Maverick transfer port question

[Patrick1]

I have a .22 Maverick Compact(500mm barrel with dual transfer ports). Recently was at the range shooting with the pellet side down,(small hole). I decided to see what the difference would be in velocity if I went to the larger port. Simple to do, loosen 1 screw (and remove the cheek piece first) flip over the slotted barrel/transfer port and ......surprise!

I had been shooting 15.89 JSB's at 880fps but after "opening up" the port to larger size, speed went way down to 742 avg. No other changes. Did I just need higher reg pressure for the larger port? Also, it was shooting way left(6 mil at 25 yards) and high after the change. Went back to the old port settings, no re-zero and everything was absolutely fine.

Confused and surprised! Can anyone explain what happened?

Settings were-

1st reg-105

2nd reg-75

Power wheel-7

IHS-3 turns

 

[Solo1]

can’t say for sure about the port but would assume you might need higher 2nd reg pressure. my set up is for higher pressure with a 25 hammer. As far as it hitting left your barrel is indexed for 9&3 o’clock if you turn it 1/4 turn it will probably index at 12&6.

 

[jps2486]

Jack up the hammer spring!

 

[2L8]

Patrick, keep us posted on your discoveries.

Your reg pressure is not high enough to compensate for your change over to the Dual-port side (take note). Decide what you would like to shoot your 15.89 (880fps) and do as @jps2486 (Paul) said. Set your HS grub to 6mm+-, and then shoot and adjust your 2nd reg up 5bar at a time to your desired speed (880fps). Then, add 20% to your reg pressure ( example,100+ 20%=120) De-tune from this +20% point using your hammer spring and "micro adjustment" bringing it back to your desired shooting speed (880fps).

Have fun and shoot straight,

Patrick

 

[MrGain]

Hey Patrick!

I was having the same experience on an m3 compact, and have been geeking out about it ever since. Havent had this much fun learning about stuff since I took my first motorbike apart. 

So, I think there's two things going on here, and hopefully one of the pros will correct me if I'm wrong. The Slug position being more open facilitates a faster flow of air up behind a slug, but with less metal in the way there's a bigger space that the burst of air has to fill, so when you rotate the barrel from the pellet position to slugs, your tune either needs more hammer to release more oomph, or increasing 2nd reg pressure so more oomph is released on the current hammer setting. 


The POI change when rotating the barrel 180 degrees is something else entirely that I read about on here (thankfully, because it was doing my nut in).

I had the same issue, tried polishing the barrel and the results were so random. Then I read about barrel indexing. Oh. Joy. Another variable. Using a marker pen, put a line on the jam nut to indicate 12.00, and also mark the barrel liner at the crown for the same position. By rotating the liner 'an hour' at a time in relation to the tightened jam nut at 12.00 o'clock, you'll see that POI rotate around in a circle and should be able to find the point where it doesn't shift left or right much when swapping between s and p positions. For me, I was able to get my scope back to optical centre because i wasn't having the dial massively left to compensate for the barrel pointing off to the right.

Ok, if that's not right, forum experts can tell me to sit the corner and re-read 'from trigger to barrel'.

 

[Patrick1]

Thanks for all your suggestions! I also asked Utah Airguns, where I got my Maverick, and they said similar stuff. I hadn't thought of the barrel indexing issue so I'll try that! my brain was telling me that "bigger port means more air passage" but I wasn't thinking about how the hammer spring affected this, too. Apparently,Per UA, the bigger port also can make the pellets go "anywhere".

Any other thoughts? They will help my learning process. I really appreciate this forums help!!!

Pat

 

[tor47]

Basically you should use the pellet side of the transfer port. It is only on high power scenarios like when shooting heavy slugs you will get benefits from using the slug port. If you retune the gun with the slug port, with the same pellet and power, you will probably loose some efficiency, and get less shots out of a fill.

 

[2L8]

Basically you should use the pellet side of the transfer port. It is only on high power scenarios like when shooting heavy slugs you will get benefits from using the slug port. If you retune the gun with the slug port, with the same pellet and power, you will probably loose some efficiency, and get less shots out of a fill.

@tor47 has a good point and worth experimenting with. You might be able to find the "sweet spot" for your 18.13's with the "P" side transfer port. Play with it following your own strict tuning guidelines.

Patrick