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can the breech of the barrel be ground down to make a more positive ramp to eliminate jams? i have a 30 round mag that works most of the time but some times the tip of the bullit hits the rear of the barrel and stops dead. Its a 189 series and thier seems to be no ramp just 2 steps, cant i grind this to a 45 angle or add metal to it so thier no step to drag on. Is there any safety reason for this or does it just not work? why does every one tinker with the mags and nobody has tried this?
 

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mark does your Mini30 work well with the factory 5 round? The problem could be in your after market 30 round mag. I don't own a Mini30, but I've never had to do any polishing on my Mini14's. breech opening. You'll have to ask the Mini30 guy's what are the best Hi Caps available for the Mini30.
 

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Hi. I wouldn't put a feed ramp in a rifle because the greater pressures they generate could/would bulge the brass where it is unsupported (where it was ramped). If it didn't blow the brass any handloads would have to be full length sized every time (I do that anyhow for autoloader) to eliminate dimensional changes. If it feeds with a different clip then it is the clip making the problem for you. JMHO:D
 

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Mark I believe the step you are talking about is the bolt seat. I would not grind on this or your bolt will not seat correctly. As a matter of fact when you change out a barrel, a gun smith has to face the bolt to match the chamber.

However you brought up an interesting point. What ramps the bullet on the Mini? The magazine ramps the bullet into the chamber by a pinching action at the last 1/8" of the feed lips. If you load a couple of rds in a mag. using your thumb to simulate a bolt, applying pressure to the case head, and observe the case "shoulder", it makes contact with the fwd edge of the magazine and kicks up slightly untill it reaches the case "body", where it remains on this plane, untill case head reaches the last 1/8" or so, then as you continue to apply presure to the round it will jump up at you (ramping). This last second ramping is caused by: (1) proper follower pressure on case (proper spring tension, and "free" movement of the follower) (2) Shape of the mags feed lips esp the last 1/8" (3) proper angle of mag to bore pitch i.e. mag latch length to align center axis of round to chamber axis.

So that is why the mag lips shape, freedom of the follower movement, and mag latch length is so important, and why mass quanity produced aftermarket mags need some tweeking here & there. Hope this helps some. ;)
 

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Your problem is almost certainly caused by the aftermarket magazine. I find the 10 round ProMag works very well.
 

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I own both Mini-14 and Mini-Thirty. Both of the 'feed ramp' areas have smooth areas where you can see how the bullets have worn a little of the material on feeding.

Also (especially with the Mini-Thirty), I find that with some of the aftermarket mags, the round is pointed way too low or way too high when it comes off the edge of the magazine. If I look at the feed throat, I can also see gouges where an obvious misfeed occured. The problem is greatly accentuated when you use hollowpoints, as the sharp lip of the hollow tip catches on the metal feed steps instead of 'bouncing' off of them.

This feeding issue is a much greater problem with the Mini-Thirty than it is the Mini-14, since the shape of the 7.62x39mm case is much more tapered throughout its length than a Mini-14 (.223) round is. Thus, a lousy Mini-14 mag will not deflect the shell as much up or down, reducing feed errors.
 
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