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Goosic
Senior Member Joined: September 12 2017 Location: Phoenix Arizona Status: Offline Points: 8792 |
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Posted: November 16 2020 at 5:23pm |
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Frameman 1
Senior Member Joined: July 30 2019 Location: SW Ohio Status: Offline Points: 382 |
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very interesting. I have reloaded some Hornady 165 gr. Bullets with a minimum load of IMR 4895 at 35 gr. With no more pressure signs using the Hornady cases that I had trouble with before.
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There are no Americans in Baghdad!!
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The Armourer
Senior Member Joined: June 23 2019 Location: Y Felinhelli Status: Offline Points: 1246 |
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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.
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Frameman 1
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I’m fairly certain that the weak link in my failed load of Hornady 308 cases with CCI 200 primers , Hornady 165 gr, SST bullets with 42 gr. Of IMR 4895 powder was the 308 cases.
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There are no Americans in Baghdad!!
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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More often than not, military loads are made using a bulk formulated propellant for a specific purpose and not directly comparable to commercial canister grade powders even though they have the same name designation (e.g. IMR 4895). Powder charge weights will vary from lot to lot as they were loaded to give a specified velocity, sometimes by as much as 2 or more grains for the same type of powder (but different bulk lot).
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.
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Goosic
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Goosic
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Shamu
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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. |
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Don't shoot till you see the whites of their thighs. (Unofficial motto of the Royal Air Force)
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Goosic
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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Shamu is right. The military (and most commercial factory ammunition) use bulk (non-canister grade) powders. For canister powders reloaders buy sold in small quantities (usually 1 lb and 8 lb) are made in lots that are carefully blended to produce very consistent (lot to lot) pressures per given quantity (i.e. weight) so that the reloading manuals apply to all lots of powder sold. Not true for military bulk powders. They do not have the same energy density, even though they have the same name. It is very risky to use reloading manuals with surplus bulk military powders. The military loads its own ammunition (by contract usually) and they specify the required velocity and max pressure, they don’t care how many grains it takes in that particular lot of powder). Pull downs of .30 cal match ammunition from different lots have confirmed this, with quite large variation in charge weights particularly for M72 .30-06 Cal Match.
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Goosic
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Goosic
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The heading of my post is," If anyone is interested." A simple No would have sufficed.
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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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. |
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Goosic
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Zed
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I was under the impression that the powder's that end up in cans for reloaders were the surplus of the powder not used for normal manufactured ammunition; which is why we often have issues finding powder when the manufacturer's ramp up production of factory ammo. I may be wrong!
I doubt that powder of one particular type would vary that much in quality between military and civilian factory made ammo. However, the fact that you've got 0.4 gr difference in load weight is likely to cause some difference in performance on target. That's quite a difference for "Match" ammo. It will be interesting to see the results comparing this ammo to your hand loads.
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It's nice to be important, but it's more important to be nice!
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britrifles
Senior Member Joined: February 03 2018 Location: Atlanta, GA Status: Offline Points: 6539 |
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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. |
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