How does Law Enforcement manage to get by with M&P15s?

[shadowspirit]

Supposedly the brunt of the cost comes from the Troy Flip Up Battle Sight and Quad-Rail, which is completely absurd, if you ask me, but then again, I bought it for $546 as a police trade-in, so I paid a mere fraction of the MSRP for a gun with nothing more than light external wear, inside it was literally Like New, probably spent most of its life in a Cruiser.

Don't ask me why S&W didn't spring for a 4150CMV 1/7 Barrel, especially when they were using them for other models. Either way, police bought them, and they remain in their LE Catalog to this very day, so evidently they're popular with police.

I'm guessing that police are of similar mindset to lysander, that the materials are sufficient for the task and S&W offers them some outstanding deals on purchasing a bundle of M&P9 Pistols with M&P15 Rifles which presumably places them beneath the cost of Colt.

As for the 1/7 twist barrel, isn't 1/9 better for bullet weights up to a certain weight all other things being equal?

[lysander]

This area had been beefed up at least four times* over the life of the M16/M4)

Top to bottom: Original design with pin; Revision B to the forging drawing, 26 May 1971, however there were a lot of forgings in stock, so it took a while for this to get into production (this change also increased the radius under the pivot lugs from R .125 to R .500); current forging design.

Regarding the A2 barrel doing nothing to prevent bending, I think I said essentially the same thing.

As for drop tests, I'm referring to drop tests of CAR-15 rifles vs. other rifles done in the 70s. When an AR carbine eventually breaks, that is where the break will happen.

Not being argumentative, just expounding.

I am always interested in learning. Any addition information on where I might find details of these tests? Author, title, date?

[1168]

This is a subject for a different thread but many are curious if Colts currently made are as good as ones in the past. Some things are different like more outsourcing if I'm not mistaken but no one has any concrete knowledge or evidence whether Colt quality has gone down.

This comes up a lot here. Colt has been outsourcing most of the gun for a long time. As far as I can tell, a 6920 is still a 6920. I have 2 newer ones, and have encountered others, like the one that one of my weekly shooting buddies has as a sole AR.

As for the 1/7 twist barrel, isn't 1/9 better for bullet weights up to a certain weight all other things being equal?

I’m unconvinced.

[T2C]

As for the 1/7 twist barrel, isn't 1/9 better for bullet weights up to a certain weight all other things being equal?

Our agency decided 1:9 twist was better overall. We had 400 M-16 rifles on loan from the Department of the Army and had to choose a twist rate on the new carbines that was compatible with the M-16 when it comes to ammunition selection.

My issued AR-15 carbine, with 1:9 twist barrel, would consistently shoot sub 1-1/2 MOA groups at 300 yards. Most rank-and-file LEO will rarely, if ever, engage a suspect at or beyond that distance.

[Hank6046]

As for the 1/7 twist barrel, isn't 1/9 better for bullet weights up to a certain weight all other things being equal?

Theoretically, yes. Practical application, not really.

[Echo40]

As for the 1/7 twist barrel, isn't 1/9 better for bullet weights up to a certain weight all other things being equal?

Supposedly it's better for lightweight bullets, but I've seen the argument go round and round with nobody every being able to successfully prove that 1/9 is "better" nor that 1/7 is "just as good" at shooting lightweight bullets because when groups are compared the difference — if any — is so minor that it can be argued that the results aren't quantifiable.

I'd be willing to be bold and say that 1/9 is optimal for 55gr-62gr bullets, but I really can't back that up, and I'd honestly just be arguing for the sake of justifying the usage of 1/9 twist barrels for civilian-grade/entry level ARs, under the presumption that manufacturers do so operating under the supposition that the target demographic is mostly going to be shooting 55gr .223 bulk pack ammo.

[shadowspirit]

Our agency decided 1:9 twist was better overall. We had 400 M-16 rifles on loan from the Department of the Army and had to choose a twist rate on the new carbines that was compatible with the M-16 when it comes to ammunition selection.

My issued AR-15 carbine, with 1:9 twist barrel, would consistently shoot sub 1-1/2 MOA groups at 300 yards. Most rank-and-file LEO will rarely, if ever, engage a suspect at or beyond that distance.

Federal, state, or local agency?

[shadowspirit]

Theoretically, yes. Practical application, not really.

Supposedly it's better for lightweight bullets, but I've seen the argument go round and round with nobody every being able to successfully prove that 1/9 is "better" nor that 1/7 is "just as good" at shooting lightweight bullets because when groups are compared the difference — if any — is so minor that it can be argued that the results aren't quantifiable.

I'd be willing to be bold and say that 1/9 is optimal for 55gr-62gr bullets, but I really can't back that up, and I'd honestly just be arguing for the sake of justifying the usage of 1/9 twist barrels for civilian-grade/entry level ARs, under the presumption that manufacturers do so operating under the supposition that the target demographic is mostly going to be shooting 55gr .223 bulk pack ammo.

About groups compared between 1/9 and 1/7 twist rates, have they been compared at short range, medium range, and long range to the point the bullet is near going transonic?

Yes about the presumption of 1/9 twists because people will be shooting 55gr ammo. I have to also wonder if people with 1/7 twist rifles also shoot 55gr the vast majority of the time as well.

[Hank6046]

About groups compared between 1/9 and 1/7 twist rates, have they been compared at short range, medium range, and long range to the point the bullet is near going transonic?

Yes about the presumption of 1/9 twists because people will be shooting 55gr ammo. I have to also wonder if people with 1/7 twist rifles also shoot 55gr the vast majority of the time as well.

Yes, I shoot 55gr through my 1/7 and 1/8 twist barrels the majority of the time for training, but all my defense rounds are 62, 69 and 77gr and because I have thousands of rounds of defensive rounds I want to ensure that they are properly stabilized. I also dont know of decent barrel manufacturers that make a 1/9 as opposed to several that make a 1/8 or 1/7

[SteyrAUG]

Top to bottom: Original design with pin; Revision B to the forging drawing, 26 May 1971, however there were a lot of forgings in stock, so it took a while for this to get into production (this change also increased the radius under the pivot lugs from R .125 to R .500); current forging design.




Not being argumentative, just expounding.

I am always interested in learning. Any addition information on where I might find details of these tests? Author, title, date?

So the drop tests stuff I read was specific to carbines only. If memory serves they were done by Malaysia which is why the HK33 got picked over the CAR 15. Full buttstock rifles really don't have the same vulnerability.

Also it was the actual buffer tube that was breaking, not the rear of the receiver. If I wasn't completely clear about that earlier, that would be the misunderstanding.