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Modding the Crosman 1077 
PostPosted: Sat Apr 28, 2007 8:53 pm Reply with quote
StevieLaner7777
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Hi all!!

I've been wanting to mod my Crosman 1077W since the day I got it, But haven't been able to as the warranty on it expires if any modifications are performed on the rifle!! Though I've already sliced off the front sight to attach a silencer to it (Not sure if that counts as a modification).

But I got bored of waiting!!!
Anyways!! Crosmans warranty doesn't cover delivery to the repair place, Which I believe would be in the U.S. neither does it cover the delivery back from the factory to the UK!!! So it will probably end up costing a lot more than just taking it down to my local gunsmiths and having it repaired there for a fraction of the cost of sending it to Crosman and back, Plus if the fix goes haywire I could have re-fixed (I think it's a word!) for free under the gunsmiths policy. Crosman... LOL

Anyways!! What decent mods are out there that have detailed instructions with them???
Ive been looking at making the trigger a bit lighter and smoother, Re-crowning the receiver, Stabilizing the barrel, Higher power mod and maybe even a HPA conversion!!!

Also should I watch out for anything whilst taking the mechanism apart (Loaded Spring etc...).

Any info would be greatly appreciated!!

Stevie Thumb Up!

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PostPosted: Sun Apr 29, 2007 12:12 am Reply with quote
AirGunEric
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Crosman doesn't have a regional service center for their guns? That's unbelievable- and really poor customer service.

As for modifications- I will post virtually all the "do-able" mods that don't involve extreme modification, such as a custom valve/chamber assembly or an external expansion chamber. Many I personally have done- some I have not, but based on the description they are accurate. How much each individual mod will add to the total output is debatable- because as I found out the hard way- once you've gotten high enough- the Co2 doesn't have enough time or space to expand completely before the pellet has reached the end of the barrel, even at 70* Fahrenheit.

Warnings:

1) The manufacturer will invalidate any warranty/warranties the minute any screw is turned- by taking the gun apart- even if nothing is changed- the warranty is gone.

2) Attempting any of these mods may or may not be legal in your area- consult applicable regional/local airgun laws before attempting (as an example, if you find you have a "detuned" version of the gun- you can be pretty sure your area has laws that restrict airguns/airgun output). Airgunhome.com and/or any of its representatives will not be held liable if you do something illegal, harmful, or hurt yourself or the gun while, or as a result of using any of this information.


The parts references.

Crosman's diagrams (which are a bit hard to see):

http://www.airgunhome.com/forumdocs/Cr1077/C1077-EVP2.pdf


Chambers Gunmaker's in the UK- much better diagram with actual part number references:










The mods:

Taking the gun apart is pretty straightforward- remove the 3 Philips screws on the underside of the stock and remove it. Remember on reassembly that the short, thicker screw goes in the front-most hole into the steel barrel band. Place the receiver/barrel assembly down on its left side and remove the straight-head screws (5 in total- but Crosman has been noted to sometimes leave out one or two) and be sure to remember the shortest screw is the one that goes on the top, forward-most hole near the barrel. Pull off right-side or what is the top panel in this working position- and be prepared for a small v-shaped spring to fly out (part #1077055). Note: you could try doing this step inside a clear plastic bag so it will be contained. The trigger spring is also likely to pop out the trigger from its positioning in the receiver, and the hammer roller pin/bushing (part #106024 on the Chambers diagram) to fall off and into the bottom of the casing. If you lose the v-shaped hammer latch spring- it is not a problem- trying to reassembly the gun with it attached to the hammer latch and its index pin (part #1077056 on Chambers diagram) is a nightmare- and these three pieces are not required when reassembling the gun anyways.


Note (a): These mods have been accumulated by searching well over 500 different 1077 mod posts on other forums and basic trial and error. You will not find a more extensive list anywhere.

Note (b): Pay particular attention to the last part of this section "Things to double check upon reassembly" not reading this part may result in Co2 leaks or other issues that can easily be avoided.

Mod 1) This is the single-most important mod to be done to the 1077, improving accuracy. Re-crown the barrel. See the re-crowning barrel sticky on the main "Rifle" page here. See Mod 2, below, for barrel removal procedure.

Mod 2) Remove the screws holding the barrel tube and barrel to the receiver, pull out the barrel and get a 24" wooden dowel or the equivalent to put down the tube/shroud to remove the front site without breaking it. Once the front sight is removed and you have recrowned the barrel itself, put the barrel in the shroud- without the front sight installed. Find some sort of sponge or a thick (i.e. 1/4" thick or more) washer with a 21/64" hole to get around the barrel inside the shroud to stabilize it inside the tube right at the front behind where the site will mount. Once you've got the shroud "stuffed" around the barrel and more-or-less centered, make sure a 1/2 of the barrel is pointing out the shroud, put the front sight over the barrel and install it back in the shroud. The idea of using a thick washer or foam is that the barrel will still move inside the shroud allowing the removal of stuck pellets from the breech area- which can, and does happen- permanently affixing the barrel solidly inside the shroud is a huge error you would regret later when a pellet gets stuck. Stabilizing the rear of the barrel in the shroud is not required- the rear of the barrel is solidly indexed in the receiver, and stabilizing it in the shroud would be redundant.

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.

Mod 4) Replace the trigger spring (part #1077-014 on the Chambers diagram) with one a bit shorter and not as strong- this will help ease trigger pull. Some people have put a (very) small screw through the rear plastic stop for the spring so it doesn't pop out as easily when gun is disassembled- if you plan to do this, be sure to use a drill to create a hole for the screw first- just screwing something through will guarantee it breaking.

Mod 5) Polish breech end of barrel (rear) so it seals to front of pellet magazine as well as possible. If you have the equipment and tools- you could also install a larger 'umbrella' on the rear of the barrel to ensure accurate pellet loading- but this is generally not required.

Mod 6) Disassemble the valve completely, and polish the stem's front bolt, rear pin, and seat areas (part #106002). You will need a inside lock ring pliers to remove the retaining ring to get to this/these parts.

Mod 7) Install a seal around the inside circumference of the valve housing (rear of part #1077A016- the housing behind the lock ring and around the valve stem). It needs to be a thin seal so it doesn't interfere with hammer travel and have a large enough hole for the valve stem end of come through without restriction. This seal may be an appropriate sized plumbing flat washer, or just about anything you can dream up- even glueing all around the lock ring would work- but good luck ever taking the valve stem out again.

Mod 8) The black (standard valve) or grey (detuned valve) spring-loaded assembly (the 'detent body') at the front of the valve (#106A010 on Chambers diagram). Install a stronger spring, and add an O-ring into the obvious slot on the outside rim the plunger (#106B036). Make sure the O-ring you install doesn't bog the plunger- but seals it somewhat. Lubricate with Crosman Pelgunoil or 100% silicone lube through the plunger hole every few hundred shots, or by putting the same on the piercing pin hole in the feed tube (it will eventually find its way through the Co2 plumbing to the valve detent)- whichever is easier for you. The idea with these mods is to seal and put as much pressure behind the detent plunger so that Co2 can come back or leak out instead of getting through the plunger hole and to the rear of the pellet, but still allow clips/magazines to be installed without prematurely wearing out the plunger (i.e. some movement of the plunger needs to be present).

Note: For a "gray" or detuned valve detent assembly- the hole in the plunger is smaller than on a standard valve detent- it can be drilled out to the same diameter as the bottom of the pellet skirt- in fact, the detuned valve plungers have a circular molding line which is exactly the right diameter to be drilled. Also, the metal plate used to keep the plunger spring from getting inside the Co2 orifice inside the assembly should have a larger hole drilled in it for Co2 flow-through to the plunger- a hole the same size as the hole behind it where the Co2 originates is adequate. For anyone with a standard valve- this is hard to visualize- but for someone looking at a detuned plunger it will be obvious.

Mod 9) Install more weight on the rear of the hammer (solder, glue on some lead maybe) - part #1077030- and/or tighten the pull of the hammer spring (part #106035) by either using a tighter spring itself, or cutting about 8mm (5/16") off the existing hammer spring steel and re-bend as appropriate to re-attach it. The idea here is to have the hammer hit the valve stem harder and hopefully a bit longer in order to ensure the maximum amount of Co2 gets through the plumbing to the pellet. Note: tightening the hammer spring increases trigger pull, adding to the hammer's weight won't.

Mod 10) Remove the piercing screen (part #38-028). It is used as a filter and as a diffuser for incoming Co2. The problem is that oil on 12g caplets eventually will gum it up and reduce Co2 flow to the plumbing. It is not necessary to remove it when the gun is new- but eventually it may be required if Co2 pressure drops for some otherwise inexplicable reason. Removing it while doing other maintenance/Mods is your choice. Personally, I have left mine installed. If and when it starts to plug up- I will remove and clean it, then reinstall.


Things to double check upon reassembly:

1) All the correct screws are going into the right holes (see disassembly outline at start for screws that are notable)

2) The hammer latch, latch pin and latch spring will be nothing but a nightmare trying to reinstall. I have yet to hear of anyone doing it correctly. Problems doing it incorrectly include shortening hammer travel- so much so that the trigger releases the hammer but it won't make contact with the valve stem- so no gas is released, and the next most common problem seems to be boogering up the plastics on the receiver- getting the two receiver halves aligned with the index pin is difficult and often results in damage to the plastics, or the pin itself. These three parts can be left out with no apparent ill-effect.

3) Be absolutely sure that the Co2 pathway is intact and sealed- for example, the Co2 transfer tube (part #1077-016) needs to be seated correctly and solidly at both ends in order to prevent Co2 leakage and/or restriction.

4) Do not overtighten any of the screws going into plastic- the plastic is not solid and will rip. After having my 1077 'project gun' apart 6 or so times, I've had to epoxy many of the screw holes in order to let the screws do their job properly. This may happen even if you don't overtighten them- but might as well be careful.

5) Hold the trigger bar over the hammer with a small flat-bladed screwdriver or other flat implement (a thin kitchen knife maybe) when re-installing the receiver side/cover- otherwise the trigger spring will push the trigger of its track- guaranteed.

6) Be absolutely sure the hammer pin bushing (part #106024) is installed for the trigger bar to ride against- better it rolls on the pin than the trigger bar directly in the hammer pin- wearing it out quickly.

7) Re-sight the gun once done- especially so if you recrowned or stabilized the barrel.


Good luck!


Got any more 1077 mods not listed here? Post them!

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Writing too much!!! 
PostPosted: Sun Apr 29, 2007 3:45 am Reply with quote
StevieLaner7777
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Christ AirGunEric you sure do write some novels as your replies!!!

I'll post back when I've read it all and come to a conclusion!!

Stevie Thumb Up!

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Finished reading!!! 
PostPosted: Sun Apr 29, 2007 5:45 am Reply with quote
StevieLaner7777
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Hi AirGunEric!

Ive read up on my local law which does not mention airgun modification as long as the Rifle does not exceed 12fpe.

AirGunEric wrote:
Quote:
The manufacturer will invalidate any warranty/warranties the minute any screw is turned- by taking the gun apart- even if nothing is changed- the warranty is gone.


Does Crosman have spy satellites that can see through buildings!!! I think not!! LOL Toilet

Just to let you know:
The Crosman diagrams don't load up on my PC at the moment (Seems that the program crashes while opening Adobe) Nothing that Ctrl Alt Delete won't fix though. You mentioned they're not as easy to use as the "Chambers Gunmaker" ones that you supplied on your last post, So that cleans that one up quickly!!.

As for taking the main mechanism apart, I will be using the clear plastic bag that you mentioned as well as impact goggles, Just to be safe as my great great uncle took out one of his eye's while dismantling his Springer decades ago!!, Though the chances of that with a CO2 airgun is minimal!!.

Stevie Thumb Up!

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Modding the Crosman 1077 
PostPosted: Sun Apr 29, 2007 6:19 am Reply with quote
StevieLaner7777
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Hi AirGunEric

I Forgot to compliment you on your great list of mods for the Crosman 1077, Must have taken ages to create!! Nice one!!!

Anyways I'm thinking of doing the barrel receiver mod for the Crosman 1077! And I was thinking whether it would be easier to do with a countersink on the myford lathe in my dads garage!! Hes got all the equipment (Three leathers including the Myford, Colchester Bantam and the Colchester Chipmaster, Two Pillar Drills/Milling Machines) I thought that I would use the Myford as it is primarily designed for more finer jobs than the Bantam or the Chipmaster which has a very high RPM for big lumps of brass, As well as having micrometers and other fine gauges and even a calculator and several conversion charts, Basically all the equipment that I will need and more as you probably know from other posts that his hobby is model engineering!!.

Just a question on Mod #5:
What the heck is an umbrella on an airgun??? Could you abbreviate on this a little more please!!

Right!! I will be getting on with disassembling the rifle then!! I will post if anything does go wrong!!! And/or when I Finnish!!

Will try and squeeze some pics in as well as I go along!!!

Stevie Thumb Up!

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PostPosted: Sun Apr 29, 2007 9:41 am Reply with quote
AirGunEric
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Hello Stevie:

Mod #5- the "umbrella" I've mentioned might be more accurately described as a tall 'top hat'- the idea being that what would be called the brim on the hat (the horizontal, flat surrounding part) would be at the rear of the barrel and its cylindrical part would be curved/cut to start out slightly larger than .177" down to .177" and be part of the barrel opening. I don't have a picture of this, unfortunately, but the idea is that it would, theoretically, aid in pellet movement from the magazine into the barrel and help ensure a maximum amount of Co2 is directed behind the pellet- not escape between the back of the pellet and the magazine. That being said, even if it stopped 75% of all pellet jams that occur- how many pellet jams occur usually? Very few typically. And how much Co2 escapes from between the magazine and barrel end- not very much as I can tell- so this mod is probably a huge time expense for little real gain, and just polishing up the barrel end a bit is alot easier and might gain a bit in respect to Co2 retention.


I would have pictures, but my digital cameras are all older and cannot take pictures close up- anything smaller than about 3" x 3" I can't get a tight enough picture without it being blurred- and all the mods are in/on parts smaller than that. Maybe someday I'll get around to buying a better digital camera for close-up work.


Also- I should have mentioned this is in the post above- lube all the areas/parts in the receiver that have wear points (i.e. the trigger guide channel, the hammer pivot, and the valve detent plunger (inside) with some Pelgunoil or 100% silicone spray lube in order to ensure everything moves as smoothly as possible. Don't use petroleum-based lubes- they tend to initiate the premature breakdown and disintegration of the plastics, of which far too much of the 1077 is constructed.

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Finnish modding the 1077W 
PostPosted: Sun Apr 29, 2007 2:30 pm Reply with quote
StevieLaner7777
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Hey AirGunEric

Your the best!!! Thumb Up!

Just look at my target that I shot shortly after finishing the mods that I performed on the rifle.


Notice the 7 shot grouping to the left of the bulls eye!!!
All the other shots were for zeroing it in!!


A few days before modding the rifle!! Scattered out a bit don't you think!!!


The mods that I performed on the rifle to achieve the outstanding Accuracy, Power and Consistency are:

(Mod 1)The barrel Re-crowning mod, I used a Countersink and turned it by hand!!

(Mod 2) The barrel stabilization mod, I used plumbing type insulation to stabilize the barrel.

(Mod 4) The trigger weight mod, I used a slimmer gauge steel spring to achieve a nice light trigger.

(Mod 9) I added more weight to the hammer by gluing two small piece of lead to the hammer.



This pic is of the rifles main mechanism before I modded it, Notice the amount of lead particles on the valve behind the "umbrella", these particles are from the pellets getting hung up on the bad receiver crown on the rifle.

the valve assemble is black so this is the full power version as there is nothing on the rifle that is grey!!



This is a pic of all the different sections of my rifle whist I had it apart.



The low un-centered barrel at the receiver end is due to the slanted angle of the barrel.



All back together again! And no missing parts!! (Even the "V" shaped spring is in it original position!!!)

Oh and thanks again AirGunEric!! I couldn't have done the mods without you!!

Stevie Thumb Up!

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PostPosted: Sun Apr 29, 2007 4:19 pm Reply with quote
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Congratulations Stevie- I'm glad everything worked out so well.

Also, I'm pleasantly surprised you managed to get the hammer latch, index pin and springs back in without major issue- I must've fiddled with it for half-an-hour the first time I reassembled the gun, never did get it perfect- finally gave up and tossed the parts in a bag. I've never tried to re-install them again on subsequent reassemblies- and don't plan to in the future.

Good work. Cool Smoker

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PostPosted: Mon Apr 30, 2007 11:58 pm Reply with quote
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Thought I'd throw an addition in here:

Get a bulk-feed system, either the Crosman AirSource or a paintball-tank setup. I finished off an AirSource tank today that I was using for testing and fiddling with. In total I put approximately 225 full-power shots through it, and wasted about another 20 on dry-fires. There was an additional 25 or so shots in it, but at constantly diminishing output- a string of 12 shots were about 25% less than the maximum, the last 12 or so were well under 300fps and you could see the pellets flying and falling.

A 12g caplet will typically put out 25-30 full power shots before it becomes dang-near useless. But today when the airsource ran out- I went back to using 12g caplets (2) and quickly grew tired of having to take them in/out.

Definetly a bulk-feed system is required. If your 1077 is anywhere near it's "maximum" factory output of 625fps (more likely 550-ish fps with 7.9gr pellets)- the gun can be a barrel of quick-shooting fun. Of course the AS cans aren't cheap...

I've decided my next project for this gun is to fashion a paintball-tank conversion setup. I figure if I can do it for less than $60 US and it's relatively light- it would be a much better unit that the MaxZBulk system available at the moment (Cooper-T seems to be in some state of semi-retirement).

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Bulk Adapters 
PostPosted: Tue May 01, 2007 2:27 am Reply with quote
StevieLaner7777
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Hi AirGunEric

I can't say I haven't been thinking about it!!

Though when I do get one, It'll have to be the Crosman AirSource Adapter! I'll get a bi-pod to go with it as the adaptor isn't what I would call pleasing to the eye and it would make it look a lot better with the bi-pod and I usually lie down or use a bench to shoot anyway!! Plus the shut off valve will come in very handy as well!!!

Stevie Thumb Up!

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PostPosted: Tue May 01, 2007 3:15 am Reply with quote
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The reason I am leaning away from the Crosman AirSource unit is it's weight and the gun's handling. It is heavy- like 2lbs heavy- really pulls the front of the gun down. Also- it totally covers the forearm area of the gun- so the only way to hold it is by the AirSource bottle itself- which I found uncomfortable.

So- my thinking is that a hose hanging off the front of the caplet tube can't weigh near as much as the AS unit, and it won't block the forearm. I may be wrong about the weight (don't know what a 4-5 foot (coiled?) paintball-style hose weighs)- but I am accurate on the forearm.

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PostPosted: Fri May 25, 2007 10:19 am Reply with quote
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I pulled the 1077 out again last night and decided to see what could be improved with some valve modifications.

I took the valve assembly apart and hogged out all the transfer ports- the main feed port in the valvebody from the Co2 feed tube (expanded from 1/16" to 3/32") and the ports on the valve head itself (3 of them) from 1/16" each to 5/64" each.

What did this gain? Not as much as I had hoped- the average velocity change from before these valve mods went up a whopping 2.5%. Now, the slowest shots came up closer to 5%, but the fastest shots only went up 1-2% overall. Other than this negligible gain- expanding these ports did seem to result in a tighter output range, with only a 13% spread from high to low velocities, versus a 16% spread before hand (again, only a minimal improvement of 3%).

So- was this worth the effort? So far, No. But I think I will try replacing the feed tube from the piercing pin to the valvebody with one having a larger internal diameter (brass or stainless steel tubing) in the future. I'm not too optimistic that this will result in anything significant- but I might as well try it to find out.

Perhaps changing the valve pressure spring to something slightly lighter would create more "dwell" time when the valve is hammered (or 'popped') open- but just expanding the port diameters alone did almost nothing for the poor 1077.

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PostPosted: Fri Jun 22, 2007 9:57 am Reply with quote
StevieLaner7777
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Hi All

I was wondering if anyone else with a barrel shroud has tried this:

Has anyone tried to stabilize their barrel with 'Expanding foam", And greased/oiled the inner shroud and barrel to stop the expanding foam from sticking??

I was thinking of doing this one my Crosman 1077W to try and stabilize the whole barrel and optimise accuracy.

Any opinions??


Stevie Thumb Up!

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PostPosted: Fri Jun 22, 2007 10:13 am Reply with quote
Alstone
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Hi Stevie why do you want to stabilize the barrel , does it move about in the shroud ?,also on your gun does it run off center from the breach end, looking at the photo it seem's to me that the barrel is looking up and the shroud is looking down, which would annoy me. If you fill the shroud with foam can you still get the barrel out ?.

By the way congratulations on the work you have done on 1077 there will be no stopping you now.

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PostPosted: Fri Jun 22, 2007 10:32 am Reply with quote
AirGunEric
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The barrel inside the shroud is moveable- it has a locking clip at the receiver to allow it to be "unlocked" and moved forward in order to remove the magazine if a pellet were to get jammed (it does happen occasionally).

I have heard of people who have used expanding foam in the shroud (the idea being that the barrel will 'wiggle' a bit side-to-side when the gun is fired- and this needs to be stopped)- but I have never heard how easily the barrel can be moved after that to clear jams. The other question becomes- if you use expanding foam to fill the space- how will you then get the lube around the barrel to allow it some movement- if you try to put a lube in when the foam hasn't hardened that likely won't work- you'll just end up with a gummy mess. If you try to put the lube on after the insulation has hardened- how will you get it in, especially if there is no barrel movement and the insulation is stuck to the barrel? A bit of a dilemma. I suspect the people who used expanding foam did not have the ability to move the barrel after that- which, in the event of a jammed pellet and/or magazine, would be problematic.

When I did it- I just used some lubed plumbing insulation at the front end of the shroud behind the sight- putting it at the rear wasn't going to accomplish anything as my barrel was firmly attached and surrounded by the breech 'seat' there.

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Modding the Crosman 1077 
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