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 .