HW99 Accuracy Issues after New Barrel

[Jimbob 2705]

Bought myself a brand new HW99 .22 and swapped the barrel over as soon as I got it, as I was stripping to fit TBT Guides and sort the galling issues out, it made sense to do it all at the same time.

It was a brand new HW50 barrel from Germany, the reason for purchasing it was I was after a shorter, threaded barrel without the open sights, and this was cheaper and quicker than faffing about with the original barrel.

I am however having difficulty getting any sort of groups at 25 yards.

I’ve tried AA Fields, JSB Exact Express, H&N FTT and RWS Superdomes, all of which won’t give me consistent groups, and you’re talking about 1.5-2” 5 shot groups, which at 25 yards I’d expect far better.

It’s not me (I’ve got my TX200 next to me which is shooting spot on), and it’s not the scope (I swapped the TX one over and still the same). I’ve cleaned the barrel and releaded it but no change.

Obvious thing to do next is to put the original barrel on and shoot it with that and see how I get on, but curiously I pushed a pellet through both barrels and found that the HW99 barrel leaves twice the amount of rifling marks on the pellet compared to the 50 barrel - bizarre! Looking down the barrel afterwards you could see that the 99 has twice the amount of rifling in it.

https://flic.kr/p/LK1tjh

Would you expect this to be normal? I assume it could be due to different barrel lengths or similar, but just curious.

The 50 barrel also doesn’t seem to leave as deep rifling marks as the 99, and when it comes to loading there isn’t much resistance when putting the pellet in the barrel (if any), but I assume when fired the pellet will expand so guess this isn’t too much of an issue.

Also, may be worth mentioning the rifle shoots about 10.2-10.4 with all the pellets besides the Superdomes which are up at 11.9ft/lb! I’m guessing this is down to pellet fit, but seems a huge jump when the Express and FTT’s are a very similar weight?

Many Thanks

[Hsing-ee]

The 50 barrel also doesn’t seem to leave as deep rifling marks as the 99, and when it comes to loading there isn’t much resistance when putting the pellet in the barrel (if any), but I assume when fired the pellet will expand so guess this isn’t too much of an issue.

Many Thanks

I would say have a look at the crown of the barrel and make sure there is nothing awry there. Are you using a silencer?

However, all barrels should give SOME resistance on pushing a pellet in, even those with throats, it's possible yours is a duff over-size barrel. The rifling marks look exceptionally shallow. Is it too late to send it back and have it swapped? The only other thing is to test it with some 5.6mm pellets like Defiants and see if they do any better.

Very frustrating problem.

[TonyL]

I wonder if the '50 barrel isn't choked?

You would usually expect the Superdomes to yield the least energy output figures of the pellets mentioned. Jim Tyler's fine work has shown us that the pellet release pressure required for Superdomes would usually be higher and also yield less energy, so very possibly the above observation of it being a very slack barrel is spot on, the slacker barrel reducing the required pressure of the 'Domes, helping them achieve the higher power?

[bighit]

I wonder if the '50 barrel isn't choked?

You would usually expect the Superdomes to yield the least energy output figures of the pellets mentioned. Jim Tyler's fine work has shown us that the pellet release pressure required for Superdomes would usually be higher and also yield less energy, so very possibly the above observation of it being a very slack barrel is spot on, the slacker barrel reducing the required pressure of the 'Domes, helping them achieve the higher power?

A choke makes no difference (according to some on here anyway) Plenty of posts on here about it Tony . Lets not start another bun fight about chokes

[mrto]

I have an HW80 that came with a screwcut barrel that in the process had lost its choke,the barrel was completely useless accuracy-wise as a result and was binned.

[dayglowfroggy]

Were the ftt 5.53 i find them really tight pellets seem to work well in my hw 's and even in old mk2 airsporter.

Since you have had the barrel off it could be a problem with the tightness of the barrel lock up pin some hw are really fussy about that also it might be a one shim barrel or a three shim barrel .

I have an 80 that is a one shim barrel.

My money would be on a knick in the piston seal .

[Jimbob 2705]

I would say have a look at the crown of the barrel and make sure there is nothing awry there. Are you using a silencer?

However, all barrels should give SOME resistance on pushing a pellet in, even those with throats, it's possible yours is a duff over-size barrel. The rifling marks look exceptionally shallow. Is it too late to send it back and have it swapped? The only other thing is to test it with some 5.6mm pellets like Defiants and see if they do any better.

Very frustrating problem.

Thanks Hsing-ee. No I've only had it a week so I'm going to get in touch with them, just the hassle of possibly having to post it back to Germany and all the funs and games of that.

Yes I tried with 2 different silencers, and without - just to rule out the possibility of clipping. Unfortunately it didn't make any difference.

When pushing a pellet through with the rod there was very little resistance, but the shallow rifling marks on the pellet show that as you said.

I wonder if the '50 barrel isn't choked?

There is resistance at the last couple of inches on the barrel, so I assume this is the choke, although it is very loosely choked I would guess, well certainly compared to the 99 barrel.

I have an HW80 that came with a screwcut barrel that in the process had lost its choke,the barrel was completely useless accuracy-wise as a result and was binned.

I was hoping that with a factory screwcut barrel it should still be choked, or whatever is required to get the best accuracy.

Were the ftt 5.53 i find them really tight pellets seem to work well in my hw 's and even in old mk2 airsporter.

Since you have had the barrel off it could be a problem with the tightness of the barrel lock up pin some hw are really fussy about that also it might be a one shim barrel or a three shim barrel .

I have an 80 that is a one shim barrel.

My money would be on a knick in the piston seal.

FTT's were 5.52, I can always I could always try different tightness on the lock up screw, but it's nice and tight and fitted with two shims - basically as it should be as factory.

Piston seal is 100%, I had the piston out to polish and fit TBT guides.

[Shed tuner]

the big power jump with superdomes, which are a larger pellet diameter, also points to a large barrel bore. 5.53 H&Ns and vintage defiants are definitely worth a go, but i suspect the barrel is not as it should be...

[Hsing-ee]

the big power jump with superdomes, which are a larger pellet diameter, also points to a large barrel bore. 5.53 H&Ns and vintage defiants are definitely worth a go, but i suspect the barrel is not as it should be...

The Hole

Is

Too Big

[Jimbob 2705]

I’ll see if I can get hold of some FTT’s in 5.53 to give them a try,

I’ve also dropped the German Supplier an email to see if they will exchange it, so I’ll see how I get on down that route.

Thanks again all

[bill57]

I have a recently purchased .22 HW80 barrel with six groove rifling. The pellet is reasonably tight in the breech but when you push it through the barrel it feels quite loose in the middle before tightening up a bit at the muzzle. I haven't used it enough to decide fully, but I'm not convinced it's going to be that great. The gun is in bits at the moment.

I'm curious to try a 5.6mm pellet through it, though the breech might just be to tight, we'll see.

[Shed tuner]

I have a recently purchased .22 HW80 barrel with six groove rifling. The pellet is reasonably tight in the breech but when you push it through the barrel it feels quite loose in the middle before tightening up a bit at the muzzle. I haven't used it enough to decide fully, but I'm not convinced it's going to be that great. The gun is in bits at the moment.

I'm curious to try a 5.6mm pellet through it, though the breech might just be to tight, we'll see.

you could try polishing out the breech end a bit, that should help nicely... quite a few HW barrels are tight about 3" from the breech... possibly assocaited with the process of swaging the barrels into the blocks..

[Jimbob 2705]

I have a recently purchased .22 HW80 barrel with six groove rifling. The pellet is reasonably tight in the breech but when you push it through the barrel it feels quite loose in the middle before tightening up a bit at the muzzle. I haven't used it enough to decide fully, but I'm not convinced it's going to be that great. The gun is in bits at the moment.

I'm curious to try a 5.6mm pellet through it, though the breech might just be to tight, we'll see.

Thanks Bill, interesting that yours is a similar amount of grooves. Mine definitely isn't that tight in the breech, as it drops probably about 5+ mm before there's any resistance. Sounds similar elsewhere along the barrel though.

Can I ask where you purchased it from?

[bill57]

I was very surprised to see the six groove rifling, it's not what you normally expect in an airgun barrel - though I think some older BSA's had relatively few grooves as well?
The original barrel from the 80 is a .177 with 12 grooves (I think, can't check it at the moment). I shortened it years ago when it was the done thing, so any choke is gone, but it's still very accurate.

ShedTuner, how would you polish out the breech? Never done that before.

[Shed tuner]

I was very surprised to see the six groove rifling, it's not what you normally expect in an airgun barrel - though I think some older BSA's had relatively few grooves as well?
The original barrel from the 80 is a .177 with 12 grooves (I think, can't check it at the moment). I shortened it years ago when it was the done thing, so any choke is gone, but it's still very accurate.

ShedTuner, how would you polish out the breech? Never done that before.

Use something like JB bore polishing compound, using a tight fitting mop loaded with the paste to literally just polish away at the first 3 inches. take a while, and slowing spinning it in a lathe helps keep things balanced, but it's well worth doing. Same technique for any tight spots you find in a barrel. It's really worth it.