Hammer Spring and POI

I found my main/hammer spring was getting weak.  I measured it at 16#.

When I put in a 20# spring it feels my point of impact lifted by about 2 in at 25 yds.  Is that to be expected?

Greetings,

An interesting Physics question.

I would suspect that the slide moving back is retarded by the heavier hammer spring.

Those few milliseconds may be enough for the pistol to rise before the bullet exits.

Cheers,

Dave

PS How did you measure the spring?

Dave,

I wondered if someone would ask how I measured the springs.

I use the same process for both recoil and main/hammer springs.  I have two brass rods that fit the inside of the springs (5/32 and 5/16) and two shaft collars for each rod.  I have drilled vertical holes through a bench so I can put the rods through the holes and trap the springs between the bench top and a shaft collar.  I then use the second shaft collar on the bottom of the rod to hold a bucket.  I add weights in the bucket until the spring is compressed to the correct length for its rating.

Some details.  The bench has a laminate top.  The holes through the laminate are clearance holes for the rods, the bottom of the spring is supported by the laminate.  I have also drilled large clearance holes under the laminate so there is no friction between the bench top and the rods.  I found a fitting that allowed me to hang the bucket on the lower shaft collar, so the weight pulls directly on the rod center line.  When I think I have the correct weight, I nudge the bucket a little, so it swings a little to let the rod settle against any friction with the laminate.

My bucket and one 5# dumbbell weights 6 lbs.  Adding a 10# dumbbell to the bucket brings it up to 16 lbs.  I used a beam balance scale to measure the bucket and dumbbell combination. I use my NRA trigger weights as additional weight in the bucket to make fine adjustments to the total weight.  At the end I use the beam balance scale to confirm the combined weight.

Fred