M69 Trainer Headspace Fix


Joshua M. Smith
January 24, 2008, 04:14 PM
M69 Trainer Headspace Fix

In cold weather, I was experiencing some spitting of hot gasses onto my shooting glasses when firing my M69 trainer. The problem was especially bad in the cold, or with hot ammo like Velocitors. Combined, the rifle wasnít pleasant to shoot for this left-hander. (I doubt right-handers would even notice the problem.)

It was suggested by a couple people on a couple different boards that the headspace tolerance was out of spec. While I couldnít disagree, I couldnít find a headspace specification for this particular rifle. One gent gave me a rough measurement Ė two pieces of Scotch tape on the rear of an empty shell should make a ďno-goĒ gauge.

By this measurement, my trainer was just in spec at room temperature. This could partially explain why it only acted up when it was cold out Ė the tolerances grew as the metal contracted. I decided to shim it up.

The first step, after checking headspace, was to disassemble the bolt. Excellent instructions exist on the Web on how to do this, and so I didnít repeat them. The instructions are located here: http://www.surplusrifle.com/romanian1969/disassemble/hs.asp

Before starting, you should be sure to have shim material in .010Ē, .020Ē, etc an a means to cut it to size. Their will have to be a center hole approximately .50Ē in diameter. I did not measure the outside, but rather waited until I put the bolt back together to get the outside diameter. It gave me a much cleaner look.

This is the finished piece. Notice the shim is hardly visible. However, itís effective.

I got lucky. The first shim I tried worked well. Disassembling this bolts is not a fun task, and believe it when youíre told you need a vice or a c-clamp.

I used a .005Ē shim on the first (and only) pass. It locks up tightly now Ė tighter than most production rimfires, and as tightly as several target rimfires Iíve tried.

I am pushed for time right now, and therefore donít have time to properly test it in the cold. However, upon firing some Velocitors out the back door on my old shooting range, I experienced no spitting whatsoever, and those did vent in this rifle even in warm temperatures. Tomorrow Iíll have to do some cold shooting and add an addendum to this report.

Some have suggested that this rifle was not made for hot loads. I assure you, it was. The receiver is all steel Ė in fact, Iíve not been able to find anything on this rifle that is not steel or wood Ė and some have gone so far as to convert their M69 trainers from .22 long rifle to .22 magnum. While I donít hold with this practice, they report absolutely no problems, save for necessarily reduced capacity of one round.

Iíll report back once Iíve fired in the cold.

Josh <><

Follow these instructions at your own risk. Neither the author nor this board will be held liable for any damages due to faulty workmanship, defective materials, or accidents or injuries of any sort whatsoever.

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Joshua M. Smith
January 25, 2008, 01:23 PM
Something I forgot to add, for everyone who reads this:

All tolerances were checked with proper gauges. The fact that the tape on the spent cartridge trick worked in my particular instance does not necessarily mean it will work for you. Headspace should be correlated with a proper set of headspace gauges even if you use the spent cartridge method.

January 25, 2008, 02:48 PM
Did you try posting this on RimfireCentral? In the Romanian forum?

Joshua M. Smith
January 25, 2008, 05:18 PM

Yes, it's there as well. I put it on several boards.

A few on Gun and Game thought it was a bad idea - in fact, user Lefty O went so far as to say that 99% of people are too stupid to do this.

That's the only board that I'm getting hammered on. The rest seem to appreciate the info.

Thank you,

Josh <><

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