7 boxes of Canadian surplus ammo. 5 of 1950 DA and 2 of the 1943 DI boxer primed 

 Intrigued by the Inconsistency of 1965 DA 7.62 ammo I have shot and pulled apart, I stripped 10 of the DA 1950’s.

 The charge weights were from 39.2 gr to 40.1

This is much better than the 7.62  have checked. Hoping to get some loads together using the bullets in the reloadable brass.

 Anyone have experience using 70 year old powder? Lol

Who did the powder look and smell when you dumped it from the case?  If it is clumped and has an acidic smell, it is bad.  

Is it nitro or Cordite?

If nitro you can use STARTING load data for IMR 4895 (NOT H 4895) & work up with all the usual cautions.

I would not bother pulling bullets, it breaks the seal and tends to reduce neck tension.  Just shoot, and use the DI cases for reloading, it is excellent brass, I get about 50 reloads with this brass.

 Going to load from 10% under the average charge weight (39.6) and see if i can find a sweet spot.

 That DA berdan primed brass will get reduced  loads of 4227 and cast lead for practice

DI is Defence Industries

DA is Dominion Arsenal

Is the headstamp on your DA cases look like this?

The DI is known to be non-corrosive primers, but I’m not absolutely certain of the DA.  

    MV = 2412 fps, ES = 78 fps, SD = 25 fps.  10 rounds grouped at 2 MOA. 

I pulled the bullets on ten rounds and subbed in a 174 gr SMK with these results:

    MV = 2507 fps, ES = 44 fps, SD = 14 fps.  10 rounds grouped at 2 MOA, 9/10 shots at 1 MOA

Note that the SMK produced a higher muzzle velocity than the Mk 7 service bullet, nearly by 100 fps. Perhaps better bore sealing due to the thinner jacket on the SMK.  

I had great success in trying a few reloads of the 1965 7.62 components. 

 My mk1 conversion really stacked them up with 40.5 gr of the stock powder/ bullet/ primed case with a seating depth of the longer end of the average military loading.

 Still had .065 jump to the lands but sub 1 moa 5 shots group with ph5 rear sight. 

Rested, as I am a novice in prone position. 

  I loaded 39-42g in half grain incremets but have yet to try the 41,41.5, 42 as my available range time ran out. However  39.5 gr was nearly as good as 40.5gr

If loading for a lever action rifle with a tubular magazine, or pistol and revolver ammunition, a crimp is necessary to keep the bullet from moving in the case. But it is unnecessary in a box magazine fed rifle.

^^^

This.

I'll share a trick. take your expander ball & chuck it in a power drill. now spin it with some verry very fine carborundum wet & dry.

Just enough to get a slick mirror finish.

It reduces the diameter minutely & increases "pull" like crimping, but without the disadvantages mentioned.

I also bought a -0.001 inch undersize .303 mandrel from Lee for use in the collet neck sizing die to get a bit more neck tension.  

If “crimping is detrimental to accuracy”, not crimping the 7.62 loads I made up would make them shoot even better? The 39.5 grain load was 1-1.5 moa and the 40.5 was 1.0 moa 

 What improvements should I expect with not using my collet crimp die?

You may get sub-MOA groups.  When the barrel in my .303 Fulton No. 4 was fairly new, it gave 10 shot groups off the bench under 1 MOA with handloads and no crimp.  With crimp, just over 1 MOA. 

The crimp die will give varying amounts of crimp (neck tension) depending on case length.  Variability is detrimental to accuracy. You will never see a bench rest shooter use a crimp die.