55-62-69

[SevenSixTwo]

My .223 Wylde is a 1:9 twist.

When you say it's difficult to 'replicate' performance on NATO ammo - one would assume you can improve it? Although I'm specifying 62gr, this is only to avoid the inevitable re-zero when I switch from surplus ammo to reloads. If you say that 69gr prefers a faster twist to my 1:9 then would it make better sense to go for the ubiquitous 55gr? Would -7gr make a massive amount of difference over short/medium ranges 100-300m?

[John MH]

You would struggle to replicate or improve SS109 performance with home loads as the powders required to get the 62 grain bullet velocity needed are not commercially available.

69 grain bullets will probably work fine in a 1 in 9 twist, 77s may also work but its recommended that they are used in 7" to 8" barrels only as printed on the box by Sierra.

55 grain bullets are fine for short range but tend to struggle further than 300 yards.

[SevenSixTwo]

You would struggle to replicate or improve SS109 performance with home loads as the powders required to get the 62 grain bullet velocity needed are not commercially available.

So, by that reasoning would you also think that I'll struggle to replicate/improve 7.62 NATO ammo at 147/150gr? How then do civilian powders provide the required welly for heavier bullets?

I'll bow to your knowledge but it's not making much sense to me!

[John MH]

7,62 is a different kettle of fish. It may not make sense but that's how it is.

[SevenSixTwo]

Can you explain further? I'm not getting how 55 and 69gr can be propelled adequately but not 62gr? Weight is weight, isn't it?

[John MH]

You cannot get 62 grain bullet velocity to 3100 - 3200 FPS, required to replicate SS109, with the commercially available powders in a .223 case. 69 grain bullet velocities generally peak at 2900 FPS but most run at 2750 to 2800 in 20" barrels, you can get more velocity in longer barreled bolt guns. Hot loads in straight pulls lead to hard extractions so 2850 FPS for a 69 is about as fast as most reloaders go. Remember, however, velocity isn't everything and faster doesn't necessarily mean more accurate.

[SevenSixTwo]

You cannot get 62 grain bullet velocity to 3100 - 3200 FPS, required to replicate SS109, with the commercially available powders in a .223 case.

Thanks. Is that specifically just a .223 case or a 5.56 case (which I'm lead to believe has thicker brass)?

Interesting stuff.

I guess what you're saying is that even if I did use 62gr Id need to re-zero anyway, due to difference in velocity...

[SevenSixTwo]

This is interesting:

Duplicating NATO cartridges (cloning)

http://www.223reloads.com/home/223-5-56 ... catingnato

Excerpts:

If you want to switch to a different powder to easily achieve these mil spec velocities without having to run max loads there are several choices, here's a few:

Powder............ published max load & velocity for 55 gr FMJ bullet

Reloader 15......max load = 28.0c gr velocity = 3390 fps
Varget..............max load = 27.5c gr velocity = 3384 fps
H4895..............max load = 26.0c gr velocity = 3315 fps
BL-C(2)............max load = 27.5 gr velocity = 3313 fps
A-XMR-2015......max load = 25.0 gr velocity = 3281 fps
A-XMR-2495.....max load = 26.2c gr velocity = 3271 fps
V-N135.............max load = 26.8c gr velocity = 3268 fps


I'm sure there are other possibilities as well.

I don't think it matters if you want to play it safe. If the data is for a lighter weight case with a slightly larger volume then surely the same charge in heavier case would produce a higher velocity. The problem is it will do so by producing a higher pressure as well. So it might not be the best way to get the "extra" velocity you want. If you like W748 or have a lot of it already or whatever is the reason you want to go with it, I think that is more important then pushing out the pills to some mil spec velocity. The max velocity listed for W748 is 98% of the mil spec velocity, IMHO that last 2% really doesn't mean s***.

-------

M193 5.56 mm 55gr 3250±40 = 26 grs. of H335

M855 5.56 mm 62gr 3020±40 = 27 grs of 748 or BallC2


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See also:

http://www.firearmstalk.com/forums/f30/ ... ing-66901/

http://www.loaddata.com/members/search_ ... ing%20Data

[SevenSixTwo]

Can you also elaborate on how 7,62 is a different kettle of fish?

[DaveB]

Most military ammunition manufacturers do not start with a particular numbered propellant - they don't pull a canister of IMR 4895, for example, off the shelf. Instead, they will buy propellant in bulk - blending and testing until they meet the required military specification for velocity, port pressure and chamber pressure. You cannot buy the propellant that they use - it simply doesn't exist as an off-the-shelf product. It also means that while the ammunition lot/batch they make today will have the same performance as the one they make next year - the propellant, in both weight and type, will generally vary from lot-to-lot depending upon what they can get a good price on in bulk. A hand-loader, with time and experimentation, can often pretty closely match the performance of military ammunition, but it will not be identical to the military round.