The x300 Ultra is the x300u
Being that you drew a distinction between x300 and x300 Ultra, and your description indicated the former is better, I was hoping to be able to find it online, but could not. If you have a link that would be great.
Possibly. Every rifle is a law unto itself. You won't know until you actually shoot the ammo. Some are comfortable with a POI within 2 inches inside 50 yards between two types of ammo acceptable. That doesn't work for me. I don't want to have to remember what the different POIs are between practice and defense ammo.
As you note, I won't know for sure until I try both. Being that I bought this gun for home defense, and the furthest distance with a line of sight inside my house is 50 feet, I guess I care whether the point of aim matches at 25 yards. If it turns that there is a substantial difference, more than 1/4" or so, I will probably sell the Remington and buy the Winchester they are now offering after having sold out the Remington, if there is any left by then. Based on the advice of other folks in the thread prior to your arrival, I went with the same weight for practice and SD expressly to avoid a difference in point of aim. But real life is what counts.
There is always humidity in the air, even in the driest desert. (The photo showing 1% relative humidity means the measuring device needs to be re-calibrated. People would know if the humidity was that extreme.)
For the record, weather.com is running 6 to 8%. I assumed the difference was location since their sensors are not in my backyard, but even 6 to 8% is extremely low. This has likely been a major contributor to the fires raging in Arizona now.
Bad ammo will teach you how to deal with malfunctions but can lead to a bullet stuck in the bore. Just trying to save you some grief. Use what you've got for practice and replace it with better ammo.
I'll see how it goes. I hope it doesn't happen, but I suppose removing a stuck bullet is also a good thing to know how to do, and certainly better to learn at the range than in a Situation.
I didn't buy the Remington because I thought it's great ammo or something, I bought it because it was the only .223 FMJ I could find from a recognized American company. I'm not married to it.
In view of your comments about it, I went looking for reviews.
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BassPro has 22 reviews, overall rating 4, all but one of the negative comments were people complaining of fewer than 300 rounds in the bucket, probably an equal number posted that their buckets were over. Only one comment complained about the ammo per se, and it was from two years ago, it said velocity varied a lot and in the poster's opinion the ammo is not very accurate.
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TargetSportsUSA has 88 reviews, overall rating 5, of which 74 are 5-star, 13 4-star, 1 3-star. I looked at the first 7 pages, only the one 3-star review complains about the performance, here it is:
I try many brands and usually look for thr magical mix between inexpensive and good range ammo. While generally happy with remmington this bucket sticks and jams where others dont. It only happens to me with these.
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Bud's has 6 reviews, overall rating 5. Feeding highly praised in two of them.
Get out & have fun with your new AR and let us know how it shoots!
Thanks.