Donuts forming 0.050" in front of shoulder?
- Thread starter asauer
- Start date
asauer said:
Size it down with the die and run your mandrel in till you feel it touch the donut, run the neck turner with carbide mandrel in and it will not touch anything but the donut. The mandrel you run in to open it up for the K&M mandrel is about a .001 bigger than the one for the neck turner so it will not touch anything other than the donut. Just be careful starting it and removing it because of the cutter …… if you heard bad reports they didn't know how to use it properly…….. jim
That's about how my 21st Century is. The problem I see is that my donut is 0.001" or less. Therefore I don't see how I'll be able to clean it up, given the slop in the mandrel fit.
Perhaps this small of a donut is nothing to be worried about, but I'm going to extend the throat and forget about it.
Perhaps this small of a donut is nothing to be worried about, but I'm going to extend the throat and forget about it.
How do you know it is a .001? The pic you have it sure looks like more. Believe me it will take it out. I said about a.001 Idon't know what the mandrel you have is nor do you know what the carbide mandrel is but if you set up with and both K&M mandrels it will be fit and every time you turn it will keep it cut out. or get a bushing die and it doesn't size the area where the donut is and it will be chamber size so it will not be an issue and you will never see it again. If you do get new brass or get the K&M set up……… jim
I am not a Gunsmith but I do have several custom made rifles in a number of calibres and I have never seen the ring marks left on your case shoulders nor anywhere else on a highly polished case after firing.
I'm now wondering if your problems are being caused by a faulty chambering job and/or reamer. I am under the impression that the finished chamber after reaming should be mirror smooth and not have crazy rings left to mark/damage cases on firing.
I also wonder if after firing what the outside of the case measures the full distance along the neck especially where that donut is on the inside and perhaps the chamber creating it..??
Once I have done my case prep on brand new Lapua cases, neck turned etc I tumble them to a mirror finish, on first firing once I wipe any carbon trace from the neck with Ballistol the whole case just shines, no rings/grooves anywhere and they still look like they just came out of the tumbler. Even after several firings.
You mentioned that your mate also had a barrel done at the same time. Is he having the same problems and also the rough looking cases after firing..??
I'm now wondering if your problems are being caused by a faulty chambering job and/or reamer. I am under the impression that the finished chamber after reaming should be mirror smooth and not have crazy rings left to mark/damage cases on firing.
I also wonder if after firing what the outside of the case measures the full distance along the neck especially where that donut is on the inside and perhaps the chamber creating it..??
Once I have done my case prep on brand new Lapua cases, neck turned etc I tumble them to a mirror finish, on first firing once I wipe any carbon trace from the neck with Ballistol the whole case just shines, no rings/grooves anywhere and they still look like they just came out of the tumbler. Even after several firings.
You mentioned that your mate also had a barrel done at the same time. Is he having the same problems and also the rough looking cases after firing..??
ridgeway
Silver $$ Contributor
Those rings are superficial and has nothing to do with the donut. I'm guessing the camera makes them look worse than what they are. I do agree with you the creation of the donut has something to do with the chamber. Like I said earlier, I'm guessing the chamber oal is short and the brass is long. When fired, the case mouth is contacting the end of the chamber and in turn flowing brass rearward and an instant donut. This probably why the op does not see any case growth. The growth is creating a yummy donut.
Then again, this is speculation and hard to do internet trouble shooing.
I had a similar situation fireforming 3x 6BR brass to Dasher. I never ever get a donut when making dasher brass. This time, of the 20 pieces I made, all had donuts. Figured it had something to do with 3x fired brass. I cut the donut out and went at it. I then measured one, they were way long for my chamber. The excess brass pushed back and formed a nice donut. Trimmed them back...donut fixed.
Eventhough the reamer print provides a dimension, does not mean that is correct. The only way to find the exact chamber oal, you gotta measure it or scope it with a case chambered.
Then again, this is speculation and hard to do internet trouble shooing.
I had a similar situation fireforming 3x 6BR brass to Dasher. I never ever get a donut when making dasher brass. This time, of the 20 pieces I made, all had donuts. Figured it had something to do with 3x fired brass. I cut the donut out and went at it. I then measured one, they were way long for my chamber. The excess brass pushed back and formed a nice donut. Trimmed them back...donut fixed.
Eventhough the reamer print provides a dimension, does not mean that is correct. The only way to find the exact chamber oal, you gotta measure it or scope it with a case chambered.
All very valid points and I would think much more to the point than incorrect case prep.
Yes, over the internet it is very difficult near impossible to come up with an exact solution. Wished I wasn't the other side of the world and could go and have a look.
Short chamber pushing the case neck back interesting, I don't see any sign of the front of the neck being forced into the chamber but I have no experience with that problem. Perhaps a check on that idea might be to shorten one case as a trial and see if the result was duplicated.
On the rings around the case shoulder, well if I saw that on any of mine from any chamber it would go straight back to my Gunsmith to rectify. I thought a "finishing reamer" as the last step was the one that gave the chamber a high quality super fine finish which I would require for a competition custom chambered job. Maybe I am just too fussy but I think that is how I end up with 0.1-0.2 MOA consistant accuracy if I can keep my concentration level high....not easy at the end of a 2 day shoot for me in older age.
I really hope that "asauer" discovers the problem and an easy cure.
Yes, over the internet it is very difficult near impossible to come up with an exact solution. Wished I wasn't the other side of the world and could go and have a look.
Short chamber pushing the case neck back interesting, I don't see any sign of the front of the neck being forced into the chamber but I have no experience with that problem. Perhaps a check on that idea might be to shorten one case as a trial and see if the result was duplicated.
On the rings around the case shoulder, well if I saw that on any of mine from any chamber it would go straight back to my Gunsmith to rectify. I thought a "finishing reamer" as the last step was the one that gave the chamber a high quality super fine finish which I would require for a competition custom chambered job. Maybe I am just too fussy but I think that is how I end up with 0.1-0.2 MOA consistant accuracy if I can keep my concentration level high....not easy at the end of a 2 day shoot for me in older age.
I really hope that "asauer" discovers the problem and an easy cure.
Mega,
Sorry if you missed it, but earlier I stated that the reamer was not ground exactly to my spec of a 0.340 neck on its entire length. I didn't check it well enough and only after firing noticed it, but the reamer has a taper in the neck that is causing this. In the attached picture it may be hard to tell, but right where the carbon stops at the bottom, I measure 0.345. The end of the neck measures 0.338, as I would expect.
This is a straight-from-the chamber case which I fired back in April. I have not tumbled them yet- this picture is a better representation of the rings on the shoulder. I'm not worried about them, and bet they'll disappear when polished. Only thing I can figure is either the reamer was a tad rough or some bits of chips did not get flushed out.
I am no gunsmith, either.
Sorry if you missed it, but earlier I stated that the reamer was not ground exactly to my spec of a 0.340 neck on its entire length. I didn't check it well enough and only after firing noticed it, but the reamer has a taper in the neck that is causing this. In the attached picture it may be hard to tell, but right where the carbon stops at the bottom, I measure 0.345. The end of the neck measures 0.338, as I would expect.
This is a straight-from-the chamber case which I fired back in April. I have not tumbled them yet- this picture is a better representation of the rings on the shoulder. I'm not worried about them, and bet they'll disappear when polished. Only thing I can figure is either the reamer was a tad rough or some bits of chips did not get flushed out.
I am no gunsmith, either.
Attachments
Ridgeway,
You have an interesting thought on the neck length, but I cannot see that as a potential cause. I have a chamber gauge made up with the same reamer, and I clearly have plenty of room left.
I think I should have been more clear in all my ramblings, but I realize my chamber (from the reamer issues) has been the source of my donut issues. My sizing die is pushing that excess crap to the inside of the neck. I thought it strange, however, that I could not get rid of or prevent them. I guess that extra generous radius leading from the shoulder to the neck on this reamer allows a ton of brass flow upon firing.
You have an interesting thought on the neck length, but I cannot see that as a potential cause. I have a chamber gauge made up with the same reamer, and I clearly have plenty of room left.
I think I should have been more clear in all my ramblings, but I realize my chamber (from the reamer issues) has been the source of my donut issues. My sizing die is pushing that excess crap to the inside of the neck. I thought it strange, however, that I could not get rid of or prevent them. I guess that extra generous radius leading from the shoulder to the neck on this reamer allows a ton of brass flow upon firing.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.