For barrel diameter, I have yet to try 5.98, but I've tried many 6.01s, a number of 6.03s, a couple 6.04s, and many other of the wider bores, including a 6.21 that I made.
From my tests, the trajectory of the 6.21 was very weird as it seemed like the BB was dropping sooner, and when I adjusted the hop to flat it would still not shoot as far.
This was with the same bucking, BBs, and Joules as the other barrel I was using in that gun at the time, so the only variable was the barrel.
For everything else, it all seems fine, but I've not done much with 6.08 or 6.12 so I won't say anything decisive about them.
I think that where
@Cripplegunner 's coming from is somewhat true, but only in 2 circumstances.
Number one is that you are getting sand or other large bits of matter in your barrel, and they are bumping the BB, or your BBs are reused/incredibly poor quality. The last one is less of a thing as BBs have gotten much much better in the past 5 years since I've been playing, with them apparently being very very bad like 15 years ago.
The second case where a 6.01 would be less accurate is because it has high spots.
A barrel with high spots (all but EdGi) will be not as accurate as it could be as there is not a smooth stream of air surrounding the BB, it is getting interrupted and is uneven at times, causing side and up/down hop unpredictably.
Or worse, the BBs are actually physically contacting the inside of the barrel and having the same thing happen, but worse.
Number one is because of the Bernoulli principle I think, and number two is just like having lots of Hopups or maybe little ricochets inside your barrel.
This will be worse with a 6.01 compared to a 6.08 if they have the same bore quality as there is more of a buffer zone around the BB, but this is only if the bore has a poor surface finish.
This is where high quality barrels or lapping come into play, as high quality barrels will have zero high spots and be 100% smooth, and lapping will wear down those high spots and make most any barrel just as smooth as an EdGi or better depending on your skills and lap type.
So to sum it up, tight bores MAY be less accurate than a larger bore, until they are all perfectly smooth, in which case they will be the same in terms of accuracy, and you would hopefully pick the tightest one so you could use a weaker spring or less gas, and run your system at a lower stress level, and maybe even reduce sound or boost accuracy through less vibrations and waves.
@kociec I haven't done any paper groupings past 40m, I shoot at steel plates past then, but I'd estimate about or better than 40cm at 70m with perfect conditions, to be conservative. I may be able to do better, but I don't want to overestimate lol.
I am currently in between guns at the moment, as I am trying to part out and sell a sniper I completely made, and I am in the process of transferring the Polarstar F2 in my M4 to a new body I have that is nearly ready, so that isn't quite ready yet.
My M4 is in gaming condition but I would not like to share it's results, as it has a couple errors of my own that are partially the reason I am making my own version of the Wolverine MTW to replace it.
In a couple months when I have traded some stuff for an outer barrel and have made a Hopup chamber that I feel is to the best of my abilities, I will gladly share shot groupings from that, and later on my second homemade sniper I will try and do the same as well.