.22 LR Conversion Kits
Submitted by UZI Talk Member Bob T.
There have been minor changes made in the kit over time, all in a quest to improve the reliability I think.
I have two original Group Industries kits, on which the Vector is based, both an early version and the last version. In the early version the bolt is more like a semi bolt. It has an outer carrier and an inner bolt. There are two operating springs, very much like the semi bolt. The one spring keeps the outer bolt forward, except when cocking. The inner bolt is controlled by a separate spring and it is the one that reciprocates on firing. The outer bolt has a port in it for the empties to eject through. The inner bolt has a sear mechanism just like the semi striker, active on one side only.
To cock the normal cocking handle is used and both the outer bolt and inner bolt are drawn back. However the inner bolt stays at the open bolt position but the outer bolt then goes forward to the battery position. When firing the inner bolt is the only part that moves. Problems with this style were a very heavy cocking stroke and a high cyclic rate (over 1600 rpm according to one person who timed it). It tended to go full auto even when set to semi. The height of the sear face was very critical and even after some adjustments to the inner bolts sear faces it still did not work well.
The later GI version, which is the one that got an excellent reputation, has an aluminum bolt very much like a regular 9mm bolt. It is about the same length and has a two steel pieces attached, one is the sear surface on the left side, the other is the firing pin block/feed block. This bolt cocks and operates just like a regular bolt with about the same amount of cocking force. The magazines were 20 round only and had two springs operating the follower. One was stiffer and short (about 1 3/8 inches long), the long one was softer (about 7 inches long). The mags were made from IMI 25 round mags, had an aluminum follower and an inner body that was also aluminum. There are at least two variations on how the 22 feed lips were made and attached. My experience with these mags has been that they feed the best of any I have tried including the Vector 20 and 28 round mags. They had either one or three round 1/4 inch inspection holes for the .22 rounds on the side so you could easily tell when they were loaded to capacity.
Skip forward to the first version of the Vector kit. The bolt is very similar to the later Group Industries bolt but is about a quarter inch shorter. It had a soft recoil spring and a cyclic rate that was very close to the 9mm. Later Vector kits have a stiffer spring and a much higher cyclic rate. Double taps with the early kit are easy but you tend to get bursts of four to five with the later Vector spring/bolt. It still had the two steel pieces. Two screws held on the side rail sear surface. The bottom rear of the bolt was closed.
The Vector magazines are not made with IMI bodies but some other Uzi mag. They have had several variations on the shape and length of the feed lips, material used for the follower and so on. These mags have been more variable in quality. I have had to return more than one because they would not feed correctly. Eventually I got six 20 round and six 28 round that are now pretty good. On all I found that polishing the top of the feed lips and making sure there are no burrs on the feed lips has helped with reliability a lot.
The later Vector bolts are even shorter than the first (by about another 1/4 inch) and machined quite a bit differently. The steel side rail insert is now held by one screw and the bottom of the bolt is open all the way to the back. In the early version the bolt bottom was closed at the rear (which is where it tended to hit the 9mm ejector). The original GI bolt was 6 1/2 inches long. The later Vector bolts are about 6 inches long.
The extractor appears identical on all these bolts, a flat piece of steel with an extractor hook on one side only.
With all these kits the barrels seem to be interchangeable. There have been differences in the shape of the feed ramp and the type of rifling (early ones were microgroove rifling even) but all seem to work, at least in the ones I have tried.
So much for the history, now for the meat.
All the kits are very sensitive to bolt closing energy, barrel position, mag position. What this means is there has to be enough energy to close the bolt, strip a round from the magazine and fire it. Any drag and you lose energy usually resulting in a failure to fire. The round chambers but there is not enough poop to make it go bang. This is evidenced by a light firing pin mark.
Some of the things that rob the bolt of closing energy are: interference with the 9mm ejector or ejector rivet, magazines that sit too high and rub on the bottom of the bolt, receiver dimensions that rub on the sides or top of the bolt, top covers that rub on the top of the bolt.
To check out these items place your bolt minus recoil spring in a clean gun with no mag. Tilt the gun up and see if gravity allows the bolt to easily slide back. Remember to hold the sear down (put the gun in full auto and keep the trigger pulled). If your bolt does not slide back and forth easily under gravity alone you are losing bolt-closing energy. Find the cause and fix it.
Now check to be sure the bolt is actually closing completely. I have seen a few where the .22 extractors rub on the barrel during the last millimeters of bolt closing. This can be caused by barrel positioning that is too high or low or by a bolt inner firing pin block that is not sitting at the right height. You may just need to bevel the extractor surfaces or it may require the barrel to be shimmed, or the inner firing pin block to be shimmed. What you are trying to achieve is full bolt closure with no drag even in the last millimeter.
Mag height - if the mag sits too high it drags on the bolt. If it is too low you get failures to feed, the bolt often hits the round halfway down its length putting a dent in the case. Solutions to this have been replacement or adjustment of the mag catch, even new trigger group housing. Check with an empty mag in the gun. Does the bolt slide smoothly over it or does it drag when it gets there.
Another mag problem is where the 9mm ejector interferes with the rounds as they rise in the mag. The rear end of the round hits the 9mm ejector and does not rise to its proper height. Trim the 9mm ejector back a tad until the .22 rounds do not hit it. The 9m ejector is hardened steel so use a dremel grinding wheel or a diamond file to trim it; a normal file won't touch it.
Make sure the inside of your mags are clean and that the follower has no burrs on it. The aluminum followers work well in the GI mags which had an aluminum inner body but not so well in the Vector mags. They switched to a plastic follower, make sure there are no burrs on the follower, that it rides inside the mag with no binding. Use a good dry lubricant inside the mag.
Ammunition problems - the kits and guns are also quite sensitive to brand of ammunition. What works great in one gun doesn't work in another. What happens is the different brands are slightly dimensionally different, the lube on them is also different. This causes rounds to sit differently and strip from the mag differently. Remember how sensitive the kit is to anything that robs bolt-closing energy, this is another area that takes energy from the closing stroke.
Given time and some mechanical skill, with an understanding of what is important the .22 kit can be adjusted so that it works very well. You might get one that works from the get go or you may have to tinker quite a bit.
Bottom line once it starts to run right you will shoot it more than you ever imagined. I have been lucky and have had ones that work well with Wal-Mart bulk Federal high velocity 550 packs at less than $9 a brick.
For more information on .22LR conversion kits, check the reference library.
Return to the UZI Talk Index
Copyright © 2003, UZITalk.com
International copyright laws DO apply to Internet Web Sites!
All Rights Reserved.
Last Modified: September 28, 2003