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Scope on full length rail vs rear mounted

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Scope on full length rail vs rear mounted Empty Scope on full length rail vs rear mounted

Post by hengehold 2/17/2024, 3:36 pm

I have been using an Aimpoint Micro mounted on the rear of the slide for a couple seasons now and last week I installed a full length rail and mounted a Matchdot II. To my surprise the heavier rail and scope generated more felt recoil than the lighter weight, rear mounted option. 

I used my rear mounted scope reduced power loads (with 12.5 lb recoil spring) for testing with the full length rail and Matchdot. I did not expect them to cycle with the increased Weight on the slide but they did. Not only did they cycle but I had to increase the recoil spring weight significantly, from 12.5 up to 16 lbs. 

In contrast however, I borrowed someone’s 1911 BE gun with the full rail and Matchdot II last summer and the recoil seemed very tame compared to what I am experiencing in my own gun. This is why I am surprised that the recoil is feeling exaggerated in my personal gun with the Matchdot II setup. 

Is my experience of more weight on the slide increasing felt recoil typical? 

If so, why do so many shooters use the larger scopes on their guns? 

-Trevor

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Post by SmokinNJokin 2/17/2024, 5:01 pm

brother recoil is a strange thing, subjective and there are a ton of other factors than just reciprocating mass weight and balance. Here’s a few that could be contributing to what you are feeling:
-Your grip strength/pressure/consistency
-spring rates (mainspring and recoil spring working together)
-firing pin stop radius and hammer cocking force
-barrel fit (upper lug contact, lower lug profile and contact)
-slide drag (peened or accu-railed)
-How you are aligning your wrist/arm/shoulder as a recoil system and how heavy and how much upper body strength do you have

Most of the people i have seen kicking butt with a heavy aimpoint 9000sc on the slide are shooting full power ammo, have an iron grip and plenty of upper body mass and strength. The dot is the biggest, strongest, best optical clarity and mates well with cycling full power ammo. 

On top of all this, you prefer a snappy recoil or slow chug? Both could be described as “less recoil” but the feel is subjective. 
Hopefully i didn’t muddy the water too much.

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Post by hengehold 2/17/2024, 9:44 pm

Thanks for the input. I guess what I felt with the borrowed gun that had a Matchdot II was more of a slow-chug type of feel and I was using the Atlanta Arms Elite 185 JHP ammo which is a little on the spicy side compared to my hand loads. I am trying to replicate that with my own gun but getting there doesn’t seem to be related to adding mass to the slide.

I was expecting that I could replace the slow-chug feel by adding weight to the slide and increasing the strength of the recoil spring. After reading your post I suppose that the upper lug engagement and lower lug might be something that is different between the two guns that I can not account for.

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Post by chiz1180 2/17/2024, 10:08 pm

The amount of reciprocating weight changes the recoil feel. From a basic physics perspective f=ma, ignoring spring and friction in the system and assuming the acceleration is equal(it probably isn’t in reality), a change in mass has an impact on force. Obviously very simplified explanation with lots of assumptions.

My primary wadgun has a 9000 on a kodiak mount. The optical clarity and durability are the main reason I run the optic. I also find the larger objective provides less eye strain. I also have a wadgun with a micro and find it a bit more challenging to shoot that a 9000.

This is a somewhat unpopular opinion by most, but recoil and the amount or “feel” is irrelevant. All guns recoil, once I accepted that fact and stopped trying to fight recoil (both from an equipment and process perspective) I found great improvement. With basic conditioning, even the “hottest” bullseye loads are very manageable.
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Post by Wobbley 2/18/2024, 12:26 am

Recoil is determined by impulse or momentum which is just mass times velocity.  How momentum transfers from gun to hand is complex, not the least of which is that the bullet recoil is minuscule to the impact of the slide.  A slide gains all of its velocity by the time the case is extracted and most of it by the time it is unlocked.  If you ignore the powder mass and the mass and force of the recoil spring during unlocking, the slide will have an impulse of around 20-25 lb-ft/sec.  By happenstance a government model barrel and slide weighs about 1 pound.  So that slide at the point of bullet muzzle exit has 20-25 ft/sec.  There is some acceleration after the gun is unlocked and the case is extracting due to the residual gas pressure.  And gas dynamics  were not my forte, so just to “ give boundaries to the problem”, if the slide doubled the velocity before it hit you’d have an impulse to the frame and its parts of 40-50 lb-ft/sec.  That goes right into your hand and that will roll the gun at your wrist.  

To reduce that you can add mass, tweak spring preload, and apply mechanical disadvantages to unlocking.  Adding mass decreases the velocity and that gives that “chugging” feel.  But the cheaper and more effective methods are adding mechanical disadvantage.  That is done by reducing the radius on the firing pin stop or eliminating any relief in the hammer.  And you can delay the barrel lug disconnect so the residual gas dynamics are reduced.   This latter method required a well fitted barrel.  Because of this it is difficult to compare the recoil “feel” from gun to gun unless they were built very similarly.
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