Joshua M. Smith
Member
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 wasn’t 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 couldn’t disagree, I couldn’t find a headspace specification for this particular rifle. One gent gave me a rough measurement – two pieces of Scotch tape on the rear of an empty shell should make a “no-go” 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 – 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 didn’t 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 .010”, .020”, etc an a means to cut it to size. Their will have to be a center hole approximately .50” 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, it’s effective.
I got lucky. The first shim I tried worked well. Disassembling this bolts is not a fun task, and believe it when you’re told you need a vice or a c-clamp.
I used a .005” shim on the first (and only) pass. It locks up tightly now – tighter than most production rimfires, and as tightly as several target rimfires I’ve tried.
I am pushed for time right now, and therefore don’t 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 I’ll 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 – in fact, I’ve not been able to find anything on this rifle that is not steel or wood – and some have gone so far as to convert their M69 trainers from .22 long rifle to .22 magnum. While I don’t hold with this practice, they report absolutely no problems, save for necessarily reduced capacity of one round.
I’ll report back once I’ve 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.
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 wasn’t 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 couldn’t disagree, I couldn’t find a headspace specification for this particular rifle. One gent gave me a rough measurement – two pieces of Scotch tape on the rear of an empty shell should make a “no-go” 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 – 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 didn’t 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 .010”, .020”, etc an a means to cut it to size. Their will have to be a center hole approximately .50” 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, it’s effective.
I got lucky. The first shim I tried worked well. Disassembling this bolts is not a fun task, and believe it when you’re told you need a vice or a c-clamp.
I used a .005” shim on the first (and only) pass. It locks up tightly now – tighter than most production rimfires, and as tightly as several target rimfires I’ve tried.
I am pushed for time right now, and therefore don’t 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 I’ll 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 – in fact, I’ve not been able to find anything on this rifle that is not steel or wood – and some have gone so far as to convert their M69 trainers from .22 long rifle to .22 magnum. While I don’t hold with this practice, they report absolutely no problems, save for necessarily reduced capacity of one round.
I’ll report back once I’ve 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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