Tuning the HW45/P1

[Steveoo]

Ok put a film of oil on the O ring and close the gun then open it again.
Check for an oil circle mark on the breech closing face.
If not, its not sealing.
The pistol will need cleaning out. The compression ratio is such that it produces enough heat to ignite any lubes inside. Clean out. Check the seal, and use a touch of pure silicone wiped around the seal for re-install…
Silicone is often frowned upon for metal to metal lube, but will be ok in this application, but more importantly does not diesel in a 45 but does seal Teflon.
Dry fires will never wreck this gun….the spring possibly but should be ok for a few dry fires to get the hard Teflon seal sized. I might do 5 or so to get an old seal re-sized.
Clean the barrel out.
All done, you could ensure the guide rod is down inside the piston, and wait for it to run in to 5ftlbs..

For further improvement beyond 5, you could purchase a TbT kit, using half the kit at the muzzle end of the gun, but getting an exact copy of the other half of the kit made up in steel for the bottom of the piston.
The ideal set up for 6

 

[cjtamu]

Thank you, sir. Plan to take it apart shortly. Right after my wife recovers from my re-doing of a 56TH ha ha. Interesting idea about the TbT kit if I can find someone to make a steel guide for me. Read some of your posts about needing weight in the piston and making a guide for the cup end. Thanks again for the help.

 

[beerthief]

Tom anytime.

If you have access to a lathe its easy. I just turned up the solid steel guide, but if not there are a number ways to tackle this issue.

One way which worked for one shooter (Who was in New Zealand of all places) was to order the Eagle cam kit off the bay and then drilling a hole through the top hat guide of 5/16” (8mm) diameter and shoving in a short rod of 8mm steel cut to the same length as the guide. He glued it in the finish. This increased the weight of the front top hat by 15 grams to give the guiding but also the required weight to maintain the power.

Another way is to simply use the OEM guide down inside the piston (worth 40 fps versus being at the muzzle end) and then shoving a spring centraliser into the bore of the spring end plug. This requires the cross pin hole spotting through whatever you use. An 1/2” Nylon bolt about 3/4 inch long can be fashioned to fit, spotted through and held by the cross pin which retains the end plug. Anything which centralises the spring at that end.

The Tinbum kit on its own is rubbish, being too light, losing a good 1/2 ftlb over stock and introducing a touch of piston bounce with heavier pellets as the piston is too light for such a light weight guide. It really requires a good 20 grams of weight. The kit is a touch smoother as the mainspring cannot cant over at the breech end but you will be lucky to make much over 4.5 ftlbs, robbing the whole point of purchasing a HW45….whichnis its power.

could you fill the O E M rolled part with melted used pellet lead ? maybe drill 2 cross pins to hold lead in tube ?

 

[Steveoo]

I do like novel resourcefulness like the above post….when you do not have Engineering tackle.

Yes you could use one half of the TBT kit at the muzzle end, but then cutting down the OEM guide to the same length of the Delrin part in the kit using a Hacksaw for inside the piston….simplest solution.
Then employ the weighting idea above if you wanted…You want 35 grams with typical 8 grain pellets.

Problem with that TBT kit is employing the light weight guide in the piston in an attempt to damp the cycle.
It works a touch, (in the damping sense) but due to the size of the column of air in the relative big volume piston, it will get a bit of piston bounce with anything above 7 grain pellets. This results in a suction milli seconds before the pellet has left the barrel, causing a loss of vel. 30 Grams ensures this does not happen and can realise 570-590fps if sealing correctly.

 

[beerthief]

so that would mean 68 8 grain pellets melted to fit inside OEM part . might be interesting to try

not enough room to make it a dead blow hammer type effect hmmmm ?

 

[cjtamu]

No bueno. Going to order a couple breech seals. Going to order a spare spring also. I see ARH has one for it. Or would I be better off with the OEM spring?

 

[Steveoo]

Cannot beat HW OEM mainsprings.

 

[csolf]

I wanted to share what I believe to be the best way to tune the HW45 pistol after approx 30 years of owning and tuning.

First, you can just leave it stock and shoot it. If you resist adding any additional lubrication, it will eventually expel, or burn off the excess lube put into it by the manufacturer. It will take a few tins of pellets to do this and will finally settle down. The components are built to last a lifetime and can be run relatively dry with no excess wear noticeable.

However, if you have the relevant skills to tune one, this is the method to use.

HW placed the rolled steel guide rod down inside the piston (opposite to any other gun) to increase the weight to the piston. This is to overcome the excessive cushion of air coming from the restrictive TP which bends through 90 degrees. It is also this restriction which generates heat which effects any lubes placed into the gun. However, having the guide down inside the piston means that there is no guiding at the loose spring end to control it where it is needed at the muzzle end. Tuning companies then supplying Delrin kits which have a shortened guides which can then be fitted at both ends to help smooth the gun and control the spring at both ends.....This is a mistake!

In this particular gun, if we make the guide/Top hat out of Delrin, we lose the valuable inertia to drive through that restrictive TP and lose a good 1ftlb or more (the whole point of owning a HW45 being its power) Such a move turns the gun into a benign 4.5 ftlb Tempest.

What we need to do is, machine the Top hat/guide and another to fit in the opposing end just the same, but out of steel. I have found if you machine a shorter guide of 30mm long, it will still weigh the same as the originally rolled steel guide because that is hollow, not solid. You require a good 20 grams and this will achieve max velocity. The shorter steel guide at the muzzle end, will stop the mainspring flailing around, prolonging its life and keeping from canting over against the wall of the piston, also increasing velocity a touch. As a bonus this muzzle end guide can act as a beneficial muzzle weight.

If you follow this advice, your HW45 will approach 570 fps with 7.8 grainers and can give 10mm groups after plenty of practise and most lube removed.

thanks for the great info!

 

[cjtamu]

Another application of silicone oil and just shooting have helped a bunch. Pretty consistently 4.5 FPE or better now but occasional 20-25 FPS drop. Going to order some breech seals and order a spare spring while I’m at it. This gun is so much fun to shoot.

 

[cjtamu]

Finally got around to taking this apart. Attached pics explain a lot. First pic would be right side of piston when installed, second pic would be left side. You can see there’s a chunk of metal missing on left side beneath the seal. Not sure if it broke off and caused the rest of the scarring or what. Awfully concentric circles on both sides. No metal in the compression tube or anywhere else in the gun when I pulled it apart. New piston is obviously in order. Steveoo or anyone that knows this gun have any ideas? Don’t want this to happen again. Thanks.

Edit: Compression tube looks great, smooth as a baby’s bottom. Gun still appeared to have factory lube. This has to be either manufacturing defect or something that happened when someone took it apart. Tried to drill through the piston with a hole saw maybe?

 

[Clickok45]

Hi Steveoo, I have noticed something odd that I would like to share with you and pick your brains.
Sorry, this is a long one!
I have an old mk1 HW45 .177 with the escutcheon (badge) on the grips that I bought used years ago and have recently bought a newer used bronze star .177 which came with what I thought were 3 replacement breech seals.
I assumed they were the ones that came with the gun from New although the guy I bought it from didn't have the original box and I can no longer find out as I no longer have His details.
The reason I'm wondering is that when I checked the breech seal on My old 45 it felt flush compared to the new gun so I thought I'd replace it with one of the new seals but after fitting it was very tight when closing the breech but not too tight as I could still press on the cocking lever past the locking point.
I did notice that the newer seals were slightly fatter looking but I put this down to the fact that my old seal was worn out.
Anyway, when I chronographed it I lost about 70 fps!
So I decided to put the old seal back in and sure enough the power returned!

Looking at TW Chambers exploded view of the 45 I guess it's possible that these could actually be replacement air channel seals (part# CR060) and not breech seals but I can't imagine Weihrauch supplying these in the box with a new gun.
This leaves me with a few questions.
1. Were the seals that came with the new gun aftermarket ones?
2. If they were genuine were they a different size in the newer versions of the hw45?
3. Were they for different parts of the gun?
4. If a new seal is even tighter when the breach is locked how come the energy has dropped?

So as to question 4 I have a theory that the new seal I put in was actually dampening or cushioning the piston too much and causing it to slow down?
I know that there were no partial blockages after the breech was locked because even if the seal "Ballooned" after locking there simply isn't enough space for it to partially block the breech.
So I guess that there needs to be a small amount of clearance for some air to escape to allow the piston to do its job.
What do you think?

 

[Steveoo]

Sorry I missed your questions.
The 45/P1 never came with spare seals, so my best guess is these are possibly non std.
The genuine part (Chambers airgun spares) sits barely above flush, which is all that is required to seal.
People get it wrong with O rings, going for more squeeze than required in a effort to get a better imagined seal, but it actually bulges the seal.
O rings actually seal correctly on barely 0.2mm of squeeze...

Also try a single dry fire with no pellet, it can re size your piston seal to the piston Chamber..
Not to be done too often ...

 

[Clickok45]

Sorry I missed your questions.
The 45/P1 never came with spare seals, so my best guess is these are possibly non std.
The genuine part (Chambers airgun spares) sits barely above flush, which is all that is required to seal.
People get it wrong with O rings, going for more squeeze than required in a effort to get a better imagined seal, but it actually bulges the seal.
O rings actually seal correctly on barely 0.2mm of squeeze...

Also try a single dry fire with no pellet, it can re size your piston seal to the piston Chamber..
Not to be done too often ...

Awesome Thanks mate I really appreciate the info. I will order the original from chambers.