why would different brand rounds make that much of a difference to your gun ? I dont own a 22 rifle btw, just curious
Hi Archie, welcome to the forum!
Different manufacturers produce their ammunition to varying specifications, with each generally offering at least a few different types of round in the same caliber. For instance, rounds may have different propellant loads and weights of bullets, which affects primarily the velocity and energy of the projectile. In addition to the ballistics of the rounds, blowback and gas-driven firearms tend to cycle differently depending on these factors also — e.g. some semi-automatic firearms will cycle poorly and produce more malfunctions on low-velocity subsonic rounds than with more powerful high-velocity rounds, due to the difference in energy imparted onto the action.
Other variations include the type of bullet contained in the round, e.g. plain round nose, hollow-point, jacketed, etc.
Another consideration is the tolerances involved in machining these rounds — while two rounds are the same on paper, manufacturing tolerances may produce actual differences between them.
These tolerances and small variations are such that two "identical" boxes of ammunition, from the same manufacturer and of the same product line — for example, two boxes of CCI Standard, both loaded with a 40gr Round Nose Head and with a nominal velocity of 1070 FPS — may perform differently in the same rifle.
This leads on to 'batch testing' — many shooters are well aware of these variations between different batches of ammunition. For this reason, there are events in which you can take your rifle to a range and have different rounds from different batches shot through your rifle to find which performs most accurately — with the aim of obtaining a stock of ammunition up to that allowed by your license conditions that will provide you with the most accuracy.
One thing that I have heard, although I've never verified it, is that manufacturers tend to produce their high-end ammunition on machinery with new tooling, and as tooling wears down (resulting in higher tolerances and more variation between rounds produced), they then use it to produce their lower-grade lines — i.e. the best and brand new tooling is used to produce the most accurate (and expensive!) rounds with the tightest tolerances.
Feel free to ask any questions you like — I'll try my best to answer them!