Any theories on tight chambering rounds ?

[Hogshooter]

Loaded up a batch of .243 Win using 105 Amax to a OAL of 2.70. Out of 50, I had about 4 that would not chamber. Actually had to tap the bolt handle with a rubber mallet to remove the live round. On all rounds the OAL and other case dimensions were the same but the difference was the diameter of the neck. The suspect rounds was measuring .277" at the neck where the in spec ones were .268". I know the spec of my chamber is .276". My question is why would 4 rds. be .009" oversize. Same dies were used and they were all loaded during the same session out of the same box of bullets. Al brass was once fired Win. Any thoughts ?

 

[tullius]

Re: Any theories on tight chambering rounds ?

mic the brass & bullets. bet it's the bullets

 

[Hogshooter]

Re: Any theories on tight chambering rounds ?

Thats my thought also but I do not have a puller for 6mm yet.

 

[Muttt]

Re: Any theories on tight chambering rounds ?

Your die could have started to unscrew from the press. I had mine do this once. As I was using the press I noticed the die had come loose and had to screw it back down tight. That's enough for your bullets to either no size down far enough, or not seat deep enough depending on which die.

Just a theory anyway.

 

[johndoe]

Re: Any theories on tight chambering rounds ?

Would love to hear the outcome please keep up posted after
you measure them up.

 

[Hogshooter]

Re: Any theories on tight chambering rounds ?

Pulled the bullet today and took a few measurements. At the base above the boattail the bullet measured .2433. Didn't have another unloaded 105 Amax so I measured a 95 gr. SST and it is .2433 also. I ran the offending case thru the sizing die and it comes out at .2727 at the neck. Then then checked a couple of sized cases that I have not loaded as of yet and they are both .2682 at the neck. I am thinking something is fubar with those bad cases. I am using a Mitutoyo micrometer good to .0001 and my micrometer foo is good.

 

[renegadelizard]

Re: Any theories on tight chambering rounds ?

This is a long shot, but is there any chance that the offending brass is dirty on the inside? What im thinking is maybe that the expander ball is picking up some srt of residue on it and actually streching the case mouth on the way out....ive heard of similar situations causing 30-30 brass to lengthen on the upstroke a good .020..like i said, this is a very long shot...i have similar issues with my 308 and havent figured it out yet...and with mine, it doesnt matter where the brass came from or what the headtamp is..at first i thought it was most likely due to once fired brass filtered in from range pick-ups...but ive been seeing it on once fired brass that came from factory loaded federal match ammo, fired out of my gun....if you figure out whats going on, let me know and ill see if it works for me as well...

 

[Hogshooter]

Re: Any theories on tight chambering rounds ?

Found the solution. The issue was in the shoulder. I went thru the rest of the loaded rounds that I had and found more that would not chamber. I removed the decapper and expander from my sizing die and ran these loaded rounds thru the sizer again. They chambered with no issues after that. I believe the problem is with the old set of Pacific dies that I have. I think that the expander has worn to the poing that it is not expanding the necks of the case enough and when I seat the bullet it is tight and pushing the shoulder back just a hair on those rounds. I am going to pick up another set of dies and see what develops.

 

[renegadelizard]

Re: Any theories on tight chambering rounds ?

how did this turn out?....right after you "figured" your out, i developed a similar problem..i think mine is with the shellholder being to thick though...

 

[Tangodown911]

Re: Any theories on tight chambering rounds ?

As I read this my guess was the shoulders were not bumped back enough. Then I thought it would be a lubing problem. Inconsistent lubing = inconsistent sizing.

 

[samnev]

Re: Any theories on tight chambering rounds ?

When I first started reloading I sometimes had the same problem. A friendly shooter advised me to get a cae length gauge to set up my dies properly. I did and never had the problem with the shoulder set back again.
The point of the dies becoming loose is a good one. I always check to see my dies are tight in my Dillion tool head before I start reloading.

 

[vman]

Re: Any theories on tight chambering rounds ?

I have found the most common reason for tight chambering to be the following... please not this list in not concise

- Shoulder not bumped back enough
- Die not set up properly (related to the above)
- Case length exceeding maximum

 

[steve123]

Re: Any theories on tight chambering rounds ?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hogshooter</div><div class="ubbcode-body">Found the solution. The issue was in the shoulder. I went thru the rest of the loaded rounds that I had and found more that would not chamber. I removed the decapper and expander from my sizing die and ran these loaded rounds thru the sizer again. They chambered with no issues after that. I believe the problem is with the old set of Pacific dies that I have. I think that the expander has worn to the poing that it is not expanding the necks of the case enough and when I seat the bullet it is tight and pushing the shoulder back just a hair on those rounds. I am going to pick up another set of dies and see what develops. </div></div>

Use imperial dry neck lube.