New Caliber 7mm rem mag--neck sizing

[dmills]

After getting started (using much advice from this site) I have been handloading .308 Win, 45 long colt, and 45-70. I have just added a 7mm rem mag to the list. I do not even have the dies for it yet.

I have been only neck sizing the .308. I read somewhere (www.larrywillis.com) that the 7 mag develops a bulge "around the case (usually after just 2 or 3 firings). When that happens, these cases will begin to stick in your chamber or they will fail to chamber at all."

Have you experienced this with the 7 mag? Are you neck or FL sizing?

Thanks. Don.

 

[627PCFan]

I'm currently shooting my 7mm brass on +10 reloadings, and I haven't seen any bulges, nor heard of any. Over time the brass ahead of the base can stretch, wear thing and separate, but never a bulge. And I Neck size only.

 

[Horsemany]

I've had some issues with brass that doesn't get sized just in front of the belt. I forget the name but someone makes a special sizer die that sizes this portion of the belted magnum. Many are the same size around the belt so the same die can be used for most belted magnums. They sell for $80 IIRC. I typically bump the shoulder back with a full length sizer and it takes 4 or 5 loadings until they swell in front of the belt. This has only happened to 2 batches of brass so far. Usually my experience is the same as JRSpicer426.

 

[loadedround]

I neck size only since all my cases are fired in the same rifle. However I do full length new cases prior to first reloading them. I have not had any chambering problen in over 15 years with my rifle.

 

[dmills]

Follow-up

Thanks for the replies. It is the Larry Willis company that makes the special die for belted magnums, and that is what prompted my inquiry. I plan to proceed with the neck sizing only.

I have read and heard about bumping back the shoulder, but I am not sure how to do that. I do have both a neck sizing die and a FL die now. Any tips on bumping back the shoulder?

Ok, I did a search and found the tips on bumping the shoulder here:

http://www.thehighroad.org/showthread.php?t=430226&highlight=bump+shoulder

 

[Horsemany]

Yep. Just set the full length sizer die up a bit more than normal so it jut kisses the shoulder. You'll have to do it eventually even if you only neck size. Mine need a full length size every 5 firings or so. Most people probably wouldn't reload enough magnum cartridges to matter. If you're a glutton for punishment it becomes an issue. When I get back into shooting the Sendero I'll probably buy that special die. I think I read he's way backordered on them.

 

[Bart B.]

Belted cases have had problems with the case body not getting sized all the way to the belt since the early 1900's when H&H first used them for their Super 30 cartridge.

Folks using belted cases to win high power long range matches setting records along the way learned to make their own special sizing die. They cut the top off a conventional full length sizing die just below the shoulder and the bottom off just above the belt clearance ring. After smoothing off the edges, this special body die was used after a full length sizing die sized most of the case and set the shoulder back several thousandths. If the fired case didn't get sized back down to new case diameter immediately in front of the belt, they cut more off the bottom of the die.

Once done, this die used as above made cases that equalled the accuracy of new belted ones. Nobody has ever got neck sized belted cases to shoot well all the time. They may get 5 or 10 shots occasionally to do well but it's rare. I've tried every belted case sizing process known to man and always got best accuracy with new cases or fired ones sized twice as described above. When military rifle teams used belted cases for long range matches, they tried neck and partial neck size cases as well as conventional full length sizing but none worked so they stayed with new cases.

www.larrywillis.com has a collet die nowadays but I think he's been out of stock for some time. I'd just get another full length sizing die (they're cheap at gun shows) and cut it off as mentioned above.

 

[Black Dime]

DMILLS,
If you pick up any once fired brass you may need a full length resizer. I neck size only also. 'Course you can adjust your FL die to necksize.

 

[Bart B.]

Black Dime states:

'Course you can adjust your FL die to necksize.

How can one do that without sizing down the body a bit and moving the shoulder forward?

I've tried this age-old sizing technique with both rimless and belted bottle neck cases but never was able to do it without moving the shoulder forward. Cases with less body taper caused bigger problems than those with more taper. When closing the bolt on a case so sized, the bolt would bind somewhat depending on how much longer the sized case headspace (head to shoulder) was longer than the chamber's.

Accuracy with loaded cases that caused the bolt to close hard was never as good as when the bolt closed without binding. Measuring a binding bolt's closed position relative to the receiver ring shows it sets at different places compared to when it doesn't bind when closed. It's much like semiauto service rifles used in competition; all the parts have to go back to exactly the same place after each round's chambered. Bumping the op rod changes the preload forces between it and the bolt and other parts which causes that round to shoot to a different place than those fired from undisturbed parts.

The above aside, neck sizing with a full length die backed off a bit or a regular neck sizing die will often produce better accuracy than cases full length sized such that their shoulder's set back too far. This happens a lot when the full length die's set in the press so its bottom touches the shell holder when sizing a case.

 

[dmills]

Thanks for the replies.

Black Dime said:

If you pick up any once fired brass you may need a full length resizer.

I use either new cases or cases from factory ammo fired in my gun.

So far I have 60 federal cases from factory ammo that I neck sized and reloaded once and then fired the reloads once. I had one reloaded case that was hard to close the bolt on, so I full length sized it for the second reload. And the bolt now closes properly on that cartridge. The rest I have just neck sized.

I plan to proceed in this manner and keep track of 3 of firings on these cases much closer than I have on the .308 Win.

Bart B. said:

They cut the top off a conventional full length sizing die just below the shoulder and the bottom off just above the belt clearance ring. After smoothing off the edges, this special body die was used after a full length sizing die sized most of the case and set the shoulder back several thousandths. If the fired case didn't get sized back down to new case diameter immediately in front of the belt, they cut more off the bottom of the die.

Bart, I think I understand what you are saying, but I do not understand how to make the special body die. Could you post a picture to two to illustrate?

Thanks.

 

[Horsemany]

Bart B.

You get around the length growing by adjusting the die body down. You just kiss the shoulder with the die. This will not usually size the body of the case depending on taper, sizes the neck, and does not allow the headspace to expand.

Most people I know who neck size with full lenght sizer dies will just kiss the shoulder.

 

[flashhole]

Every FL die I have ever used to partialy size the case (i.e. bump the shoulder back a bit) has sized the webbing on the case to various degrees. For those case I want to leave the neck alone and just bump the shoulder I bought the Redding Body Die. I use the Lee Collet Neck Dir on my 7mm Rem Mag with great success. Never a bulge or other problem. My handloads are very accurate in my Sauer 202.

 

[Bart B.]

Horsemany answers:

You get around the length growing by adjusting the die body down. You just kiss the shoulder with the die. This will not usually size the body of the case depending on taper, sizes the neck, and does not allow the headspace to expand.

Every rimless and belted bottle neck case I've tried neck sizing by "just kissing" the shoulder has resulted in the body being reduced in diameter by a few thousandths. Cartridges used were .222 Rem. .243 Win., .270 Win., 7x57 Mauser, .308 Win., .30-06, .30-.338 and .300 Win. Mag., 7.65 and 8mm Mauser. This is with RCBS and Bonanza full length sizing dies. I asked RCBS about this at their plant showing them examples. Their reply was "That's normal."

Have you measured with a micrometer fired cases at the pressure ring and shoulder before and after sizing this way?

 

[Bart B.]

dmills, I made my own belted magnum "body" dies as such.

First, I used a hack saw to cut the top of the die off about 1/16th inch below the shoulder. Measuring up inside the die to the shoulder will show how far up from the die's bottom the shoulder is.

Second, I cut the bottom of the die off about 1/16th inch above the belt clearance counterbore.

Third, I clamped the cut off die top up in a machinist's vise then moved it around under a grinding wheel to square off the top of the die. Reversed the die and squared off the bottom of the die the same way.

Fourth, I polished the sharp edges at the top and bottom with fine emery paper so as not to scratch or scar cases.

I've made others by chucking the die in a lathe headstock then turning off the ends to the same points.

In resizing belted case, I first use a normal full length sizing die without the decapping rod (I push out primers in a separate die before cleaning the cases) but it's neck is lapped out to about 2/1000ths inch smaller than a loaded round's neck diameter. The die's set in the press such that the shoulder gets set back about 4/1000ths inch. All of which full length sizes the case to within 1/16th inch from the belt where the pressure ridge is.

Then I replace the full length die with this body die and adjust it such that the belted case body gets sized all the way to the belt. The body die's bottom edge may well barely touch the belt. Diameter of the case at the belt's front edge should be what new cases are. If it isn't after body sizing, you have to cut off a bit more from the body die's bottom.

I can get 20 to 25 reloads per case with max charges doing this.

 

[Horsemany]

Bart. B

Many variables here. Yes I've measured some of the cases I size this way. I've seen the same as you that there is a slight resizing on some case body's when sizing this way. A lot depends on how much taper the cartridge has and how sloppy your chamber is. A tight chamber is not expanded out much after firing and therefore does not get sized when just kissing the shoulder. This brings us to another variable....Kissing the shoulder. You may be doing more than just kissing the shoulder if you're seeing significant sizing at the web IMO.

 

[flashhole]

Bart - can you post a picture of your set up?

 

[Bart B.]

Horsemany, regarding what is a "tight" chamber, does a chamber at SAAMI specs qualify as a "tight" chamber?

I ask because that's what all of mine are. All are cut with Henricksen or Elliott reamers (probably the best made and favorites of 'smiths building match rifles) ground to SAAMI specs. I don't have any factory barrels with "factory" chambers that are sometimes at the big end of specs. In measuring fired case body diameters then comparing them to full length sizing die diameters at the same place, all the dies are smaller by a few thousandths. Dropping a fired case into an inverted die, it sticks out of the die an inch or so. Case bodies start sizing down before their neck starts going into the die's neck.

I've got several full length sizing dies for .308 Win. and .30-.338 mag. They've got about two thousandths spread in body diameters; normal for all sizing dies. Putting a GO headspace gage in the shell holder, topping the ram, screwing the die down to just touch the gage then locking it in place sets the die in the RCBS Rockchucker press to match chamber headspace. Running cases up into the die then pulling them out before the case neck goes into the die's neck reduces body diameters all the way from shoulder to pressure ring. Not by much, but a thousandth or two depending on fired case and die dimensions. Sizing case bodies and not their necks with all the dies so set reduces case body diameter which pushes their shoulder forward several thousandths as measured with a case headspace gage zeroed on the GO gage. Press spring/stretching is the reason this happens. Similar results have been observed with other rimless and belted bottle neck cases.

Best accuracy I get is when the fired case shoulder's set back a couple thousandths. This can only be done when the die's set in the press such that its static (no case in the shell holder) position with the ram topped is less than fired case or chamber headspace. As the fired case goes into the full length sizing die, its body gets sized down first and the neck is last. The first time I measured all this stuff, I almost fell out of my socks as I didn't think this was what happened. In checking with other folks, I learned they've observed the same stuff.

 

[Horsemany]

If you're sizing the body by ".001 or .002" I'd say you have accomplished the goal of NOT full length resizing. .001" over the circumference of a case is next to nothing wouldn't you agree?

I have to admit most of my trials and tribulations with this has been with 22-250 that has a bit more taper than most. I believe kissing the shoulder will size the body less the more taper you have on the case.

 

[Bart B.]

Horsemany, thanks for providing the cartridge you've worked with. That Savage case and its parent .250 Savage has about the most taper of any cartridge. No wonder you get little body sizing using the method you describe.

I measured case diameters, not circumference as you mentioned. Circumference is 314% greater than diameter.

 

[Horsemany]

Bart B.

I understand the difference between diameter and circumference. I realize your measurement was for diameter. I was simply stating that considering it's a round object .001 isn't a whole of sizing IMO. Wouldn't you agree? If you're sizing a .001 that means being a round object you've taken it in 1/2 a thousandth each side. Almost nothing.

I also never stated 22-250 was the ONLY cartridge I've ever loaded this way. I've kissed the shoulder with success on 7mm Rem Mag, 308, 270, 243, 300wsm,and 6ppc. Most of these other cartridges I've either gone to bushing neck sizers or other sizers. But the technique did effectively size mostly the neck with these cases. It does work and is a technique used by thousands of reloaders. You're idea of creating a die to effectively size the lower portion of the case sounds promising.

 

[Bart B.]

Here's pictures of the belted case body die like the ones I've made. A complete full length sizing die's shown next to the one I cut the top and bottom off per information posted earlier.

 

[Bart B.]

Horsemany, I agree, sizing a case body only a thousandth or two ain't very much. But according to industry standards, anytime all of the case that expanded against the chamber wall that gets reduced by sizing is "full length" sizing.

I've no idea why your cases other than the .22-250 don't get their body diameter reduced by partial sizing, but if they don't that's fine by me. I'm not measuring them and the dies that size them.

There's many, many thousands of folks who partial/full neck size with full length sizing dies and do so because they get better results that way compared to how they "full length" size with the same dies. More often than not, it's because they screw the die down to where it touches the shell holder and set the fired case shoulder back way too far. Everyone's free to size their cases any way they want. I'll continue to do what's shot the smallest 15+ shot groups I know of that beat the pants off any neck sizing process has done that I know of.

Meanwhile, the pictures I posted of a body die made from a standard die show how easy it is to make. Hardest part for me to do was squaring the ends as I didn't have a lathe when I made my first one. Borrowed a lathe to make a couple others and it took about 15 minutes to turn off both ends of the die and polish their inside edges. Any 'smith worth his business card could make one out of a die you supply.

 

[ForneyRider]

You can also partially neck-size. Basically, you are only putting enough grip on the bullet deemed necessary.

I neck-size Remington/Winchester brass and have more than a few reloads without annealing and brass looks and performs like it was the 1st reload. I am below max by few grains typically.

 

[Horsemany]

Bart B.

I am interested in having one in 7mm Rem Mag. Have you made one for a belted magnum? Can the die body be adjusted down farther without touching the lip for the belt? It doesn't look like you trimmed off that end of the die in your pic.

 

[Bart B.]

Horsemany, those pictures are ones I got off the RCBS web site then edited the one shown as a body die to be close to what I and others have made. My dies are in boxes buried downstairs awaiting my finish of the shop in our new house. Soon....soon, I'll be back to normal. The die's bottom is flat as a mirror so when it's set in the press, one can see how close it gets to the belt on a magnum case when it's sizing bodies only.

The .30-.338 body die I mentioned is for .338 Win. Mag. cases necked down to 30 caliber. It's also used for .300 Win. Mag. cases full length sized with a .30-.338 normal full length sizing die to make the Keele (long neck) version of the .30-.338. I (dangerously) assumed that when I mentioned sizing cases all the way to the belt, readers would know I was using belted magnum cases. Shame, shame on me! Sorry I didn't make this clear.

When properly set in the press, a fired case first run through a conventional full length sizing die to set the shoulder back a few thousandths will get sized by this body die all the way to the belt. One has to make a test with the ram all the way up and carefully see that the die doesn't set the belt's front edge back at all. That's where the belted case headspaces on for best accuracy. Use a magnifying glass on body die sized cases to make sure the die doesn't mar the belt and if one has the front edge of the belt buggered up, toss that case and a howling alley cat.