Improving T4-18 accuracy

BrightCandle

BrightCandle

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I have a T4-18 and I am pretty unhappy with the range and accuracy. At 30m the spread of fire is at least 3 feet horizontally and more vertically. I really can't get any more range out of it, the rounds drop off shortly after that. Since getting the gun FPS has dropped from 315 to 290 and I can literally see the inconsistency in the hop being applied to each round, its taking a lot of overhop to reach that far at all and accuracy is impacted as its impossible to zero the gun properly due to the high flight path BBs take at that range, I am using a substantial hold to be able to fire at all. Online accuracy tests with my gun reviewed and others seem to suggest mine is not achieving what you would expect, groupings down to the inches at 30m would be a dramatic improvement. I can't hit a human in the open at 30m at all, so I am fairly certain the gun is not functioning as it should.

From tests I have done indoors at 10m my accuracy has dropped off. Initially I could get 1 inch groupings, now its more like 4 inches at the same range as before. Chronograph tests show a fairly stable FPS, its not varying by more than about 5fps across 10 shots, so I think the air seal is consistent but I would have to void the warranty to do an airseal test on the cylinder/piston/head.

I have a couple of thoughts about how to go from here:

1) Just get a different gun and sell the T418 CQC. One thing I keep seeing on forums is that accuracy tends to be best around 450mm inner barrel length, below that there is a reduction (how much I don't know) and past that it can have no benefit or even be a bit worse. Thus I would likely replace it with a more standard M4 instead of the CQC model I have now which is only 350mm.

2) Replace the hop bucking, replace the spring to restore power (site is 350 fps so 110 spring) and potentially upgrade the barrel. Void my warranty and try and get the gun to function better with upgrade parts. If the air seal turns out to be an issue then do cylinder head (Double O ring), piston head and fit a nozzle replacement and get that air seal behaving as it should. Would have to keep the cylinder do to the EBB.

3) Should this sort of problem be covered by the warranty and hence I should just send it back for repair?

4) All of (2) + a new inner barrel. The G&G top techs are meant to have 6.03 tightbore barrels already, so I am wondering if I should get a higher quality 6.03 like a Prometheus or PQI and whether that will be a decent improvement. Will replacing the bucking help as well? I am certainly considering trying a G hop since its relatively simple to do and the current hop looks like its terribly inconsistent.

I don't really know what to do with my lemon gun, my opponents have more range and better accuracy in these moderate range engagements and I am loosing engagements I ought to win if the gun was more accurate. I am typically using 0.25g Blaster BBs if that makes any difference here (ie decent quality somewhat heavier BBs although I have bought some 0.28g Blaster Devils to try as well).

Thoughts?

 
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your grouping at 30m should be dinner plate sized at most, there's definitely something going on.

you say the FPS is between 290 and 315, does it jump about in that range between shots or is that just from 2 separate occasions at a chrono? if it's not consistently shooting with a 5-10fps variance or less you've most likely got an air seal issue somewhere.

I'd also recommend having a good look at your hop rubber, a worn or ripped (even the tiniest amount) rubber can cause huge accuracy issues.

Cleaning the barrel is of course a standard maintenance thing, I expect you've already done it, if not, give it a go, it'll help.

However, if the gun's still in-warranty, call the retailer and ask them what to do about it. Most likely they'll say that guns deteriorate over time and that it's standard wear and tear, depending on how long you've had it and how much you've used it they may be right. They'll almost certainly be able to offer to give it a bit of a tune-up and get it back to new though.

 
BrightCandle said:
I have a couple of thoughts about how to go from here:

1) Just get a different gun and sell the T418 CQC. One thing I keep seeing on forums is that accuracy tends to be best around 450mm inner barrel length, below that there is a reduction (how much I don't know) and past that it can have no benefit or even be a bit worse. Thus I would likely replace it with a more standard M4 instead of the CQC model I have now which is only 350mm.
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Standard M4 inner barrel is only 363mm long.

 
I have one of these and they fire great with groupings at 30m of 8inches mine is firing around 300fps. Alarm bells ring when your fps changes that much then you start having problems. Your guna need to take it out check it over make sure the barell is clean the hop and nub are both there in right place doing there job ect because you should not need to change the G&G barrel and bucking as the ones the top tech come with are amazing. Something has got to of moved inside in the wrong place, i bet its something very minor.

 
It's a consistency thing... Somethings overly worn, or low quality. Air seal can be fixed at home, as can most other issues. I would really suggest a new bucking, then better hop unit first off... The inconsistency in airflow will make a difference to a new hop, but much less than a bad hop will have on a consistant air seal... It's the best part to upgrade for this sort of issue. It also requires very little "tech" work.

Stock barrels are good enough

Stock internals are generally good enough (bad manufacturers not withstanding)

Stock hops... Usually prone to wear and distortion.

It's probably something as simple as a worn bucking...

Or... Send it off to someone to look at... I'm not sure it's a warranty issue... Depends how old the gun is...

To go through your thoughts...

1) I wouldn't sell up for such a small issue. And barrel length will have very little effect on the accuracy in a normal gun (generally speaking). My M4, after work can do head shots at 50m ish and that has a cqb length barrel

2) if your gun is young enough to potentially be in warranty... It's highly unlikely the spring has gone... Your just losing the power you do have... Either through the front or back of your hop. Possibly internally, but unlikely...

3) I'm not sure it's a warranty thing... Check with your supplier.

4) a barrel won't hurt, but it won't fix your accuracy issue... Not by the amount you need to reduce groupings by 3ft at 30m

If I were you, I would do bucking, test, possibly hop chamber... Test... Come back... I would imagine it's just the bucking, though.

 
After yesterday's testing of my T4, reading this sort of sounds familiar except... I set up a target at 30m, like you the BB's were going about 3-4 ft each way. Luckily my friend is in the Cadets and he allowed me to use the indoor firing range (30m tunnels with no draught) I set up a target (A4 piece of paper) and shot about 1000 BB's into it. Concidering it was my first real go with the gun i'd say about two thirds were hitting the paper. Having spoken to my local shop and jay83 i'm going to switch to a .28g for outside use as it's looking like the wind may have been causing the horizontal variation. The other issue I had was with the G&G mid cap mags. They say they hold 120 bb's yet if you put anything over 85 in (Yep I hand counted them) the first 35 are "derping" out of the barrel and are barely reaching 10 meters. When the mag is filled with (Upto) 85 BB's I can full auto the lot without any issues!

 
Snakeeyes75 said:
After yesterday's testing of my T4, reading this sort of sounds familiar except... I set up a target at 30m, like you the BB's were going about 3-4 ft each way. Luckily my friend is in the Cadets and he allowed me to use the indoor firing range (30m tunnels with no draught) I set up a target (A4 piece of paper) and shot about 1000 BB's into it. Concidering it was my first real go with the gun i'd say about two thirds were hitting the paper. Having spoken to my local shop and jay83 i'm going to switch to a .28g for outside use as it's looking like the wind may have been causing the horizontal variation. The other issue I had was with the G&G mid cap mags. They say they hold 120 bb's yet if you put anything over 85 in (Yep I hand counted them) the first 35 are "derping" out of the barrel and are barely reaching 10 meters. When the mag is filled with (Upto) 85 BB's I can full auto the lot without any issues!
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yeah there has been talk of the mags "derping" with the first 35 falling out of the barrel. Personally you could take the mag apart, which is what I would do, but you should probably buy some different mags. PMAGS or MAG mags (according to jay). Defininetely use .25s+, im going to start running .30s when i get my G&P

The wind will of course greatly effect .20s however .28s are much more reliable in terms of wind and accuracy.

As for the OP, if it was me I would talk to NH shooter (i know hes posted here and you probably already have) and maybe get him to have a look of you don't think it is air seal or the hop up.

 
team flex said:
yeah there has been talk of the mags "derping" with the first 35 falling out of the barrel. Personally you could take the mag apart, which is what I would do, but you should probably buy some different mags. PMAGS or MAG mags (according to jay). Defininetely use .25s+, im going to start running .30s when i get my G&P

The wind will of course greatly effect .20s however .28s are much more reliable in terms of wind and accuracy.

As for the OP, if it was me I would talk to NH shooter (i know hes posted here and you probably already have) and maybe get him to have a look of you don't think it is air seal or the hop up.
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Plenty of mags need a bit of breaking in before they reach their full potential. This could very easily be the case here. A small amount of silicone oil down the feed tube followed by successive loading and reloading (NOT firing through the gun mind, just load the mag then manually release the catch and let the BBs come out into a bag) would very possibly help. Don't use that particular batch of BBs again though as they'll potentially be contaminated with oil.

It's worth trying before you start splashing loads of money on mags you might not need at any rate. The G&G high cap that came with my SCAR for example feeds flawlessly every time.

Also 0.3g BBs aren't really worth trying unless you're planning on running your AEG at over 350FPS. 0.28g are about the highest I would look to go with in a standard AEG to be honest.

 
Lozart said:
It's worth trying before you start splashing loads of money on mags you might not need at any rate. The G&G high cap that came with my SCAR for example feeds flawlessly every time.
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I bought 2 of the G&G mid caps thinking they would be perfect but compaired to a real cheapo one they don't compare! The high cap that came with it, as you say is really good and if I wanted to go down that route i'd consider buying more. I'll try the whole silicone down the feed tube, what i'm noticing is that after the 85th BB you can feel the spring getting much tighter and it seems like that's the point you have to stop. Any more creates the Derp problem :(

 
Snakeeyes75 said:
I bought 2 of the G&G mid caps thinking they would be perfect but compaired to a real cheapo one they don't compare! The high cap that came with it, as you say is really good and if I wanted to go down that route i'd consider buying more. I'll try the whole silicone down the feed tube, what i'm noticing is that after the 85th BB you can feel the spring getting much tighter and it seems like that's the point you have to stop. Any more creates the Derp problem :(
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Have you checked that they haven't just sent you the wrong mag? G&G do both 120rd mid caps AND 79rnd mid caps. That would certainly cause the sort of problems you describe! :)

 
yeah, there shouldn't be any point where you have to start forcing BBs in.

 
Snakeeyes75 said:
Hmm, Maybe I just have a couple of duff mags? As you reach maximum capacity should you feel more resistance than say the first 2 thirds of the mag?
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You may have a couple of duff ones, it's possible. Yes you'll feel more resistance as you fill the mag (you're compressing a spring after all) but you shouldn't feel like you're forcing the BBs in.

 
They probably just sell them as a higher capacity mag than they actually are.

 
I just had a bit of a google for reviews on these mags and most people think they're amazing and have no issues BUT I did find this on a customer review on Amazon.com:

BUT, loading it up with a speed loader is a lot tougher than other mid-caps and can't be done on the fly in battle like I hoped. You have to push down on the speed loader a lot harder after the first 50 or so bb's. But the trade-off is that it feeds a lot better.
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Lozart said:
You may have a couple of duff ones, it's possible. Yes you'll feel more resistance as you fill the mag (you're compressing a spring after all) but you shouldn't feel like you're forcing the BBs in.
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I've just had a go with a friends cheapo mid cap and the feed was perfect! I felt the resistance whilst loading again about 2 thirds of the way through but no derps which is the main thing. It also fit the magwell much better.

 
You can fix the tight fit. What I did was grind out the spine at the back of the magwell, which isn't there on an M4 magwell. This will loosen up the fitting.

I have messed with the hop and bucking today and found that the bucking isn't coming down straight into the barrel. I fitted a Prometheus purple bucking I have and twisted the barrel until its actually straight so that the hop applies correctly. Will test it out tomorrow to see if that fixes the spread (although hard to tell at 10m) and also test the airseal to see if I need to do anything there as well.

 
In the end I decided while I had the gun open to try a G hop using a prometheus inner and outer bucking. I didn't do anything else with it, I didn't open the gearbox although I do have a replacement 110 spring for it at some point in the future but I want to test each part individually.

I have just done a chrono and FPS is at 305 with .2g blasters. Its not the 315-320 it came out of the box but its also not varying very much at all, the lowest I saw was 303 and the highest was 306, so its really consistent again as well as only a little below its out of the box performance. The groupings on paper at 10m with 0.2g's are down to 1 inch horizontally again, but vertically its less than 1cm. The 0.28g BB drops the grouping further and I am pretty certain I am seeing my limits in those and not the guns, its less than 1cm and its about the sort of groupings I get with a 22 olympic class rifle off the block.

I'll try it out this Saturday at TWA and I'll see how the g hop performs. I am hoping based on this initial accuracy and zeroing in that the gun is now going to shoot a lot more like it ought to and I might finally be impressed with it again. Its funny my other G&G also needed work to its hop up unit as well.

 
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