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Fitting Remington Model 504 extractors.

Not all gun parts, right out of the package, are ready for functional installation. The Model 504 Remington is no exception.

In working with three Remington Model 504 target rifles, all showed a defect in cartridge extraction. This was particularly true when attempting to extract unfired cartridges from a Bentz match chamber where the bullet would engage the rifling leade. Extraction was sometimes a problem with full velocity loads where the fired cartridge would fully obturate the chamber and cling more tightly to the chamber wall.

The underlying problem was in the hook effect of the extractor, a part which is located on the right side of the bolt. .22 rimfire bolts are often described as having two extractors, though this is not the case. The extractor is positioned on the right side of the bolt and extracts the cartridge case, whereas the laterally-opposing, similar-looking part on the opposite side of the bolt is the ejector. It serves two purposes. First, it holds and helps in aligning the cartridge as it is picked up from the magazine and cams over the case rim when a cartridge is loaded as a single shot.

Its secondary purpose is to hold the cartridge, loaded or fired, in alignment with the bolt face as the bolt is withdrawn until the case contacts the ejector lip. At this stage of extraction and ejection, the left side of the case rim bumps the extractor lip and jumps off the ejector, throwing it out to the right. Both the extractor and ejector have angled noses and are spring loaded within a slot and hole in the bolt. Understanding the function of these two little parts is the key to understanding malfunction causes and their correction.

Extractor Hook Angle Problem

A close inspection of the Model 504 Remington extractor showed the hook angle to be too open, causing the hook to slip off the case rim during extraction, sometimes leaving the case in the chamber. The secondary contributing cause for failure to extract was too weak an extractor spring, which allowed the case rim to slip off the extractor too freely as the case was partially extracted.

Solution And Testing

Two basically simple remedies were applied in correcting the problem. The extractor is easily removed by simply swinging it outward from the main axis of the bolt. A spring and plunger hold it in position. Caution must be exercised to not lose this tiny part or the spring and plunger.

Carefully examination of the extractor hook showed a slight angle away from square, which will cause it to slip off the case rim. I used a small machinist file to correct this angle. Be sure not to remove metal from the very tip of the extractor as the angle is being re-formed. After changing the extractor hook angle I replaced the existing spring with a stronger one, which was also a bit longer.

The parts were tested for function by chambering and extracting actual live rounds as the gun barrel was directed at a safe backstop. This was done from the magazine and single loading. I then fired several live rounds using both match ammunition as well as higher velocity loads. In all cases extraction was without flaw.

Conclusions

It is not infrequent for a very small gun part to cause a big problem. Where extraction failure is the case, it must be solved. Sometimes small changes solve the problem as we saw here with the Model 504 Remington. Sometimes we must dig deeper.
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Title Annotation:WORKBENCH
Author:Johnson, Norman E.
Publication:American Gunsmith
Date:Oct 1, 2014
Words:586
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