Any experts on how magazines function?

[Dave3006]

I have a Mini-14 and several PMI 30 round magazines. These are considered the good magazines. In thousands of rounds, I have never had a malfunction.

I noticed recently, while manually cycling some rounds through the gun with PMI mags I have not tested yet, that some of the rounds would have the tendency to feed "tip down" slightly and get hung up on the feed ramp. It mostly happens as the magazine is starting to become empty.

Is manually cycling rounds through your gun a good indication of magazine performance?

The biggest difference I can see is the effect of recoil to push the rounds back in the magazine and make sure the magazine spring pushes the round all the way up in the mag. My theory is that manually cycling the mag does not give it the extra "bump" the mag needs to have the bullets settle in place before feeding. Since Mini-14 do not have anti-tilt followers, this might be an issue.

Does this make sense? Or, am I completely wrong?

 

[gdm]

im no expert but had my share of mini14s and mag issues

dave, I always give a mag a gentle "rap"on the back before inserting them into rifles.picked up this habit awhile back in the military and it seems to help settle rounds in a magazine.

pmi mags are excellent mags.when hand cycling the action,dont force the bolt forward,pull it all the way back then let go and let the bolt move under its own spring tension.Im going through similiar magazine issues with a german 98 bolt action,with which I have zero experience in these ol but great shooters. mag springs seem to be the biggest culprit in feeding problems. wolf springs makes a replacement that doesnt retain "memory" when keeping the mags full for a extended length of time.cheaper springs will stay partially compressed after removing the rounds, resulting in all kinds of issues.factory ruger hicaps have a small dimple on the mags which also keeps the mags from too much movement in the magwell during the whole cycle of firing and ejecting.good mags are key in the ruger 14 performance.I dont see any reason why one couldnt get a follower from a ruger mag and insert it in another brand if you suspect that might be a issue.

 

[Scorch]

Actually, the recoil effect pushes the rounds FORWARD in the magazine (as the rifle moves backwards under recoil, the cartridges tend to remain stationary, as per Newton's 1st law).

While cycling the action by hand may give indications of big problems, it is not a reliable indicator of magazine feeding performance. Mostly because you cannot cycle the action as fast as the rifle does. When you fire the rifle, the action cycles as the rifle is recoiling and moving, causing multiple vectors on the cartridge (a vector is a force acting upon an object). If the spring in your magazine in ot stron enough, or if the feed lips of the magazine are too soft or rough, you will have problems feeding even though cartridges will feed every time you cycle the action by hand.

Buy the best quality magazines you can find. If your life depended on it, would you want the $9.95 aluminum magazine or the $19.95 steel magazine?

GDM- replace the magazine spring in your M98.

 

[Dave3006]

Thanks Scorch. I am an engineer. So, I am having some physics flashbacks reading your post.

I see what you mean about the cartridges staying stationary during the initial part of recoil. However, as the gun finalizes it's rearward movement and produces the "kick" on your shoulder, wouldn't this force have the effect of moving the cartridges back in the magazine? It seems to me, the kick effect would be a short timeframe / high impulse event moving the rounds back having the ultimate effect of helping the tip of the rounds to settle?

What do you think?

 

[Dre_sa]

id say that cycling by hand is not a great reoresentation of magazine performance. this is ultimately because the bolt isnt moving as fast as if it were fired.
for example, when manually cycling my friends p-38 i get a few misaligned rounds, but when shooting i havent had any malfunctions... yet.

 

[redhawk41]

I agree that cycling rounds by hand is not the same as when the gun is fired. The velocity of the bolt and carrier will be lower which leads to a lower magnitude force acting on the round. This lower magnitude force may not be enough to overcome friction encountered on the feed ramp.

F = (2x)i + (4y^2 - 7)j - (13z)k

Hehe, how's that for flashbacks (BTW I made that equation up.)

 

[Scorch]

Dave-
The rounds shift forward due to the sudden move (moment) going from rest to full speed in microseconds. The rifle actually slows down over a much longer period due to the plasticity of your shoulder and the effects of moving masses inside the weapon (bolt, op rods, etc).
During initial recoil, the entire weapon begins moving backward as soon as the round is fired. Before the bullet reaches the muzzle, the gas system starts to move and the bolt starts to unlock but not open. This causes a delay in the rearward motion of that mass, which delays the counteraction of recoil forces. When the bullet clears the muzzle of the rifle, the burning gases encounter a wall of stationary air and propel the rifle backwards (so-called jet effect). But by that time, the rifle has accelerated, slowed, and re-accelerated. I believe the initial impulse from firing the round is what drives the rounds forward in the magazine. It happens immediately upon firing, whereas felt recoil is spread out over the entire fire/unlock/extract/eject/feed/lock cycle. By the time you feel most of the recoil, the bullet is so far away from the muzzle it is no longer in the picture.
To answer the second part of the question, no this does not settle the rounds in the magazine because the feed lips are designed to hold the rounds but allow feeding, so they are more open towards the front of the magazine. This prevents the rounds from moving back into place on their own. If you want to settle the magazines, slap the back of a loaded magazine against your hand before loading the mag in the rifle. This settles the rounds against the back of the mag and the cartridge heads in the narrowest part of the feed lips.