Fine Tuning SVI Mags
While Shooting my new SVI Limited blaster in a match Sunday, I experienced one stoppage due to a "nosedive". I'm using SVI 140mm tubes with Grams followers, springs and basepads. Shueman Ultimatch barrel with a polished feed ramp. #12.5 recoil spring with a stainless steel guide rod and 1 Wilson shok buff. 180gr Zero fmj loaded to 1.200. I had tuned the feed lips on the tubes to .382 ~ .385 front and .390 ~ .395 rear.
If I try to feed a round in the chamber by letting the slide push the round foward very slowly until it touches the feed ramp and then let go of the slide, the round will nosedive and not feed. A light push on the slide and the round jumps right in.
After the match I was discussing this with a fellow SVI shooter and he has his mag lips beveled slightly right at the very point of release about 1/16in. The points on the end were slightly rounded and highly polished.
I took one of my mags and tried this. It now will feed no matter how I try to cycle it by hand. Before I go crazy and screw up all of my mags does anybody think this is the wrong thing to do? It seems to allow the round out of the tube just as the round starts to devlop pressure on the feed ramp.
Any and all thoughts welcome.
I also noticed that if I keep the grooves in the front of the mag tight enough to prevent any side to side movement of the round as it exits the tube, the rounds do not feed as smoothly. They seem to feed smoother if they can move a little.
One more observation. I noticed that the last 2 or 3 rounds have a different angle than the rounds do when there are more in the mag. The nose is higher on the last 2 rounds and they don't even seem to touch the feed ramp as they go in. Is this normal or am I missing something?
In case you have not noticed, I want to be totally anal about this. I am seeking perfection.
Besides polishing the inside with his big tumbler and blueprinting for 20 round capacity (which I do not need, mine hold 20 easily), what can Beven do that I can't?
Quote: from Erik Warren on 4:48 pm on Mar. 21, 2002[br]Get rid of the shock buff, then if that doesn't work, send your mags to Grams.
I'm not experiencing much of a problem (only 1 nosedive in about 1500 rounds), I just wanted to know all of the tricks.
Did you put the "Enos" bend in your Gramms Spring? Have you any idea why the last couple of rounds are angled differently?
Heres what I have done so far. I have opened the front of the feed lips to .400 and put a slight bevel on the front end of the feed lips and polished the crap out of the feed lips. The rounds feed much smoother now. I can not cycle the slide by hand no matter how slow I go and have the round not feed. X What should the distance be between the 2 grooves in the front of the feed lips that keep the bullet straight? Should I have them tight enough to touch the round or open them up a little?
P.S. THANKS for all of the advice so far! You guys are great!
The ribs in front of the feed lips should be wide enough as to not pinch or touch the rounds as they feed up. If they do, this condition only slows the upward motion and causes a nose dive.
If the last couple rounds have a different angle to them while hand feeding, I would not be concerned. As long as they feed correctly, don't worry about it. Hand feeding cannot compare to how the mag feeds when firing the gun.
One fail to feed in 1500 rounds is doing pretty good, and this could be caused by something else. Change your recoil spring often, especialy when running a spring as light as you are. Polishing the feed lips is good, but is the least of the concerns you shoud have with the rest of the mag tube. Polish everywhere the cartridge rubs when feeding up the tube, and keep them clean and lubed.
I didn't bend Bevans springs, though I have done the modification on Wolf springs with variable results.<br>As well as the nosedive problem you describe, I could never get clean last round ejection with SV followers, most of the time the case was munched on the hood, so now I'm using Bevans and so far they have been perfect.<br>I know others use the SV stuff without complaint, I'm just stating my observations.
Great information guys..thanks X Beven, do you look at the same areas when tuning mags for 9 X 23/38 super...is there anything special that needs attention when dealing with taper cases vs straight wall cases.
Look for all the same things, but OAL of your .38 ammo should be no longer then 1.235" for round nose bullets, and 1.225 for flat points or hollow points. Some STI/SV mags can handle ammo longer then these numbers, but most won't, so I recommend this as a fit all dimension. Internal dimensions should be checked, mostly for a "too wide" condition in the double stack area, so the rounds don't try to pass each other and get stuck side by side. Otherwise, straight wall or taper wall, the mags get the same treatment.
Here's one more super-trick mod. Get some 600 grit wet/dry sandpaper. Then you have to find something with the same radius as your feedramp - a 40 case works perfect for me. Wrap a single layer of the sandpaper around the case, or whatever, clamp the barrel in a bench vise, and polish the ramp, moving the sandpaper up and down the ramp in the direction the bullet feeds. Keep polishing forever, until you can see from inspection that the entire ramp has been polished. This can make a big difference, much bigger than you might think. <br>Before you do it, hold the barrel in one hand and a loaded round in the other. Hold the round parallel with the barrel and press the nose on the feedramp and push it up the ramp - feeling the resistance. (It kind of feels like phonograph record.) Then do it after the polish job - you should notice a big difference. (All the spinning type polishers actually polish the ramp in the wrong direction.)
Shot a match Sunday and the feed problems are gone.
Now I have a new problem. 3 out of 5 of my mags don't drop free anymore. They all did before I started monkeying with the feed lips.
Tell me the secrets of a "drop free" mag now please.
Do a little "investigatin." Take out the spring and followers of the offending mags, remove the slide and mag catch assembly, and then figure out where they are dragging.
Maybe some Prussian Blue or Dykem would help. Paint a little on and see where the rubbing is. A felt marker might work in a pinch.
after adjusting the feed lips maybe the slide stop ledge on the follower is going over and being caught by the slidestop?
doooooh! I never thought of that. I followed your suggestion and I found 2 things.
1) after making the lips on the bottom of the mag parallel so the Gramms base pads would work, I had slightly bowed the back of the tube out and it was rubbing.
2)this is the one that took some digging. If I pushed in the mag release all the way, the inside of the mag catch on the button side was touching the tube. If I pushed the button real fast, it would capture the tube and re-catch it before it fell. Upon closer inspection, I found a little ridge on the inside on the mag catch on the button side. Some judicious filling and I think that problem is gone. I think that this was the main problem. I don't understand why it did not happen before but, oh well.....
I had thought of that but they wern't dropping with rounds still in them. Good thinking though and thanks.
I used sight black. Worked great. Thanks! T
This project has been a lot of fun and it would have taken longer without the help of my friends. I consider everyone here a friend and its a good feeling to know that I can get so many different outlooks on problems without someone telling me to "take it to a pro". At the last match, there was a gunsmith there trying to give me a hard time about building my own gun. At the ne X t stage, his shit f#&ked up. All I said was, I guess I have heard the last about this from you (with a wry grin). You can bet that I take a great deal of pride from doing it myself (especially when it works).
I'll keep ya'll updated on my progress.
"Why it didn't happen before"
If you increased the outside dimensions of your mags whilst tuning on them, you limited the slop that allowed the mag catch miss with the button fully depressed.
Shot a small 5 stage match Saturday and the gun ran perfect. I had 2 opportunities to run 20 rounds and drop an empty mag. I really liked that!
Now if it will do it in the Alabama State match this weekend I'll be a happy camper!
Edited by Erik Warren, 28 March 2003 - 11:26 AM.