Ammo reliability criteria for home defense AR

[Medusa]

My search fu might need, to borrow the phrase of a well known poster here, to train at a better dojo. So I apologize if I missed threads on this. Links are welcome.

when selecting home defense ammo for an AR, how many rounds do you experienced folks run through the weapon, typically, before calling it acceptably reliable? Usually on a handgun I’ll run at least 200 rounds to be sure, and I could certainly do this on my carbine - just, rounds off Doc’s list are not inexpensive. I’ll gladly make the investment as required, because unreliability at need is the most expensive. But still, I thought I’d ask If the threshold is typically lower, higher, or the same in terms of figuring out what can be relied on. Thank you, as always.

[GJM]

My search fu might need, to borrow the phrase of a well known poster here, to train at a better dojo. So I apologize if I missed threads on this. Links are welcome.

when selecting home defense ammo for an AR, how many rounds do you experienced folks run through the weapon, typically, before calling it acceptably reliable? Usually on a handgun I’ll run at least 200 rounds to be sure, and I could certainly do this on my carbine - just, rounds off Doc’s list are not inexpensive. I’ll gladly make the investment as required, because unreliability at need is the most expensive. But still, I thought I’d ask If the threshold is typically lower, higher, or the same in terms of figuring out what can be relied on. Thank you, as always.

What carbine, what magazines, what ammo?

[Medusa]

Bcm 14.5 elw, pin and weld to 16.1, adm lower.

ammo...well, that’s tbd. I was leaning toward the gold dot 75 gr soft point, but I’m not married to anything right now. I feel like in general I know how to test handgun self defense ammo for reliability, so the question by its nature is not, how do I test ammo x for reliability [eta] or how do i test specific carbine made by _ but just how many rounds generally do you need to see function reliably before you consider any specific ammo to be gtg in your [ar carbine] weapon.

mags are mk2 pmag and hybrid lancers, 20s and 30s. Would expect to have two 30s ready to go when I select an ammo.

[ST911]

Simplest: Shoot a basic load (or 2) of whatever ammo you've chosen through some well used magazines in your hot, dirty gun. That will be a good indication.

[GJM]

Some carbines have issues with soft points.

For a high quality carbine like you have, for utmost reliability, I would use GI 20 rounders, or GI 30 rounders with the Magpul follower, loaded down two rounds below capacity. Then I would load Just one round of PMC 55, and see if it locks back. If it does, after 10 or 20 rounds of that, I would next shoot a few magazines as fast as I could. If that is all still good, I would shoot a 20 and 30 round magazine (actually 18 and 28) of your chosen carry load, and if that is working, add some lube and call it good.

This is just my approach, and I am sure there are other more comprehensive vetting methods.

[Nephrology]

Some carbines have issues with soft points.

For a high quality carbine like you have, for utmost reliability, I would use GI 20 rounders, or GI 30 rounders with the Magpul follower, loaded down two rounds below capacity. Then I would load Just one round of PMC 55, and see if it locks back. If it does, after 10 or 20 rounds of that, I would next shoot a few magazines as fast as I could. If that is all still good, I would shoot a 20 and 30 round magazine (actually 18 and 28) of your chosen carry load, and if that is working, add some lube and call it good.

This is just my approach, and I am sure there are other more comprehensive vetting methods.

Remind me, what is the rationale behind downloading mags?

[DpdG]

My experience with GI mags particularly is if loaded to full capacity they are really hard to seat on a closed bolt. It also feels like the feed lips hate life when loading the last round. Pmags and Lancers don’t seem to suffer either problem as much/if at all, but if for no reason than commonality, I download all mags.

Edited to add- I am no expert and wouldn’t argue with anyone else’s preferred method. Honestly I don’t think it really matters too much one way or the other, with the exception of effort to insert on closed bolt.

[Cookie Monster]

Remind me, what is the rationale behind downloading mags?

Because Clint Smith told me so.

I am not a rifle guy but took some rifle classes and decided to minimize needed bandwidth and just to listen to Clint.

[LittleLebowski]

Remind me, what is the rationale behind downloading mags?

There is often a problem with inserting a fully loaded mag on a closed bolt and also, sometimes a fully loaded mag could be dropped and spill rounds. I always download by one.

[Casual Friday]

Remind me, what is the rationale behind downloading mags?

A fully topped off magazine may or may not be easy to seat on a closed bolt. This is both magazine and rifle dependent. My Colt, LMT, and BCM lowers have no issues seating a fully loaded magazine on a closed bolt, which I've confirmed by testing each and every magazine I have in rotation.

My Aero lowers are hit or miss with topped off USGI 30 rounders, but they seat PMAGS and the handful of 20 round USGI mags that I have just fine.

Downloading to 18/28 is a practice that alleviates those concerns and is a good across the board approach if you have lowers/magazines that are iffy.

While not definitive or scientific, if you load to capacity and you can't push the rounds downward in the magazine with your thumb at least 1/8" of an inch or more, you may have problems loading on a closed bolt.