6mm dasher bolt jams intermittently when feeding

[charlieyankeesierra]

This question relates to my second 6mm Dasher, this one based on a Kelbly Atlas Tactical action that was chambered using a PTG/Grizzly Norma dasher reamer a few weeks ago [I have another 6mm Dasher based on a Rem 700 action]. There are only about 25 rounds down the barrel at this point. It's extremely accurate. The issue I've run into is that the bolt jams intermittently when feeding. It jams once every 5 to 10 rounds when the bolt is 0.8" from going into battery (see pic below I took just after it jammed). It always jams at the same point. No amount of reasonable pressure will allow the bolt to close when it jams. However, if I back the bolt off a few tenths of an inch (it moves freely backwards), the jam is resolved and the bolt closes normally without issue. The Atlas Tactical bolt has a hook extractor. I looked at the chamber using a Lyman bore cam and there was nothing that seemed out of place. [My other 6mm Dasher based on a Remington 700 action also uses bottom metal, and feeds from a magazine and ejects completely consistently; it has an m16 extractor.] Any suggestions?

(P.S. The image was taken after a jam using a cartridge without a primer or powder.)

 

[boltfluter]

Any chance the bolt may be hanging up on the mg feed lips? Just a thought.

Paul

www.boltfluting.com

 

[Gottschall]

Show pics of case. Look for marks on bullet or case. Use marker to color round before you chamber it. Jeff

 

[RussellJ]

Show pics of case. Look for marks on bullet or case. Use marker to color round before you chamber it. Jeff

My guess is that the bolt is catching on the magazine. Place shims between the stock and the bottom metal, I had to do this on a Rem. 700 with a detachable magazine.

 

[Gottschall]

At the point of jam can you drop the mag out? It sounds like Russellj got right. Jeff

 

[charlieyankeesierra]

When the mag is dropped at the point of the jam, it still remains jammed.

 

[carlsbad]

You've probably looked carefully at the front of the bolt. Look at the cocking piece and the bolt handle, especially the "other end" of the bolt handle. Check that your rear action screw isn't too long. --Jerry

 

[charlieyankeesierra]

The bolt only jams when feeding a cartridge, and then only occasionally.

 

[charlieyankeesierra]

It seems like the cartridge might be occasionally riding on top of the extractor and then causing the jam when it enters the chamber canted slightly at an angle. I went ahead and opened up the bevel on extractor face and as I worked through taking off little bits and checking to see if it was enough, I heard the extractor click and the jam then resolved at one point. I also took one turn off the extractor spring. It seems okay now, but only time will tell. I'm not willing to work on the spring any more without a spare on hand. Thanks for everyone's help so far.

 

[Kurz]

Intermittently or inconsistently might be the way the cartridge is leaving the feed lips of the magazine and jamming the loaded round into the feed ramp or chamber, stopping the bolt from advancing. This can occur with the sharper shoulder of an improved case or the mouth of the case getting jammed. Sometimes the feed ramp needs attention or the magazine feed lips in conjunction with the follower/spring.

Hold the rifle in a vise then feed from the magazine and watch carefully. Feed it 100 times if you have to but watch each time for the position of the ones that get jammed.

Regards.

 

[Alex Wheeler]

At the point in your picture the case shoulder is about .4 into the chamber. My guess would be the back edge of the chamber is sharp and is catching the side of the case rather than funneling it in. Are you seeing any scratches on the side of the case it jams on?

 

[SDWhirlwind]

My guess would be the back edge of the chamber is sharp and is catching the side of the case rather than funneling it in. Are you seeing any scratches on the side of the case it jams on?

Had a 223AI that usually 1rd from every mag would have same situation as your pic. Finally pulled the barrel and chamfered the edge a bit more at the back edge, polished a cast follower and replaced the sheetmetal one I first used. Smith that recut to the AI originally I think hit it with a piece of 320gr or so and that was it. Now feeds 97+% of the time, maybe just a bit hangup every 25 or 30rds which I can live with. Not much body taper on it and sharp shoulder (IIRC only .002 or so per side) so case has to align with chamber near perfect or everything has to be really smooth or polished.

Used to be frustrating as all get out when coyote hunting with it and fight getting a round into the chamber in a hurry. So think Alex is spot on!

Edit to add that IIRC it had more of an issue feeding from left than right sides. Is yours consistently one side or random. Reason I say is that if there is an issue moreso with one side or other as long as you have it apart give that side more attention.

 

[charlieyankeesierra]

At the point in your picture the case shoulder is about .4 into the chamber. My guess would be the back edge of the chamber is sharp and is catching the side of the case rather than funneling it in. Are you seeing any scratches on the side of the case it jams on?

This may well be what is taking place. There is some limited scratching on once fired cases. However, the dummy rounds I've been using to repeatedly test feeding show a fair amount of scratching on the case sides. I'll go ahead and pull the barrel and chamfer the edge of the chamber. As an aside, my perfectly functioning dasher was built by you, although I acquired it from a second party. Thanks for this info.

 

[Alex Wheeler]

Go easy on the chamfer, you dont need much.

 

[charlieyankeesierra]

I was able to put 100 rounds through the rifle today after only having adjusted the extractor as noted above. No jams occurred at all, so I'm going to consider it cured for now. Thanks everyone.

 

[NZVarminter]

I had a 20Br that would jam when feeding. It was quite a tight chamber and I found the case pinching near the base as it fed into the chamber. I think the combination of tight chamber and sharp edge on the chamber mouth was causing it.