G'Day Fella's,

I recently purchased a near new (2H) Norinco copy of the M70/64 bolt action rifle, in the above caliber. In my line of employment, I design and manufacture a variety of firearm related items including supersonic firearm sound suppressors/silencers/Cans.
I would like to thread the muzzle of this new rifle and do a little Subsonic work with it. So I would appreciate any advice, knowledge and reloading data, you gents might have at hand on this subject!

Doh!
Homer

What's the twist rate on it?
What are you hunting?
How far do you plan to shoot?

G'Day Fella's,

Antelope Sniper, as soon as I get a chance to measure the Norinco factory barrel for Twist rate, Groove Diameter etc, I'll post the details.
As to Hunting and range Distance, I haven't thought much about this.
Whilst I have had a lot of hunting experience (in the distant past- FJWH) with SKS rifles in this chambering, I assume with Subsonic Loads I would be restricted to 100 to 150 yards/meters. I suppose it all depends on how accurately, the Norinco barrel shoots?

Doh!
Homer

Since it is a bolt action, either use Trail Boss or Unique.. something in that burn rate, depending on the weight of bullet you want to use..

I'd consult Lyman's Cast Bullet Manual # 3, which is fairly available at least on this side of the Pacific..

if you can't find it, PM me and I'll set you up with some reload data, specific to powders available down in Oz...

Seafire, I was checking out Trail Boss on Quickload and it looked really promising. Very low muzzle pressures, so I'd expect it to be easy on the supressor.

G'Day Fella's,

Thanks for that Sea Fire!
I have a copy of Lyman's, Cast Bullet Manual #3, I'll have a read of this and go from there!
Also from what I've already read, Trail Boss powder seem to be the powder of choice for Sub-Sonic loads!!!

Doh!
Homer

If the twist would handle it, I'd be loading 174gr round nose over Trail Boss, with a target velocity around 1050 fps. Mind you, I've never loaded for supressor, but the numbers sure look good.

G'Day Fella's,

Antelope Sniper FYI, I just measured up the hard chrome lined barrel, on the above Norinco rifle.

It came in as follows;

Twist = 1 in 10" or 1 in 254mm
Groove Diameter= 0.3125" or 7.94mm

Doh!
Homer

For hunting with any jacketed bullet you'll want to use one with as blunt a nose and as heavy as available because you'll get no expansion. The RN that AS recommends is a good choice. You might also consider loading the Hornady 174 FMJ backwards.

If you cast bullets at all a dead soft (30-1 or 40-1 alloy) and GC'd Lee C3120185-2R and hollow pointed with the Forster 1/8" drill will also work very well.

Tail Boss seems to be the current powder choice for such loads and i may try it also. I have been using Unique in my subsonic loads with suppressed rifles for years with complete success. Suggest you use a chronograph to work up the load when the rifle is suppressed. Work up until any shot of a 5 shot string "cracks" briefly just outside the front of the suppressor. Note the velocity and back off 50 fps from that average velocity. That then tells you the max average velocity of any load with that bullet that won't crack regardles of the powder used.

Different shaped bullets will have a different velocity where they "crack" because its the speed of the air moving around the bullet that causes the "crack" not the velocity of the bullet. A blunter shaped bullet will need a lessor velocity to not "crack".

Larry Gibson

G'Day Larry,

Thank you for your input into this subject, much appreciated!
I just spent a couple of days away up the mountains but it was not great weather for me to be hunting. It was great weather for hunting, I just didn't feel like getting wet, as it was almost always very windy, drizzling and on occasions, snowing!
OK, I'm getting soft in my old age!!!
I tried out the new NorChester, as I have dubbed it, and whilst I have addressed most of the stock issues, there are a few metal issues that need to be resolved. Primarily, it won't feed any cartridge from the Left Hand side of the box magazine. I have worked out what needs to be done but when I get a chance!
It shoots OK but again it wasn't great weather for accuracy testing.
I ordered three thousand assorted bullets on Friday, plus a box of 180 grain Sierra Spitzer (0.312"), as that was the only heavy .303 bullets, they had. I will have a play with these, Subsonically to see how they go.

I thought about casting up some bullets, as another option. So I will see which way I will go (as in), a 174gr or 220gr mould?

Larry, as you say from what I have researched, up to a Maximum of 10 grains of Trail Boss, seems to be the way to go with Sub sonic loads.

I have a Ohler 35P chrono, that I will be using to work up these loads over.

I found almost 400, 123gr .310" jacketed bullets (Hornady & Taipan) under my loading bench the other day, so they will do for some Supersonic hunting and suppressed work.

Larry, AS and others, if you would like to see my current range of Supersonic suppressors, send me a PM with your email address and I will forward you an image and description to you.

Doh!
Homer

Doh!
Homer

Hommer, at subsonic velocites, I'm not certain the 174gr would stabalize in a 1/10 twist. The 123-125gr bullets you have should stabalize just fine. Larry also has a good idea. A cast bullet with 2-3% tin should hold it's shape in the rifling, and still have an opportunity to expand at these low velocities.

G'Day Fella's,

AS, I think you have something with the barrel Twist Rate. Even more so as I just seen where the SKS standard barrel, has a 1 in 7 1/2" Twist! Also, this barrel of mine, may be a 1 in 9.6" Twist, not 1 in 10"? I just done a rough test when I checked it out.

I will Google up the "Greenhill Formula" and calculate what twist is required, once I have some bullets in my hand.

Life is full of all kinds of interesting adventures and side tracks, so time will tell!

Doh!
Homer