HW95 low shots

[MrChipShoulder]

Hi,

I have a new HW95 in long barrel .177.

Without writing pages of words, the problem I seem to be having is the barrel is dipping (breach opening) when the piston hits the bottom of it's stroke. Over a 10 shot group at 18 yards you will typically get an OK group (3/4") and a few shots lower than the group up to 3" low. Trust me when I say I've tried everything but no matter what I do, this shot pattern is the same. It was suggested to me to add a 'pre-load' spacer behind the breach lock spring. I did that, 1.4mm was the thickest spacer I could fit before the spring would bind and not allow the latch to work, so not much pre-load. I've tried all sorts of tension on the breach pivot bolt, same result, group and low fliers.

Is there anything I can do to stop the barrel dipping. The gun is the standard HW scope only version with barrel weight and no open sights. The gun is at 11.35 foot pounds and has a max deviation of .18 foot pounds over 10 shots. So the power is in the right spot and consistent.

Is this a 'known' issue on new HW brake barrels?

Thanks for any help.

[TonyL]

Hi Rob,

Sorry to hear that it's still not behaving.

If the issue is down to harsh piston landing, that would suggest either a piston seal or breech seal issue. But I think you've replaced the piston seal and you say the velocity consistency is good.

Barrel latch lubed? If preloading it hasn't worked, maybe try a new spring?

And I wonder if reducing mainspring preload may help? Just wondering, like. It'd be funny if the fps didn't suffer adversely and yet the action become more forgiving.

I also understand that you've now also tried a wide selection of pellets?

Please, please double check the stock fastenings, the new bracket that's affixed to the cylinder that the front stock screws go into. And the scope fastenings. Did you try a different scope?

How are you resting the rifle when shooting the groups?

If all the basics above can have their boxes ticked, my money would still be on the breech latch and I wouldn't be giving up on this fine rifle just yet.

[Rapidnick]

You say 'new'? If it is really new under warranty then I'd take it back to where you bought it and claim on the warranty. DO NOT attempt any work if you want the warranty to be honoured.
If I was presented with that rifle out of warranty I would firstly tighten the barrel pivot bolt and secondly, remove the barrel to see whether both the shims (thin shiny washers) are in place. I'm sure you have done both so send it back for a replacement under warranty would be my preferred option.

[Rapidnick]

Hi Rob,

Sorry to hear that it's still not behaving.

If the issue is down to harsh piston landing, that would suggest either a piston seal or breech seal issue. But I think you've replaced the piston seal and you say the velocity consistency is good.

Barrel latch lubed? If preloading it hasn't worked, maybe try a new spring?

And I wonder if reducing mainspring preload may help? Just wondering, like. It'd be funny if the fps didn't suffer adversely and yet the action become more forgiving.

I also understand that you're now also tried a wide selection of pellets?

Please, please double check the stock fastenings, the new bracket that's affixed to the cylinder that the front stock screws go into. And the scope fastenings. Did you try a different scope?

How are you resting the rifle when shooting the groups?



If all the basics above can have their boxes ticked, my money would still be on the breech latch and I wouldn't be giving up on this fine rifle just yet.

Tony you seem to be forgetting that this is a NEW gun!! Rob should not have to do anything along the lines you are suggesting. He should send it back and get a new rifle or his money back.

[MrChipShoulder]

Barrel latch lubed, - yes.
reducing mainspring preload, - reduced down to 10fp, same outcome.
wide selection of pellets, - yes.
stock fastenings, - yes.
front stock screw bracket, - yes.
scope fastenings, - yes.
different scope, - yes.
How are you resting the rifle when shooting the groups, - Bean bag on the wood stock, same as every other gun I ever shot.
New piston seal, -yes.
De-burred tube, -yes.
Breach bolt adjusted all ways, - yes.

New breach lock spring, - no, but it's a new gun, 100 shots old.


I can't send the gun back as the very first thing I did was pull it apart and de-burr and polish it's guts and fit a vortex kit in it as it was very twangy and nasty to shoot, as I'm told most HW's are. My guarantee is no more, so it's a dead one week old new gun as it stands now. I'm guessing I'm going to have to sell it as a dead broken new gun only worth the value of it's stock or brake as spare parts !!

The Vortek kit has now been removed and the gun is back to the stock spring (properly lubed now !!)

[TonyL]

Tony you seem to be forgetting that this is a NEW gun!! Rob should not have to do anything along the lines you are suggesting. He should send it back and get a new rifle or his money back.

Nick, as per Sunbeam's post above, it's a bit late as he stripped it and fettled it straight away.

Rob, it really is a big shame that you didn't test before stripping as we'll never know if the problem existed beforehand. Although twangy, it may well have shot very accurately.

I had to finish my first post early as the dog dog was barking to go out.

I think what we need to establish here is whether there's a "mechanical" issue going on (like the breech opening upon firing) or whether it's a very acute hold sensitivity issue. Generally, depending on the weight of the gun and the weight distribution, the muzzle will rise during the compression stroke and dip during piston bounce (surge). Could you do me a favour, please......Using a very, very soft hold, trigger hand hardly contacting the gun and the only pressure from that hand is the middle of the pad of the trigger finger on the blade. The front of the forend resting on a very soft, padded rest. I find this "long and flat" "hold" the most forgiving on a hold sensitive gun. Whereas the rifle supported closer to the balance point allows more "flippy nonsense".

If it's a hold sensitivty issue, we can work on that by softening the cycle (especially reducing surge) or by increasing weight and/or altering the weight distribution.

I just know we'll get there and wouldn't want to see you writing this gun off just yet.

[Roundshot]

Breech seal? If it's a tiny bit too thick, it can cause inconsistent lock up.

[TonyL]

Breech seal? If it's a tiny bit too thick, it can cause inconsistent lock up.

Very good call, Ted.

[MrChipShoulder]

The breach seal 'seems' OK, and the lock up 'seems' to close with a good clunk.
I can't detect anything that is stopping the breach from fully closing, it sounds and looks good.
The locking latch is well lubed (from the inside as well!)
The pivot has been adjust all ways from lose to too tight. It is now set as it felt from new, a little on the stiffer side.

My only thought is the barrel weight is too heavy, causing the barrel to dip when the piston hits the back of the TP. That would certainly dip the barrel as the pellet is coming down the barrel. But surely Weihrauch wouldn't make the weight (handle) to heavy to work correctly?

[TonyL]

As Ted's suggestion is such a cheap and easy one to undertake, I'd say it's certainly worth a try.

As for the barrel weight, I have no experience of the latest guns with the barrel weight. Mine is an earlier barrel weight one. But I'd doubt whether that would be the cause.

Give it a try with the resting method I suggested earlier, please.

If you did think it's a balance issue, you could try adding some weight at the rear of the gun temporarily to see how that alters things. A heavier scope is sometimes all that is needed. Or you could try strapping something heavy to the butt end (as I say, just a temporary thing to see if it changes things).

In your opinion, does the firing cycle feel harsh to you?

[MrChipShoulder]

I can't see this problem being a hold issue,if it were that hold sensitive, I'd get rid out of principle. I shoot my TX200 in exactly the same way at the same distance, on the same bench, at the same target and I can get every shot through an 8mm hole or smaller. I understand some guns are 'hold sensitive', but up to 3" off target is a problem beyond hold I think?

[MrChipShoulder]

When the gun was brand new, back form the shop, it was absolutely horrid to shoot, twangy and harsh. The Vortek kit made it lovely. Now I've put the gun back to stock (selling the Vortek kit!) and lubed the spring properly as it was very dry, it shoots OK. It has a little twang, but not too bad, it would do if it were the only way and accurate!

I think this problem would have been there from the start as I can't see that I've done anything to cause this. I doubt polishing and de-burring could make it this bad. I only polished out the burrs in the end so a new seal could go in without ripping it apart. The original seal had a damage skirt.

So do I need to buy a new breach seal and breach lock spring?

[CapitalBee]

My guess on the barrel weight is that it isn't the cause. The same barrel configuration is used for the HW98 and the sleeve will most likely outweigh the slip on barrel weight. I, like Roundshot, had lock up problems when changing breech seals. However, that was on an HW30 with the ball bearing detent, but 0.1mm made a real difference on lock up repeatability. Maybe try the gap between breech and cylinder face with some feelers, you might have some out of tolerance condition with a hole position on the pivot point.

[TonyL]

Yes, I would have to agree that a 3" difference in impact point would be a huge effect at such close range. And I'm not trying to suggest that it WILL be that. But, if we were to highlight the issue by means of elimination, you'll then know which direction your efforts are to be steered in. Many, many 95s are not hold sensitive to this degree. But if hold sensitivity were to be highlighted as the cause, that action plan can come into play........weight distribution, tuning etc.

[TonyL]

So do I need to buy a new breach seal and breach lock spring?

It's certainly worth giving those a go, Rob. If they did the trick it will have been an inexpensive fix and saves you from giving up on this rifle.