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Discussion Starter · #121 ·
I know this thread is a little old now but I have an update on the 5.98mm ESC barrel that I put into my Electric Sniper Rifle (ESR)
Originally I was annoyed because the result that I got from the 5.98mm inner barrel was the same energy as the 6.00mm inner. So no advantage to the tighter bore and the extra money that I put into the rifle. I then put the 5.98mm barrel aside and left it for a few months.
The other day I got it out and cleaned it just with a rag, cleaning rod and a drill press for 20 minutes. I then put it in my rifle and as a result, the energy has increase. I am guessing I may have cleaned away an issue that may have been in the rifle.
The original 6.00mm inner barrel was 460mm long. This got 3.3 joules. The 5.98mm barrel I got was longer; 530mm. Since the 5.98mm had a tighter bore it should give more energy efficiency as there is less waisted air.
Anyway, the 6.00mm gave me 3.3 joules and the 5.98mm has given me 3.48 joules. So a little gain over the 6.00mm.
I then stuck in a 6.01mm x 470mm inner barrel to give a comparison to a normal sized tight bore that most people would use. This got 3.2 joules.
So, overall this is the results.
6.01mm x 470mm = 3.2 joules
6.00mm x 460mm = 3.3 joules
5.98mm x 530mm = 3.48 joules

I now am wondering if the 5.98mm barrel could have been a little longer. None of us know how much more efficient these really tight bore barrels are.
So if you are pushing the boundaries and want the most efficient, then try the 5.98mm.
 

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In theory tighter is more efficient but I think it’s SO little that it really won’t be noticeable. I think you gained power soley due to the length. Slap a 6.01 or 6.03 in there thats 530mm and see what happens.

OR, even though the bore may be so little to not see a difference, MAYBE it’s enough to change the cylinder to barrel ratio causing noticeable outputs.
 

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.03mm /.0012 is quite a large gap, and when

For example, your 470X6.01 should be 13.333cc give or take depending on bore quality, how much air space in the hop window around your contact nub, barrel crown, and whatever else, while a 5.98 with that same volume will be a 474.7mm, so a surprisingly large amount of barrel length to have the same volume.
If both barrels were 470mm you'd have a .133cc volume difference, a small but still significant amount.
 

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Between 6.03 and 5.98 there's definitely a power increase. My 5.98 310mm shoots about the same power as my 6.03 363mm. The 5.98 shoots a little less powerful with lightweight bb's buth more powerful with heavier weights. I do think a tighter bore will have some other benefits in aegs and springer guns. A tighter bore will create a pressure spike easier because there's less waste off air around the bb when the piston starts traveling. Also a concave patch will help this because it seals the bb better to create pressure faster. This doesn't really apply with gas guns or HPA since the pressure is instant. Silicone sword made also a good point, there will be air wasted in the barrel window therefore a r hop or something comparable will benefit too in filling that gap making the barrel more efficient.
 

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Discussion Starter · #125 ·
In theory tighter is more efficient but I think it’s SO little that it really won’t be noticeable. I think you gained power soley due to the length. Slap a 6.01 or 6.03 in there thats 530mm and see what happens.
Originally I tried a number of 6.01mm inner barrels from shorter to longer to see what gave the highest energy rate. The best cylinder to barrel ratio for that particular barrel diameter and bb weight was 470mm. So 470mm was the best for 0.48gm in the SR25
I then thought that I would try a 6.00mm. I did want to get a longer inner barrel but could not find one and so I had to settle with the 460mm one. This did gain energy but I do believe that if I went longer it would have given more energy. So I could have tried 500mm or maybe more.
Finally I got the 5.98mm. This was longer because I knew that we had less air loss compared to the bigger diameters. So I got the 530mm. I do wish I had got 600mm and then slowly cut it down and tested it to see what was the best cylinder to barrel ratio.
So overall, it is the length that allows for more energy. But the only reason why I could use the longer inner barrel was because I had less air loss around the bb due to the tighter bore.
 

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So I've been pondering the question of efficiency and would like to present an alternative view on tbb. All figures below are rounded to 2 decimal places as we are already measuring in mm and anything further seems overkill.

Let's take a standard BB diameter of 5.95 and convert it to area is 27.81mm squared.

A tbb 6.01 barrel area is 28.37mm squared.
This means that 0.56mm squared space is available for air to escape around the BB

A tbb 6.03 barrel area is 28.56mm squared.
This leaves an area gap of 0.75mm squared.
Roughly a 1/3 more air is able to escape around the BB.

Now obviously with the tighter bore barrel the fps is higher as the piston uses the pressure more efficiently as less air escapes around causing a higher pressure on the air behind the BB.

It a law of diminishing returns clearly with tbb but I do wonder if we are miss judging how efficient the more Extreme tightbores are. The fact the .02mm equates to such a massive % change in wasted escape air does seem to not correlate to the existing model/understanding of cylinder/barrel ratio.
 
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