The Mossberg 940 JM Pro is a popular semi-automatic shotgun, prized for its reliability and versatility. One of its attractive features is the ability to swap barrels, allowing you to tailor the shotgun to various shooting disciplines and hunting scenarios. This guide delves into the process of swapping barrels on your Mossberg 940 JM Pro, covering everything from the necessary tools to troubleshooting potential issues.
Why Swap Barrels on Your Mossberg 940 JM Pro?
The modularity of the 940 JM Pro is a significant advantage. Swapping barrels allows for quick adaptation to different shooting situations. For example:
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Changing Gauges: Easily switch between 12-gauge and 20-gauge barrels, depending on the game you're hunting or your personal preference. This adaptability makes the 940 JM Pro a truly versatile firearm.
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Adjusting Choke: Different barrel configurations offer various choke options, influencing shot pattern and spread. This is crucial for hunting different game at varying distances. A tighter choke for long-range shots on waterfowl, for instance, is easily swapped with a more open choke for close-range upland bird hunting.
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Specialized Barrels: Some aftermarket barrels cater to specific purposes, like specialized hunting configurations or competition-oriented designs.
Tools and Materials Required for a Mossberg 940 Barrel Swap
Before beginning the barrel swap, gather the following:
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Mossberg 940 JM Pro Shotgun: This one's essential!
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New Barrel (compatible with your 940 JM Pro): Ensure the barrel is designed specifically for your shotgun model.
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Allen Wrench (appropriate size): Check your Mossberg 940 JM Pro manual for the exact size required for the barrel nut. The size varies slightly depending on the model and year of manufacture.
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Clean Patch or Rag: To wipe away any debris or fingerprints.
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Gun Oil (optional): A light application of gun oil to the barrel threads can aid in both installation and removal, as well as protecting your firearm.
Step-by-Step Guide to Swapping Barrels on Your Mossberg 940 JM Pro
Disclaimer: Always practice safe firearm handling procedures. Ensure the firearm is unloaded and the chamber is clear before attempting any maintenance or modification. Consult your owner's manual for specific instructions and safety guidelines pertinent to your Mossberg 940 JM Pro.
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Unloading the Shotgun: This is paramount. Double-check the chamber and magazine to confirm the gun is completely empty.
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Remove the Forend: Carefully detach the forend from the receiver. The method varies slightly depending on the model, but it generally involves releasing a latch or button.
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Locate and Loosen the Barrel Nut: The barrel nut is located at the junction of the receiver and barrel. Use the appropriate Allen wrench to loosen, but do not completely remove it at this stage. Turn counter-clockwise.
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Remove the Barrel: Once the barrel nut is loosened, gently pull the barrel forward and away from the receiver.
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Install the New Barrel: Carefully align the new barrel with the receiver and push it firmly into place until it's seated correctly.
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Tighten the Barrel Nut: Use the Allen wrench to tighten the barrel nut securely. Don't overtighten; you should feel firm resistance. Overtightening may cause damage.
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Reattach the Forend: Carefully reattach the forend to the receiver.
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Function Check: Before use, cycle the action a few times to ensure smooth operation. If the firearm malfunctions, re-inspect the barrel installation.
Troubleshooting Common Issues
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Barrel Won't Go In: Ensure you are using the correct barrel for your Mossberg 940 JM Pro model. A slight misalignment can prevent installation. Carefully realign and try again.
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Barrel is Loose: If the barrel nut is not sufficiently tightened, the barrel may become loose during firing. Re-tighten the barrel nut following the instructions above.
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Malfunction After Barrel Swap: If the shotgun malfunctions, it may indicate an issue with the barrel installation or a problem with the new barrel. Re-examine the steps above, and if the problem persists, consult a qualified gunsmith.
This guide provides a general overview. Always refer to the Mossberg 940 JM Pro owner's manual for specific instructions related to your model and to ensure safe and effective operation. If you are unsure about any step in the process, seek the assistance of a qualified gunsmith. Safety should always be your top priority when handling firearms.
