[yocan]

I understand M4 ramps are for heavier bullets up to 77 grains, and I like no I love the ballistics of the Marine 1/7 twist with 77 grain bullets. But I was wondering how light of a round can you fire with a 1/7. Just thinking SHTF, if I can't have 1/14 twist with 55 grains, or 1/7 I won't use a 556, I'll stick to my AK.

Basically how light of ammo can you use with 1/7? Just wondering and if you use light ammo with civilian lead tips and such, how do they handle 1/7?

 

[AZXD]

1/7 is pretty fast ... I'm sure you could get away with 50g ... But I'm thinking you might have trouble with anything lighter unless you are reloading ... lightest bullet weight for 223 with 1-9 twist - TheFiringLine Forums ... It's a short thread, but a guy is saying he has shot 35g stuff with a 1/7 ... It sounds like you might need to experiment.

 

[The Knight Of Light]

I have shot 35gr Noslers with a 1-7 twist to 200 yards with no ill effects.

It really depends on the barrel. Things to consider are...

How sharp the rifling is, how well the barrel was crowned, how the M4 ramps are angled, how sharp the M4 ramps are, short, medium, standard, or long gas system, and what bullet you are using are all factors in how your rifle will handle certain ammo.

 

[ORD]

I know people who use 45gr loads in a 1/7 twist AR all the time with no signs of keyholing, etc. I can't imagine that you'd want much of anything other than 55gr ball for SHTF situations anyway given its ease of availability and price as compared to other 5.56 ammo. Same for "civy" lead-nosed stuff around the 55gr range. The 1/7 will work perfectly well for 55gr.

 

[BDZ71]

1/7 works fine with 55gr 5.56

And thats a common weight. You probably could do some 45gr if you had to. But personally I dont stick anything littler than 55gr in my 1/7. And she does fine

 

[mtcraigco]

IIRC, 1/7 spins 55grn FMJ ammo fast enough it just about guarantees destabilization/fragmentation on impact with a soft target down to about 2400fps or about 200 yds. Soft points would be even nastier.

Remember, it's the yaw effect and subsequent bullet breakup that makes the 55grn FMJ load effective. Once you get below the velocity threshold for that effect, it just punches clean holes in things.

So basically the 55grn in a 1/7 twist is an excellent SHTF/urban load as you are relatively unlikely to be engaging targets beyond the 200yd range.

It's been awhile since I brushed up on my .223 ballistics with different loads but that seems about right. Correct me if I'm off.

 

[BDZ71]

IIRC, 1/7 spins 55grn FMJ ammo fast enough it just about guarantees destabilization/fragmentation on impact with a soft target down to about 2400fps or about 200 yds. Soft points would be even nastier.

Remember, it's the yaw effect and subsequent bullet breakup that makes the 55grn FMJ load effective. Once you get below the velocity threshold for that effect, it just punches clean holes in things.

So basically the 55grn in a 1/7 twist is an excellent SHTF/urban load as you are relatively unlikely to be engaging targets beyond the 200yd range.

It's been awhile since I brushed up on my .223 ballistics with different loads but that seems about right. Correct me if I'm off.

Yes. Basically the exact same thing I learned somewhere.

BTW.. Mark, I ordered another Supertuck today.. This one is for my cousin. I was so happy with mine I put him on the idea. :mrgreen: