Summary solution without the details:
New magazine springs corrected my problems on two Interarms HSC’s. Springs came from Wolff Company, PA. Wolff Stock #72263, Mauser HSc XP MAG SPRING +5%. Package of (3) cost $17.29 plus $4 first class postage. Hope this info helps someone.
Here are the complete details:
I own two Interarms HSc’s purchased at different times from different sources and with widely different serial numbers.
Both have feeding issues. #1 fails to feed most of the time with just about any FMJ ammo. Gun#2 will frequently have issues on one of the last three rounds in a mag. In both cases the slide fails to close and the bullet is wedged pointing sharply upward in the breach. I was cautious to not assume that both guns had the same problem even though it looked that way. I am also not a believer in the often heard: “ Polish the feed ramp.” That should never be required unless there is obvious corrosion.
I measured the spring tension exerted by the follower on the last round by holding the magazine upside down on a postal scale and pressing downward until the follower retracted approx one rounds’ distance. The pressure was approx 1lb 10oz measured on three different magazines with original springs. I replaced the springs and the new pressure required to depress the follower was now approx. 3lbs 8oz for each magazine.
Both the old and the new springs are 12 turn springs however the old springs are 4.75” long whereas the new Wolff springs are 5.75” long.
Went to the range and fired 50 rnds through each gun without a single jam. I call that success.
A comment on ammo:
When I was first researching the issue with gun#2 that mostly worked properly, I found my feed problems were the worst, by far, when using Federal American Eagle FMJ ammo. I noticed that when viewed in profile the American Eagle FMJ is more fully rounded or bull nose shaped versus for example; Armscor or Magtech, both of which fed somewhat better though both still had problems. After the new springs the American Eagle had no problems BUT I will not use it for this gun in the future because of the apparent greater tendency to FTF.
And finally, the ammo I really wanted to be able to use is a Hard Cast Flat Nose by Underwood BUT it is still a total jam every time even with the new springs.
