New to me malfunction?

[riverratt]

I have recently picked up an SR1911 chambered in 10mm. I am shooting decently warm loads with a 180gr at 1250fps, chronograph confirmed. NOTE: This malfunction does not occur with the "10mm light" loads that are offered by most manufacturers.

The malfunction that is occurring is that the slide is locking to the rear leaving the last round in the magazine. This has occurred with both factory supplied magazines.

My theory is that the last round is shifting too far forward under recoil causing the follower to shift and engage the slide stop.

Perhaps I'm wrong, but if this is the case I believe a stiffer magazine spring would solve this issue. Can anyone confirm this, or offer guidance from experiencing a similar issue and how it was resolved?

[rc]

Same things happen with one of my two 10mm Kimbers. I suspect the dimple on the slide stop needs to be deeper. The 1250fps loads recoil a lot more than that 1050fps ones.

[Nathan]

Let me get this straight….1 round it mag, slide locked back, no other rounds in the gun, right?

Sounds like the last round is getting loose and smacking the slide stop when rising to feed. Earlier rounds do not due to faster feed rate. ….or is it caused by the follower. Flat, convex or concave follower? Dimpled? I wonder if the dimple is causing this??

[riverratt]

Let me get this straight….1 round it mag, slide locked back, no other rounds in the gun, right?

Sounds like the last round is getting loose and smacking the slide stop when rising to feed. Earlier rounds do not due to faster feed rate. ….or is it caused by the follower. Flat, convex or concave follower? Dimpled? I wonder if the dimple is causing this??

Correct. It has 2, 8 round magazines. On the 2nd to last shot, he slide will lock to the rear, leaving the last round in the magazine. It will do this maybe 1 out of every 10 magazines.

I did run several mags through doing a drill (3 shots center mass on 3 targets, mag change, 3 shots to the head at 15 yards) there were no malfunctions.

[44 AMP]

Perhaps I'm wrong, but if this is the case I believe a stiffer magazine spring would solve this issue. Can anyone confirm this, or offer guidance from experiencing a similar issue and how it was resolved?

I strongly doubt a stronger magazine spring will do anything other than make you magazines more difficult to load. Might be of some use if your problem was your gun was not locking open when it should, but that's not what you described.

My theory is that the last round is shifting too far forward under recoil causing the follower to shift and engage the slide stop.

With the gun empty, open the action and allow the magazine to lock the slide back. 1911 pattern guns generally use the magazine follower contacting and lifting the slide stop into position to lock the gun open.

Check you gun and see if this is what it does. Note the position of the part of the follower that operates the slide stop, relative to the magazine body and feed lips when it locks the slide open. It should be at, or very nearly at the upper limit of follower travel.

Now, take the mag out, and put a round in it. Just one. Look and see where the part of the follower that works the slide stop is NOW. It should be well below where it was, due to the diameter of the round, and unable to reach the slide stop lug because the round in the magazine prevents the follower from moving high enough to make contact.

GO ahead and test your theory about the round "moving forward" allowing the follower to shift and contact the slide stop, by moving the round forward in the magazine (outside the gun) push it forward, do it in small steps, keep an eye on what the follower does.

My guess would be the follower goes nowhere, as long as the case is held between the magazine feed lips. Even if only the rim of the case is held by the feed lips, the follower won't go anywhere. Once the case is clear of the magazine, THEN the follower can rise up and work the slide stop, but not before.

What you describe, gun locked open last round IN the magazine, means that the magazine follower is not a likely suspect.

The most likely suspect is you. Only happens on next to last round, only when shooting heavy recoiling loads. One possible cause is that you are bumping the slide stop, (or. more accurately, it is bumping you) engaging it early. Possible to happen without you realizing it. This is simple enough to check, have some other people shoot the gun with that ammo and see if it happens when they shoot it.

The other likely suspect is recoil acting on the slide stop itself, overcoming the spring tension from the plunger holding the slide stop in position. Heavy loads, next to last round, meaning the gun is lighter than when fully loaded, might just be enough.

Take a close look at your slide stop where the plunger bears against it. Is it flat ? or is there a dimple for the plunger tip to fit into.

Both kinds of slide stop are found, which style does your pistol have??

Recoil can overcome the flat faced style more easily than the style where the plunger actually has a recess (dimple) to fit into.

Usually not an issue with standard round (9mm, .38Super, .45ACP) recoil levels, but it can be at higher recoil levels, which is what you are shooting.

IF it is recoil engaging the slide stop early, there is a balancing act you have to take into consideration. You need to find the right amount of tension on the slide stop so it stays in place under recoil, but not so much that the magazine follower can't operate it.

If your slide stop doesn't have a dimple, putting a small one in might solve your problem. If it does have a dimple, enlarging it SLIGHTLY (deepening it also) might solve your problem. Increasing the tension of the pluger spring might solve your problem, BUT BE AWARE that if you make too much of a change, the slide stop might get "locked" in place so the magazine no longer locks it open when empty.

Be prepared to purchase a replacement slide stop, if you go to far. Best would be to buy a replacement slide stop, and do the work on it.

OR have a gunsmith work on it, so that if HE goes too far, the cost of the replacment is on him, not you.

Good Luck, and let us know how it works out.

[Aguila Blanca]

I concur that the cause is probably the last round moving forward and tripping the slide stop. The dimple may help. Another possibility, especially if the "warm" loads are round-nose, is to slightly re-profile the inner lug of the slide stop. A tell-tale is if you see copper-colored deposits on the slide stop.

[riverratt]

Thanks for the in deapth explanation AMP!!

The most likely suspect is you. Only happens on next to last round, only when shooting heavy recoiling loads. One possible cause is that you are bumping the slide stop, (or. more accurately, it is bumping you) engaging it early. Possible to happen without you realizing it. This is simple enough to check, have some other people shoot the gun with that ammo and see if it happens when they shoot it.

I haven't ruled that out 100% either. I am quite accustomed to heavy recoiling firearms, but only in revolvers. The recoil of the 10mm is pretty tame and controllable in comparison to my magnum revolvers, but there is always a possibility that I could be bumping it under recoil.

I did have my Son shoot it, it did it to him as well. But in all fairness, he is not accustomed to handguns hardly at all.

The reason I was so focused on the round moment causing this is that was the first thing I noticed. The flat nose of the bullet was actually just past (or flush with) the edge of the magazine with the slide locked to the rear. I just thought that had to have something to do with it.

I concur that the cause is probably the last round moving forward and tripping the slide stop. The dimple may help. Another possibility, especially if the "warm" loads are round-nose, is to slightly re-profile the inner lug of the slide stop. A tell-tale is if you see copper-colored deposits on the slide stop.

The rounds I was shooting were Aguila 180gr FN and Magtech 180gr FN. The Aguila were chronoed with a 5 shot average of 1262fps, and the Magtechs were cronoed with a 5 round average of 1243fps.

The last round in the mag had definitely shifted forward. Is it enough to contact the slide lock? I will have to investigate this a bit further. I did not see any copper or brass on it, but I wasn't looking for it either.

[Aguila Blanca]

Originally Posted by riverratt

The rounds I was shooting were Aguila 180gr FN and Magtech 180gr FN. The Aguila were chronoed with a 5 shot average of 1262fps, and the Magtechs were cronoed with a 5 round average of 1243fps.

Both of those appear to have a profile somewhere between round-nose flat-point and truncated cone, but definitely slightly rounded behind the flat point. I would look more closely at the slide stop for brass/copper deposits.

Or ... the next time it happens, take note of where the round sits in the magazine. Drop the magazine, remove the recoil spring, push the slide all the way back but DON'T lock it with the slide stop ... then insert the magazine and see if the bullet contact the slide stop lug.

[jetinteriorguy]

You could check the spring in the mag to make sure it’s not installed backwards, thus possibly allowing the follower to tip enough with the bullet moved forward. If you have ever disassembled the mags from cleaning they may have possibly been installed backwards.

[riverratt]

I concur that the cause is probably the last round moving forward and tripping the slide stop. The dimple may help. Another possibility, especially if the "warm" loads are round-nose, is to slightly re-profile the inner lug of the slide stop. A tell-tale is if you see copper-colored deposits on the slide stop

This right here could very well be the issue. I had went out after work and fired 2 boxs of ammo. I only had 2 malfunctions, one was ammo related, but the other did follow the same pattern as the issues I've been having. 7 rounds of the mag ran fine, then the slide locked to the rear leaving 1 round in the mag.

The last round is moving forward in the magazine and it appears to be contacting the slide stop, as there is traces of copper on it.

Also on a side note, this lot of Winchester silver tips that I have are not sufficiently crimped to prevent bullet jump. The other malfunction I had the loaded magazine got bound up with 4 rounds remaining. It took a bit of finesse to get it to release. When it did I noticed the bullets were seated at different deapths. After getting home I measured the C.O.L. and the 4 remaining rounds in the mag were all between 1.58" and 1.65". The rounds that were left in the box were all between 1.45" and 1.50"

[bamaranger]

Early slide lock is not an uncommon thing with 1911's. I chased this problem on my two recent import guns, a Tisas .45 and a RIA 10mm. I experimented with different magazines, bullet profiles and grip changes until I finally decided that the culprit was inertial and recoil forces. On both those guns I ended up dimpling the face of the locking lever where the plunger bears.
As 44AMP noted that is a balancing act and it is possible to dimple too much.
If I were to chase those gremlins again in my guns, I would NOT dimple first. See below.

Another culprit in the same problem can be a weak plunger tube spring. A weak plunger spring will not bring sufficient tension through the plunger to bare on the face of the slide lock...resulting in the inertial pre lock. On my guns I mixed and matched slide stops from three different pistols in chasing the problem. I also swapped plunger springs, and modified the tip of the plunger. It was indeed a good bit of trial and error.

If the OP is indeed ONLY experiencing the prelock on the next to last round, I am still suspicious of cause. I would think an inertial prelock would occur more randomly. I would try a different magazine from the two factory ones ( a guy can't have too many mags anyhow....right?) Ruger uses Metalform mags or at least they used to, and a standard suggestion for a quality replacement is Wilson. Perhaps a different mag will present those last rounds differently and eliminate the prelock.

If the condition persists, and I was suspecting an inertial prelock, I would then change the plunger tube spring. An inexpensive part and easily swapped that has a direct bearing on the amount of tension delivered to the slide stop via the plunger (literally). I would change the plunger spring BEFORE I dimpled. If it persists, I would dimple LIGHTLY.

I'll get flamed for this last bit, but if I suspected an inertial prelock, I would
try a shok-buff plastic gizmo to the recoil spring and if reliablity did not suffer, would add one to a 10mm as a matter of routine. If one can soften the blow of the slide to the frame, one might lessen the liklihood of a inertial prelock too. Along the same line of thought, I would add a new recoil spring, especially on a used gun with unknown round count. On my 1911/10mm, I added a square bottom firing pin retaining plate as well, all in the name of making the gun shoot softer.

Tweaks like this have been characteristic of any 1911 I have ever owned and most all needed a bit to run right. In fact, the only 1911 that has not needed some TLC was my grandad's circa 1917 Colt, which has very long since been retired.

[44 AMP]

I would think an inertial prelock would occur more randomly.

It could, but I'd think that would depend on a number of factors inconsistently combining to reach the "tipping point".

Consider this, the gun has to recoil away not just hard enough, but also fast enough that it leaves the slide stop "behind". While the recoil is "up" in the hand, due to where it is held, well below the bore line, it can be "down" in relation to the slide stop lever's rear, the inertia "holding" the lever in place, just long enough. The point of the plunger and spring are to hold the lever in place, so it moves with the gun, until lifted up by the magazine follower.

SO, lets look at what the OP says is happening. First, it only happens shooting the heavier loads, and second it happens on the next to last round.

Each round is generating the same amount of force on the gun, BUT, as each round gets fired, the gun gets lighter. This changes the mass the recoil force is moving, and so would (slightly) change the amount and speed the gun recoils at, and I THINK that when the gun gets down just the right weight, and speed recoiling in the shooters hands it us just barely enough to cause that "inertial pre-lock"

IF that is what is happening, its quite possible that a new, full strength for the load level he's shooting, recoil spring might slow things down enough for his problem to go away.

Assuming, of course, he's not accidently bumping the slide stop (support hand?) as it recoils. I forgot to ask, so now I will, Riverratt are you shooting with the "thumbs forward" grip style??

If you shoot the gun with the problem loads using only one hand, does it still lock open early??

[bamaranger]

AMP,
Now that IS interesting....that the gun gets LIGHTER as rounds are expended.
I hadn't thought of that and it makes sense considering his problem.

Interesting thread.

[Jim Watson]

10mm is a silly millimeter skinnier than .45.
Maybe the step in the follower is just not held down far enough with only one round.
When you run out of other ideas, try bending one down a little.

[Nathan]

Does it have a shock buff or anything limiting full slide stroke? At full stroke, the slide stop should be pushed down.

[riverratt]

Riverratt are you shooting with the "thumbs forward" grip style??

Negative. I shoot with my support hand forward creating back tension with my support thumb over my dominant thumb, but curled downwards.

I have smaller hands and cannot reach the slide release without breaking my grip. Which I do not believe is occurring as I do not need to reposition my grip at any point.

By the way, there is a small dimple for the plunger to set in on the slide release.

[44 AMP]

Thank you. Since there is no hand/finger/thumb near the slide stop to bump it during heavy recoil, we can pretty much rule that out,

A stronger plunger tube spring might solve the issue, but that will also push harder against the safety. That might make it more difficult to operate. Again, balancing act, there's no free lunch, etc. And, of course, a personal judgement call. Personally, I don't mind a fairly stiff safety, one that positively "snaps" into both positions doesn't bother me, but then my thumb still works about as good as it did when I was a young man. Sadly, most of the rest of me no longer does..

Right now, I would suggest you get a "heavy poundage" recoil spring for your heavy loads, and see how that works.

Now that IS interesting....that the gun gets LIGHTER as rounds are expended.
I hadn't thought of that and it makes sense considering his problem.

It is something not often thought about, because most of the time it doesn't matter, and its not something easily felt while shooting, but it might matter when conditions are just right.

10mm round weigh what?? I don't know, but since an ounce is 437.5gr and your 10mm round has a 180gr bullet, then with the case and powder its got to be close to half an ounce, per round. SO, by the time you're down to round #7 the gun is about 3 ounces lighter than it is with a full magazine. That might be enough to matter.

[riverratt]

Right now, I would suggest you get a "heavy poundage" recoil spring for your heavy loads, and see how that works.

Thanks for the imput. I was planning on getting a bit heavier spring anyways because the slide seems a bit slower than it should be. I had 2 rounds not make it up the feed ramp on a full mag when pressing the slide release, it chambered fine when "slingshot". Keep in mind that this was on 2 of the first 3 mags I put through the gun and I haven't had an issue since.

I did watch one of Hickok45's videos where he was reviewing this model. It appears that he was having a similar issue when shooting the Buffalo Bore loads. I could be wrong on the ammo type though.

It is highly possible that Ruger put a lighter spring in it to accommodate the "normal" 10mm loads that are essentially .40 S&W +P.

[riverratt]

10mm round weigh what??

About 270gr each. So 270÷437.5=0.62oz a piece. 0.62×8=4.96. A mag loaded with 8, 180gr 10mm with 9gr of HS-6 is approx 5 oz heavier than an empty mag

[tangolima]

Reliable ejection sets the upper bound of spring stiffness (weight). Reliable chambering sets the lower bound. I lean towards heavier spring for less felt recoil, although stiff spring can possibly speed up peening of the slide stop holes in the frame.

Since the op has observed occasional failure to chamber, it would be a good reason to put in heavier spring. Maybe that would help improve the original issue.

-TL

Sent from my SM-N960U using Tapatalk

[Steve in Allentown,]

Originally Posted by 44 AMP

Right now, I would suggest you get a "heavy poundage" recoil spring for your heavy loads, and see how that works.

What would you think of fitting a
flat bottom firing pin stop and/or dropping in a heavier than standard mainspring?

[ocharry]

i think i would try a stronger mag spring...its cheap and if it dont work you havent really hurt anything

i also like steve's idea of doing a flat bottom firing pin stop...that would change the felt recoil impulse and keep the slide in battery just a tad longer

i think it is right on the edge of being there and just needs a tweek or two...and the firing pin stop is a good tweek anyway...a flat bottom pin stop was the original design

i like doing the cheap changes first..no hard impact...the fact that the round is sliding forward and could be bumping the slide stop tells me there is a soft fix out there...heavier mag spring? pin stop..change the recoil impulse? ( i would do that anyway)...heavier main spring with a flat bottom pin stop...big change in recoil impulse....no hard changes and pretty cheap to do......if you change the pin stop to a flat bottom (with a very small raidus) you will like what it does to the gun.....it does make the slide work a little harder when the hammer is down....thats why the army had it changed to the way it is now...for combat ease of working the slide

just my thoughts

ocharry

[44 AMP]

What would you think of fitting a
flat bottom firing pin stop and/or dropping in a heavier than standard mainspring?

I think "don't fix it unless you know its broken" and when troubleshooting a problem only changing one thing at a time is the best method.

MAYBE either or both of those things will wind up being needed, but I wouldn't jump right there, to begin with.

A possible additional concern is, will the increased stiffness affect the gun when not shooting the heavy loads?

Changing the recoil spring is simple and easy, and could well be something needed to do in order to shoot heavy loads, swapping back to a lighter spring for lighter loads if the gun isn't reliable with lighter loads and the heavy recoil spring.

Changing out the firing pin stop and hammer spring is not mechanically difficult but it is more involved than just swapping recoil springs and its best if we can avoid having to do that.

I say go with the heavier recoil spring for heavy loads, first, and then, if that's not enough, do more.

[Aguila Blanca]

Originally Posted by Steve in Allentown

What would you think of fitting a
flat bottom firing pin stop and/or dropping in a heavier than standard mainspring?

It may help to understand the history of the "small radius" (not "flat bottom") firing pin stop before jumping to install one. The M1911A1, according to Ordnance Department blueprints, us a firing pin stop with a radius of 7/32" and the generally accepted recoil spring weight (for a full-size pistol in .45 ACP) is 16 pounds. The original M1911 (not the M1911A1) specs called for a recoil spring of around 14 to 14-1/2 pounds, with a significantly smaller radius to the firing pin stop (around 1/16").

In addition, John M. Browning didn't refer to the recoil spring as a "recoil" spring, he termed it an "action" spring. While it certainly acts to dampen slide energy in recoil, its primary function is to return the slide to battery. The small radius firing pin stop made it difficult for some soldiers to rack the slide manually, so for the M1911A1 the Ordnance Department increased the radius to make it easier to rack the slide. They also increased the strength of the recoil spring to somewhat compensate.

Much more recently, several manufacturers have taken to using an 18-pound recoil spring in full-size pistols where the expectation is use in dirty, dusty environments, in order to reduce stoppages due to crud interfering with chambering new rounds.

Before doing anything, I would want to know what the existing recoil spring strength is. According to Wolff Gunsprings' web site, the Colt Delta Elite in 10mm takes a 23-pound recoil spring -- significantly stronger than for the ,45 ACP pistols. Before changing anything, I would test the existing recoil spring. If it's not 23 pounds, or pretty close, that's the first thing I would replace.

[riverratt]

I put a 24# recoil spring in it on Friday. In all fairness, it is a borrowed spring out of my friends SR1911 that he has modified to shoot .45 super.

The spring definitely slowed the slide down a bit as my brass was only getting thrown 8-10 ft instead of 15ft. I had zero malfunctions in the 100 rounds that I shot Saturday.

There was still copper marks on the slide lock, filling that down a couple thousandth may be my next move if I still have issues.