Do you know what powder is used in those 7.62 rounds ?

It could be that the Hodgdon is 'hotter' than the NATO, or vice versa.

I don't think that you can really make proper comparisons without knowing the characteristics of both powders.

There should be info online giving the muzzle velocity out of a M14 National Match Rifle at a specified distance from the muzzle (usually 78 feet), that would give some indication of how hot the load is.  

Its a "Canister Powder" a version of the commercial one with the same designation, but not quite as tightly controlled when made in giant batches.

The military orders ammo in bulk so they simply adjust the load for Mil-Spec as they're reloading "a batch" of several million rounds.

No, not saying that at all.  All I’m saying is that commercially published reloading manuals intended for canister grade propellants won’t provide an accurate estimate of chamber pressures for military loads that use bulk powders, the charge weights may not correlate (and typically don’t).  That does not make the military ammunition unsafe in 7.62 chambered rifles for they are loaded within the military specified max average pressures (unless QC was very bad which would be extremely improbable with a Match loading).  

If you chrono that ammo out of your converted No. 4, the velocity will give you a comparison to your own handloads with that same bullet loaded with IMR 4895.  Pressures will be similar if the MV is the same.   

It will be interesting to see the results comparing this ammo to your hand loads.

The IMR propellants we buy are not identical to what the military buys.  The Canister grade propellants we buy are controlled from lot to lot to give nearly the same burn rate and energy density.   If you called up the makers of IMR powders and asked them to sell you some of of their IMR 4064 used by the Lake City plant in loading military 7.62 NATO ammunition, they will probably sell it to you as long as you bought an entire lot, likely several tons. And this lot is unique, no other lot is identical to it.   Then you will need to run pressure tests to develop the load to give he desired velocity.  Charge weights are generally not the same between bulk powder lots, they may occasionally be very close.  

Over the years, even canister grade propellants may change in load density, which is why reloading tables get updated to reflect current production.  

You may or may not measure a difference in velocity with your IMR 4064 handloads, it’s not likely they will have identical velocities to the M852 Match.  M852 was loaded with IMR 4895 per TM-43-0001-27 to a velocity of 2550 fps 78 ft from the muzzle in the M14 National Match rifle, not a particularly hot load and may be perfectly fine in your No. 4 conversion.   I say “may” because I don’t know the chamber pressure for that lot of M852 military bulk powder used in making these cartridges.  

There is lots of info on this subject on the various other forums from contributors who worked in military ordinance and at the ammunition plants.  I’m not making this stuff up, it’s a well known fact.  Reloaders have made mistakes assuming that military bulk powders sold as surplus years ago was identical to commercial canister powders, particularly in IMR 4895, it is simply not the case. 

You might want to weigh the cases if your going to reload them, they may be heavier than commercial brass, adjust reloads accordingly.  I drop 1 to 2 grains when using military 7.62 brass per Sierras (and other) manual and I have chrono’ed a difference in velocity between lighter commercial cases and thicker heavier military cases.  The latter has less air space which affects burn rate. 

I have a handful of those.

I was given them by a match shooter using an M1a. He told me he would never re-load them.

I used them as test beds for setting up annealing times.

Are you referring to my fired cases?

If so its just the residue of the "Tempilstick" heat sensitive crayon I use when setting up. It turns black when it hits the target temperature.

The excerpt was from the 7.62 Match Cartridge Accuracy Improvement Program by J.W. Hettel and went on to explain the the new knurling was moved lower on the case to .300" from the head as opposed to the original .500" from the urging of competitive shooters who were also reloading the cases after the fact...