Barrel profiling

There are probably a reasonable handful of people in this country who profile barrels in house and I do a modest number for ourselves and occasionally others RFD’s, however I always think it is rather special when I profile something out of the ordinary such as this one.

This is a dummy barrel to check the profile of a barrel destined for a Colt XM177E2 replica build, the only difference being the original barrel was 11.5″ in length and this one is 12″ to keep the build within the UK 12″/”4″ laws, or barrel length not less than 12″ and overall length not less than 24″

Why the test run? Well as much as I have confidence in my programming it is always nice to run the part in a soft metal first to confirm fit and this run exposed a tightness where the front sight base (FSB) fits which is annoying as I am good to the original drawing, albeit at the upper end so the FSB must be on the tight side and we have a stack up of tolerances. I will modify my program accordingly.

This was nice to machine as I did not need a steady due to the short length. Cycle time was a very steady 21 minutes and a few seconds and I will need to increase my feed speed on the finished article to leave some machining marks as the original would have had.

Chamber will be 5,56×45 NATO and it will be attached to an A1 upper and skinny hand guard.

Next job is machining the muzzle device which is a flash hider/sound moderator combination.

EDIT – In case you were wondering what an XM177E2 is I have attached an image from http://retroblackrifle.com/ who are my go to on-line reference for such things (Hope you don’t mind guys!)

Sound moderators

As well as designing and manufacturing our own sound moderators in house, we can supply and fit other makes when requested. Today was a Wildcat Predator 12 on a .308 Win Howa and as the Howa is pre threaded in 5/8″ UNEF it is just a matter of ordering it in and screwing it on, or nearly..

Firstly I like to correctly fit the rear bushing which means removing the bushing, screwing the moderator on, measuring the diameter of the barrel immediately behind the moderator and boring the bushing to suit.

People ask what the purpose of the bushing at the rear of a reflex moderator is and really, it serves a couple of purposes. Firstly it prevents excessive radial loads and damage to the moderator female thread where it is screwed on to the barrel and secondly, it allows the manufacturer to design a fairly generic back end to the moderator which can then be tidied up with the bushing.

I usually bore the moderator bushing with +0.25mm on the diameter of the barrel, or around 5 thou all round which is ample for expansion and general use. People ask why and there is an easy answer, it is my preference.

 

A Dremel is not the tool for opening the bushing and I seriously question why a person or shop would do this. It takes probably 25 minutes to measure, bore and fit the bushing, explain the safe use and maintenance of the sound moderator, fill in the table 1 of the new owners FAC and kick them out of the door and joking aside, I would always sooner spend 25 minutes explaining things and giving them a correctly fitted moderator, more to the point, we do not charge separately for this service.

I have read various views on bushing clearance and the implications of its lack of so I have added a picture of the moderator I run on my Accuracy International. It is a custom reflex with a stainless steel front and inner tube and an aluminium rear body, at the rear it is bushed with an internal O ring that contacts the barrel. Accuracy wise it works very well.

Once the bushing is bored and fitted I walk the customer through the do’s and don’ts of sound moderators. Never leave it on your rifle after you have been out shooting, regularly strip and clean the internals, keep an eye on any O’rings fitted and replace them if required and most importantly, lubricate the threads on the muzzle and the moderator with a wipe of copper grease or similar. WD40 will not do!

…and why am I telling you this? Because you need to know.

Butt pad grinding…

Butt pad grinding is a necessary evil in this trade.
 
Someone at some point is going to ask me to change the length of pull of their shotgun/rifle and fit a new butt pad. Last week was typical of this with three shotguns requiring new pads with one to be balanced at the same time.
 
The owners were looking to reduce felt recoil so we agreed on KICK-EEZ pads which are manufactured from Sorbothane and really do have a dramatic impact on recoil, the downside is it is like grinding chewing gum and is one of the filthiest jobs I can think of, well other than actual polishing.
 
I had not planned on writing about this job so I have missed a few images however it was when I saw the state of the grinder that I felt it was worth a picture or two.
 
First job is determine exactly where the stock should be cut, I wrap the wood in masking tape on the underside and cut area to protect it and measure and mark multiple times.
 
Then off to the band saw, I use a Startrite vertical machine with a 1/4″ bi-metallic blade. This is one machine that I always keep a blade guard on and it is worth taking a lot of care when setting up as not only can you mess the stock up, you can also very easily remove the odd finger or two.
 
The key points here are keep the stock horizontal and I add shims taped to the underside in the wrist area to ensure this is correct and secondly use a guide which is adjusted and locked in place for each job. The cut takes only a few seconds and gives a remarkably fine finish, however I can finish on the 300mm bench sander as needed.
Time to attach and mark the pad, probably the most awkward part is marking the vertical centre line and I check this a couple of times before marking with a sharp wax pencil, once done I can locate the pad in place and mark the top hole with a correctly sized transfer punch. I always drill a pilot hole for the screw, and once in place I can mark and drill for the bottom screw and securely fit the pad.
At this point I need to mark the material to be ground away. In the past I would scribe and chalk the line in however this leaves a line that is hard to see and the scribe can ride up and mark the wood so I use a white wax pencil which gives a clear line to work with and cannot damage anything.
 
Next job is fit the butt pad, I use a fixture that is attached to the bench grinder and replicates the angle of the butt from the wrist area. With the pad in place I start grinding, this is a truly filthy job, especially if you have a 2-3 pads to grind in one go and I end up covered in rubber as does that part of the workshop regardless of extraction.  If you are wondering, I use 150 grit Aluminium Oxide, it is a bit slower than say an 80 grit however it is a lot harder to take too much material off and gives a finish that needs a lot less finishing.
I test the fit and grind further as required and finish with foam sanding blocks, this gives a smooth finish with any previous grinding marks removed.
Finally, I oil the freshly cut section of the butt, grab a coffee and then fit the pad securely. I usually give the sides of the pad a light coat of a beeswax polish I make for my own use and it leaves the ground sides looking good.
One concern here is fit of butt pad to butt and I aim to have no step in the transition between the two. If you wish to do this job yourself I recommend aiming for the same or with the pad being very slightly larger than the pad so you can always finish it with a sanding block and in the absence of a sanding block use some 220 grit Aluminium Oxide paper wrapped around a piece of wood.
As well as producing a lot of rubber/Sorbothane dust the disk itself clogs up badly and I use a dressing block  to remove this build up. It is a piece of natural coloured rubbery material, I have no idea what it is however it works superbly and restores the disk to as new in a couple of seconds. You can see the pad sitting on the top of the grinder table. Before you shout, yes the gap between table and disk is wider than it should be and this is deliberate and allows the ground away material to be sucked down into the extraction port.
Final job on a Browning 325 was to balance to the pin and this required an additional 118 grams of weight in the butt stock. Sorbothane is not as dense as hard wood and the customer had added extended chokes to a gun that was already balanced quite a bit forward hence the weight required.
I typical need to add anything from 105-120 grams to bring the gun back to the pin with material added or removed if the balance needs to be moved back or forth.
So that was the middle bit of grinding and fitting a butt pad, I will take some pictures when I remember so you can see the marking, cutting and final job.

The Shooting Shed Støtteben F/TR bipod MkV – Another run.

I keep getting asked about our Støtteben bipod so it must be time to make another run of 25. For those of you who have not seen one, the Støtteben has a proven track record and is in use by multiple national teams and is well represented within the F Class league.

The SHED Støtteben bipod is manufactured from 6082 T6, A4 and 316 stainless with some Nylon washers thrown in for good measure so it is not going to rust!

This tried and tested super wide and super light F/TR bipod is the evolution of the original SHED ‘Plain’ bipod and is lighter, wider and sleeker, it has many new features such as the T Nut assembly and has a second fixing which is an M6 grub screw designed to screw into a dimple in the rail to give a second locking point and also act as a recoil lug, this means the bipod is always returned to the same position on the rifle when it is fitted. The elevation screw pitch has been reduced to give finer elevation control yet still with the left/right hand thread system so no more winding for 10 minutes to get the height you need. The feet are wider with added radiuses to give even tracking regardless of the width the bipod is set to.

Finish is vapour hone with hard anodising so a very flat black without any shiny bits to reflect light. The leg sections from the elevation fixings to the head are solid sided to give maximum rigidity and triangulation and this also gives somewhere to put the name of the bipod ‘Støtteben’ Which for those of you who do not read Danish means stabiliser. Støtteben are the stabiliser wheels children have fitted to their bicycles so now you know.

Vital Statistics:

Main bipod assembly: 6082 T6 aluminium.
Finish: Vapour honed and black anodised surfaces.
Screws: A4 Stainless Steel.
Elevations shaft: Stainless Steel
Elevation nuts: 316 stainless steel
Weight: Approximately 610 grams
Weight with optional toggle locks fitted: Approximately 674 grams
Weight of optional toggle lock 32 grams (1.15 Ozs)
Maximum recommended width: 785,0mm (31 Inches)
Maximum recommended height: 380,0mm (13.5 Inches)

Accompanying the bipod is a spares/options kit comprising of:

1x Elevation nut retaining clip.
1x Toggle lock and washer.

Price for the latest iteration MkV of the Støtteben will be £295.00 with the new version featuring some minor tweaks to improve tracking and aesthetics. Price for advance orders will be £265.00 and the bipods will be available Q4/2019

Triggers and trigger weights.

I am often asked to adjust and/or tune triggers and one thing often becomes apparent and that is people have no real concept of trigger weight.

Many years ago I was asked to service and adjust a sporting Sako trigger to 3.5lbs, which I did, the customer tried it when he came to collect the rifle and declared it was far too heavy. Well it was on exactly 3.5lbs and it turned out he wanted something closer to half that. Lesson learned for all of us.

In an ideal world I will make the adjustment whilst the customer is with me until we reach a weight that suits the customer.

The one thing that always worries me is when people make their own adjustments and fail to check the operation and safety of the rifle afterwards and I cannot over stress the importance of such checks. If in doubt, leave it alone or ask a grown up. Lighter is not always better!

I remember working on an F Class rifle a few years ago and commenting on just how horrendous the 2oz (55 grams) trigger was.The owner admitted later that it had failed in a competition and he shot the last few rounds by carefully closing the bolt to take the shot, so it was effectively slipping over the trigger sear as the handle was depressed. it reminds me of an F Class competition once when the competitor to my left was taking his first sighter, there was a shot followed by “Oops”

Anyway, this particular trigger job was an Anschütz 1807 and I was asked to increase the trigger weight and give it a once over.

First job always has to be to check the operation and confirm the existing trigger style and weight and this one was set to a scary 5-8 grams, I would hate to shoot it with cold fingers!

These days I use a Lyman trigger pull gauge, I misguidedly lent my old electronic gauge out and never got it back hence the Lyman. These are actually quite accurate and I sat down with a known weight and ran numerous tests when it first arrived and I would say it is accurate to +/- 1 gram which is quite an improvement on the more traditional spring gauges and tins of shot on a piece of string. Of course the accuracy is dependant on the way you use the gauge and yanking the trigger back with the gauge will give vastly overweight figures.

What I do like about the Anschütz triggers is the range of adjustments for sear engagement, first and second stages and trigger weight and these are one of my favourites. This particular trigger has now been cleaned and set to ~100 grams

What can you best do to keep your trigger in good working order? Well, avoiding contamination with bore cleaning solvents and oil is a good start. I always use a Cleaning rod guide/Bore guide (Obviously) and trap a piece of kitchen roll folded in half under the back of the guide to prevent the ingress of contaminants when cleaning.

If you need to clean a trigger in the field, remove the trigger, hold it in the same orientation as you would shoot the rifle and pour a liberal amount of lighter fluid in from the top, this will flush a lot of the contamination and gunk away and when the fluid dries it leaves a slight residue that aids in lubricating the trigger until you can get it checked and cleaned properly.

DO NOT dump the contents of a can of brake cleaner followed by a liberal coating of gun oil and certainly do not put WD40 near it as you will be back to square one.

Do not lighten your standard trigger excessively and always, always check the operation before use.

And why am I telling you this? Because you need to know.