Neck turning, donuts and Forster Die
I've been reading about donuts and I have a few questions to ask and I'd like your opinion as well. I'm about to start neck turning my 22-250 Rem. brass and I've never done this before.
I've been using the Foster Bushing Bump Neck Sizing Die with the .251 Neck Bushing. Below is an example of the Bump Die.
It appears to me the unsized part of the neck is now the new shoulder. I measured this unsized part to be .259 (.008 over the sized neck). Now if this is the new shoulder, I'm considering turning the neck just into the new shoulder. With the bullet pressed in, the neck only increases to .252. The loaded cartridge chambers fine. As shown in the picture the only part sized is approximately the top .210" of the neck and the shoulder. The rest of the brass is not sized at all. If I understand what I've read thus far, I don't think there is a reason for donut to build.
I'm aware that normally brass is full length sized and expanded before turning the necks just into the shoulder.
1. Should I still full length size the brass before tuning the necks?
2. Would it be reasonable to neck turn to the apparent new shoulder?
3. Just how thick is a donut when it forms?
4. With this die, where would the donut most likely appear, if at all?
5. Should I do whatever I decide and learn from experience?
[img width=600 height=238]http://davidwgray.com/images/Bushing_Bump_Die_Pic.jpg[/img]
Re: Neck turning, donuts and Forster Die
To start welcome to the site.
Neck turning is one of them things that doesn't need done. The only time I would recamend turning a neck would be to fit a tight neck chamber, or just a very light cleanup to fix consintrisity problems. Things to remember is a SAAMI chamber will have a large neck in so that it will be safe with all brass, and cutting brass only makes that brass smaller, and makes it work harder. (The brass has to move more to fill the chamber, and then sized back down to hold the bullet, working brass will make it hard.)
Most bushing dies, will not size the entire neck portion of the brass. To clarify what a donut is, it would be a bulge in the inside or outside of the case neck after firing. If you have a bulge from sizing the case it would be do to the sizing process. If I am reading what you have posted, you are over sizing the brass, and this is what is giving you the bulge. A term for this is creating a false shoulder. (This is done on rounds that will be stretched to blown out shoulders, like a 6 dasher, or AI chamber.)
General rule about neck sizing bushing is you take the thickness of your brass multiply it by two, then add the bullet diameter. Once you have this measurement you subtract .002-.004 off and that will give you your neck bushing diameter. For example if your brass measures at .010 you take .010 x 2 and get .020 you would then take that .020 and add it to the bullet diameter or .020 + .224 = .244 this number is what your loaded round should measure. Most people like about .002 neck tension on a bullet, it will give a firm hold that you can not push the bullet back into the case, when pushing it against a bench. With that said if your loaded round measures .244, then your neck bushing needs to be a .242. (.244-.002= .242)
Getting into donuts, donuts usually appear when a case is changed from it parent cartridge size. For example to make a 30BR you would size up a 6mm Br, to a 30 caliber. There will be a donut formed because what was once the shoulder is now part of the neck. With the 30BR you would then cut the donut out, and most times people use a Robinette reamer to chamber the barrel so they have a .330 tight neck chamber, so now they need to cut the brass from its original .012 size down to .0098 thickness. Because of the tight neck they cut the donut out when they neck turn the brass. Donuts also form when you neck brass down, like a 22BR. A 22BR is made from 6mm BR brass, and is necked down to 22 cal. Again a tight neck .250 chamber with .012 thickness brass the donut is cut out when the brass is cut to the chamber. I usually firform my brass before I cut the necks, and this blows the donut out. The other way a donut is formed is when a piece of brass is fired repeatably with the same bullet, at the same seating depth. It takes many firing to get this to happen. Then this donut can be cut out with an inside neck reamer. Again done unsized after the case is fired.
Getting into neck trimming, the cutting mandrel of the cutter should be mated to an expanding die. the brass should not be re-sized, but expanded so that the neck fits the mandrel.
With that all said: Do you have a tight neck chamber?
What is the size of your loaded rounds? (Thickness of the neck and bullet from one side to the other measured with calipers.)
Re: Neck turning, donuts and Forster Die
82boy: Well said and explaned. Turning necks IMHO is taking up too much trigger time. ;)
Tight neck chamber? Well, if you must. Good thing we don't all think the same. ;D
Re: Neck turning, donuts and Forster Die
My fired and loaded brass measures .252 and I estimate the chamber is .253. I was sizing the necks to .249 which is -.003 and decided to go up to .251 in attempt to improve on the recent .201 group. It was suggested to me to turn the necks to equalize the grip around the bullet. My goal is 3-5 shot single hole. I can get the first two shots in a single hole but the third is a little out.
Re: Neck turning, donuts and Forster Die
Quote:
Originally Posted by DaveSavage
My fired and loaded brass measures .252 and I estimate the chamber is .253. I was sizing the necks to .249 which is -.003 and decided to go up to .251 in attempt to improve on the recent .201 group. It was suggested to me to turn the necks to equalize the grip around the bullet. My goal is 3-5 shot single hole. I can get the first two shots in a single hole but the third is a little out.
If your neck is truly .253, and you loaded round is at .252 you will have problems with strange fliers, that is not enough clearance between the brass, and the chamber. For a loaded round of .252 I would size with a 250 bushing. The .249 bushing would also be fine, would not go smaller than that. Do you have a consintricity gauge? The main thing is to see if your consintricity is off.
On your groups size a .201 5 shot 100 yard group would be a good group. The main thing is not to try to get small groups but get an average group size. For a Savage I would say a average .350 ish average groups size would be about ideal.
You may have other factors going one preventing your groups from being small. To start have you just tried one bullet, or other bullets? Have you tried seating depth, and different powders, and charge rates? Do you have a good solid rest, and rear bag? Are you using wind flags?
Re: Neck turning, donuts and Forster Die
Quote:
Originally Posted by 82boy
If your neck is truly .253, and you loaded round is at .252 you will have problems with strange fliers, that is not enough clearance between the brass, and the chamber. For a loaded round of .252 I would size with a 250 bushing. The .249 bushing would also be fine, would not go smaller than that. Do you have a consintricity gauge? The main thing is to see if your consintricity is off.
No matter what size the of the neck size bushing I use, after the bullet is pressed in, it will always go back to .252 because the bullet is .224 and the thickest part of the neck wall thickness is .014. The size of the neck bushing only controls the amount of tension that holds the bullet. The only way to increase clearance between the brass neck and chamber is to turn the necks to decrease the thickness or send my new barrel back to Shilen.
So the question here is, do I really need more than .001 clearance? But this is getting away from my original O.P.
No, I do not have a concentricity gauge. I just roll the cartridge across a flat surface and do a visual inspection.
Quote:
On your groups size a .201 5 shot 100 yard group would be a good group. The main thing is not to try to get small groups but get an average group size. For a Savage I would say a average .350 ish average groups size would be about ideal.
I agree, .201 is very good and acceptable. I believe the new Shilen barrel is can achieve one hole groups.
Quote:
You may have other factors going one preventing your groups from being small. To start have you just tried one bullet, or other bullets? Have you tried seating depth, and different powders, and charge rates? Do you have a good solid rest, and rear bag? Are you using wind flags?
Yes. All the above and different primers. My average for the 75 grain Berger VLD is .121. I'm working now with the 80 grain Berger VLD.
Re: Neck turning, donuts and Forster Die
You must be misunderstanding me. Your original post you said that you have a bulge in the area where the neck meets the shoulder. I am saying that you are over sizing the neck with the selection of bushings. Yes you are correct, the neck bushing will not change the neck thickness, only the neck tension, but you only need .002 neck tension, so the bushing you need to be using is the bushing I quated the.250 bushing. what I am getting at is the neck is forming a donut because the die is only going to size that brass down to that point on the case, when you put in a too small of bushing , you are under sizing the case causing the budge you are getting. When you place the bullet into the case it will expand the neck back up.
You are going to need more clearance that .001 between your loaded round and the chamber specks. Call shilen and ask what the speck is on their reamer, and that will tell you neck thickness. You may have to cut your necks .001 to get there.
On consintrisity you will never figure anything out just rolling the round over the table. I reject rounds that have more than .003 runout measured at the ogive of the bullet. You will never see .003 runout.
On groups size measurements , what are you calling a "one hole group," and a "group that measures .201?" A groups that measures a .201 will look like one hole, that is ragged. Unless you do some magore work to you gun, changing out stocks, and so forth, I think you got it going good. Just for reference here is a picture of a 5 shot 100 yard group that measures at .210. http://i34.photobucket.com/albums/d1...scan0003-3.jpg
Re: Neck turning, donuts and Forster Die
Dave,
82Boy has provided some good advice. Here's my take on it. If, after considering it, you do find that you need to turn a thousand off the neck OD to get proper clearance, you SHOULD NOT use the "new shoulder" as a stop for turning. You need to use the original case shoulder, after F/L sizing. Reason I say that is IMO 22-250's stretch quite a bit with repeated firings and you will eventually get some brass flow into the lower neck area (the portion that goes un-sized with your bump die). I've noticed that brass growth is not uniform case-to-case. SOme grow more / faster than others. That means you'll have a wreck of a batch of cases over time, with unknown and unknowable amounts of variability in the lower case neck. One the things we try to do in reloading is to eliminate variability, so having the cases absolutely uniform before turning is critical.
What I'd do is:
- F/L size with the expander ball removed from your die (so the expander does not induce stretch)
- Trim all the cases to uniform length
- Expand them with an Expandiron
- Turn them all
Then, check the neck ID to see if you have your normal neck tension, if so, go load and shoot them. If not, run them through a bushing die and impose the neck tension you want, then load and shoot.
That's what I'd do - others may have other opinions; I'm fine with that too......
Elkbane
Re: Neck turning, donuts and Forster Die
You are discussing two different issues, whether to turn necks or not in order to improve neck tension, and donut formation and how to avoid them. Yes?
The 308 brass for my F/TR matches your 'false neck' diagram exactly. This is my desired brass configuration. It usually takes about three or four firings to achieve this. I too only partial neck size the top 2/3's of the neck. When comparing your procedure to mine, I only neck size between firings and never shoulder bump unless absolutely necessary.
Donuts may never be a factor for you. It will only effect the loads that require a deep seating depth. If you're shooting heavies, your free bore is likely long enough to allow you to seat the bullets out long enough so that the bearing surface is ahead of the donut area anyway. Yes? If not, you could get a throating reamer and cut the free bore a little deeper to accommodate your bullet of choice. My solution for the donut problem is that I just don't got there.
I'm not clear as to why you think you need to start tuning necks. Is the case neck thickness uniform and concentric?
If it isn't then neck turning will correct this, as you already know. And for me, would be the only reason to want to turn necks.
You've said that you have a .253 neck chamber and a loaded round has a neck of .252. There are no chambering of extraction issues. Neck die selection should be able to modify the neck tension to the limits of the brass potential. If I still had tension issues, I think about getting a different brand of brass.
B
Re: Neck turning, donuts and Forster Die
Dave, I've got a little different take on this. Though all have made excellent points. The Forster dies are designed to leave a slight bulge @ bottom of neck to alleviate donut problems. The "bulged" portion of the neck should be fitting into the neck of the chamber if the sizing die is adjusted properly. At least it does on my Forster dies. If your cases have been fire-formed at least twice. the .259" "bulge" diameter is probably within .0005" of your ACTUAL chamber neck diameter. To prove this, take a twice fired cartridge HD space measurement & compare to reamer specs. The illustration of the bulge shown on the Forster die data can easily be confusing & they make a statement to that effect........ Hope I understood what you're trying to convey. :D
Re: Neck turning, donuts and Forster Die
Dave, I gave your question more thought & have a suggestion. I use the Forster dies for 3 different cartridges. I use the older F/L dies. I've found these dies will push shoulder back up to .008" comparing twice fired case to sized case w/ die set firmly to shell holder. If you don't have a cartridge HD space gauge you could substitue a 32ACP case or similar over the case nk. to get a pretty accurate reading ( emphasis on PRETTY accurate.) W/ .008" set back & wanting .0015" set back, put a combination of a .005'' & a .0015" feeler gauge together & put the combination gauge between shell plate & die when setting up the die. Set it firmly. Don't know if your shoulder bump die has same tolerance as my F/L dies but worth a chk. ........ Also, If you're considering nk. turning, chk run-out of case @ shoulder B4 & after sizing. Your neck should be perfectly centered to base or .001" or less run-out................. Don't tell me you've got that RV parked right next to a PD town :'(
Re: Neck turning, donuts and Forster Die
Thanks for all the feedback. I decided to do a little experimenting and I have some good news and bad news.
I turned the necks on some full length sized brass and some with the Foster Bushing Bump Neck Sizing Die. On the Foster die, I only turned the necks up to the unsized ridge. I only cut off .0005, just enough to make an even cut.
I did confirm with Shilen that the standard neck chamber size is.254. So I think I'm fine with that.
To keep this short, it turns out that my rifle shoots better with the full length sized brass. Below is a picture of the good news.
http://graystarcity.info/images/22-250Group.jpg
Now the bad news. I could not get consistent groupings. As I stated before, I could get 2 shoots in nearly a single hole but the third would be off as much as 3/8 inches. Sometimes there wasn't a good group at all. I found that 15 pieces of brass out of 100 sorted first fired brass developed cracked flash holes. The second firing nearly all the brass flash holes cracked. Occasionally after firing, there appeared to be overpressure conditions even though the load was the same for each. I believe now that has to be caused by the flash holes cracking. Below is a picture of the brass. I posted this picture on Winchester's Facebook page and I haven't received a response.
[img width=458 height=450]http://graystarcity.info/images/D-Gray_Brass.jpg[/img]
Re: Neck turning, donuts and Forster Die
Quote:
Originally Posted by gotcha
Don't tell me you've got that RV parked right next to a PD town :'(
Not now but I'll be heading that way soon. I've been invited to eastern Idaho.
Re: Neck turning, donuts and Forster Die
Re: Neck turning, donuts and Forster Die
I cut the sharp edge out of the primer holes to help eliminate the cracked primer holes.
