5.56 NATO Loads?

[TooTaxed]

Folks, I'd like to load a batch of 5.56, and I have available 55-gr FMJBT military surplus bullets (new/unmarked from Midway) and 4895 powder. I plan to load ten ea. 23.0, 23.5, 24.0, and 24.5 gr loads for 100-yd accuracy test purposes. Does anyone have any pet loads including pressure data?

My rifle is a "new" condition Colt SP1 CAR-15 that has been in storage for over 20 years. The barrel is stamped "C MP Chrome Bore" but does not appear to identify what the bore twist is. Can you tell me what the barrel twist is?

 

[444]

Obviously, I have no way of knowing for sure, but my guess would be 1:12 which should be fine for the 55 grain bullets you plan on using.

 

[timuchin]

Mark your cleaning rod..

Run it into the bore with a tight patch, and measure the distance it takes to make one complete revolution. As for loads, I shoot 62gr. SS109s with 24 grains of bulk powder. Widener's usually has some good deals on surplus bullets and powder. You can't beat $8/lb.

Tracer bullets. How cool is that?

 

[TooTaxed]

EXCELLENT suggestion! Thanks.

 

[1911 guy]

twenty year old rifle

unless it was some kind of souped up model, it will be a 1 in twelve twist. That was the standard until the 62 gr. bullet became the standard.

 

[P0832177]

You need to do the leg work yourself for your gun! Pressure data is going to be gained by using the Model 43 Personal Ballistic Laboratory setup ORI or by paying one of the labs to attain actual pressures for you. Otherwise you guess is as good as mine! Suit the load towards your weapon, and that way you have the ammo tuned for your application

 

[TooTaxed]

I note that the Hodgdon Manual has pressure data for 55-gr bullets and H4895: 24.0 gr (2893 fps and 37,800 cup) and 26.0 gr (3099 fps and 46,400 cup)...Though I'm using IMR 4895, I'll assume they are the same and I'll estimate from that...can't be very much difference anyhow, and the pressures are well below max.

 

[Zak Smith]

Do not assume IMR4895 == H4895. They are similar but not identical.

There is no need for the Oehler 43 or paying a ballistic lab-- just follow the safe reloading practices we've been using forever and don't be stupid.

-z

 

[Khornet]

My CMP DPMS rifle

likes 25.0 gr IMR 4895 with a 55gr FMJBT. I've not chronographed it, but it shoots fine and is accurate.