62gr M855 or 55gr M193: Must choose ONE or THE OTHER for 16" bbl 1:7 twist

[Eurodriver]

No. As a general rule the 5.56/.223 77 TMK will upset sooner, penetrate shallower, and be defeated easier than it's SMK counterpart. The TMK does have a higher BC and gives you a slight edge at distance.

Credit: BHA Website

Attachment 70514

Attachment 70515

That's a 20" barrel compared to a 14.5" barrel...how is that apples to apples?

My experience shooting white tails and hogs with 69gr SMKs and 77gr TMKs (also not apples to apples, but out of the same rifle) shows immensely better terminal performance with the TMK.

[georgeib]

That's a 20" barrel compared to a 14.5" barrel...how is that apples to apples?

My experience shooting white tails and hogs with 69gr SMKs and 77gr TMKs (also not apples to apples, but out of the same rifle) shows immensely better terminal performance with the TMK.

Certainly not apples to apples, but wouldn't the faster bullet from the longer barrel typically open up sooner? I think this shows even more dramatically how much earlier a TMK will open up compared to an SMK, no?

[davidjinks]

TMKs are superior to the SMK.

That's a 20" barrel compared to a 14.5" barrel...how is that apples to apples?

My experience shooting white tails and hogs with 69gr SMKs and 77gr TMKs (also not apples to apples, but out of the same rifle) shows immensely better terminal performance with the TMK.

[ST911]

That's a 20" barrel compared to a 14.5" barrel...how is that apples to apples?

Not intended as apples to apples but to show the general difference overall (neck, upset, etc), the trend is the same. I couldn't find the comparison photos I was looking for at the time.

My experience shooting white tails and hogs with 69gr SMKs and 77gr TMKs (also not apples to apples, but out of the same rifle) shows immensely better terminal performance with the TMK.

TMKs are superior to the SMK.

What does "superior" mean here. In what way?

[davidjinks]

Superior probably wasn’t the best word to use. TMKs are better than SMKs in regards to BC and the ability to fragment better. TMKs have a shorter neck length when comparing both SMK and TMK.

BC for 77 Gr TMK: .420
BC for 77 Gr SMK: .372

BC for 69 Gr TMK: .375
BC for 69 Gr SMK: .301

What does "superior" mean here. In what way?

[WillBrink]

Certainly not apples to apples, but wouldn't the faster bullet from the longer barrel typically open up sooner? I think this shows even more dramatically how much earlier a TMK will open up compared to an SMK, no?

Strictly depends on the design of the bullet and it's intended velocity range/envelope to perform as intended within that range.

[pag23]

This thread took a weird turn.

But a lot of good info....

[33XRAY]

Is it 1/7 that groups better with green tip? It's a no brainer ipso facto

[davidjinks]

Through .mil testing, it was shown that a 1:9 twist barrel was the most accurate barrel for M193 and M855.

The only thing that screws with the M855 is the steel insert at the tip. They’re not always concentric/straight when they’re made.

Is it 1/7 that groups better with green tip? It's a no brainer ipso facto

[lysander]

Through .mil testing, it was shown that a 1:9 twist barrel was the most accurate barrel for M193 and M855.

The only thing that screws with the M855 is the steel insert at the tip. They’re not always concentric/straight when they’re made.

Source?

I know of no report where M855 was ever tested in 1-9 twist by the Army.

EDIT:

The only report I know of that even mentions M855 and 1-9 twist rifling is "Analysis of the M16A2 Rifle Characteristics and Recommended Improvements," by the Army Research Institute. The report does not actually test anything, but speculates on all the ways the M16A2 could have been better (for the Army). The claim that 1-9 twist, is just that, and unsupported claim by the authors of that report. And further, the report states that the claim would have to be tested to validate it.

I can find nothing in any report about M193 and 1-9 twist done by the military. All the formal 1-9 twist testing was done with XM287 and XM288 ammunition in the XM207E2.

The 1-9 twist rifling was never considered for M855 weapons because the M856 tracer required a faster twist, and therefore never tested.