I was waiting to package up my MRC 458 Lott which has to be sent back because the wrong contoured barreled was installed on it.
I decided to see how it would feed just for the heck of it and found an interesting situation.
I am using new unfired Hornady brass which chambers fine without a bullet in the case. When I seat a bullet without crimping the case the area about 3/16's of an inch above the case belt swells just enough to cause the round not to chamber propery. Both the bullets I used were seated shorter than the COL (3.6). I even tried full length sizing a case first but the same results. "Smoking" the bullets revealed they are not hanging up on the lands.
Obviously the bullet seating is causing just enough unmeasureable distortion at the base of the case to prevent it from chambering. I am wondering is this a sign of a chamber being cut to tight? I have "smoked" the area where it is hanging up and it seems to be the same area every time, an area that covers about 1/5th of the diameter of the case.
I can force the round into the chamber and then of course it will work fine but something is amiss here and I am not sure what it is.
Barrel is being replaced as it is but my curiousity has the best of me. Would this be a simple fix by polishing the chamber?
I did measure the brass both before and after and can not detect any difference greater than .001, if that much. The cases are scratched where the resistance starts.
Thank you

I'm guessing that you are feeding the round out of the magazine. If so, the cause is probably simply that the case is not fully up under the extractor and is pushed up into place as the cartridge is seated into the chamber. Does the same problem exist if you feed the cartridge into the chamber singly (like a push feed)? Regards, Bill.

Actually I was just dropping the round into the chamber by hand and then trying to close the bolt.
Once the round is forced into place and the case is downsized to match the chamber then it feeds either by hand or by working the bolt.
Either way it went back to MRC for a new barrel contour but I suspect a to tight chamber.

Very well could be a to tight chamber, but the fact that the brass without bullet chambered fine makes me say there is something else/also going on here. But you sent it back apparently, so we'll never know.

There's not a chance your sizing die is out of spec and oversizing the cases is there?

I was using unfired brass.

After two weeks Hornady finally emailed me back and we exchanged a few emails and seems the problem is probably an incorrect seating die. Once the bullets were seated the cases would become distorted (think of a banana).
Since the cases are being bent it causes the neck to hit on one side and then the base sticks on the other side.
The chamber was cut properly. This is Hornadys fault and not the fault of Montana Rifle Company

quote:

This is Hornadys fault

I've seen this problem several times. I ususlly called it user error caused by the user setting the die up incorrectly. Help me understand what was at fault with your die?

Seating die caused the brass to distort. Hornady told me the die was designed to seat round nosed bullets. I was trying to seat Barnes XXX and Swift A frames. This is a quote from Hornady:

"I'll take a look at the alignment sleeve and bullet seater, it may not get a good hold on those bullets. I believe that the seater was designed more the RN style bullets".

By the way, how could I possiby be setting up the seating die incorrectly? I did not have the die set to crimp.

quote:

By the way, how could I possiby be setting up the seating die incorrectly? I did not have the die set to crimp

OK I believe my past comments to others are still correct. Problems I had seen people have in the past were just what you mentioned more or less over crimping or having the die set to crimp without a groove. Or simply crimping when they thought they weren't do to long cases or a die that slipped. Sounds like the bottom of the seater might be hitting the brass just like a crimp issue.

I had missed the comment in your first post about not crimping. Something to watch for on those rounds that have a lot of round noses bullets.

Brass can tend to be a bit long when new and may need to be trimmed to size. Brass shouldn't swell in the middle if seating a round, however, if the cartridge has been expanded for the bullet seating it will need to be crimped to bring it back to spec.

John

It did not swell in the middle nor was it to long. Actually it was about .005 to short.

Brass became bent. Imange if you will a banana shaped round, but only off by a few thousands at best. After the neck would enter the chamber the rear of the brass kept it from fully chambering. Major "scratches" on one side of the neck and then on the opposite side of the case 3/16's above the belt.
When you roll the brass across a glass surface you can see how it became distorted.
A learning lesson for sure. I returned the Hornady "New Demension" dies and ordered the Reddings.

Sounds like Hornady designed the seating stem around their own bullets. I guess Redding will modify the stem for you if it is required.