Slide travel measurement

Froneck · Sep 13, 2020

Does anyone have a good way to measure slide travel on semi-auto .22 pistol? I Shoot precision pistol competition. Work on my target pistols and quite a few friends pistols. Currently I have a high end .22 Feinwerkbau AW93 that has issues. At Camp Perry Army pistol smith thinks recoil spring is light. (my son is on the AMU pistol team) I would like to find a method to measure slide travel when shot using target ammo. High speed camera would be kinda expensive. BTW when not shooting I run a completely outfitted machine shop.

Paolo_MD · Sep 14, 2020

I'm not familiar with that pistol and do not know what are the moving parts during the firing cycle.

Anyhow, a low-tech way I would approach the problem is to glue a light-but rigid-pointer to the slide, so that the end touches a straight and smooth part of the frame (or a flat plate you can attach where is convenient). Cover that part of the frame (or the plate you attach) with soot (carbon black) and let the tip of the pointer scratch it with minimal friction.
This should give you a fairly accurate measurement of the travel of the slide and, if the pointer is light, it shouldn't interfere with the cycling.

Paolo

Froneck · Sep 14, 2020

Ooops! I meant to post this in gunsmithing so if a monitor can move it as it is a bit off topic here.
Problem is the slide moves at very fast speed. Moves the about 1-1/8" travel back and return in less than a second. There is no place to mount the smoked plate. The lower part under the slide moves about 1/2" along with the slide at the last 1/2" of travel as a recoil buffer.
I have been thinking of making something that would hold a rod near the last part of the travel being the slide is moving at the slowest speed at that point having to compress all involved springs and soon to reverse direction. The rod can be something very light to not absorb any reward energy nor much inertia so that it travels farther than actual.
The issue I have I think is failure to completely close. What is happening is I'm getting low bullet velocity from time to time. About 2 or 3 sometimes more in a match that requires 90 shots. Low velocity results in low impact. I'm using top quality and rather expensive target ammo so it's not ammo related plus using the same ammo in another gun the issue does not happen. I know it occurs because recoil is reduced and sound is lower. Quite often the next round fails to feed. In addition it all happen in a freshly cleaned and oiled gun as well as one that has been shot for a while.

Paolo_MD · Sep 15, 2020

Your diagnosis sounds reasonable and makes me suspecting that the chamber has tight tolerances and might interfere with slightly more lube on the bullet.
Regarding mounting, I was thinking about CA glue that can be removed with some acetone.

Paolo

thermite · Sep 15, 2020

Problem as I see it is you will need to renew the 'traceboard" many dozens of times before you "catch" the intermittent departure from the norm. And even when you do, you won't be any closer to "why" it happened off that measurement, alone.

Ammo only exhibits the fault in THIS one handgun, and intermittently, at that?

Check your lockworks. Trigger is how consistent?

Ultimately, how consistently is your primer being struck?

Inspection of the shape and depth of the impact zone on the rim of the ejected cases alone, one to the next, and both to another handgun can show you if that is an issue.

Froneck · Sep 15, 2020

Problem is when shooting a match the case is thrown to who knows where so it can't be examined.
This gun is typical of many pistols from Europe. Disconnector resets very early so trigger will operate long before breach is closed. Trigger on the AW93 is of the modified purchased Russian pistol that uses a double sear. Trigger is completely adjustable and works great after some modification by me.
There are 4 spring involved in slide movement as well as the hammer spring. Once hammer is locked back it adds nothing to closing the slide. It has the typical slide spring that is in use alone for about 90% of the travel. The slide will impact a piston type recoil buffer with 2 springs inside when depressed it moves the lower portion compressing another spring. However all that happens in about 1/2" or so of the finial travel of the slide. The remainder is handled by the recoil spring that lessens the force as it closes the breach. What I want to do it eliminate as much as possible the force of the recoil buffer springs and add the force to the recoil spring increasing finial closing pressure. Chamber is fine, ammo will fall in with only it's own weight. If round is pushed up out of magazine the round enters the chamber flawlessly. All that was checked by Army AMU gunsmiths at Camp Perry. They claim that the spring pressure when the slid id closed seems light. What I want to do as mention lower buffer spring weight, increase recoil spring yet have the slide travel the required distance. So if I can measure the travel I and change recoil springs to determine which weight will allow needed travel. There also might be another issue, being that all those springs are compressed when slide is fully open it accelerates to the closing point then bounces back and the recoil spring at that point being at the least amount of force will not re-close the bounce open.

Photo is work of in progress, Grips were changed to Colt 1911 type. Item below the barrel and slide is lower half with recoil buffer springs inside. Scope mount was lowered and all aluminum anodized black. However the problems existed before any modifications. All changes were made by exactly coping original, still have originals and if replaced there is no changes.

thermite · Sep 15, 2020

Froneck said:
Problem is when shooting a match the case is thrown to who knows where so it can't be examined.

Well surely!

But thats why you take it away to your own range and run a couple of hundred rounds through it with the assassin's catch bag on the port. Ranges don't always even allow brass recovery. It can lead to careless risks, and the recyling helps cover their costs.

Or just go and get a better pistol if not worth the investigation.

Froneck · Sep 15, 2020

That Pistol is top of the line, sells for $2500 not including the scope. I also have another, its a MatchGun 2. That one sells for $3500.
Feinwerkbau makes Olympic grade pistols. Their Air pistol is considered one of the best!
I know what is happening, I've found a couple of the brass while shooting behind my shop, the case was bulged indicating slide was not closed.
As to brass collection, every range I've shot matches at allow shooters to pick-up the brass. I've shot at all the ranges east of the Mississippi that run NRA Precision Matches. 2 of the matches are centerfire and one of the 2 must be the .45acp. All of us target/match shooters reload and want our brass.
Ranges that don't allow the brass to be picked-up are usually for shooters that can't shoot! Buy a box or 2 of ammo and throw lead down range. Then go home and don't bother shooting for a while. I shoot 90 rounds per week, during the shooting season with matches I average 360 rounds per week some time twice that much.
What I want to do is be able to measure the amount the slide moves as I change recoils spring weight!

thermite · Sep 15, 2020

Froneck said:
That Pistol is top of the line,

Not no more, it ain't.

If you don't want to do the detective work, at least try other springs at a hundred rounds per each, BARE minimum.

J_R_Thiele · Sep 16, 2020

I would suggest confirming that the same thing occurs with other brands of match ammunition, and with other lots of the current ammunition. I assume you are testing of ammunition by lot numbers in the gun and then buying a case or more of what shoots well. If you are buying the same manufacturer and grade of ammunition you my have a bad lot. It happens.

As for your question. From the drawings found here

Exploded drawings | Feinwerkbau GmbH

It looks like you could make a replacement "cover" - part 2500.220.1, which would be modified by being deeper in depth, and having a tapped hole on the upper left or right. The hole accepts a threaded rod of X length. The rod is threaded into the hole until it contacts the back of the slide. Measuring the length of the rod not threaded in gives you the distance from the slide to the back of the cover. Next, melt some lead onto the rod, and shape it into a cone. Thread this in a known distance so it just clears the back of the cover, fire a shot, and see if the slide impacted the point on the cone. Gradually increase the depth you thread it in between shots until it does impact the cone. When it does, measure the length of the rod with the now deformed end, take the measurement of how far the rod was in, and calculate the slide travel.

If the gun is safe to fire with the rear sight removed you may be able to put in a small ball or cylinder of clay where the slide will impact it and show the rearmost travel of the slide.

With any of the above, be careful.

Froneck · Sep 16, 2020

Yes I have tried various lots of ammo.The problem has happened with all of the .22 ammo from SK, Eley and RWS and the cheaper CCI. To test the gun at Perry the AMU used Eley pistol match that they tested. Not sure if your familiar with Army AMU, their shooters are the top in the country. Their Gunsmiths are the best there is! Plus they try everything and test everything they use. Problem happens with all lots and all brands of ammo, it don't happen often but enough to be a problem. A .22 match requires 90 shots. What might also be happening is that the problem might occur at a lesser degree so it is not as noticeable nor effect bullet velosity as much.
I don't know what 2500.220.1 is. It's listed as a cover that might have been used to cover the cleaning hole in the back of the frame. That hole is to allow a cleaning bore brush to be used on the chamber side rather than the muzzle end. It might be in the parts for the sight that was included with the gun. The Dealer had a scope base made to fit the location where the rear sight was, however it didn't work well and version 2 was it's replacement. However it to failed and version 3 was provided. It too was junk! So I copied 3.5.560.107 and used Titanium not Aluminum. To help with movement I have a pin press fitted in the rear to fit into the cleaning brush hole, also a snug fit. The one scope I purchase was a high end red dot by insight, had doctor base. I didn't like it so purchased another that had Weaver type mount so I made an adapter as seen in the photo. Later not liking the height I removed the adapter and cut the Titanium lower with Weaver mount design. Granted I did some modifications but some of them were to solve the issues I had before making changes. In addition I've talked to other that have the AW93 and they have similar issues. One I was typing to cure was failure to lock back after last round was shot. I think I found the problem and soon will be testing to see if I did.
Back to 2500.220.1 That hole is covered by the hammer, if there was enough room to put a pin in to crush lead it would have to be very short but would strike the firing pin not the slide.Probably will not work.

J_R_Thiele · Sep 16, 2020

Never having seen the gun in person and going by a parts drawing presents some challenges in knowing what lines up where.
Anyway to make a "dummy" 3.5560.107 that woulds have a blade that would go down beside the firing pin and hold some lead for the slide to impact? Same idea as before- but different implementation.

Sounds like this is a known issue with the gun. Is this something that some of the guns do sometimes, and other guns never do? FWB makes very nice guns- and very accurate ones. This requires a close fit on some of the parts. I wonder if the problem occurs from tolerance stacking. Each part is within tolerance, but when assembled the combination leads to a fit that is too tight or too loose.

Have you tried different ways of lubricating the gun to see if that makes a difference?

Froneck · Sep 16, 2020

thermite said:
Not no more, it ain't.

Pardini has taken over as the most used Olympic .22 pistol. I'm thinking of buying one. What I like about the AW93 it was a rebuilt version of the Russian Baikal IZH 35M a pistol I have and like though it's a rather crude build. I also copied the IZH, made all the parts, changed things I didn't like on the IZH. My son liked it and when still at home was breaking JR records with it. He also won Jr. Champion at Camp Perry using it in the .22 phase. Feinwerkbau from what I have read purchased the rights to make the Russian IZH in which I feel has the best trigger of any .22 I've seen. I also have a Hammerli 208. That gun works perfectly all the time!!!! But it's trigger is not the best! Testing springs as you suggest is not the best, if slide doesn't travel proper distance it could cause trigger problems in this gun.

J_R_Theil I have the lube the AMU is using and recommends privately. Being the Army they can't support anything. I also tried the Gun Lubricant by Lucas as well as others. I think the issue is with the recoil buffering system, as far as I know it's the only pistol with it. For it to function it will require lighter recoil spring. One problem is that the recoil spring can't be removed easily from the guide rod. That small bushing in front of the spring will not come off. I was told by the gunsmith working for the dealer that sold the gun that when removed it's all most impossible to put back so that it will not come off. I do have the material to make another guide rod and bushing plus every spring kit Brownells sells.

thermite · Sep 16, 2020

Froneck said:
thermite said:

Not no more, it ain't.

Pardini has taken over

Click to expand...

No, Frank, that isn't what I meant.

Legendary good maker, should not be happening, etc does not help.

It IS "happening"

What I meant was that no matter how good the reputation, no matter how good the one you have USED TO BE. the fact that it has come up with an unpredictable fault means that "something" is no longer as good as it HAD BEEN on THIS PARTICULAR ONE.

I'm serious about "capturing" and comparing fired brass.

Put grip-plate bag mount for a capture bag on it and go where you can fire until you have the fault you are looking for "happen" or have a large enough sample to sit and compare

.. striker pattern

.. and any other marks on the brass ....under magnification

... AS IN mayhap find evidence of damage in feeding every now and then.

"etc"

Too many different ammo samples have been tried to blame the food.

The problem is in the eating of it.

And you may find the evidence has been there, all along, laid out on the ground of the range.

That won't fix a problem.

It might show you where to look for the "real" cause of the problem.

Kept 48,000 rounds of 7.62 NATO already in magazines for my unit at Long Binh.

Loaded 18 rounds to each 20-round magazine.

Because of what we had all learned about M-14 magazines.
Not the battle rifle itself.

Sometimes it is not that complicated after all.

Dumb s**t bites mankind in the ass far more often than brilliance.

Froneck · Sep 16, 2020

This pistol is relatively new since it hasn't been used much. Maybe 500 rounds thru it. As I mentioned I did find cases behind my shop where I test fire it and did find some with bulged brass, I know the slide is not closing. It would be hard to tell how open the slide is because when the hammer strikes the slide it will push it forward a bit until the pressure stops it. Bulged area was between 1/8" to 3/16" long.

J_R_Thiele · Sep 16, 2020

The FWB site has 5 different drawings based on serial number, with the last one being the "light" version. Which drawing corresponds with your gun?

thermite · Sep 16, 2020

Froneck said:
This pistol is relatively new since it hasn't been used much. Maybe 500 rounds thru it. As I mentioned I did find cases behind my shop where I test fire it and did find some with bulged brass, I know the slide is not closing. It would be hard to tell how open the slide is because when the hammer strikes the slide it will push it forward a bit until the pressure stops it. Bulged area was between 1/8" to 3/16" long.

Well f**k's sake! Have you been looking to set up to measure something not even involved?

Just get a stiffer spring into it, and try again. Not hard to make. Do 4 to 6 at a go. Use only what comes best after heat-treat.

Store-bought SHOULD be better. Ones you make ARE better, if only because you bin one Helluva lot of rejects getting one "right". The material is cheap enough.

Heat-treat of springs can even get to be fun. Sorta like some folk are into slot-machine gambling or swimming frozen rivers, naked, anyway!

Get "smokestack" jam on partial ejection? THEN it is TOO stiff. Back-off a tad.

That simple, "blowback" actions are when altering bolt mass or fluting chambers (See CETME) is not an option.

Just targets here. Not defense, law enforcement, or military life or death grade springs. Put a little fun in your life and ... what? Maybe a spring in your step!

Proud of my springs. Firearm needs much else, I never owned it in the first place.

J_R_Thiele · Sep 16, 2020

"One problem is that the recoil spring can't be removed easily from the guide rod. That small bushing in front of the spring will not come off. I was told by the gunsmith working for the dealer that sold the gun that when removed it's all most impossible to put back so that it will not come off."

You could try a test temporary (reversable) fix by making a short tube with a slit that could be crimped on to the end of the rod while you have compressed the spring out of the way. The increases spring compression may help the slide fully close.

On the cases you have that are bulged- are there any marks on the case in front of the bulge suggesting the case was misaligned when it tried to enter the chamber?

Froneck · Sep 16, 2020

I have the one that's 4th on the list. As far as I know the light version has an Aluminum housing for the buffer, Standard version is Steel. The Aluminum housing can be purchased so I did and have both.
I did make a spring guide without the bushing, the bushing is not needed but it helps with assembly and stops the spring from launching across the room when the slide is removed. I have experimented with various springs and in addition to all the springs from Brownells I have all those similar in size from McMaster Carr. Problem with adding a shim to further compress the existing spring is that it nearly totally compressed when slide is open.
There are a lot of possibilities as to what is happening. Typically the IZH has a light slide and uses a heavy recoil spring to keep the slide closed. The AW93 is very similar being it's design is taken from the IZH. If the slide doe not go back far enough it limits the time the next round has to move up in the magazine. Another issue could be the slide is starting to open too soon. I thought that if I had something to measure slide movement would held determined the cause of the problem. Maybe investing in a high enough speed camera might be the solution.

J_R_Thiele · Sep 16, 2020

High-Speed Camera Rentals

You can rent a high speed camera for a lot less than I thought.

A high speed camera would not only allow you to see what happened, but also the timing and duration.

Go for it and let us know what you find.

Slide travel measurement

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