Firing Pin Stop mod [Archive] - Glock Talk

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arclight610
01-22-2012, 14:11
Anyone have any first-hand experience with using the originally specified firing pin stop in their 1911? After doing a Google search, it seems like almost everyone is claiming reduced muzzle flip. I'm thinking about getting an EGW firing pin stop to do this mod, but I want to see if anyone else on here has done it first. What about reliability?

DRAGON1970
01-22-2012, 23:49
The best way to get over percieved "muzzle flip" is to practice and shoot. The .45 round is not what most would consider to be a heavy recoil round. Shoot, shoot and shoot some more.

Yes, I have had guns with the original FP stop and beveled stops.....no difference to me.

1911Tuner
01-23-2012, 11:03
A lot of misunderstanding at work...specifically pertainting to that firing pin stop radius and what it actually does...but also on how the locked breech short recoil pistol functions in general.

I've created quite a stir with that small radius...and it all started when I fitted a stop for a guy back in 2005 to stop his extractor clocking problem. He started yellin' about how much it reduced the recoil in his pistol, and it spread like a gas fire.

Let me state for the record that it's not a recoil reduction device...though it does have a small effect on that...and I've never put it out there as any such thing. My reasons for using it were strictly as a reliability enhancement...to slow the slide a little more in recoil. The original spec radius on the stop was .078 inch...or 5/64ths. When the originals dried up, I started making my own stops, and took it a step further by using a 1/16th radius. I owe George Smith a debt of gratitude because when he introduced his oversized stop with a square bottom, I didn't have to spend those hours fabricating the things any more.

The EGW stop...fitted closely to stabilize the extractor, but not tightly press-fitted...with a 1/16th radius has been SOP for me for several years now. I usually install one before I even take a newly acquired pistol to the range to wring it out. I have a pair of range beaters that have seen nearly 200,000 rounds each...and the stops have been there from day one...so there are no concerns with added stresses on anything.

It also might be interesting to note that neither pistol has ever been run with a spring heavier than 16 pounds, and for 3/4ths of their lives, the springs were 14 pounds. I did try the first shock buffs in them last year out of curiosity...and tossed'em after about 500 rounds.

All the ammunition has been hardball or hardball equivalent reloads. 230/830 and 200/890...and aside from having no bluing, the impact abutments are fine.

arclight610
01-24-2012, 13:05
A lot of misunderstanding at work...specifically pertainting to that firing pin stop radius and what it actually does...but also on how the locked breech short recoil pistol functions in general.

I've created quite a stir with that small radius...and it all started when I fitted a stop for a guy back in 2005 to stop his extractor clocking problem. He started yellin' about how much it reduced the recoil in his pistol, and it spread like a gas fire.

Let me state for the record that it's not a recoil reduction device...though it does have a small effect on that...and I've never put it out there as any such thing. My reasons for using it were strictly as a reliability enhancement...to slow the slide a little more in recoil. The original spec radius on the stop was .078 inch...or 5/64ths. When the originals dried up, I started making my own stops, and took it a step further by using a 1/16th radius. I owe George Smith a debt of gratitude because when he introduced his oversized stop with a square bottom, I didn't have to spend those hours fabricating the things any more.

The EGW stop...fitted closely to stabilize the extractor, but not tightly press-fitted...with a 1/16th radius has been SOP for me for several years now. I usually install one before I even take a newly acquired pistol to the range to wring it out. I have a pair of range beaters that have seen nearly 200,000 rounds each...and the stops have been there from day one...so there are no concerns with added stresses on anything.

It also might be interesting to note that neither pistol has ever been run with a spring heavier than 16 pounds, and for 3/4ths of their lives, the springs were 14 pounds. I did try the first shock buffs in them last year out of curiosity...and tossed'em after about 500 rounds.

All the ammunition has been hardball or hardball equivalent reloads. 230/830 and 200/890...and aside from having no bluing, the impact abutments are fine.

So, it sounds like a good investment for such a small part. Thanks for very informative post, as its exactly what I was looking for.

1911Tuner
01-25-2012, 02:59
arclight. There are benefits to the small radius. Recoil was never really a consideration for me because the felt recoil with a 40-ounce .45 caliber pistol never troubled me enough to worry about it. What I noticed was that the pistols were a bit less "bouncy" when I pulled the trigger...but a dramatic change? Nah.

Agent6-3/8
01-25-2012, 08:53
I run square bottom EGW's on both of my 1911's. While perhaps not the intent, I personally believe that it does have a small effect on recoil.

ca survivor
01-29-2012, 12:23
can't see why a firing stop will have any effect on recoil.

Wolfgang
01-29-2012, 12:42
can't see why a firing stop will have any effect on recoil.

I think it's physics.

At one time it was explained in depth on another site. Maybe Tuner will 'splain it, coz I can't.

faawrenchbndr
01-29-2012, 14:41
can't see why a firing stop will have any effect on recoil.


It's all about the radius of the corner of the firing pin stop, this effects
how easily the slide pushes rearward on the hammer.

Picture this,.......
It's harder for a truck to roll through a steep banked ditch, compared to a
90 degree sided ditch. The truck travels slower through the steeper ditch.

If a firing pin stop, with a tighter corner radius is installed, it slows the
slide as it is trying harder to push the hammer rearward.

1911Tuner
01-30-2012, 07:17
I think it's physics.

At one time it was explained in depth on another site. Maybe Tuner will 'splain it, coz I can't.

Let's start at the beginning.

In the short recoil pistol, the slide moves at the same instant the bullet moves, assuming a condition of zero headspace. At nominally 1/10th inch of slide travel rearward, the bullet exits and the slide coninues on conserved momentum, further compressing the spring and finally striking the impact abutment.

Fully 90% of what we recognize as recoil...muzzle flip...comes with that impact. The rest is in compressing the spring. We get almost nothing as a result of the actual action/reaction event of the round firing.

The faster the slide is moving as it compresses the spring, the sharper the felt recoil. Conversely, the slower it moves, the longer the duration...and the "softer" the felt recoil.

The slower the slide is moving at impact, the less the muzzle flips. A simple matter of mass and momentum.

The smaller radius on the bottom of the stop modifies this in two ways. The lower contact point with the hammer reduces the mechanical advantage in overcoming the hammer's inertial mass and the mainspring's load.

This causes the slide to lose momentum just as rearward acceleration begins, which has a greater effect than trying to decelerate it after it's gotten a full head of steam. Think of stabbing the brake briefly on a drag car just as you launch it.

Secondly...and maybe more importantly...the bullet exits earlier relative to the slide's position which not only gives the spring a little more time to decelerate the slide...but it removes the force that accelerated the slide earlier in its recoil cycle.

The effect on recoil is small. Many people can't actually feel a difference, but most report that "something" is different...and nearly all state that the gun shoots flatter...or that the sights come back on target easier...and those who shoot action stages report that their split times are a little faster. Many have to amend their recoil control to keep from dipping the slights too low as they bring the gun back on target.

ca survivor
01-30-2012, 07:39
It's all about the radius of the corner of the firing pin stop, this effects
how easily the slide pushes rearward on the hammer.

Picture this,.......
It's harder for a truck to roll through a steep banked ditch, compared to a
90 degree sided ditch. The truck travels slower through the steeper ditch.

If a firing pin stop, with a tighter corner radius is installed, it slows the
slide as it is trying harder to push the hammer rearward.
Right, I understand this, but the bullet is long gone by then, barrel unlock and the gun already recoiled.

1911Tuner
01-30-2012, 09:45
Right, I understand this, but the bullet is long gone by then, barrel unlock and the gun already recoiled.

Let's go by the numbers.

Bang. Slide is driven rearward, grabs the barrel by the lugs and hauls it backward with it. At 1/10th inch of slide/barrel travel rearward, the bullet exits, and all force is removed from the system. Any further movement is due to momentum...bullet and slide.

Another .010-012 inch more travel, and the barrel reaches the beginning of the linkdown point. At .200 inch, the barrel lugs are completely disengaged from the slide's lugs. At .250 inch, the barrel is full down in the bed and the slide continues on momentum.

You don't feel much actual recoil from the round firing, if any at all. What you feel as recoil is from the spring compressing and pushing backward against the frame...and the biggest jolt comes when the slide impacts the frame. By the time that happens...assuming 230 grains at 830fps mv...the bullet is about 20 yards downrange.

Remember...your perception of recoil with an autopistol comes from the spring and the impact...not from firing the round. Anything that you do to change the slide's velocity and reduce its impact will have an effect on felt recoil. The small radius stop, along with a full-power mainspring accomplishes that without using a heavy recoil spring...which becomes a force vector the instant the slide starts to move. The heavier the spring, the harder it pushes on the slide and the frame.

Finally...Understand that the "recoil" spring's job is to return the slide. Whatever else it does is incidental.

harrygunner
01-30-2012, 18:00
A gunsmith installed an EGW flat firing pin stop in my 10mm 1911 when I had it built. I bought another to install myself in my .45ACP 1911.

John Moses Browning understood classical physics very well. When soldiers complaining about how hard it was to pull back the slide, he realized that reshaping the firing pin stop would lengthen the moment arm for the force the slide places on the hammer.

Shortening the moment arm transfers more enery from the rearward moving slide into the mainspring.

1911Tuner
01-31-2012, 06:59
John Moses Browning understood classical physics very well. When soldiers complaining about how hard it was to pull back the slide, he realized that reshaping the firing pin stop would lengthen the moment arm for the force the slide places on the hammer.

It's doubtful that Browning was involved in the change to the now standard 7/32nds radius, which was implemented in January 1918.

harrygunner
01-31-2012, 12:23
It's doubtful that Browning was involved ...I'm impressed with the person who chose such a simple, yet effective way to solve the problem within the constraints of a production product.

1911Tuner
01-31-2012, 12:52
I'm impressed with the person who chose such a simple, yet effective way to solve the problem within the constraints of a production product.

Instead of an even more simple and more effective way...Cocking the hammer before attempting to cycle the slide. Or...if that wasn't acceptable...teaching the conscripts to cycle the slide via the opposing hands push method.

It was really a non-issue, IMO. It's not like it required two or three times the strength to do it with the smaller radius in place.

harrygunner
01-31-2012, 13:59
I agree, the soldiers could have overcome this issue with different techniques. I rack the slide as you described, the way my instructors taught me, so no problems here.

The soldiers' "problem" reminds me of one of the reasons my company has done well. I demanded we listen to our customers and find innovative ways to meet their needs even if those needs made less sense to our scientific types and programmers.

Maybe that's why I liked the 1918 mod, from a "customer support" perspective. However, I've gone back to the flat firing pin stop on both my 1911's.

ca survivor
01-31-2012, 14:35
well you guys made me want to try one and I order a flat firing pin stop, was not easy to find, will see when it gets here.....thanks

ColCol
02-04-2012, 19:38
I bought the EGW FP stop, filed a small radius and honed it, fitted the sides to my slide and between that and installing new 11# springs and dimpled followers in my XSE commander, it got rid of my ftf issues. I suppose the addition of the new FP stop aided in slowing the slide down enough to let the magazine and ammo keep up. Either way, it enhanced feeding for me.

harrygunner
02-13-2012, 16:56
Few will care, but I found the physics of the square bottom, small radius firing pin stop to be interesting. The subtle part was how the mainspring is finally compressed the same amount no matter how the firing pin stop is cut. This means the total work the slide does against the hammer is the same no matter how the cut is made.

The answer is the square cut alters the shape of the curve of work the slide does as it pushes the hammer back, forcing the slide to transfer more energy into the mainspring at the beginning of the slide's motion.

The lower point of contact of the slide against the hammer causes the hammer to rotate through a larger angle per unit of slide motion. This causes the hammer spur to compress the mainspring more per unit of slide motion.

So if I were to do the integral of differential work the slide performs, it's greater over intervals at the beginning of movement. The total area under the work curve is the same, but in the later intervals, where slide hits the frame, the slide is moving slower.