.223 A I Sticking Cases

[pennytoo]

I have a Sako .223 converted to the A I configuration and I have a problem with cases failing to extract. In fact I am unable to open the bolt unless I give it a sharp rap with a wood block or soft mallet.
I tried a detailed cleaning of the chamber and bolt recesses and believe that all is clean. Next I pulled the striker from the bolt , added a coating of J B paste to a fired case and "worked" the case into the chamber about fifty strokes. The case took on a very fine "sanded" appearance over the front 1/3 and rear 1/3 with an un affected portion in the middle. I measured case diameter all along the length and it tapers smoothly ( as well as I can Mike it).Next I cleaned all, reassembled, applied a very light coat of oil to bolt and fired ten rounds. Two were hard to extract but yielded to a sharp palm stroke.
Before I go any further with this I would ask if any other LRH members have any clues or suggestions?

 

[MTBULLET]

at what pressure are your loads running ?
case length?
new re chamber job?
is OAL correct for this rifle?

 

[pennytoo]

I am shooting once fired cases which after fire forming have a length of 1.68" to 1.72".
I am loading Barnes VG 36 Gr. bullets in front of 26 Gr. of A2230.
I can't measure pressure but it should be at or below 50,000, based on 223 Rem data. Primers are not flattened and case heads are not expanded.
OAL is consistent with 223 Rem length, actually a bit shorter.

Thanks for your interest,

bob

 

[pennytoo]

I forgot to state that this is a new rechamber job.

 

[Trickymissfit]

I am shooting once fired cases which after fire forming have a length of 1.68" to 1.72".
I am loading Barnes VG 36 Gr. bullets in front of 26 Gr. of A2230.
I can't measure pressure but it should be at or below 50,000, based on 223 Rem data. Primers are not flattened and case heads are not expanded.
OAL is consistent with 223 Rem length, actually a bit shorter.

Thanks for your interest,

bob

I don't have the data for the newer lot of 2230, but 28 grains in a standard .223 case should be about 48K. Are there any marks on the case OD? If so you may need to polish the chamber walls with 400 grit black paper. When you run the case thru a full length die; how much is it sized down? Should be about .003" to .005"

The case shrinkage on fire forming is normal, but in your case seems a bit excessive, and makes me wonder is the chamber is a little oversized. I would think the case should shrink in the .035" to .040" range. You are getting about .040" to .080" of shrinkage!
gary

 

[pennytoo]

Thanks, I am going to do some more work and measuring, and post info I obtain.

 

[dmontana]

can you post a picture of a fired case that may help us see if there are any problems with the chamber. You may want to get a hold of the guy that chambered it to have him give it a look also.

 

[pennytoo]

Yes, I will send photos. I did visit with my friend who reamed the chamber and we used his bore scope to examine he chamber. He did not see anything out of the ordinary and said that he had done several others with that reamer with no problems.
The only thing I noticed that looked odd is that the left bolt locking lug has a rough or gauged working surface I carefully stoned smoothed the surface cleaned all with no difference noted.
I plan to shoot again and carefully observe all. I will orient all cases the same way to see if there are any visible bulges or scuff marks in any particular location.
Because the problem seemed to be less after running a cartridge case coated with JB paste about 50 strokes into the chamber, possibly it is a bit too rough? Maybe I should look at polishing further?

Thanks for your interest

 

[pennytoo]

Attached are pix of the three fired cases . I rotated them to show all sides.

Thank you, bob