I have a problem I brought up a while back and was wondering if you guys could explain how this can even happen with an aproperiate reamer?.

This is on my 300 Ultra. Before fireforming new cases, with a black marker I placed a mark on all cases over the "R" as in R-P on the Remington case stamp.

I then indexed each case before firing with the mark at exactly 3 O'clock viewed from the rear.

I already suspected the problem and is verified with each case checked now after firing.

Now to the point... The cases have runout in the neck at the 2 O'clock position of .005" - .006" every time. This means the neck is obviously not in line with at least the case shoulder, so this is the question.

How can a chamber be cut with the neck off center with the shoulder or case body? I can see the whole chamber being off center with the bore but not the neck with the body... Isn't this basically impossible to do with a single reamer even if it isn't cutting on all flutes at the neck or body?

Only one way I can figure this happened. The rifle was accurized and when the bolt face was cut etc the barrel was turned back one thread, the smith did remember this part. It was done some time back. My thoughts are he could have used an Ultra reamer in a smaller caliber somehow and then used a seperate reamer to move the neck area forward just a bit but cutting it out of round at the same time. One thing that makes me doubt this is that brass OAL needs to be shorter than the book trim to length or it headspaces on the mouth.

It seems this part was not moved forward at all but may indeed be shorter. I have carefully measured it several times using a modified case with a section cut out of the neck on a sized case. I used the ring cut off, which was split and pinched then slipped over the loaded dummy round and left long. Chambering produced the same .002" shorter than the trim to length each time.

The reason I say this is that he may just have reamed the body/ shoulder forward, leaving the neck alone and ending up eccentric using a smaller caliber reamer with a larger pilot. Is this possible? Is it fixable by setting back and rechambering?

I am using Redding S neck dies and just indexing the runout to 3 O'clock so they still chamber. I can't help but wonder how much accuracy is dagraded because of this either. I'm just single feeding target shooting with it if your wondering.

Thanks for the help.

Brent---

I emailed you instructions for making a chamber cast.

Put the cast in the concentricity guage and know for sure what the chamber is.... If the chamber is short take it back to the one that did it....it's a safety concern and his responsibility to repair.

My guess is that you're seeing the differernce in concentricity in the neck because the case neck is not uniform in thickness. That means it expands and shrinks at different rates and winds up off center.

Brent,
This is the sort of problem a gunsmith might be faced with when dealing with a factory barrel and chamber. The chances are very good that the original chamber was eccentric to the bore, to the threads, and to anything else in the neighborhood! If the gunsmith chambered with a reamer with a non standard neck (small), and if the reamer had a very tight fitting pilot, it might be possible to shift the body of the chamber over by a couple thou. If the reamer neck was of standard diameter it might still be possible to move the body over and end up with a neck that is out of round since the reamer cut on one side. This is why, when doing a job that entails setting the barrel back it is wise to check the original chaber very carefully. If it is crooked you will have a tough time ending up with a proper job. To avoid a problem such as you describe a smith might be as well off to dial in the chamber then run the reamer with no pilot at all. The reamer will cut to center and the chamber will be as it was. This for a minor deepening of the chamber. No matter how you do it, if it starts crooked it stays crooked.
A chamber cast will give you a definite reading as to whether of not the chamber body is indeed eccentric to the neck. Regards, Bill.

JBelk, do you think you could e-mail me those same instructions. Thanks

Heck I might as well ask you too:
Jbelk, could you e-mail me those same instructions for chamber casting, I imagine one has to get some Cerrosafe to do it with though.
Bill

Yikes!!! I got 40 request!!!

Here it is. Buy a pound of sulfur from the feed and seed store. Drug store sulfur is too expensive.

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REPOST--

Clean the chamber very well and then swab with a very light coat of light oil. WD40 works fine for this. Stick a patch about half inch ahead of the throat. Now melt some flowers of sulfur over low heat ( you DONT want it to catch fire...it STINKS!).

Heat the barrel in the chamber area with a propane torch (Yes, the action better be out of the stock) until its just too hot to hold on to. Now carefully pour the melted sulfur into the chamber all the way to the top. you'll see a funnel appear in the center. that's normal. Wait about five minutes and gently knock the cast out and be sure to catch it. The dimensions will be about .0001 smaller than actual...that's plenty close enough. WRITE DOWN THE MEASURMENTS!!!!! You'll need it later and the cast will change and become smaller with age. Use the measurements you get when its fresh.

You can do the same with your dies if you want to get really curious.

A loaded round MUST measure at LEAST .002 SMALLER than the neck of the chamber.

A fired round should not be more than .005 bigger than a loaded round.

A RESIZED case should be no more than .002 smaller than a loaded round.

These measurements are for the best accuracy, you VERY seldom find commercial chambers, and dies and neck thickness’ that come close to this.
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thanks Jack.

Thanks JB, I'll do it. Disregaurd the email question, I see you've answered it here. How does this work as compared to cerrosafe?

Everyone, thank you for the insight. I had wondered about the uneven neck thickness but runout would be in random locations, not just at 2 O'clock. The smith that rechambered it was thinking the same too. I have not had ONE case in over 60 cases NOT have it's offset at "exactly" 2 O'clock so I'm pretty convinced, just wondered how the hell it happens mainly.

My only consideration was to have it set back enough to clean the whole neck area up and use a tight neck this time too. Still may but it's only a factory barrel and I just don't want to put the cash in it and not a longer cutom tube. It just sucks knowing it's off and my new Redding S neck die will do nothing to make the necks concentric again. I shot some just neck sized anyway today, haven't rolled them on the runout guage yet to see if it got worse, stayed the same or what but I indexed them to the same locaion in the chamber to see what happened to groups and runout. Groups were a bit better but with a Nosler Ballistic Silvertip not the regular BT. Both were the same good load, we'll see how it goes. Thanks again guys.

Thank you JBelk:
I appreciate you and others offering us your experience and helping us out.
Very nice to know that we have a way of finding out how to do something properly the first time.
Priceless resource in my opinion.
Thanks
Bill

Here's a couple posts I thought you guys would like to read copied from Benchrest Central using cerrosafe. Much the same...

I would ad to Steve's directions, that I place a light coat of oil in the barrel & chamber before pouring. And I use a borescope to set the cleaning patches only 3/4 to 1" into the rifling.
I have cast ALL my match chambers. But I usually do it when the barrel is off the rifle. It's a lot easier that way.
Be sure to clean the bolt raceways and lug engagement areas before use. I have had a little piece cause me BIG headaches. It didn't hurt anything. I just couldn't figure out whay it was so tight to cam over.
Be careful,
Victor

Tim,
I push two (one at a time) cleaning patches into the barrel so they end up two inches ahead of the throat, to form a dam. I have ground a dewey style jag flat (blunt), so the patch will stay ahead of the jag, and I can remove the rod and jag without pulling out the patch.
I then clamp the rifle muzzle down in a padded vise. You can pour from the rear of the action (bolt removed) or you can pour through the ejection port of the action.
I then make a small funnel from a piece of aluminum foil. I form the narrow part of the funnel around a pencil, and remove the pencil when finished. I make the funnel so that the large end will rest on the action, and the bottom of the funnel to just go inside the chamber. This allows me to pour the liquid cerrosafe into the aluminum funnel and have it trickle into the chamber. When I can see the cerrosafe filling to within 3/8" of the top of the chamber, I quit pouring the cerrosafe, and let it cool according to the package directions.
IF YOU POUR TOO MUCH, AND IT GOES WHERE IT SHOULD NOT, DON'T WORRY. YOU CAN EASILY REHEAT THE CERROSAFE WITH A BUTANE TOURCH AND JUST POUR IT OUT, AND START AGAIN. THE CERROSAFE WILL NOT ADHERE TO ANY METAL!
I then carefully inset the dewey rod (with the blunt jag) into the muzzle end of the barrel, and give it several good "rapps" with the heal of my hand. Each "rapp" will move the casting rearward a little bit, and you can feel how much it moves depending on how hard you "rapp" the cleaning rod. Push the casting up into the action until you can easily grasp it with your fingers.
Measure according to the directions "cooling period" of the cerrosafe. Have fun!
Steve Torode