Optic + Rail Weight - How Much is Too Much?

First topic message reminder :

I was watching a thread here about a guy looking for a new rail to mount on his Range Officer, and some of the responses by both advanced shooters and pistol smiths got me wondering if there is a known range of acceptability when it comes to weight on your slide and reliability. For instance, I have a Range Officer with a Matchdot II and a Marvel steel rib. The total weight of all of that hardware is 9 or 10 ounces. I'm using an 11lbs recoil spring and 4.8 grains of HP-38. This combo is both accurate and as reliable as I have found without raising the powder level too high. If I drop the powder down to 4.5 or 4.6 grains, the shells don't eject consistently and will cause a malfunction. If I drop the recoil spring down to 9 pounds with any load, the slide won't go back into full battery every time with SWC bullets - even with a throated barrel, thus causing a malfunction. If I raise the recoil spring weight to 13 pounds, even with 4.8 grains of powder, the shells won't eject properly, but the gun will go back into battery more easily. With the setup I'm at currently, I will get a malfunction about 1 every 100 rounds. Is that an acceptable, common, or standard malfunction rate? Obviously when that malfunction comes up, it costs me an alibi. 

Hypothetically, if I switch to an aluminum rail (I hate working with aluminum, by the way) and an Aimpoint, I'll bet I would shave at least 5 ounces off my slide weight, which would invariably make the gun less finicky, and allow for more margin of error with the slide weight/recoil spring/feed angle combination. 

I just recently helped my dad mount a steel RRA bullseye rib w/adjustable rear sight to his Range Officer to try and get him setup for bullseye competition with me, but with his rail (6 ounces) his setup will be an extra ounce or two even heavier than mine. Now I'm wondering if I steered him in the wrong direction. Any opinions on this?

thanks,

Dave

daflorc wrote:What are the 3 different mag styles? I replaced the stock steel followers with Wilsons which are some sort of plastic awhile back.

Wadcutter, GI (tapered) and hybrid. I think most of the aftermarket mags are wadcutter style, like Wilson and McCormick.  Checkmate makes all 3 styles.

http://www.checkmatemagazines.com/index.php?option=com_content&view=article&id=314&Itemid=367

Google   1911 mag feed lips   and you will find examples of the three styles

daflorc: try 7075 aluminum, much stronger and it's not as gummy as the other grades. I use it quite a bit and if I can elect the grade of aluminum when making something I use 7075. It will also anodize as well as the other grades if you want the black color. Also understand the recoil spring is not the only thing involved in the opening but is the only thing in closing, Hammer shape and main spring aide the recoil spring during the ejection cycle. Hole distance in the link is another factor in the opening but not as easy to work on since there is more involved with changing the hole distance. Also in closing the disconnector also is involved, though minor and for a short time. Many smiths are cutting a grove for the disconnector from the face of the slide that contacts the cartridge tapered downward until it ends just before the disconnector slot. That grove must end so the disconnector is away from the sear at the point the slide allows the hammer to engage the sear.
 If making a base check the rings you intend to use. Also look at the dovetail milled in most micros. Seems as if someone is casting all the aluminum housing as the all are similar. The dove tail is about 20mm wide and is wider than the base. A metal clamp in the opening made for it is drawn against the one side of the base and the dove tail on the same side does nothing. I machine my base to fit the dove tail. The scope can't be lowered onto the base and the clamp screw needs to be removed to allow the scope to slide onto the base with a snug fit. Then the screw inserted when the scope is above the slot made for the screw. I also use stainless steel screws to mount the base because the expansion rate if greater than steel and is approaching that of aluminum but it to is less.

Froneck wrote:daflorc: try 7075 aluminum, much stronger and it's not as gummy as the other grades. I use it quite a bit and if I can elect the grade of aluminum when making something I use 7075. It will also anodize as well as the other grades if you want the black color. Also understand the recoil spring is not the only thing involved in the opening but is the only thing in closing, Hammer shape and main spring aide the recoil spring during the ejection cycle. Hole distance in the link is another factor in the opening but not as easy to work on since there is more involved with changing the hole distance. Also in closing the disconnector also is involved, though minor and for a short time. Many smiths are cutting a grove for the disconnector from the face of the slide that contacts the cartridge tapered downward until it ends just before the disconnector slot. That grove must end so the disconnector is away from the sear at the point the slide allows the hammer to engage the sear.
 If making a base check the rings you intend to use. Also look at the dovetail milled in most micros. Seems as if someone is casting all the aluminum housing as the all are similar. The dove tail is about 20mm wide and is wider than the base. A metal clamp in the opening made for it is drawn against the one side of the base and the dove tail on the same side does nothing. I machine my base to fit the dove tail. The scope can't be lowered onto the base and the clamp screw needs to be removed to allow the scope to slide onto the base with a snug fit. Then the screw inserted when the scope is above the slot made for the screw. I also use stainless steel screws to mount the base because the expansion rate if greater than steel and is approaching that of aluminum but it to is less.

If you want aluminum with the lowest expansion rate use 2024. Stainless vs alloy screws are contradictory to the expansion rate of aluminum. If otherwise, Boeing would be using stainless rivets instead of aluminum rivets. Go figure....

Ever try to drive a steel rivet?  Lotsa luck

But the vast majority of fasteners in Boeing airplanes now are titanium hi-look pins which are more like a nut and bolt.

Expansion of Aluminum is about .000013 per degree per inch depending on the grade. 7075 is 13.1 and 2024 is 12.9 so I think the strength of 7075 vs 2024 is better than  .0000002" advantage in expansion
 Standard SS screws are 18-8 that has a .0000096 rate of expansion so the difference between it and Aluminum is about .0000035
  Steel depending on the alloy as there are many so an average of .000007
 Therefore SS in closer to to Aluminum than Steel.
 I understand that attaching a scope base with screws is probably less than 1/4" in length so there is not much of a difference unless the gun is on the bench at Perry in the hot Sun. Then the difference in yield strength gives the lower expansion of SS and the high yield strength of 7075 (83ksi for T6 treatment) an advantage ver 2024 (69 ksi for T6) both are far better than 6061 (45 ksi for T6) (ksi =1000psi)
 I have been using the 7075 with stainless steel screws for years with excellent results.

Having my own scope bases made is more than I bargained for - I'd rather just use the Marvel rail I already put on my gun and tweak the gun to accommodate the weight of the scope and rail, and tweak my dad's gun to accommodate the RRA bullseye rib and scope on his.

I'm not sure what Marvel uses to make the mounts but many shooters use them and work well. As far as weight the AMU is using the AimPoint 9000SC with a full length scope base (fits on the the total length of the slide from bushing to hammer slot. It is purchased and not made by the AMU and may be a Marvel. The Aimpoint 9000SC is quite heavy and most of the other scopes are quite a bit lighter. As I mentioned before. The recoil spring is the only spring involved in closing the slide and simply attempting to get a gun to function by lowing the weight of the recoil spring can lead to problems. If you start to see Vertical stringing after lowering the spring weight it may be that the spring is too light to completely close the slide. Another will be that the slide never closes enough to allow the gun to fire of possibly never load the round from the magazine at all.

Update:

My dad's range officer with the matchdot II (5oz) steel leupold rings (5oz) and RRA rail with adjustable rear sight (6-7oz) has been functioning flawlessly with SWC light bullseye loads. I didn't even have to throat the barrel. Got lucky!

I've seen pictures from KCs facebook where he takes scope rails and cuts weight off them.

All of you are amazing, I am reading through this and am amazed at the knowledge that is being shared. Truly a great discussion. Thank you all.