Accuracy issue and zero question

[Hamster82]

Hi all,

I’ve been having some issues with my G&G TR16.

It runs reliably and never have feed issues but have recently picked up a flip up magnifier that is letting me see where my shots are hitting at further distances.

At about 50ft with the rif rested (so it’s not me moving the barrel) I’m getting groupings of about a foot!

Using RZR’s and ASG Blasters in .25g and getting the issue with both.

So far I’ve cleaned the barrel and replaced the hop rubber (air seal is all good), any ideas on what to try next?

Also a random question about zero - does changing BB weight affect zero?

I’m likely to be running .25’s and .28’s and trying to work out if I will need to re-zero each time I swap?

Pic for attention 

View attachment 87230

 

[BigStew]

what rubber and nub have you fitted? are you actually measuring the range? is the place where you testing exposed wind could be effecting the spread also stick to one brand of BBs when setting the hop. 

 

[Hamster82]

what rubber and nub have you fitted? are you actually measuring the range? is the place where you testing exposed wind could be effecting the spread also stick to one brand of BBs when setting the hop. 

Maple leaf Macaron 75 with the standard TR16 nub.

range measured when target was set out at 50ft and no wind on day of testing.

with the BB’s I was using the RZR’s for testing (150’ish shots whilst adjusting hop) then swapped to the blasters which had the same issue.

 

[Fatboy40]

Maple leaf Macaron 75

That seems maybe a bit hard for only 0.25's?

All the guns I have, and look after for others, have only 60 degree Macaron's for hopping 0.25 and 0.28, and in my DMR I use a 70 degree MR.

 

[Hamster82]

That seems maybe a bit hard for only 0.25's?

All the guns I have, and look after for others, have only 60 degree Macaron's for hopping 0.25 and 0.28, and in my DMR I use a 70 degree MR.

Do you think a 60 degree would be a better option to help with accuracy?

also will the stock TR16 hop nub be fine alongside or should I be looking at something else?

 

[Fatboy40]

Do you think a 60 degree would be a better option to help with accuracy?

Yes, it will be an improvement (if we're talking an AEG, 350 limit shooting 0.25), however any change may be small (accuracy is all incremental, better inner barrel + appropriate bucking and nub + good hop unit applying consistent pressure + minimal vibration of the guns internals + appropriate BB for the situation + the human beings skill, so that hopefully each and every shot taken is identical).

 

[Tactical Pith Helmet]

Some people swear by a 70deg rubber, but I've never managed to get one to work at sub 350. 

I have used a plain G&G nub with an ML but they seem to work better with the omegas that they are designed for.  

 

[Hamster82]

Some people swear by a 70deg rubber, but I've never managed to get one to work at sub 350. 

I have used a plain G&G nub with an ML but they seem to work better with the omegas that they are designed for.  

Cool I will see if I can get hold of a 60 degree and an Omega, already have a Prommy barrel and been gradually upgrading bits to get up as close to legal limit as I can, currently hovering around 345 but accuracy isn’t quite there yet.

 

[Badgerlicious]

Could be some movement in the hop arm? Some gearbox shims either side of the pin would hold it in place if that is the issue. 

 

[Cyberlawyer]

I'm not seeing a problem here. Assuming you are chronoing at 350fps (on .2g BBs) and are at a true measured 50m. I'd say a 12" group with .25g BBs is actually fairly decent, that's pretty much 100% hit ratio on an A4 sheet of paper at that distance (yes I know A4 is only 12" along the longer edge which is why I said pretty much).

You will improve your grouping by moving up to .3g bbs at the cost of longer flight time (absolute range may also vary).

I think a lot of people under estimate how terrible a ballistic projectile the humble BB is. Remember a 500 fps sniper rifle hurling .4g BBs at 350 fps (approx 500 fps on a .2g BB) is only reaching out to about 80-85m.)

In response to the question on zero it depends on what range you set your zero and how you set your hop (i.e. do you set it to have a trajectory as flat as possible or for a lift at the end to get max range). If you zero to 10m then the path of the BB will be pretty flat whatever weight BB or hop set you use). At 20m you will see a difference, if you set your hop aggressively for max range it could be significant, but if hop is set for a flat flight path it will be quite small. Beyond that yes the zero will change.

 

[Hamster82]

I'm not seeing a problem here. Assuming you are chronoing at 350fps (on .2g BBs) and are at a true measured 50m. I'd say a 12" group with .25g BBs is actually fairly decent, that's pretty much 100% hit ratio on an A4 sheet of paper at that distance (yes I know A4 is only 12" along the longer edge which is why I said pretty much).

You will improve your grouping by moving up to .3g bbs at the cost of longer flight time (absolute range may also vary).

I think a lot of people under estimate how terrible a ballistic projectile the humble BB is. Remember a 500 fps sniper rifle hurling .4g BBs at 350 fps (approx 500 fps on a .2g BB) is only reaching out to about 80-85m.)

In response to the question on zero it depends on what range you set your zero and how you set your hop (i.e. do you set it to have a trajectory as flat as possible or for a lift at the end to get max range). If you zero to 10m then the path of the BB will be pretty flat whatever weight BB or hop set you use). At 20m you will see a difference, if you set your hop aggressively for max range it could be significant, but if hop is set for a flat flight path it will be quite small. Beyond that yes the zero will change.

That may have been my mistake explaining, I’m zeroed at 50 feet (about 15m) as that’s the best I can manage in the garden.

with my play style I tend to engage at 30-50m’ish until up close (happy to let the younger bloods rush ? ) I suspect at that range I’m wanting more than is realistic but 12” groups at 15 meters feels wider than it should be in calm windless conditions - I’d be happy with that at 50m though! ?

Hop is set to be as flat as possible but as I only play once a month or so testing and tweaking at longer ranges is few and far between

 

[Cyberlawyer]

Ah ok sorry I misread 50ft to be 50m. At 15m that is a pretty poor grouping IMHO. Please bear in mind my main airsoft hobby is target shooting and 3 gun stuff so I am more focussed on accuracy than many skirmishers.

First thing is check your power is consistent shot to shot by putting 10-20 bbs in quick succession through the chrono and see if there is a variation. Your nozzle seal might be good on a one off shot, but not quite as good for shots in rapid succession as it gets a bit 'hung up' on the rubber before it fully seats. If this is the problem the solution can be as easy as a thin smear of silicone oil on the nozzle to allow it to reseat easier after each shot.

Then look at your barrel. Is it clean, is the bore smooth (I.e free of defects or corrosion that won't clean out) is it straight and is the muzzle end properly crowned. Most of these are fairly obvious, the crowning one is less so, but the idea is to allow the air behind the bb to escape the barrel in a controlled way so it doesn't create turbulence that will upset the BB. All but the cheapest barrels will be crowned fine from factory, but If you did shorten a barrel its something to look at.

Then look at your hop rubber. Most rubbers will be fine, but check for internal mould lines or other inconsistencies. More importantly check how it fits with your barrel and hop unit. While the seal might be fine, does it all line up without forcing anything or deforming the hop rubber, does the pressure pad sit fully in the hop window without getting bound up. Personally I love Maple Leaf rubbers in my MWS GBBR, but they only really play nice when paired with a crazy jet barrel as they need a bigger hop window than standard, and then I have to take 0.5mm off of the side tab that fits in the hop unit with a razor blade. If I don't do any of these things it will fit and work fine and even deliver good power, but it has a dramatic effect on consistency.

 

[Hamster82]

Ah ok sorry I misread 50ft to be 50m. At 15m that is a pretty poor grouping IMHO. Please bear in mind my main airsoft hobby is target shooting and 3 gun stuff so I am more focussed on accuracy than many skirmishers.

First thing is check your power is consistent shot to shot by putting 10-20 bbs in quick succession through the chrono and see if there is a variation. Your nozzle seal might be good on a one off shot, but not quite as good for shots in rapid succession as it gets a bit 'hung up' on the rubber before it fully seats. If this is the problem the solution can be as easy as a thin smear of silicone oil on the nozzle to allow it to reseat easier after each shot.

Then look at your barrel. Is it clean, is the bore smooth (I.e free of defects or corrosion that won't clean out) is it straight and is the muzzle end properly crowned. Most of these are fairly obvious, the crowning one is less so, but the idea is to allow the air behind the bb to escape the barrel in a controlled way so it doesn't create turbulence that will upset the BB. All but the cheapest barrels will be crowned fine from factory, but If you did shorten a barrel its something to look at.

Then look at your hop rubber. Most rubbers will be fine, but check for internal mould lines or other inconsistencies. More importantly check how it fits with your barrel and hop unit. While the seal might be fine, does it all line up without forcing anything or deforming the hop rubber, does the pressure pad sit fully in the hop window without getting bound up. Personally I love Maple Leaf rubbers in my MWS GBBR, but they only really play nice when paired with a crazy jet barrel as they need a bigger hop window than standard, and then I have to take 0.5mm off of the side tab that fits in the hop unit with a razor blade. If I don't do any of these things it will fit and work fine and even deliver good power, but it has a dramatic effect on consistency.

Cheers for the reply, barrel is clean and shining. It’s a Prometheus 6.03 and no visible defects or issues.

10-20 rapid shots through chrono vary from 344-351 fps - not entirely sure if 7 fps is a range to be concerned about?

Hop rubber seems fine and again no visible defects, it fits snugly and though it does need some gentle persuasion nothing needs forcing and can’t see any deformation whilst manipulating.

that’s about the extent of my tech knowledge but am going to try a maple leaf nub to see if that helps.

By all accounts it should be consistent and accurate as anything and I’ve got a feeling I’m missing something but for the life of me I can’t work it out.

 

[Cyberlawyer]

7 fps is well within the margin of error, so that's not the problem. It sounds like you have covered all of the basics. I might be grasping here but have you done a volumetric calculation between the barrel volume and the cylinder volume? An under volumed cylinder can have a bunch of strange side effects. The ratio between cylinder volume an piston volume is a black art and I'm no expert suffice to day cylinder volume should exceed barrel volume with some margin for error.

Also I did mention it previously, but try .3g BBs some guns just like heavier BBs

 

[Hamster82]

7 fps is well within the margin of error, so that's not the problem. It sounds like you have covered all of the basics. I might be grasping here but have you done a volumetric calculation between the barrel volume and the cylinder volume? An under volumed cylinder can have a bunch of strange side effects. The ratio between cylinder volume an piston volume is a black art and I'm no expert suffice to day cylinder volume should exceed barrel volume with some margin for error.

Also I did mention it previously, but try .3g BBs some guns just like heavier BBs

You can lost me at volumetric calculations! ?

that whole side of things is indeed a dark art to me but I will definitely give some .3’s a try

 

[Cyberlawyer]

Just to correct my previous statement. It should say the ratio between cylinder volume and barrel volume is a black art. However the calculation its self isn't that hard.

Just work out the internal air volume of the barrel and the internal air volume of your cylinder and compare them the cylinder volume should be bigger than the barrel volume

The maths bit is here https://www.omnicalculator.com/math/cylinder-volume just plug the numbers in.

 

[Fatboy40]

I might be grasping here but have you done a volumetric calculation between the barrel volume and the cylinder volume?

You could well be onto something there.

Patrol Base states that this rifle has a 463mm inner barrel, and that's a bloody long inner barrel if the cylinder is just a bog standard 3/4. 

@Hamster82 If you've not personally replaced the cylinder yourself, so already know why type it is, maybe pop off the top of the receiver and take a photo for us to see of the side of the gearbox that shows the hole / cut-out on the side of the cylinder.

 

[Hamster82]

You could well be onto something there.

Patrol Base states that this rifle has a 463mm inner barrel, and that's a bloody long inner barrel if the cylinder is just a bog standard 3/4. 

@Hamster82 If you've not personally replaced the cylinder yourself, so already know why type it is, maybe pop off the top of the receiver and take a photo for us to see of the side of the gearbox that shows the hole / cut-out on the side of the cylinder.

Not sure if these will help and the barrel is a 460mm prommy 6.03

just about to the maple leaf 60 and omega nub.

View attachment 87343View attachment 87344

 

[HutchBelfast]

You could well be onto something there.

Patrol Base states that this rifle has a 463mm inner barrel, and that's a bloody long inner barrel if the cylinder is just a bog standard 3/4. 

@Hamster82 If you've not personally replaced the cylinder yourself, so already know why type it is, maybe pop off the top of the receiver and take a photo for us to see of the side of the gearbox that shows the hole / cut-out on the side of the cylinder.

I'd physically measure your barrel length if I were you. My JG M16A1 was meant to come with barrel at whatever length but when measured it was shorter by about 50mm.

Still though, the piston that came standard in the gun had a hole but supposedly for the length (and new longer barrel I installed) you want a full cylinder - no holes.

 

[Fatboy40]

Not sure if these will help

They do, thank you, however that black plate / mock bolt on the right side of the gearbox is hiding the other side of the cylinder so we can't see what sort of hole it has ?