Colt Delta Elite Recoil System

[flightsimmer]

The small radius on the firing pin stop adds a little delay to the slide. Not much, but when things are moving fast, a little change can have a large effect. It does this by lowering the stop's contact point with the hammer, reducing mechanical advantage in accelerating the hammer. The resistance...the outside force...comes from the mainspring's load and the hammer's inertial mass. Those things must be overcome, and there's only so much driving force and momentum available. The more of it that's expended in overcoming the hammer's movement...the less there is left to keep the slide moving.

By delaying the slide that extra bit, it puts the bullet farther along in the barrel relative to the slide's position, and the bullet escapes earlier...relative to the slide's position...which removes the accelerating forces from the slide earlier. Think of it like a drag race driver stabbing the brake just as he launches the car. Once that momentum is lost, it can't be regained...so the slide is moving slower as it compresses the spring...and slower when it hits the impact abutment. Lower velocity means lower momentum...and impact momentum is what flips the muzzle.

Much is made of the short variants requiring heavy springs in order to keep the slide from hitting the frame "too hard"...but that comes from a basic misunderstanding of the physics involved and of the mechanics of the gun itself. Mostly, it's a misunderstanding of the spring's true function. The spring is there to return the slide...not to decelerate it. That it does do that is incidental.

It's moving faster because of its lower mass...but with the recoil spring removed from both pistols...the 5-inch and the 3-inch...it will hit no harder. It can't. Momentums are equal in both directions. It can't have more momentum than the bullet, even though it's moving faster than the more massive slide...and momentum is what whacks the frame and causes it to move.

In reality, the short, low mass slide probably doesn't hit the frame as hard, all else assumed to be equal. The shorter barrel causes a velocity loss, and because momentums are equal and momentum is a function of Mass X Velocity...the short slide has less momentum than the 5-inch gun.

And to expound further...With equal springs...equal outside force...the short slide will still hit with less impact momentum.
The lower the mass, the faster it decelerates when it encounters a given outside force. More...the higher the velocity of a given mass...the harder a given outside force fights it, and the faster the moving mass is decelerated faster.

Timing:

There will be no timing issues. Springs don't affect timing. Timing is mechanically fixed and the timed function will occur at the appointed place, regardless of how fast or slow the machine runs. Springs affect time, which is a function of speed and distance.

Has anyone experianced a shift in the impact point after changing the firing pin retainer and springs? Just curious.

10mm, when you care enough to send the very best.

 

[1911Tuner]

Has anyone experianced a shift in the impact point after changing the firing pin retainer and springs?

A shift in which impact point? Slide to frame impact point is fixed. It can't shift. Hammer to firing pin stop contact point is lowered, which reduces the mechanical advantage...which makes it harder for the slide to cock the hammer...which absorbs some of the slide's speed and momentum.

 

[flightsimmer]

A shift in which impact point? Slide to frame impact point is fixed. It can't shift. Hammer to firing pin stop contact point is lowered, which reduces the mechanical advantage...which makes it harder for the slide to cock the hammer...which absorbs some of the slide's speed and momentum.

OK, assuming the bullet is in the barrel for the same length of time, which it is, is the barrel unlocking at a slightly different time in the recoil cycle, there by effecting the impact point of the bullet on the target? Or has the bullet already left the barrel when it starts to unlock?
If we are slowing down the slide, even by a miniscule amount by changing the FPS (firing pin stop) does it effect the impact point on the target?
What have others experianced after they have made the recommended modifications on a Colt, Delta Elite hand gun.

10mm, when you care enough to send the very best.

 

[TexasRifleman]

Or has the bullet already left the barrel when it starts to unlock?

I think so but it's just a guess. I just did this overhaul on my Delta and it shoots the same anyway. Only have 100 rounds or so through it since then, but I didn't see any difference at all in the way it shoots, just easier to manipulate with the lighter recoil spring.

 

[1911Tuner]

OK, assuming the bullet is in the barrel for the same length of time, which it is, is the barrel unlocking at a slightly different time in the recoil cycle...

The barrel can't unlock at a different time. You've got time confused with timing. They're not the same thing. Timing is mechanically fixed. Time is a function of speed and distance.

The barrel reaches the start of linkdown at nominally 1/10th inch of rearward travel, regardless of where the bullet is and regardless of how fast the system is moving. The only thing that changes is the bullet's location relative to the slide's...and that's straight line. So, there will be no change in point of impact from that function. There may be a change because of the slight difference in the recoil dynamics, but it'll be very slight.

Autopistols aren't subject to the same impact shift under recoil as revolvers are because the actual recoil from the ballstic event isn't solidly connected to the frame. With the auto, the "gun" is the slide and barrel. The frame is essentially just a gun mount and a housing for the controls. The only connection between the gun and mount is through springs. What you recognize as felt recoil...muzzle flip...mostly comes from the slide impacting the frame, and by the time that happens...a 230-grain bullet at 830 fps is about 20 yards downrange.

 

[flightsimmer]

(Quote) The barrel can't unlock at a different time. You've got time confused with timing. They're not the same thing. Timing is mechanically fixed.

No! No! that's not what I'm saying, I know the mechanical timing is the same.
I'm talking about the barrel? slide lifting up during the recoil moment as, before or after the bullet exits the barrel.
Is the bullet in the same place down or out of the barrel when the barrel unlocks from the slide.
I guess the only way to know is after I change mine and see what happens. It is accurate enough to tell if it was changed.
The EGW, FPS should be here today and the springs, tomorrow.
I should have the FPS fitted by then.

(Quote) Autopistols aren't subject to the same impact shift under recoil as revolvers are because the actual recoil from the ballstic event isn't solidly connected to the frame. With the auto, the "gun" is the slide and barrel. The frame is essentially just a gun mount and a housing for the controls. The only connection between the gun and mount is through springs. What you recognize as felt recoil...muzzle flip...mostly comes from the slide impacting the frame, and by the time that happens...a 230-grain bullet at 830 fps is about 20 yards downrange.

OK, that makes sence.

10mm, when you care enough to send the very best.

 

[1911Tuner]

Is the bullet in the same place down or out of the barrel when the barrel unlocks from the slide.

By the time the barrel links down, the bullet is long gone.

 

[flightsimmer]

OK, the new EGW, oversized 9mm/38 Super/40 cal. FPS came in the mail today. I got it carefully fitted and reblued. Installed a standard G.I. recoil spring guide and temporarily used a G.I. .45 recoil spring untill the new springs from Wolff come.

The slide of course is much easier to pull back but it is noticeably harder to start it coming back which is what were after in the first place. I'm anxious to try it out.

One thing I'm still not clear on is whether the use of a recoil buffer pad is needed or not or does it even matter?

10mm, when you care enough to send the very best.

 

[1911Tuner]

Again...Other than for a few rounds to test it...if you're using full-house 10mm ammo, I'd stick with Ned's recipe. I learned a long time ago to listen to the man with experience, and I don't have a lot with the 10.

No shock buffer With Ned's set-up is necessary unless it just makes you feel better. Might not be a bad idea if the GI spring is true USGI spec...which is about 14 pounds.

 

[flightsimmer]

I have searched the internet for articles by Ned Christiansen but I have not found anything on the Colt, Delta Elite 10mm. Where can this article be found?



10mm, when you care enough to send the very best.

 

[1911Tuner]

He didn't write an article. He told me about it when we were discussing the firing pin stop radius.

 

[flightsimmer]

Springs came today and I've got them installed now. It really makes it a lot stiffer to get the slide moving. I tried it without the recoil spring installed and it took 17 lbs. of effort to get the slide to start moving back. I made the mistake of not measuring it before I changed the firing pin stop and springs but I'm not in the mood of changing it back just to find out, sorry, maybe sometime when I get bored and want something to do.

The new 18-1/2 lb. recoil spring really adds a lot of effort to racking the slide back, but there again I forgot to measure it with the stock Colt springs.

Oh! BTW, It went from a 4 lb. trigger pull to a 5 lb. pull with the heavier hammer spring.

Now to get time to go try it out.

10mm, when you care enough to send the very best.

 

[1911Tuner]

Hm. The stock Colt recoil spring is listed at 22 pounds. An 18.5 variable rate spring should make it easier with the hammer cocked.

The added effort to get the slide moving is caused by the combination of the heavier mainspring and the small radius on the firing pin stop. Once the hammer moves as far as the half-cocked position...true half-cock position...its influence ends, except from a little friction.

 

[flightsimmer]

(Quote) Hm. The stock Colt recoil spring is listed at 22 pounds. An 18.5 variable rate spring should make it easier with the hammer cocked.

I didn't buy a variable rate spring, just a standard rate 18-1/2 lb. Delta Elite spring, part# 42118 From Wolff Springs. They state that the factory Colt Delta Elite spring is rated at 23 lbs.

I tried it with the hammer cocked and it required 14 lbs. effort to get the slide moving.

With the hammer down it required 28 lbs. effort.

Maybe I should check it with the original dual recoil spring set and see what effort it takes with and without the hammer cocked.

10mm, when you care enough to send the very best.

 

[flightsimmer]

OK, curiousity got the best of me.

With the stock Delta Elite dual recoil spring and the hammer cocked, it takes 9 lbs. effort to get the slide moving.

With the hammer down it took 25 lbs. to get the slide moving. This was with the 25 lb. hammer spring because I didn't want to go to the trouble to swap it out again.

10mm, when you care enough to send the very best.

 

[1911Tuner]

Yep. Been tryin' to tell the folks that the mainspring's got more influence on the slide's acceleration than the recoil spring while the bang event is goin' on.

 

[Zerstoerer]

Just got the Wolff 10mm spring, listed at 23 lbs and man, is it stiff.
My hands/fingers slipped off the slide several times trying to rack the slide.
Should I keep it locked open for a while? Will that wear the pressure down more so then shooting it?
Also got the Ed Brown full metal, short spring guide and it fits perfectly with the correct diameter.
Have not had time to shoot it yet. Will report.
And yes the plastic soft feeling is gone, metal to metal against the stop.

By the way the Wolff recoil spring is shipped with a free firing pin spring. Don't know why they do that - should I drop that one in also?
Do they even wear out much?

 

[Zerstoerer]

Also got a Wilson Combat 9 round mag. Looks wide at the top but fits o.k.
Need to shoot it.

 

[flightsimmer]

(quote) Just got the Wolff 10mm spring, listed at 23 lbs and man, is it stiff.
My hands/fingers slipped off the slide several times trying to rack the slide.

Is that the 23 lb. recoil spring? I'll bet it is stiff, I got the recommended 18-1/2 spring for hot loads and it is stiff enough at that. I also used the 25 lb. hammer spring.

10mm, when you care enough to send the very best.

 

[TexasRifleman]

Yes, swap the firing pin spring when you swap the recoil spring. They don't wear out as quickly but they perform an important safety function (without Series 80) so you don't want to get to the point where it's worn out.

 

[BBBBill]

Just got the Wolff 10mm spring, listed at 23 lbs and man, is it stiff.
My hands/fingers slipped off the slide several times trying to rack the slide.
Should I keep it locked open for a while? Will that wear the pressure down more so then shooting it?...

And when it "wears down", it will be less than 23# and therefore not strong enough?

Better to get the 18-19# recoil spring, 25# mainspring, and square bottom firing pin stop to set it up properly.

 

[flightsimmer]

OK! I got to shoot my Delta today, not under the conditions that I would prefer, but! I did get to shoot it.

I wanted to check accuracy but couldn't and I wanted to see how the ejected brass behaved but didn't.

The gun behaved quit nicely. I wish that I could get slow motion video of it in action but I cannot. The fired brass looked very good as well as the primers.

I fired both my hottest ammo (135gn Nosler JHP @ 1412 FPS with 13.8 of AA7) and my lighter load of 175gn cast lead @ 1340 FPS. Anything less and I would just use my .45's.

I'm happy but I still want to shoot it under my ideal conditions later though.

10mm, when you care enough to send the very best.

 

[Demitrios]

If you don't mind me posting a question, what problems do you run into when you have a 1911 on a 3" to 4" slide on a compact platform? What weight springs would you need for something like that?

 

[1911Tuner]

what problems do you run into when you have a 1911 on a 3" to 4" slide on a compact platform? What weight springs would you need for something like that?

The problems are most often due to the lack of slide mass and momentum to feed and return to battery. So much spring is needed that it can cause short recoil cycle.

The other problem is that...for many of those pistols...you don't have a wide selection of springs to choose from, and most of the ones that are available only go up in strength.

 

[Demitrios]

In that case who makes some of the heavier/thicker walled 1911 slides? What weight slide would you reccomend and weight weight springs to put in to something like that?