Cartridge feeding issue, sticking towards the end of the cycle - photo/slow-motion video attached

[ormandj]

I’ve got an issue where I will have perhaps 3/10 rounds get stuck when almost chambered.

I took a video to try and determine what is going on, and from what I can tell, the cartridge is ”popping up” and bouncing off the top of the receiver, then being caught by the bolt on the outside of the bolt face, leading to it wedging at an angle (rear to the right, front towards the left) in the chamber, so it won’t allow it to feed fully.

Check the whole video, but 1:20 shows it fairly clearly. It’s low-quality because it was recorded at 240fps, apologies for that. The rifle is wobbling quite a bit as it’s just on a tripod on carpet.




What can be done about this? I’ve tried tweaking the magazine somewhat, but I feel like I’m flying blind. I don’t want to just spend a ton of time bending the magazine lips all over to no end.

 

[DRAKENBURG]

Is the extractor able to ride over the case rim? From the photo you shared, it seems like it can't. Might just be the shadow.

If a round manages to go that far into the chamber, I don't think the magazine is to blame.

When it jams again, take a pin and press the rear of the extractor and see if it can chamber the round.

 

[ormandj]

Extractor can, and ejector can be fully depressed. It is also just a hair below bolt face rim so not proud.

The photo has the cartridge base over the side of the bolt face which happens when the cartridge bounces off the receiver. If it doesn’t bounce up and off it chambers fine.

 

[hafejd30]

What if you try tweaking the mag so the round sits with the bullet a bit higher. Instead of straight toward the feed ramp maybe angle it slightly upwards. Try to make it a bit less “violent” when the round let’s go of the mag

 

[ormandj]

What if you try tweaking the mag so the round sits with the bullet a bit higher. Instead of straight toward the feed ramp maybe angle it slightly upwards. Try to make it a bit less “violent” when the round let’s go of the mag

I can try that this evening, thank you for the suggestion!

 

[OREGUN]

What’s the round catching on? By the time it’s that far toward the chamber, it’s hard to imagine what’s holding it from “self-centering”. Some part of the action? The barrel face? If it was mine, I’d probably start with widening the feed lips a little and going for a slightly more nose high attitude. What happens if you run the bolt more gently…or run it like a gorilla…as hard and fast as possible?


ETA: on closer look, maybe just up higher in the mag…not any more nose up. Send pics of the loaded mag, straight on from the side and the rear.

 

[Steel head]

Acts Like a savage when the ejector is a bit to long.

 

[ormandj]

What’s the round catching on? By the time it’s that far toward the chamber, it’s hard to imagine what’s holding it from “self-centering”. Some part of the action? The barrel face? If it was mine, I’d probably start with widening the feed lips a little and going for a slightly more nose high attitude. What happens if you run the bolt more gently…or run it like a gorilla…as hard and fast as possible?


ETA: on closer look, maybe just up higher in the mag…not any more nose up. Send pics of the loaded mag, straight on from the side and the rear.

I ran a borescope down earlier to figure it out and as far as I can tell it’s just pressure against the chamber wall or chamber mouth since it’s caught on the rim of the bolt face so it’s being driven with the nose to the left and the base to the right.

The jam happens more frequently when not run quite as hard. Will get those pictures soon.

 

[ormandj]

Acts Like a savage when the ejector is a bit to long.

I checked protrusion since that was my first assumption. It’s just slightly (and I do mean slightly, maybe a few thousandths at most) below the bolt face rim. I didn’t measure but it isn’t sitting proud of the rim. I had the problem even with the ejector removed.

 

[ormandj]

Here is a closer shot so you can see better how the base is caught against the nose of the bolt, causing the round to bind in the chamber somehow.

 

[bas402]

What caliber is this? Is this on reloaded cases or virgin? When you finally get it to chamber does the bolt have resistance on it while closing?

 

[b6graham]

what does it do when single feeding a round versus mag fed?

 

[ormandj]

Headspace was checked, no problem there. 6.5CM on this one. Brand new cartridges from three different lots of factory ammunition to reduce issues. No resistance on close that's abnormal.

Single feeding if I align the cartridge without the left/right angle is no problem, but if I position the cartridge the same way, it will bind the same way.

I ran 10 virgin cases through the action 10 times through a magazine. Check out the brass (just put a couple in the photo, they all look like this) - I'm wondering if there's something up in the chamber, maybe some shoulders need breaking:

 

[KZP]

Send this thread to Altus as well. Maybe they have seen this before and know a fix.

 

[ormandj]

I’m having two more actions sent. The ejector wasn’t the issue (happened without); I didn’t get around to messing with the extractor.

The brass is hanging up on the chamfer to the mouth of the chamber. I tried to take some pictures of this with a jewelers loupe and my phone, so apologies on quality, but it’s a fairly sharp edge.

Checking a few other barrels with my fingernail and fingers (super scientific) they feel like the edge has been broken, so it’s a difference, but I’m not sure if it’s related or not. Just figured I’d add a data point.