Many thanks to reader Ross from Arizona who prompted me about the Weihrauch HW 97K air rifle, of which I had written a lot about in the past.

air rifle target group

Weihrauch HW 97K accuracy test

No news is good news, they say, and that is certainly true with my 97K.  I have not written about it in some time because I am more than happy with its performance.  This morning I took the 97K out of the gun safe where it has been hibernating these past three months.  I gave it a tough test – a straight up 5 shot group at 25 metres, without any pre-conditioning shots.

The first shot was a slight flyer, to be expected as the gun coped with settled lubrication and rest effects.

Otherwise I could not complain at the group.

A very brief recap of the whole saga.  I bought my 97K about five years back.  Initially, the performance was excellent, everything I had hoped for.

Then there followed a very prolonged and frustrating period where accuracy fell off.  I sort a lot of advice from all quarters and followed through on that.  I am sure everything contributed, but I think that the key points in resolving the issue were as follows.

The Sportsmatch AOP55 adjustable mount was crucial in avoiding the accuracy issues that arise due to excessive reticle adjustment needed to correct for barrel droop.

Buy the best, air gun specific scope you can afford.  The 97K wrecked its share of scopes that were supposedly air gun rated.  I changed scopes seven times in my quest for a scope that could handle the jolt of the big German springer.  After fitting a Hawke Airmax EV 3-9×50 AO I have had no more problems.  My recent testing of the Aeon scopes also leads me to believe they would be a great choice on the 97K.  These are scopes I have personal experience with and can recommend on that basis.  I am sure there other equally as good scope models available, but look for scopes of recognized quality, specifically designed for air gun use and well represented on the rifles of competition shooters.

Test lots of pellets and stick with the one that gives you the best accuracy.  My belief is that accuracy is all important in air rifles, especially if you intend hunting with them.  Occasionally, if hunting rats inside sheds, I will use hollow point pellets within a range of 10 metres.  Otherwise I stick with the H&N Field Trophy Target (FTT) 14.66 grain .22 calibre pellets.  Many other writers, with much more credos than me in air rifle shooting, have also found these to be one of the most accurate pellets.  Also, it is the 5.53mm variety of the FTT I use.  There is some speculation about production variations leading to accuracy problems with any air rifle pellet, so when you have found your preferred pellet, buy yourself a good supply of the same lot number.

Get your rifle tuned.  Some folks do this themselves.  There is plenty of advice and Youtube videos on fitting tuning kits to air rifles.  Personally, I opted to have mine tuned by experts and was very happy with the result.  In that regard I can highly recommend the services of Geoff at Airgun Sports Australia.  Their comprehensive report on my rifle follows on below.

……………………………..

Background

The above rifle is approximately two years old and normally resides in Far North Queensland in the Cairns region.

The rifle has been reportedly been producing inconsistent muzzle velocities and had been suffering from inaccuracy issues in recent times.  This latter may or may not be related to its inability to produce consistent muzzle velocity.  It has been sent back to the importers on two occasions under the current ownership and on both occasions with allegedly the same problems.

It was originally diagnosed with damaged piston and breech seals.  These were replaced and the rifle returned to the owner.  The rifle functioned normally for a short period before the reemergence of the same issues.

Once again the rifle was returned to the importers for assessment.  After a prolonged period, the rifle was returned to its FNQ home with a clean bill of health.  It is understood that they reported that there was nothing ‘wrong’ with the rifle.  

Initial Findings

Once the custody of the rifle was secured, it was important that  information was recorded both in writing and pictorially. Photographs have been captured but are too large to be included in this report.  They have been saved electronically.

Observations, issues and remedies are as follow.

 There was a considerable amount of surface rusting on the rifle’s metallic components.  The corrosion was concentrated around the cocking arm and barrel areas with the most disconcerting oxidisation located within the breech and transfer port area.  Oxidised particulates adhered to the face of the breech seal, transfer port and the chambering section of the bore.  This was of great concern.

 The end cap for the barrel weight/muzzle break was removed for inspection, cleaned and replaced.  The crown appeared in good order.

 All the screws that secured the rifle to the stock (fore end and action screws) were extremely loose.  This may have contributed to problems related to accuracy and POI.

 The rifle was removed from its stock and where possible, surface rust was removed by gently rubbing the surfaces with ultra fine (#0000) that had been saturated in Ballistol.

 The O-ring at the end of the cocking arm was removed to allow access to the rust within the grove where the O-ring sat.

 The cocking arm retainer was cleaned and treated.

 There was evidence that indicated that this rifle had been dismantled at some stage prior to me receiving its custody; punch marks, scratches on the action, uneven surfaces on trigger assembly pins and cocking arm pins.

 The breech seal was left in place and its face cleaned with a cotton bud that had been treated with air gun oil.

 There were several dents and scratches on the stock indicative of normal use.

 The bore was cleaned using a pull through and only required five patches to become sufficiently clean.  There were no signs of rust within the bore.

It was important to prevent further corrosion and to keep the rifle as original as possible for the initial testing and baseline data collection.

 Three shots were fired to make sure that the rifle was functioning as it should.  These were done using the H&N FTTs that accompanied the rifle and through a freshly cleaned barrel. An average of approximately 670 fps was recorded.  The rifle was dieseling heavily but not smoking.  Previous recorded data showed that it was production in the region of 660 fps prior to the second trip back to the importers.

 The owner’s scope was remounted and roughly sighted in for 30m based on the above velocity and calculations for POI at 15m.

 Two different tins of H&N FTTs were used for the initial chronograph testing. The original tin (Batch CN 121126.90284.12) and a new tin purchased from ACME Firearms (Batch CN 130124.9006.13). Therifle was dieseling with both batches.

 A dozen pellets were shot from the respective batches with the following recorded.

o Original FTTs:   692–714 fps, spread of 22 fps.

o New FTTs: 699–711 fps spread of 12 fps.

 Being an older tin of pellets, surface material on some of the pellets displayed visible oxidation.  These were discarded.

 Under slightly difficult conditions, the accuracy of both batches of pellets was compared by shooting three groups of five shots at 25m.  The photograph has been included electronically.  Results were inconclusive.

Servicing and Tuning

Once baseline performance of the rifle was established, the task of servicing and tuning the unit commenced.

 The stock was removed to allow a detailed inspection.

 More evidence was discovered to indicate that the rifle had been disassembled previously. The trigger block unscrewed from the rest of the action with very little coaxing, pointing to the possibility that the thread had been ‘cracked’ on a previous occasion(s).

 Once the spring and spring guide was removed, the spring guide presented with longitudinal score marks that may have been left by the spring’s constant rubbing during shot cycles.

 The spring itself appeared excessively dry and exhibited a pronounced curve. This spring curvature is unusual for a Weihrauch air rifle.

 There was evidence of corrosion between the anti-bear trap mechanism.

 The spring guide had excessive play when inserted into the spring.  This would have contributed to shakes and vibrations during firing, and would have also produced a pronounced‘twang’.

 The piston, piston seal and compression chamber was covered in an excessive coating of light oil/grease.  This would be the source of dieseling.  It was symptomatic of having oil injected into the compression chamber via the transfer port.  A practice not recommended for any air gun.

 The breech seal appeared damaged.  On removal from the transfer port,  it appeared as though there was a chunk taken out of one of its edges. Metal fragments were also discovered on its underside and where it normally sat around the transfer port. Not something one would expect to find and would have definitely contributed to pressure losses.  The transfer port and breech area appeared uncompromised.

 The piston seal showed evidence of dieseling as well as having been slammed into the transfer port on a regular basis.  Indentation on the face of the seal was clearly visible.

 On the removal of the piston seal with a wooden tongue depressor, there were what appeared to be gouge marks from what looked like the removal of the seal(s) using an inappropriate tool.

Cleaning and polishing

 The piston, pressure chamber, piston cylinder, trigger block and other metal parts were degreased.

 The action screws and minor scratches on the rifle we ‘reblued’.

 The safety pin was cleaned and repainted with“Fire engine red”enamel paint.

 The piston body and seal seat were polished using ultra fine wet and dry paper. As were the piston shaftand trigger engagement section.

 Without taking apart the trigger assembly, accessible metal to metal contacts were polished.

 A replacement spring was sourced and Matt Winser manufactured bespoked delrin parts for the new spring and return the completed unit for installation.

 Locally manufactured piston and breech seals were sourced.

 Rust was removed from the breech and transfer port areas and the area oiled.

Reassembly Process

All the parts were reassembled with suitable air gun grease applied to the appropriate areas.  An extremely light coat of silicone grease was placed on the face of the breech seal. The piston seal was left unlubricated.

The entire rifle was given a coat of gun oil.

The rifle was test fired to ensure full functionality.  It was then placed back into its stock.  A drop of Loctite 243 was placed on the action screws prior to being screwed into place.  This was to prevent them being shaken loose during firing cycles, and affecting rifle’s accuracy. The scope was then remounted on to the dovetail rails.

Rifle Optimisation

This part of the process was critical in validating the success of the work that has been done. The bore was re-cleaned prior to commencing. The rifle was sighted as described in a previous section.

Three (3) H&N pellets were used as the rifle had previously shown a liking for this brand of pellets.  The following pellets were tested by shooting threex 5 shot groups at 30 m.

 H&N FTT with 5.53 mm head size.

 H&N FTT with 5.54mm head size.

 H&N FTT with 5.55mm head size.

A small number of the above pellets were also lubricated with a wax base lubricant and a similar testing regime applied.

It was determined that the H&N FTT 5.53 mm preformed best from being lubricated. It must be qualified that this exercise is not conclusive base on the small number of pellets shot andthat the rifle worked best under the conditions at the time for an individual.

The best performing pellets were also Chronographed to assess variability in its muzzle velocity in the revamped rifle.  The above information is in an accompanying spreadsheet with the relevant photographs.

Summary

 Approximately 50 pellets were Chronographed with the data collected supporting and improved velocity with much smaller spread. E.g. Better Standard Deviation.

 The ‘twang’ and multi directional vibrations have been replaced with a definitive thud and unidirectionalrecoilthat is easily managed.

 Shot grouping and accuracy appeared to have improved using H&N FTT 5.53 mm that has been lubricated with a wax based compound.

 The cocking and shooting cycle appeared much improved compared to the original setup.

 The injection of Molybdenum based grease into the cocking arm where a spring loadedpin is located has eliminated a secondary‘twang’that was created by the said spring.

 Having used this rifle extensively during the optimisation phase, the objective of this project has been achieved; creating a Weihrauch HW97K that shoots accurately and smoothly.