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Posted: 6/13/2009 9:51:30 AM EST
[Last Edit: 6/13/2009 10:02:08 AM EST by Inverted_Polarity]
Hello. I just wanted to share my experience with the Spike's Tactical .22LR conversion. First off I want to give credit to two threads with a wealth of information for tuning the ST-22 conversion. ST-22 Semi-Auto Tuning Guide and ST-22 & .22LR Conversion Kit: tweaks for feeding problems . Both these posts are a great place to start if you are having problems with your ST-22.

I got my ST-22 conversion and installed it. I proceeded to begin shooting. In the beginning I had quite a lot of FTF, FTE, and stovepipes. From reading the the above posts, I trimmed my recoil spring twice, removing 3 coils each time. That solved the stovepipes.

I was still getting FTF and some FTE but not as many as before. So I proceeded to polish my feed ramp and the chamber. I used some Cratex polishing bits in a Dremel. (For those who don't know what a Cratex bit is, it is a peice of hard rubber that comes in various shapes that has tungsten carbide impregnated in it as an abrasive). I began polishing with a Fine bit and then an Extra Fine bit and removed all the tool marks from the feed ramp and polished the mouth of the chamber. I then used a small wooden dowel with a slot on the end to accept a small strip of 1000 grit sand paper. I placed a drop of gun oil on the sand paper and then chucked the dowel into a drill and proceeded to polish the chamber. I then switched to a strip of 2000 grip sand paper and repeated. It did not take long to get the chamber to a mirror finish. The end result was that this solved all my FTF and now my conversion will feed ANY ammo I throw at it.

But I still had some other problems. I was still getting FTE's and also some light primer strikes that would not ignite the rounds. Most of the FTE's would happen after the light primer strikes where I would have to cycle the charging handle to remove the round that did not fire. But the extractor would not grip the rim firmly enough to remove the round. Upon further examination, I determined that the extractor had two problems. Because the extractor is set at an angle, only one corner of the extractor was touching the rim of the casing. This was enough to extract and eject the empty case after a round fired but not enough to extract the round by manually racking the charging handle. The other problem was that the stock extractor spring was way too weak to properly grip the rim of the case. So I remove the extractor by tapping out the roll pin that holds it in with a small punch. I then used an India stone to shape and bevel the edge of the extractor so that it makes better contact with the rim. I also replaced the stock extractor spring with a much stiffer spring. I used an AR15 stock rear sight base spring. It is the same diameter but much stiffer. The end result is that now my conversion extracts and ejects the empty casings much more consistently and with much more force than before. With the stock spring, the ejected cases sometime ejected fine but other times they barely cleared the camber or not at all (stovepipes, and jams). And when I have a round that does not ignite, a manual cycle of the charging handle extracts the unfired round easily.

Lastly, I was still having light primer strikes which would not always light off the rounds. I tried a different lower with a stronger hammer spring and it still did the same thing. I then wondered if maybe the firing pin spring might be too stiff. So I removed the firing pin retaining roll pin and removed the firing pin and spring. I found two things. The hole the firing pin moves back and forth through is very rough and could use a good polishing. Secondly, in my opinion the firing pin spring is way too stiff. I replaced it with an AR15 flip down trigger guard detent spring. It is the exact same diameter as the stock firing pin spring and fits perfectly. It is weaker than the stock spring but yet still strong enough to not get any slam fires. After replacing this spring and re-assembling, it has solved my light primer strikes. Now when I get a round that does not fire, it is because it is a dud round.

That is it. Now I am going to go burn some more ammo. Hope this helps out people who are having trouble. As always, your mileage may vary. This is what has worked for my kit. Be safe. Thanks.
Link Posted: 6/13/2009 12:05:20 PM EST
Going too short on the recoil spring also lead to light strikes, as can rounds that fail to fully chamber. One side effect of strengthening the extractor spring is that the stronger spring can cause the bolt to stay open slightly due to the extractor hook bottoming out against the groove in the breech.
Link Posted: 6/13/2009 6:06:45 PM EST
I was having light primer strikes both before and after shortening my recoil spring. And I only shortened it by 6 coils. But after I changed to a lighter firing pin spring, I have not had any problems with light strikes. I still do get the occasional dud round (I confirm that the duds are bad rounds by trying to fire them off at least 3 or 4 more times).

As for as my extractor is concerned, it was not working very good at all before I modified it and changed to a stiffer spring and now it is. This is what has worked for me. I just wanted to post my experience in the hope that it may help someone else with their problems.
Link Posted: 6/14/2009 3:05:09 AM EST
Great write-up!
Link Posted: 6/14/2009 2:23:33 PM EST
Originally Posted By Inverted_Polarity:As for as my extractor is concerned, it was not working very good at all before I modified it and changed to a stiffer spring and now it is. This is what has worked for me. I just wanted to post my experience in the hope that it may help someone else with their problems.


Yup, the extractor can definitely benefit from some tuning. I had to slightly bend back the hook on mine so it would hold the rounds against the breech face.
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