BTAS Conversion for Weihrauch HW100
The reason for this post:
I bought a brand new Weihrauch HW100KT in .22. After some use I became aware of its lack of power. Also, while cleaning it one evening, I tried to remove the moderator (Silencer) which resulted in my barrel spinning round in the breech block. My clumsy attempts to hold the barrel still in order to remove the ridiculously tight moderator ended in tears as I managed to scratch the barrel.
I went in search of information on how to increase the power of the gun and found reference to a modification by a company called Ben Taylor & Son (BTAS). There was little info out there but I found the BTAS web site and sent an e-mail requesting what could be done for my HW100. Ben replied with "we do not do modifications to the HW100, only a full conversion for £295". I then tried to find info on what was involved in this "conversion" and if it was worth the cost quoted, after all, this is almost 1/3rd the cost of the gun! There was no description of the work on the website and I don't believe in asking any tradesman if his work is worth the money, the answer would be obvious, so I tried to get the information from what I thought would be the best source...previous customers, i.e. You guys out there on the forums with the experience.
Following certain "heated" discussions on the airgunBBS I received an offer from Ben Taylor to have my HW100 converted at no charge. In return and completely unsolicited by Ben, I promised to write a totally unbiased, factually based account of what is involved with having the conversion done. If, like me, you are wondering about a few things, i.e. "is it worth it"; and "what do you get for your money" etc, then hopefully this will help you decide.
Why bother having work done, especially on a new/nearly new rifle?
Well, that is a question only you can answer, in my case, my reasons were:
A). Under powered and after 2500 to 3000 pellets was still only putting out 10 - 10.5FtLb. whether this is important or not is subject to debate. My rifle struggled to knock over/reset targets at the 45-50yd range when the kill zone was hit. Also, after taking two rabbits @ less than 30yds and having to despatch them with further shots, even though the initial shot was nicely placed, for me it was an issue.
B). Slight air leak: Over time the air pressure in my cylinder would drop, again, to some this may not be an issue.
C). Anti-Tamper: Stories of power creep that can in time push the gun over 12ftlb, & could land you in a lot of hot water. If this were to happen and judging by all the comments I've read, it certainly does, the gun would need to be returned to Hull Cartridge for adjustment (horror stories of long turn-around times and then there's the postage costs). Also just how long it takes for this to manifest itself I have no idea, so I either put up with an under-powered gun for who knows how long, only to eventually send it away to be re-adjusted to a legal limit at a later stage or get it sorted.
D). Barrel security: My barrel was so loose and I have heard reports of others the same which results in the barrel spinning in the breech block. A second securing grub-screw can only be a good thing.
Ben Taylor & Sons:
On arriving at the premises I was greeted by Ben and after exchanging pleasantries we got down to business. First Ben showed me the individual components that go to make up the BTAS regulator and FX air cylinder (see photos included throughout) that had been CNC machined. As there is a limited demand for this type of work, the components are manufactured in blocks of 50, so as you can imagine, they are not "off the shelf" cheap items. These components all.
While showing me the components Ben explained why he considered it necessary to swap out the original regulator and replace it with his own design. There was an awful lot of engineering speak which I will not try to replicate here. The easier version is that while the HW100 is not by any means a bad gun, the regulator (as on most guns) has a range of available shots, over which there is a power curve where the first and last batch are inefficient with the middle batch being at their best. This apparently renders all but approx 40% of available shots inefficient with loss of velocity and changes in Point Of Impact throughout the range. Bens regulator is designed in such a way as to remove this power curve and send all the shots with a constant velocity. As long as there is over 100 bar pressure in the cylinder, each available shot will be fired @ 11.5ftlbs. This is so until the cylinder pressure drops below 100 bar when there will be an immediately noticeable and very marked drop off in pellet velocity.
Why change the HW100's cylinder?
The regulator, which used to be located in the action of the HW100 is now in the air cylinder and the FX cylinder is the one it was designed to fit. There are other advantages too, the FX cylinder as used by Ben is lighter than the Weihrauch original. In the .177 rifle, a 1Lb saving is gained, in the .22 it is only a half pound.
List of work carried out:
1). Separate action from stock and completely strip the action.
On inspection Ben found that several of the Allen screws in my gun had been over tightened and the heads "chewed".
2). Remove HW cylinder, separate action from breech block.
3). Machine and fit blanking plug for vent under the stock screw (see photo).
The original vent at this location is no longer required. It is replaced by Bens Stock Screw Vent Blank.
4). Machine top of block and fit grub screw as second fixing for barrel.
The Gun in its original state only has one grub screw, located under the barrel, which secures the barrel to the breech and can often be found to be too lose.
5). Strip out the Anti-Tamper and with carbide drill release adjuster and leave adjustable.
Although after Ben's Mod power creep should never happen, if it does, at least I am now in control.
6). Increase hammer stroke by 1.5mm.
This is done because as standard, the hammer spring is so powerful that when the trigger is pulled, the hammer pin strikes the knock-open valve as intended, to fire the pellet, but then strikes it again, wasting a 2nd minute puff of air, which should not happen. Machining (lathe) 1.5mm from the length of the hammer pin overcomes this issue. It was while doing this that Ben discovered the badly manufactured hammer pin in my gun. At first we thought the hammer pin was bent, but when unscrewed from its seating, he found that the pin was straight but the screw thread into which it is located had been machined on the skew. Although it was not possible to re-machine the screw thread, Ben used the lather and a dial indicator to straighten the hammer pin.
7). Strip out all original regulator components.
8). Machine and fit blanking caps into all redundant regulator holes in block.
9). fit tube adaptor to front of action.
10). Assemble regulator , setup and fit to FX air cylinder, ensure correct orientation for vent hole.
11). Reassemble complete action and set desired velocity
12). Leave the system pressurised for minimum 12hrs check for pressure and leaks, rectifying if necessary.
On my rifle, no rectification has been necessary.
13). Machine and supply filler probe.
So, why £295:
The components which go to make up the regulator cost a minimum of £50, the FX cylinder and plug a further £45 and all other bespoke parts a total of £24, so a total of £119 is for the parts alone. As all the components are machined in small numbers they can never be "cheap".
The main process took approximately 3.5-4 hours and that was using components that had been pre CNC machined, so does not take into consideration the time spent on the manufacturing side. Then after the 12hrs waiting time (I went back to Ben's the next day) there was a further half hour or so spent checking and testing, then reassembling action to stock. So all in all I would say time spent on the job was a minimum of 4.5hrs, so even @ £20 per hour for the gunsmiths time you are already looking at £90.
I can't say how long it takes to make all the parts but setting up the machines and feeding them with the raw materials must be considered, so let's say it takes only 2 hours, our labour bill is up to £120 and that is, as you can see, a very conservative estimate. Add the £120 labour costs to the £119 component costs and you can see that even with the conservative estimates we are not too far adrift from the £295 charged. We haven't considered the overheads of the business, i.e. electricity, tool wear & coolants used in the machining process or ground /industrial unit fees etc. and let's face it, Ben Taylor does not do this for fun, there has to be some margin for profit too. Having spoken with Ben I am informed that £40 per hour is a fair estimate of a gunsmiths/engineers time and to be honest, when you consider that in comparison with a plumber, plasterer, car mechanic etc, it does not appear too excessive.
On the face of it the job does seem a lot of money, especially when all you would normally see on collecting your rifle is the fact that it no longer has a pressure gauge and you need a different filler probe. However. I hope my photos and explanation go some way to illustrating just what it is that you have spent your hard earned cash on.
The bottom line is that I am much more satisfied with my rifle now than when I first bought it. Having been privileged to see exactly what goes into the conversion, and the quality of every component, I would be more than happy to recommend Bens work.
In my case a quite serious design/manufacture defect was discovered and rectified (see item 6) which would probably have gone unnoticed for quite some time and until premature wear or failure of the hammer system occurred. That alone was a very positive benefit to the process and also operation of the trigger is now much smoother as a result.
Then there is the securing of the Barrel by a 2nd grub-screw, not major, but must be considered an improvement over the standard supply none the less.
The air leak is cured.
Consistency of power: My .22 HW100 now does over 100 shots all around the 11.5ftLb mark and as described earlier, using my Skan chronoscope, a very tight tolerance on the velocity of each shot has been achieved. On a subjective note, I notice a big difference when my pellets strike the knock-over targets at the 45-52yd range, before they used to apologise for knocking on the kill zone, now they positively smack them and can be seen to bounce off quite violently.
Is there anything I would like done differently?
Well, I would like to see included in the deal a sealing probe to keep dirt, dust and foreign matter from entering the FX cylinder filling port, these currently have to be obtained separately from Steve Pope at V-Mach. Also, after the conversion there is no manometer (gauge) fitted to the air cylinder which I would like to have, if only as a quick check as to how much air is left in the gun. However, these are only MY preferences, it may be that others don't need or use the guns gauge, although I suspect that everyone who has the conversion will need the port seal probe.
I haven't had the problems dealing with Ben that some folk have described previously. I can only speak as I find and that is to say I found him to be friendly, approachable and helpful if somewhat difficult to get hold of at times. Bearing in mind he works alone and often with machines running, I think I can understand this and allow for it.
The more cynical amongst us and particularly those that do not know ME, will be quick to suggest that as Ben did this work F.O.C, I would obviously give a positive response. I can only say that is not the case. As I promised in a previous thread on the airgunBBS (before it was wiped from the boards), I would describe the work done as honestly, factually and accurately as I could and at the end of the process I would say whether I had a positive experience or that the end result was not what I had hoped for.
I hope that from my description and photos, those interested can see exactly what they will get from a "BTAS Conversion". I will say that for my part, irrespective of whether I paid for the work or not, I can now see the benefits Bens work brings to the gun and I am very pleased with the end result.
List of photos:
Stock-Screw-vent-blank-02 (fitted into action)
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Had mine done and it is fantastic.
Was always reticent about free-floating the barrel but it has made a load of difference.
No more chasing a zero when you fill or the temp changes.
Well worth the cash and I would recommend it to anyone.
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