Why Slide Mount Instead of Frame Mount?

[sparky]

Why do most bullseye shooters have a slide mounted red dot instead of a frame mounted on? I would think the frame mounted one would be more reliable.

[Misny]

For me it was simplicity. I had a BoMar rib and switched it to a Clark scope mount. Easy greasy! Having said that, some folks think that with a slide mount your scope stays aligned with the barrel and so it should shoot more accurately, even with some slide to frame slop. Some also think that the recoil impulse feels better with a slide mounted scope. One advantage of the frame mount is that one can use much lighter loads with a reduced recoil spring weight. It appears that the majority of 1911 shooters in our sport use the slide mounted scope.

[dronning]

+1 on what Misny said.

Slide mount use to be able to mount closer to the bore center line but some of the frame mounts can get pretty low too. Frame to slide fit is much tighter now with the use of CNC machines by gunsmiths so loose slides isn't much of an issue anymore.

KC Kustom Creations has one of the slickest slide mounts for an Aimpoint H1, he notches the slide so the H1 mounts right to it - no rail. KC built 2 1911's for me, a 9MM and a 45, so I could keep my same loads, I went with the Red Buff frame mount. I was shooting a Les Baer with a bridge style frame mount before.

- Dave

[Isabel1130]

Why do most bullseye shooters have a slide mounted red dot instead of a frame mounted on? I would think the frame mounted one would be more reliable.

It is a personal choice. Slide mounts usually put the scope lower, and you see less dot movement. They also don't tend to come loose, which a frame mount will if you take it off for cleaning.

However, if you like to shoot light loads at the short line, a frame mount will give you generally fewer Alabis. It is the same as shooting iron sights for load data.

With a slide mount you have to be really careful not to get your recoil spring too light because it can cause accuracy and lock up issues with the gun.

There are some dandy frame mounts out there, but they are not cheap, another factor to consider.

[Sa-tevo]

With a slide mount you have to be really careful not to get your recoil spring too light because it can cause accuracy and lock up issues with the gun.

As a new user of a slide mount, can you expand your thoughts on this? I am trying to fine tune the balance of my springs and my 50/25 yard loads.

[Isabel1130]

With a slide mount you have to be really careful not to get your recoil spring too light because it can cause accuracy and lock up issues with the gun.

As a new user of a slide mount, can you expand your thoughts on this? I am trying to fine tune the balance of my springs and my 50/25 yard loads.

I would not go any lighter than a 10 pound recoil spring, and 12 would be better. You really need to talk to a gunsmith about these issues, and it depends a lot on your gun.

A custom gunsmith will have a recommended load for his guns because he will know what you need.

I am not him. I do know from my reading and conversations with my very fine gunsmith friends, that the recoil spring is not there to absorb recoil. It pushes the slide closed again on the next round. Too weak a spring, and that won't happen. Worst case, the gun could fire out of battery. Too strong a spring, and your spent rounds won't eject.

Tell me your powder, bullet and gun, and I will try and give you some recommended loads that have worked for me and my friends. Do you know the weight of your recoil spring?

[Sa-tevo]

I'll start by saying that I'll have to sort all this out myself for my configuration, and I appreciate your input.

I recently had a Clark rail installed on my Range Officer for a 25mm Ultradot. My 50 yard load is swaged 200gr swc over 4.0gr BE and my 25 yard load is swaged 185gr hpswc over 3.8gr BE.

After installing the rail and using a new Wolff 10lb recoil spring the 25 yard load would often eject forward and had intermittent lockback after the last round. No faults with the 50 yard load. Installing a 9lb Wolff recoil spring all was fine, 25 yard brass ejected rearward and lockback was fine. My slide mount doesn't have the "Ka---thunk" slow feel my friend's slide mount 45 pistols have, but the slide does feel a little harsh at the rear of travel. No peening noted yet.

The Springfield mainspring and housing was switched out early on to a standard 1911 configuration, unsure of the installed mainspring after a bullseyesmith trigger job, but probably 21 or 19 pounds. Stock barrel, .200 slide stop.

[Isabel1130]

I'll start by saying that I'll have to sort all this out myself for my configuration, and I appreciate your input.

I recently had a Clark rail installed on my Range Officer for a 25mm Ultradot. My 50 yard load is swaged 200gr swc over 4.0gr BE and my 25 yard load is swaged 185gr hpswc over 3.8gr BE.

After installing the rail and using a new Wolff 10lb recoil spring the 25 yard load would often eject forward and had intermittent lockback after the last round. No faults with the 50 yard load. Installing a 9lb Wolff recoil spring all was fine, 25 yard brass ejected rearward and lockback was fine. My slide mount doesn't have the "Ka---thunk" slow feel my friend's slide mount 45 pistols have, but the slide does feel a little harsh at the rear of travel. No peening noted yet.

The Springfield mainspring and housing was switched out early on to a standard 1911 configuration, unsure of the installed mainspring after a bullseyesmith trigger job, but probably 21 or 19 pounds. Stock barrel, .200 slide stop.

Interesting. I don't think there is much difference accuracy wise between your two loads. If you are using the Zero lead hollow points or any other, bump up your powder to 4.0 and try using them for both the long and the short line. They will shoot in my gun. 4.0 of Bullseye over a 185 LHP is my long line load for now.
I am switching to WST after Perry.

4.0 of Bullseye is probably overkill for a 200g LSW. Try 3.8 for that load. For some strange ballistic reason, heavier bullets need less powder.

Before you assume that a load won't work, clean, and oil the gun, and put at least 500 rounds of some thing through it.

Especially with a new gun, there is a break in period.

If I may ask, what part of the country do you live in?

If you are getting a rough snap at the end of slide travel that it an indicator that the slide is slamming into the back of the frame, and either your spring is too light or your loads are too hot.

Oh, and only change one thing at a time. Crimp should be .369 for everything I think?

[C. Perkins]

Shooting a 5" 1911 all I ever used was a 12# recoil spring.
Now that I shoot a 6" long slide I use a 16# recoil spring.
The real purpose of the recoil spring is to force the slide forward into battery while stripping a new round from the magazine.

As far as 200gr vs 185gr loads use more powder for the lighter and less for the heavier.
Has to do with pressure and time curve with the weight of the projectile.

Was using 3.8 of BE under 200gr swaged and 4.0 of BE under 185gr swaged using a 12# recoil spring in a 5" 1911 with a slide mounted UD.

Now I shoot a long slide with 4.8gr of BE with jacketed 185's that always locks back with a 16# recoil spring and once in a while the last spent round is sitting on top of the deleted magazine and have to flick it out into the brass catcher; perfect...

Point is that heavy is less powder vs light is more powder; goes against the grain, but it is what it is.

P.S.
Hello Kate :)

[Sa-tevo]

I think we are getting into the weeds here. The 200/4.0 BE is for 50 yard accuracy, the 185/3.8 BE is for 25 yard recoil recovery. Why shoot a long line load at 25 yards?

If I could find a one-bounce/bunny-fart/bullet-sticks-in-the target-backer 25 yard load that didn't require a spring change between long line and short line I'd go for it. The other Perfect would be loads that didn't need a sight adjustment between stages.

[C. Perkins]

I think we are getting into the weeds here. The 200/4.0 BE is for 50 yard accuracy, the 185/3.8 BE is for 25 yard recoil recovery. Why shoot a long line load at 25 yards?

If I could find a one-bounce/bunny-fart/bullet-sticks-in-the target-backer 25 yard load that didn't require a spring change between long line and short line I'd go for it. The other Perfect would be loads that didn't need a sight adjustment between stages.

Since you know all the answers, then why do you even ask questions or comment ?

I will leave this thread on one note.
With the above load I did not have to change my dot adjustment from long to short line or vice versa.

Sheese, some people just cannot accept help.

Goodbye;

[Rover]

Hey Clarence,

115F here. Enjoy your coolth.

[C. Perkins]

Hey Clarence,

115F here. Enjoy your coolth.

Yah; I saw that Rover and I do not miss it at all :)
I will take the 70's

[Sa-tevo]

Kate and Clarence,

After an evening of playing with a spring tester I found out my 9 pound spring was actually a 7.5 and my new springs read on their values. I reinstalled the 10 pound spring and it locked back 19 out of 20 times with my 25 yard load in testing. Perhaps the friction has decreased a bit in the slide since then? I think the slide may have gotten pinched slightly when it was drilled and tapped for the red dot rail.

This low spring rate value may have contributed to poor lock-up and lower scores this season than when I shot at the CMP Talladega Marksmanship range when I first competed with the red dot installation and the 10 pound spring. They were my highest 45 scores this year.

Pax?