I still read alot of posts on multiple forums about Marauder issues. Normally, accuracy issues. Lets start off with a few simple tips that apply to all air rifles not just the Marauder. Airguns shoot a pellet with a very low BC (ballistic coefficient) which hinders the pellets ability to cut through the wind and fight gravity. This can be the cause of "flyers" or pellets that don't land within the majority when shooting a group. Most pcp air rifles also need to be "tuned" to achieve full potential of that particular gun. Specifically in the case of the Marauder, I have owned around a dozen marauders in all 3 calibers and the Marauder pistol as well. I can assure you that every Marauder I have owned and worked on needed tuned!! Shooting the factory "tune" can be another reason for accuracy issues. Alot of Marauders come from the factory shooting what is called a "descending" shot string. Meaning that when filled to say 3000psi, the first shot is the fastest and every subsequent shot gets slower and slower. This is not condusive to shooting accurate groups. The list can be rather large when trying to find the root cause of your Marauders accuracy issues. Causes can include: trigger poorly adjusted, barrel needs cleaned or maybe deburred "lapped", bad breech seal, bad barrel, baffle clipping, barrel/shroud movement, and a host of other problems. WOW!! Sounds like alot could go wrong and cause you issues. It really isn't that difficult to fix these issues and that is the point of this post. If you have a few basic tools and even a small amount of mechanical ability you can get your Marauder shooting good. If you are to timid or don't have tools or the ability to try fixing things on your own, then I highly recommend sending your gun to a reputable tuner that will return your gun shooting to its full potential. For those that might want to attempt things on their own, read on!! Be aware that the ONLY way to tune any airgun is with a chronograph. There is no other way to tune an airgun but the use of a chronograph!! If you plan on staying in this hobby for any amount of time, do yourself a favor and buy a chronograph if you don't already have one.
DISCLAIMER: High pressure air is very dangerous!! Before attempting to open up the airtube, make sure that it is degassed of ALL air!!
The Marauder is marketed and sold as a budget PCP. Something that the average Joe can afford to buy and get into the world of PCP air rifles. What does that mean?? Well, it means that many of the steps that the high end airgun makers would take are skipped. Lesser quality materials are used and the fit and finish are less than stellar. However, that doesn't mean that a Marauder can't shoot extremely well. Just means it probably will need some TLC to get it performing they way it was intended to.
When I purchase a new Marauder, I strip it down completely. Degass the airtube and strip the entire gun down. Note: If you are not modifying the valve or installing an aftermarket valve or regulator, there is no need to degass and disassemble the front portion of the airtube. This only requires a few allen wrenchs, crescent wrench, and a dowel rod or pvc pipe to push the valve and gauge block out. Once the gun is stripped down, I like to start with the barrel. I always inspect the crown and bore for any damage or obvious signs that the barrel could be a problem. Assuming it looks good, I will lap the bore, leade, and crown with jb bore paste and kroil. Also check the air transfer port in the barrel for burrs and deburr if neccesary.
I will then polish up the bolt and make sure the bolt slides very smooth in the breech and set the bolt tension via the flat head screw on top of the breech. I pull that flat head tensioner out and apply alittle blue loctite and then set the bolt tension.
Install a new breech o-ring (which is caliber specific) and reassemble the barrel and breech. Use a magazine to properly set the barrel "head space". This is an important step as you might not be able to insert a magazine if you don't get the "head space" set correctly. At this point, I will clean all the baffles and the shroud tube. Then, I reinstall the shroud and baffles so that the top end is one complete assembly and ready to bolt back to the air tube.
As noted, you only have to degass and completely disassemble the airtube if modifying the valve or adding aftermarket parts. It does make this next step much easier if the whole air tube is apart. I take a small diamond file and knock down any major burrs that exist inside the airtube where the hammer rides. Normally the slots for the hammer pin and sear have a slightly burred or raised edge that I will knockdown with a file. Then I go to a 1' ball hone and proceed to hone the airtube so that the hammer has a super smooth surface to ride on. I also clean up the gauge block hole and breech screw holes. This will keep o-rings from being damaged during reassembly.
Next is the hammer. Using a dremel with polishing compound and a felt cone, I polish the hammer to a mirror finish. At this point, you can tap the blank hole in the hammer for a set screw that will keep the striker from backing out. In stock form, strikers tend to back out which will affect your tune. Tapping the blank hole and installing a nylon tipped grub screw will eliminate this from happening. If tapping the hole is not an option, then using blue locktite or vibra tite is a good alternative. I have went as far as getting the gun tuned then pulling out the hammer and installing o-rings between the striker head and the face of the hammer to keep the striker from backing out. This is a major issue on almost all marauders and if nothing is done, The striker will back out. This is one reason I like the WAR hammer because it is tapped and has a nylon tipped screw to hold the striker firm enough that it can still be adjusted, but never back out or move unless you move it.
Now it is time to reassemble the airtube. I use a silicone spray to lube the hammer, some you graphite and some use nothing. Lubing is a personal preference and I will leave that up to you. Once the airtube is reassembled, it can be "married" to the top end (breech/barrel assembly).
At this point, I polish all the trigger group components and remove the "lawyer spring" then re assemble. Now the trigger can be adjusted to your liking. Keep in mind that if you are like me and prefer a single stage trigger, the marauder trigger can be adjusted to a single stage trigger. Mine are all set single stage at 7oz as measured by a Lyman digital gauge. I also use alittle silicone spray on the trigger group before reassembly.
Now you can finish assembling the gun. One of the weak links to the Marauder is the barrel band. The free floating idea is what leads to alot of POI changes and is easily knocked around when shooting and especially hunting. You can install o-rings to "unfloat" the shroud, drill and tap the stock band for set screws to securely hold the band, or buy one of the aftermarket barrel bands that are available. The stock barrel band is a major issue leading to POI shifts and other accuracy issues.
Now you are ready to tune. There are alot of online resources that can help with tuning and I will not go to far indepth as it will just take to long to explain. Your goal is to get a certain number of shots from a certain fill point to all stay within a velocity that is a maximum of 4% from the highest velocity. Some also measure this 4% from the average velocity. Regardless, you want an ES(extreme spread) that is 4% or less. The further you plan to shoot, the lower your ES needs to be if you want accuracy. The Marauder has 3 adjustments. The hammer spring tension, striker length, and VMS screw that can all be used to tune the gun how you want within the limits of the stock parts.
Part of tuning is finding the pellet that your barrel shoots best then tuning to get the most accuracy out of that pellet/barrel combination. So, lets assume that the gun is tuned perfect to a certain pellet, your scope holds zero and is working properly, but your groups aren't all that great. What could be wrong? You already "blueprinted" the gun and removed most of the variables that can lead to problems. First check the baffles and shroud cap for any signs that pellets are "clipping". If that is not the problem, then what could be wrong? My reasoning for "blueprinting" a stock Marauder is simply to remove the possibilities that its the guns fault. I further remove another variable by finding the best pellet and tuning the gun for that pellet. I made sure there are no clipping issues and I know for sure that my scope and mounts are good. Now, lets go one step further and eliminate the human error factor. If you can garuantee that neither the wind or your shooting is causing the issues than maybe you have a sub par barrel??
There are so many variables that can lead us to unhappiness with our Marauders. Learning the steps to remove these variables as possible causes of accuracy issues or other problems is the key. Crosman does have a history of barrel issues. But, I have had a number of barrels over the years that were deemed "bad" by others, that I was able to make shoot well and in a couple of cases, ended up with a really great barrel.
This is just a brief overview of the steps to fixing or even avoiding problems with your Marauder. I would have loved to go into much greater detail, but what I have above took me much longer than I had planned. I will not claim to be an expert airgunsmith, but I have been very succesful at making Marauders shoot really good and hope that I can help others on their quest for Marauder performance and accuracy. I do not tune guns or sell products. I am just a guy that loves the Marauder platform and hoping that what I have learned might be beneficial to others.
There are some great resources when it comes to the Marauder. The marauder air rifle forums has alot of great info that can be very helpful and is a must visit for marauder owners.
https://docs.google.com/document/d/1Jn0RFfnH9YnFaEbT5ynizTnIyJ9DG6u5htJ_65R9P5g/mobilebasic?pli=1 this is a great resource that might be of some value to marauder owners.
http://www.network54.com/Forum/79537/thread/1302911557/Marauder+.177+and+.22+O-ring+list this list has been very helpful for o-ring sizes.
DISCLAIMER: High pressure air is very dangerous!! Before attempting to open up the airtube, make sure that it is degassed of ALL air!!
The Marauder is marketed and sold as a budget PCP. Something that the average Joe can afford to buy and get into the world of PCP air rifles. What does that mean?? Well, it means that many of the steps that the high end airgun makers would take are skipped. Lesser quality materials are used and the fit and finish are less than stellar. However, that doesn't mean that a Marauder can't shoot extremely well. Just means it probably will need some TLC to get it performing they way it was intended to.
When I purchase a new Marauder, I strip it down completely. Degass the airtube and strip the entire gun down. Note: If you are not modifying the valve or installing an aftermarket valve or regulator, there is no need to degass and disassemble the front portion of the airtube. This only requires a few allen wrenchs, crescent wrench, and a dowel rod or pvc pipe to push the valve and gauge block out. Once the gun is stripped down, I like to start with the barrel. I always inspect the crown and bore for any damage or obvious signs that the barrel could be a problem. Assuming it looks good, I will lap the bore, leade, and crown with jb bore paste and kroil. Also check the air transfer port in the barrel for burrs and deburr if neccesary.
I will then polish up the bolt and make sure the bolt slides very smooth in the breech and set the bolt tension via the flat head screw on top of the breech. I pull that flat head tensioner out and apply alittle blue loctite and then set the bolt tension.
Install a new breech o-ring (which is caliber specific) and reassemble the barrel and breech. Use a magazine to properly set the barrel "head space". This is an important step as you might not be able to insert a magazine if you don't get the "head space" set correctly. At this point, I will clean all the baffles and the shroud tube. Then, I reinstall the shroud and baffles so that the top end is one complete assembly and ready to bolt back to the air tube.
As noted, you only have to degass and completely disassemble the airtube if modifying the valve or adding aftermarket parts. It does make this next step much easier if the whole air tube is apart. I take a small diamond file and knock down any major burrs that exist inside the airtube where the hammer rides. Normally the slots for the hammer pin and sear have a slightly burred or raised edge that I will knockdown with a file. Then I go to a 1' ball hone and proceed to hone the airtube so that the hammer has a super smooth surface to ride on. I also clean up the gauge block hole and breech screw holes. This will keep o-rings from being damaged during reassembly.
Next is the hammer. Using a dremel with polishing compound and a felt cone, I polish the hammer to a mirror finish. At this point, you can tap the blank hole in the hammer for a set screw that will keep the striker from backing out. In stock form, strikers tend to back out which will affect your tune. Tapping the blank hole and installing a nylon tipped grub screw will eliminate this from happening. If tapping the hole is not an option, then using blue locktite or vibra tite is a good alternative. I have went as far as getting the gun tuned then pulling out the hammer and installing o-rings between the striker head and the face of the hammer to keep the striker from backing out. This is a major issue on almost all marauders and if nothing is done, The striker will back out. This is one reason I like the WAR hammer because it is tapped and has a nylon tipped screw to hold the striker firm enough that it can still be adjusted, but never back out or move unless you move it.
Now it is time to reassemble the airtube. I use a silicone spray to lube the hammer, some you graphite and some use nothing. Lubing is a personal preference and I will leave that up to you. Once the airtube is reassembled, it can be "married" to the top end (breech/barrel assembly).
At this point, I polish all the trigger group components and remove the "lawyer spring" then re assemble. Now the trigger can be adjusted to your liking. Keep in mind that if you are like me and prefer a single stage trigger, the marauder trigger can be adjusted to a single stage trigger. Mine are all set single stage at 7oz as measured by a Lyman digital gauge. I also use alittle silicone spray on the trigger group before reassembly.
Now you can finish assembling the gun. One of the weak links to the Marauder is the barrel band. The free floating idea is what leads to alot of POI changes and is easily knocked around when shooting and especially hunting. You can install o-rings to "unfloat" the shroud, drill and tap the stock band for set screws to securely hold the band, or buy one of the aftermarket barrel bands that are available. The stock barrel band is a major issue leading to POI shifts and other accuracy issues.
Now you are ready to tune. There are alot of online resources that can help with tuning and I will not go to far indepth as it will just take to long to explain. Your goal is to get a certain number of shots from a certain fill point to all stay within a velocity that is a maximum of 4% from the highest velocity. Some also measure this 4% from the average velocity. Regardless, you want an ES(extreme spread) that is 4% or less. The further you plan to shoot, the lower your ES needs to be if you want accuracy. The Marauder has 3 adjustments. The hammer spring tension, striker length, and VMS screw that can all be used to tune the gun how you want within the limits of the stock parts.
Part of tuning is finding the pellet that your barrel shoots best then tuning to get the most accuracy out of that pellet/barrel combination. So, lets assume that the gun is tuned perfect to a certain pellet, your scope holds zero and is working properly, but your groups aren't all that great. What could be wrong? You already "blueprinted" the gun and removed most of the variables that can lead to problems. First check the baffles and shroud cap for any signs that pellets are "clipping". If that is not the problem, then what could be wrong? My reasoning for "blueprinting" a stock Marauder is simply to remove the possibilities that its the guns fault. I further remove another variable by finding the best pellet and tuning the gun for that pellet. I made sure there are no clipping issues and I know for sure that my scope and mounts are good. Now, lets go one step further and eliminate the human error factor. If you can garuantee that neither the wind or your shooting is causing the issues than maybe you have a sub par barrel??
There are so many variables that can lead us to unhappiness with our Marauders. Learning the steps to remove these variables as possible causes of accuracy issues or other problems is the key. Crosman does have a history of barrel issues. But, I have had a number of barrels over the years that were deemed "bad" by others, that I was able to make shoot well and in a couple of cases, ended up with a really great barrel.
This is just a brief overview of the steps to fixing or even avoiding problems with your Marauder. I would have loved to go into much greater detail, but what I have above took me much longer than I had planned. I will not claim to be an expert airgunsmith, but I have been very succesful at making Marauders shoot really good and hope that I can help others on their quest for Marauder performance and accuracy. I do not tune guns or sell products. I am just a guy that loves the Marauder platform and hoping that what I have learned might be beneficial to others.
There are some great resources when it comes to the Marauder. The marauder air rifle forums has alot of great info that can be very helpful and is a must visit for marauder owners.
https://docs.google.com/document/d/1Jn0RFfnH9YnFaEbT5ynizTnIyJ9DG6u5htJ_65R9P5g/mobilebasic?pli=1 this is a great resource that might be of some value to marauder owners.
http://www.network54.com/Forum/79537/thread/1302911557/Marauder+.177+and+.22+O-ring+list this list has been very helpful for o-ring sizes.
