CZ 527 mag modifications

[B4408]

Following on from Flip's thread "Questions for Camel and Missed" I thought I needed to test how a 221 fireball case would work in my 223, a 204mag is same size, and what was involved in modifying the mag if needed. My thinking is that if the 221 works a 20VT(don't have any 20VT cases) would be similar. Most info I have read say it does but some say there can be minor feed problems. So I wanted to prove to myself if it would work or not. Why, for a cheap 204 to 20VT conversion.

So I loaded the 223 mag with some dummy 221 rounds. The first thing you notice is that you are pushing the cartridge down and back onto the neck and shoulder of the one already in the mag, this is because the mag is to long. With the 4th and 5th rounds it is a nuisance and something you need to look at to do, would be a pain in the dark spotlighting. A 20 or 17 calibre would probably be harder again because of the bigger shoulder.

.221 in 223 mag

Once in the mag they chambered and ejected with no problems when cycled normally. Follow link to video
http://youtu.be/oJxct8JLE0E
If I worked the bolt really slowly( no practical reason to work the bolt this slow) 1 in 4 rounds would kick up and jamb.

The next step was to modify the mag by putting a 9mm spacer in the back, new follower and spring.

mag modification comparison

221 in 223 modified mag

modified mag

Making the spring is the tricky part. I bought some 1mm piano wire from the hobby shop and bent it into a reasonable shape after a couple of attempts. Unfortunately the wire isn't springy(that's the limit of my techno speak on springs) enough and distorts with five rounds in the mag so I only used four. The 221 rounds were normal to load in the mag and chambered and ejected perfectly. Follow link to video.
http://youtu.be/SAAR_td6C5w

So 221 length rounds will load from an unmodified 223 mag but work even better from a modified mag. Wish we could easily get CZ527 in 221 Fireball like the US can.
It was a bit of fiddling around but learnt a bit on the way, any spring specialists out there?
Hope it answers some questions for others.

regards
Bruce

"Its all part of the journey" Teepee

[MISSED]

Nicely done Bruce

I think you would have to temper the piano wire as eventually after use it would collapse

[stinkitup]

Hmm interesting I was looking at my 527 mag for my 5.7 mmj. Uses a hornet mag. Quite hard to put in the mag I think for the reasons stated above for the 221 fb cases.

Maybe a spacer would help the short cases to put in.

Ryan

[B4408]

Missed
My first thought is thicker wire but now I'm thinking of trying an extra wrap for the spring so each coil is doing less work and not over compressed. Trial and error research....

Bruce

[adamjp]

Make yourself a spring former - a mandrel to wrap it around.

Once you have it wrapped around the mandrel, just lightly heat it with a blowtorch. You are not trying to get it red, or really even change colour. You will know it is the right temperature as the wire will stop pulling out of the mandrel and sit tight on it.

A little trial and error will get you where you need to be fairly quickly.

[Camel]

Well done Bruce, I like that. When I had my Fox Mod 2 in hornet, then later in K-hornet, I actually took the rear spacer out of the magazine and had to make a slightly longer follower, I managed to get an extra 3mm of room, which made it a lot easier to use Spitzer type projectiles.

[B4408]

adamjp
I used a bit of wood for a mandrel and gave it a tap with a soft faced hammer, will try your method next attempt.

Bruce

[MISSED]

Bruce try this site it may help you out especially with tempering or normalizing the spring steel wire.

http://firearmsdesigner.com/?p=247

[Flip]

That's great work,

thanks for sharing very informative

Cheers


flip