw the FL Die in 1/16th turn and repeat the above.

When adjusted to P-FLR properly, the bolt closes on an empty, length-trimmed case, with a slight bit of resistance. This indicates you have a crush fit between the case-head/case-shoulder and the bolt-face/chamber-shoulder. That ensures the longest possible case life, helps prevent case-head separations and increases the accuracy potential of your rifle/load combination.

Best of luck to you.

I had problems with Lee FL dies, the bolt of my Tikka T3 270 WSM was forcing while closing on reloaded rounds. I had to grind 3/100 of a mm. (0.0013") from the bottom of the sizing die; it was a shoulder problem. Now it's ok.

HC got it right (did I say that )

If you are neck sizing with a FL die, you can only size the neck about 2/3 to 3/4 of it. If you set the die to resize more of the neck than that then you are sizing the case body which will push the shoulder forward and cause the crush fit. The crush fit will not be alleviated until you have adjusted the die in far enough to start pushing the shoulder back.

If you want to neck size get a Lee Collet Neck Sizer or a Redding Type S Bushing Neck Sizer. They do not size the body like all other neck sizing dies but have the additional benefit of not having to lube the inside of the neck and usually far less runout.

I think also that the straight taper of the case body on WSM's bring the case body size into the crush fit problem more than a tapered case like a 30-06. I only reload for 1 WSM and I was astounded when I could not neck size only once fired brass without a crush fit. On normal cases I can neck size 3 to 4 times before I have to PFLR.

kraky is right about the Stoney Point Head and Shoulders Gauge. It is one of my most valuable tools and has allowed me to understand what is going on with the shoulder position during sizing.

Thanks you guys, for all you detailed explanations, everything makes sense now!

I used an approach similar to wildboar's only I put the shell holder on my belt sander and took .015" off it, allowing the die to size another .015". Now, that is way too much, so I use my Stoney Point gauge to creep up on the .002/.003" of bump I want for slick chambering.

I measured the RCBS shellholders for 7 mm Rem Mag and the WSSMs and found them to be the same. Never contacted RCBS about it--don't know what they might say.

All:

This has been most informative. I've had a similar problem in resizing brass for my Kimber in .300 WSM. It is very tight chambered in the first place, often reluctant to close on factory ammo. But, when I started reloading for it, I couldn't get ANY brass to chamber, even with full length resizing. I was using Hornady dies, which I used without any problem to reload for my Browning A-Bolt. On a whim, I bought a set of RCBS .300 WSM dies and was able to resize the brass enough to chamber in the Kimber. When I have rounds that won't chamber, they usually have a very slight bulge at the shoulder, not near the case head, which prevents them from chambering. I think the comment about lubing the expander ball regularly is probably the most important thing you can do. I THINK that the necks are actually being pushed down and with the sharper angle of the shoulder on the WSM series, it's easier to SLIGHTLY bulge the shoulder. Has anyone had this problem with other cases with a sharp shoulder angle, such as the 6 PPC or .22 PPC?

Good thread......

MKane160

In my 300WSM, I have trouble closing the bolt after around 3 firings. i usually only resize about 2/3 of the neck but when they become hard to chamber i just run them through the FL die and set the shoulder back a tad and they chamber fine for a few firings then i have to do it again. havn't noticed any difference in accuracy from the first time the shoulder has been set back to the next time its fired when only 2/3 of the neck is sized. if that makes sense

I believe that these problems are mainly linked to the considerable thikness of WSM brass, as well as the sharpness of the shoulders.

I contacted the die maker about these types of problems and said that I had taken down the shellholder. They said that there is so much inconsistancy in the first batches of brass that it was hard for them to pick the dimensions of the die so that it would size some down enough and not work the living crap out of other brass.
Having a "shaved shellholder" for me has been the answer and it will stay in my reloading tool arsenal!!

Swarovski ----- Thanks for the post, I thought I alone had the problem until you pointed it out. I had a chambering problem with the first 20 cases I loaded, about half were to entirely to tight. I screwed down the die and just finished resizing 150 pieces of .270 WSM that all chamber very smoothly. Good shooting.