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Thread: Cros 1077 trigger mag mod

  1. #1

    Cros 1077 trigger mag mod

    Cros 1077 trigger mag mod. Sorry that this is such a long post for a simple magazine mod on an unavailable target toy. But I owe it to Bartman and Mudbug and AirGunEric to give these guys the good news.

    “Mod 3) Get a piece of 200-grit sandpaper and sand off the plastic molding lines on the magazine holder's pull-out lever (part #106014 on Chambers diagram)- it is almost always rough and can cause a slightly higher-than-absolutely required trigger pull by always rubbing against the walls of the clip. Taking apart the clip in an attempt to put in a lower-tension spring can be done- but I personally saw no improvement in trigger pull as a result.” – Author unknown, compiled in January, 2007.

    Well, I personally cannot feel the difference of 8 ounces in a 9 pound trigger. However, consistency can be improved and half pound of trigger pull can be removed from the 1077 magazine alone. To answer the Craftsmanship Thread to Eric’s 12 January 2012 post; yep, you can build a better Crosman 1077 magazine. Ifin’ you are lucky enough to have the pre-2007 collector’s item.

    Of course, the following information invalidates all warranties, expressed or otherwise, and is written for entertainment purposes only and should never be tried at home as it may be illegal, lethal or possibly fun. Not to mention, you could put somebody’s eye out. The good news is that I post with public domain rights to reprint. Copy left with no Copyright!

    First, the results: Then you can decide if you think it is worth the effort of reading the “how I done it.” The undisturbed factory magazine takes a 10.2 ounce pull to extend the tongue of the magazine mechanism. Fully tuned the “tongue pull” was reduced by 7.1 ounces to a 3.1 ounce pull. The actual average trigger pull was reduced by .9 of lb or 14 ounces. I have no idea why it would be different from the tongue pull?

    Just replacing the spring made the most difference in the average tongue pull weight. Spring change alone reduced the pull by 6.4 ounces to a pull of 3.8 ounces. However, these average pull weights are the median values noted, give or take an ounce, in 3 or 4 out of ten pulls.

    Just tuning (sanding the rough edges) and using the factory spring the tongue pull weight reduced by 1.8 ounces to an average pull weight of 8.4 ounces. However, the average pull occurred more often, and only outside the average by ½ ounce and only 2 or 3 times out of 10 pulls. By sanding the rough edges there seems to be a reduction in the mechanism “catching” internally and, it produced more consistent pull weights.

    Magazine type - Spring Pull wt. oz. Improvement
    Undisturbed 10.2
    Tuned factory spring 8.4 1.8 oz. & consistency
    Un-tuned lite spring 3.8 6.4 oz.
    Tuned lite spring 3.1 7.1 oz. & consistency

    The below targets are from a tuned mag and an undisturbed factory mag (in the pictures called “untuned”) It is very subjective; I can only say that the tuned mag targets seem like more closely bunched groupings. Seems to be? In any case, it is no worse, and the trigger pull is a little lighter and smoother.
    1077 009.jpg
    1077 003.jpg
    1077 004.jpg
    1077 005.jpg
    OK, here is a farm boy tune up for you all! Alls ya need is yer Swiz Army Nife and yer set… Seriously, I could do this with a Camper model if I wanted to gum up the file and nick the scissor edge. I used the following: a #2 flat blade, wire nippers, 2 or 3 click-type ball point pens, tweezers (from the Swiss army knife?) a solid flat table, 200, 400 & 600 sand papers, spare 22XX/13XX trigger spring and “Lock ease” or other graphite lube.

    OK it took more than sanding the two sides of the slide to get the mag that smooth. I found 5 points and 7 or 8 rub spots that need attention. When I had everything ready… I loosened the two screws holding the two haves together and gently took the two sides of the shell apart. I captured the spring with the tweezers and covered the adjoining parts to avoid an AD. (Accidental discharge of parts about the room.)

    With the 200 grit on the solid table I rubbed the points of the 5 marked edges in the pictures below. Just cutting the sharpness off the edge, I did not sand the plastic pieces unnecessarily. Unlike metal, one will not be able to polish the finish back on to the surface if you disturbed the surface. After getting the points off, I finish the “cut” plastic with the 400 and 600 grit papers.
    1077 mag 047.jpg
    1077 mag 049.jpg
    1077 mag 052.jpg
    1077 mag 010.jpg
    The molding process creates a number of protrusions that can catch or snag passing parts and cause extreme differences in trigger drag. The arrows below point at the 7 white dots (and again, in the bottom photo, the two cut points) on the parts that need to be smoothed out. It was better to use lighter, 400 and 600, grit and sand longer than to use heavy (200 ha ha ha) grit.
    1077 mag 015.jpg
    I cut my new spring from a .015 wire ball point pen spring. The factory spring is .0185 wire and you can just look at the wire and see the difference. I picked a light ball point pen spring to replace the factory spring and cut it a couple coils longer than the factory spring. The lighter spring requires a greater preload to press the linkage arm back down the slide. And, when I found that it was not enough strength to press the arm down?….

    That is why I need 3 pens…. Cut another one a couple of coils even longer than last time (4 coils more length than the factory spring). It still “feels lighter” when compared to squeezing the factory spring. I put the factory closed end of the cut spring against the arm and the cut end down in the “hole.” The tweezers come in handy here too.

    Before installing the mag body spring and the screws; I assembled the insides and held the works in my hand and operated it to be sure it would rotate a clip. I capture the lock pin handle along with the “top” half and gently slide the top half assembly over the works. If operating the magazine tongue pushes the clip once, and, not again, most likely, the spring tension was too weak to push the arm down the slide. Once it is working I took the last step by increasing the tension in the mag body spring. When reassembling the parts, I apply a bit of “dry-lube” to the contact spots

    A spare 22xx/13xx trigger spring or an equivalent is going to be used to replace the mag body spring. I went to an Ace Hardware to find a #90XA spring. It is 1.5 inches long and 5/16 wide and has .038 wire. Finding any spring the length of the factory spring with a wire heavier than the .0275 wire of the factory spring would work; preferably with more, or, tighter windings because that will give a cut edge with a flatter open end. At first, I cut the spring the same length as the factory spring.

    I put the factory closed coil side of the cut mag body spring on the side with all the mechanism on the table for final assembly. Once all screwed together I had a magazine that clings tighter in the mag well. It cannot hurt to have less movement in the magazine that holds the pellets as they flop around on their way to the barrel. Any less vibration has to be an improvement. Unfortunately, I needed a pair of 6 inch channel-lock pliers to get the mag out of the well now!!! ha ha ha. Sorry about that. I guess I needed to cut another quarter or half coil off of the spring until the spring was weak enough to take the mag out using only 2 hands, without the assistance of tools he he he.

    I can imagine that crowning the barrel and, especially, shimming the muzzle end of the barrel will enhance accuracy. Further work on the internal trigger mechanism will also reduce trigger pull weight.
    Furthermore, and, in the future, I hope to improve the spilling gas phenomena as well.

    However, this is all taking a back seat to my exploration for the one 2240 mod “that makes the most difference?” I have read these words describe all kinds of replacement parts from a Poly TP to a steel breach; from an extended bolt to a heavier hammer spring, everything seems to create the one greatest improvement to the humble 2240.

    Soon, I might post some questions about pneumatics in hopes to set out some theorems to be tested… Farm boy style.
    Attached Images Attached Images

  2. #2
    It is about time I got around to adding the missing picture and straightening out the "chart" that fell apart.

    First the Stats:

    Magazine type - Tongue Pull wt. - oz. Improvement
    Undisturbed - 10.2 oz.
    Tuned w/factory spring - 8.4 oz. - 1.8 oz. & consistency
    Un-tuned w/lite spring - 3.8 oz. - 6.4 oz.
    Tuned w/lite spring - 3.1 oz. - 7.1 oz. & consistency

    This is still ugly, but, if it does not collapse upon posting it is better than the previously posted chart.

    The other parts that need "sanding" in order to tune the mag body are in the picutres below that I did not have room for in the original post:
    1077 mag 018.jpg

    As for my finding a half pound reduction in trigger pull and the referenced post finding no improvement... Well, you may or may not find all this effort producing any substantial improvement. I, in no way, am an authority, nor, have I put in the time researching the original compiler did in making a list of improvementmods. Call it beginners luck that I got different results at all.

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