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

[NYH1]

All of our carbines (14.5" and 16") and rifles (20"), all 1 in 7 twist shoot better with 55gr. M193 than 62gr. M855. Unless it's a really good deal, I don't buy 62gr. M855 anymore.

NYH1.

[NickySantoro]

Long ago I had significant experience with M193. It works well.

[1168]

Taking a round to plates can cause pulmonary/cardiac contusions as well as pneumothorax. It's common to have broken ribs when soft armor or plates are struck.

Absolutely. Getting shot sucks. Getting shot in the plate sucks less, and has a greater percentage of positive outcomes.

[T2C]

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.

I don't have any test data, just personal observations. I shot M855 and SS109 in High Power Rifle competition at reduced courses out to 200 yards. The RRA Match upper with a 1:8 twist shot much better groups than the 1:9 twist with M855 and SS109. The 55g M193 shot through the RRA upper did not group as well at 200 yards as the M855 and SS109. The M193 shot much better groups at 200 yards when fired through the 1:9 twist barrel. When Smith & Wesson tried to secure a department contract to sell carbines to my agency, I shot 55g M193 in one of their carbines with 1:7 twist barrel at 100 yards. Accuracy was horrible. I shot 5-1/2" groups at 100 yards discounting flyers that opened the groups up to 8 inches. A 1:9 Armalite carbine shot 2" groups at the same distance. The S&W sales rep was pissed off.

[NQNPIII]

When Smith & Wesson tried to secure a department contract to sell carbines to my agency, I shot 55g M193 in one of their carbines with 1:7 twist barrel at 100 yards. Accuracy was horrible. I s.

Must not be the same model they sell at the LGS. Only one I've held was a 1:9

[T2C]

Must not be the same model they sell at the LGS. Only one I've held was a 1:9

They were touting the 1:7 twist barrel at the time. The sales rep claimed the 1:7 carbine could hold 1 MOA with 55g FMJ ammunition.

[NQNPIII]

They were touting the 1:7 twist barrel at the time. The sales rep claimed the 1:7 carbine could hold 1 MOA with 55g FMJ ammunition.

Oooooops! MY brother is with FHP. He used his personal DPMS Panther for a duty carbine until they got issued piston operated Sigs. He like the Sig, says it's nose heavy.

AFAIK the M&P have MIM parts in their FCG's. It was a really smooth trigger for the price back then. Last I saw was $899 at KYGUNCO. Stupid price.

[davidjinks]

Sorry I didn’t answer you sooner. Give me some time and I’ll pull up some of the testing.

At the end of the day, the 1:7 was chosen due to the tracers that were being used.

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.

[T2C]

Sorry I didn’t answer you sooner. Give me some time and I’ll pull up some of the testing.

At the end of the day, the 1:7 was chosen due to the tracers that were being used.

That was my understanding. The slower twist rate barrels would not stabilize the tracer rounds?

Did shooting in arctic cold conditions have something do to with the choice in 1:7 barrel twist rate as well?

[mark5pt56]

That was my understanding. The slower twist rate barrels would not stabilize the tracer rounds?

Did shooting in arctic cold conditions have something do to with the choice in 1:7 barrel twist rate as well?

That was the 1n12 from the 1n14 in arctic conditions.