Hi,
I have a trued Rem 700, it was originally a 223 and has been rebarreled to 17 Mach 4.
I've purchased the Remington mag box, follower and spring for the 17 FB.
I'm having several feeding
issues since fitting these parts.
1. Sometimes the left hand round jumps up at the front and occasionally it jumps right out of the rifle when ejecting the previous round.
2. Sometimes rounds from either side of the magazine fail to feed smoothly into the chamber, usually the projectile tip contacts the rear of the barrel, the feed ramp has been polished and the angle altered slightly but neither has helped.

Any suggestions?

Have owners of genuine Rem 17FB's had similar problems.

Are the feed rails on 223 rem 700's different from feed rails on 17FB actions?

Thanks for your assistance

The 700 rem are not the best for a 17 fb conversion. I have seen a couple with the upgrades mag box and follower, sako extractor and the ejector modified and they still jam and do not feed very well. most use them as a single shot. There is a difference in the rails.
I had a 700 in 17 and had some minor problems and they were mainly self inflicted.
rifles that I have seen that work good with the 17 is Sako A1 and the CZ actions.
Dave

Did you try feeding with the original box and follower?
When holding the rifle upside down with the floorplate open, take a look at how the lips on the magazine box fit the receiver. Often they are bent to far in and the receiver rail makes almost no contact with the cartridge, hence the popping out when the bolt is opened. also try feeding with different combinations of the old box, new follower, switching up the spring etc. I keep a combination of about 6 of each part in the shop and often a combination that was removed from one rifle because it didn't work, will function properly in the next. Not much help to you.
In your case you will need to adjust the lips of the magazine and hopefully you can find the right modification to get things to work.

Option "B":

rechamber to FL .17-223

The rifle companies are just rediscovering that short, low-taper cartridges do not feed well in bolt guns. Unfortunately, they are using the customers as a test platform...

I do know that the extractor on my factory built rem 700 221FB is positioned on the upper left side of the bolt face (opposite of 700 .223 ) to accommodate the shorter cartridge upon ejection. May or may-not have any correlation.