Weird recoil impulse with light springs

[MoNsTeR]

My set up:

6" .40 w/bushing barrel

Cominolli 6" SS guide rod w/standard buffs

slide is ~13oz and set up to use normal 5" recoil springs

I've been shooting it for a while now with a 14# spring, mostly because I had one and it's what I used in my 45. I've messed around with a 12# a little bit and I like it; it shoots noticeably flatter and maybe even a little softer.

BUT there's a problem. Once in a while, maybe every 20 or 30 rounds, I'll feel the slide cycle with a completely different recoil impulse. The best way I can describe it is that it feels like the slide is bouncing off the frame at the end of its travel, as if it picked up forward velocity from something other than the push of the recoil spring.

Not only is this worrisome, it's very distracting (it REALLY jumps out at me when it happens). Anyone have any idea what could be causing it? I've already ruled out spring bind, and I'm out of ideas.

[Detlef]

most likely, it has nothing to do with the recoil spring itself but with the magazines, their springs, and the feeding of a new round. When it *nearly* gets stuck (bouncing off the ramp) on its way up in the chamber, that's the feel I observe. It's usually an indication of imminent failure to feed (which you should get every now and then?) and best fixed by tuning the mags/mag springs.

--Detlef

[Flexmoney]

My first thought was it could be the disconnector hanging up a bit...but, I like Detlef's idea better.

[Larry White]

Your mag springs are just about whipped. The next rd is slightly nose down and is hitting too low on the ramp, thats the bump you are feeling. New IMSI springs will make it go away. Larry

[Merlin Orr]

How many rounds through your gun?

I have very close to the same setup with my 6" and have experenced the same thing - I think. I am running a 16# spring. I only have had a chance to shoot about 1k round through my new gun.

[mcoliver]

BUT there's a problem. Once in a while, maybe every 20 or 30 rounds, I'll feel the slide cycle with a completely different recoil impulse. The best way I can describe it is that it feels like the slide is bouncing off the frame at the end of its travel, as if it picked up forward velocity from something other than the push of the recoil spring.

Are you sure you're thumbs are not rubbing the slide a bit during this time? I particularly notice a weird recoil feeling also but only during times when my thumb hits the slide and with a very low weight spring.

If not, well, it could be the mag spring as advised above.

[MoNsTeR]

It's not the mags or the springs. The mags are Dawson-tuned STI's with Grams kits, and have fed perfectly since I bought them. There's about 2500 rounds on the gun between those 5 mags, so I really doubt the springs are even beginning to wear out.

I'm also pretty sure I'm not thumb-dragging, but I'll check next practice session.

[Loves2Shoot]

Do you chamber check all your ammo? That happens sometimes, when I shoot my "no go" ammo.

[Greg G]

The feeling I get is a slight hesitation before the slide goes forward, seems to be due to the feed ramp getting dirty. I make sure I clean the gunk off the feedramp regularly and have not had the problem since, I run an 11lb spring. You could also look at the way the beach face hits the top of the disconnector. My breach face was getting slightly hung up on the top of the disconnector and taking some speed off the slide, a new disconnector has been fitted and the breach face has been smoothed on the bottom where it depresses the disconnector and runs a heap better with light springs..

just my 2c

[EricW]

I'm still thinking it's the mag follower hanging up. I have the Grams kit too and spraying the inside of the mags with silicone spray dramatically improved the feeding. Before the spray, full mags fed less positively than half empty mags. Now, it's muy bueno all the way from bottom to top.

[Detlef]

only when you say *Grams tuned mags with Grams kit* will we accept that it's not the mags & springs. 2500 rds through the gun can do it, that's about the amount of use it takes for spring *set* to kick in...

--Detlef

[MoNsTeR]

I appreciate all the suggestions, but I think I mightn't have been clear enough. I'm hearing ideas that might explain the slide seeming to hang up or close slower, but I'm getting the sensation the slide is closing FASTER.

It only happens when the load "overpowers" the selection of spring. My normal major load (5.0 N320/Berry's 180/1.2") and factory 180's feel fine at 14# and "bounce" at 12#. My steel load (4.9 N320/WC 155/1.2") feels fine at 12# and "bounces" at 9-10#.

[Detlef]

hm...noone overpowers noone else: If the recoil spring is too heavy for your load, your slide doesn't travel all the way back and you won't feed a new cartridge. If the recoil spring is too light, it cannot reliably strip a new cartridge from the mag and feed it into the chamber. Anywhere in between, timing & *feeling* changes, but total slide round trip time (*cycle time*) is nearly constant. Anywhere in between, the slide always closes faster with a stronger spring (though it opens slower).

What you experience may just be the changes in timing and feeling, the mind is easily fooled into thinkiong something is *faster* or *slower* when it's just different. Also, when I have a friend change recoil springs for me (and not tell me which one), I cannot reliably tell whether the 14 or 12 lb is installed (though they *feel* a bit different)

[MoNsTeR]

I agree that would normally be the case, but this feels far from normal. Indeed, the fact that it feels so counterintuitive is the whole reason I'm confused.

I'd bet anyone $100 I could tell the 14# and 12# apart blindfolded, the difference is so extremely dramatic. And that tells me something's wrong.