If your Remington 7400 or new 750 is jamming there is a very SIMPLE fix! The first thing you must determine is the type of jam you are experiencing. If your auto loader is NOT ejecting a spent round then this fix is the solution to your problem, If your auto loader is ejecting the spent round but not driving a live cartridge home then this is not the remedy and you should first try a new clip and a thorough cleaning (with one exception which i will explain later.)
If your Remington auto loader is CLEAN and well LUBED and you are not ejecting the spent casing then you need to remove the fore arm and with a quality pair of large sharp jawed of diagonal wire cutters remove ONE coil from the return/mainspring. Place a piece of clear shipping tape on the receiver so that the edge of the tape covers the bolt handle slot just enough to cause the bolt handle shaft to "dent" the edge of the tape when it is pulled fully to the rear of the receiver. This is the gauge to let you know when the bolt has been fully thrown to it's most rearward position in the receiver by the gas operation system. Your bolt MUST reach it's full rearward movement to engage the live round in the mag!
Load your clip with 4 rounds and one in the chamber to cause full pressure and drag on bolt.
Fire the rifle. If it did not eject the spent round, load a new round and "dent" the end of the gauge tape then clip another coil off and repeat the procedure.
Important to know is that you must stop clipping coils as soon as the tape is dented showing full rearward movement of the bolt! I have repaired many 7400's and a couple of the new 750's with this method and the worst that can happen is you clip too many coils and have to replace the mainspring and start over.
As long as the spring clipping was stopped as the bolt fully reached the rear of the receiver you will have ample spring pressure to close the bolt and load a new round.
P.S In the begging I mentioned an exception to the rule and here is the explanation.
If your firearm is ejecting a spent round but not picking up a new one then this fix will also work because most likely your problem is that the the bolt is traveling far enough to eject the round but not fully to the rear to pick up the live round.
Use the tape "gauge" at the rear of the bolt slot to determine if the bolt is traveling fully to the rear.
This method will put an end to the term JAMOMATIC.
I have never over cut the spring by cutting one coil and testing ONE at a time. Every Rem. auto loader I have repaired in this fashion has stayed fixed and functioning perfectly.
good luck.