Inner barrels; quality really makes a difference to FPS

[Liam Porter]

So, while experimenting with my guns and inner barrels, trying to get the best set-up I could for my M16, I noticed an unusually high FPS. At first, I thought it was me mis-reading the chrono, or the chrono being silly, so I tried again and got the same FPS. I then dismantled the gun and changed a variety of parts, trying to figure out what was causing it. I did the barrel last, as I thought this would make the smallest difference, it actually made a huge difference.

I'm comparing two barrels of almost equal length (14mm difference) and a 0.02mm diameter difference, a MadBull 6.03x509mm and a PDI 6.05x495mm. Both barrels were cleaned thoroughly before each different set-up. I expected them to have roughly the same FPS, because the PDI one is wider, but better quality, whereas the MadBull one is tighter, but lower quality.

The following FPS readings are averages over 15 shots, done in 5-shot groups, with the guns dismantled (cylinder set, barrel, hop unit, hop rubber, hop nub and all tape removed) every 5 shots to double check the air seal and hopefully remove anomalous results. [FPS values to the nearest 5 FPS.]

The results I got from different set-ups:

L96, with full Laylax cylinder and PDI hop unit, with Teflon tape airseal: MadBull barrel: ~520 FPS, PDI barrel: ~590 FPS.

L96, with full Laylax cylinder and ASPUK hop unit, with Teflon tape airseal: MadBull barrel: ~500 FPS, PDI barrel: ~570 FPS.

L96, with full ASPUK cylinder and PDI hop unit, with Teflon tape airseal: MadBull barrel: ~510 FPS, PDI barrel: ~565 FPS.

L96, with full ASPUK cylinder and ASPUK hop unit, with Teflon tape airseal: MadBull barrel: ~465 FPS, ~520 FPS. [Not sure what happened here, the FPS values are lower than expected when compared to above.]

Hop rubber used: MadBull red, and R-Hop patch.

Hop nub used: small square cut from an eraser.

Hop was set for 0.40g BBs, FPS tested with Excel 0.20g BBs, which were over-hopping like mad.

M16, with Teflon tape airseal: MadBull barrel: 320 FPS, PDI barrel: 365 FPS.

Hop rubber used: MadBull blue, regular (no R-Hop).

Hop nub used: standard G&P.

Hop unit used: standard G&P metal hop unit.

Hop was set for 0.25g BBs, FPS tested with Excel 0.20g BBs.

Highest FPS reading with L96: 601 (first set-up, with PDI barrel), lowest FPS reading with L96: 454 (with last set-up, MadBull barrel).

Highest FPS reading with M16: 368, with the PDI barrel, lowest FPS reading with M16: 313, with MadBull barrel.

 

[M_P]

 

[Ian_Gere]

Thanks for that, Liam.

Any chance we could have the FPS data without rounding up/down? Also could you take a pic of how you do your Teflon tape seal?

Edit to add: Oh wow, if I want a PDI barrel for the SVD I want for my next gun, it'll only cost me £183.92 shipped!

I may as well get 2, just in case, eh!?!

 

[Airsoft-Ed]

I was going to get a PDI barrel for my .338, it was listed as £130.

Thankfully my wallet was saved by it being out of stock.

 

[Liam Porter]

Any chance we could have the FPS data without rounding up/down? Also could you take a pic of how you do your Teflon tape seal?

If you had asked yesterday, I would have said yes. But, I don't have them any more, they were all in a notepad file, and I was going to go back to it today, but my PC turned itself off overnight and it didn't save anything.

I've also lost settings for quite a few programs, which I spent a while changing last night, so annoyed about that too.

I'll get pictures and more results when I get time, which will (hopefully) be Sunday.

 

[Ian_Gere]

Cheers Liam.

@Ed: lol let your wallet tremble as much as mine then... that price I quoted is from crw

 

[Liam Porter]

Those prices are pretty high, you can get them straight from PDI for less than that. Dearest is 10,605 Yen, which is just under £70, plus delivery, VAT and taxes, but still cheaper than above.