RTV Bedding a Lee-Enfield No4

Improving and repairing firearms. Rifle bedding, barrel work, stock replacement and other ways to improve your firearms.

RTV Bedding a Lee-Enfield No4

Post by in2anity » 16 Jul 2020, 10:08 am

Accurizing a Lee-Enfield no4 is hardly new ground. What is novel (as far as I am aware) is the use of RTV (Room Temperature Vulcanizing) gasket silicone as the barrel bedding agent. I merged the idea from my dealings with RTV silicone bedding lever gun forends (to obtain better consistency under match-like conditions).

RTV silicone "vulcanizes", bonding with tremendous tenacity. An RTV silicone bed is also slightly cushiony; the magic elixer that will not produce or allow significant stressing between the forend and the barrel and should far outlast the old cork solution. Following Roger Wadham's advice in his "Complete Book on Lee Enfield Accurizing" book, the suggestion is made to use cork strips in a centered bedding location. I surmise RTV silicone offers the same, if not a superior level of support, while still offering that bit of breathing room as the barrel heats.

The no4 is considerably easier to "accurize" vs an SMLE because the barrel is almost completely free floating out of the grease. There is also no SMLE-style nose cap to deal with. From the factory, the only contact point along the barrel of a No4 should be a small platform at the very tip of the forend, which should offer between 2-6lbs of upward pressure on the (otherwise free-floated) barrel. It goes without saying, the No4 also sports that rear mounted aperture sight with the slightly heavier contour barrel; both desirable for competition Service Rifle.

bedPre.jpg
Red areas were how my particular No4 originally bedded. The action could be better bedded.
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I'll therefore break what I did to accurize my no4 into three parts, which closely follows along what is suggested by Wadham.

PART 1: BEDDING THE ACTION

Firstly we need to understand how our action interfaces with the forend. Remove the action from the timber forend as normal.

removed.jpg
Lots of old oil and mung that needs cleaing up
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Spray the timber around the action area with WD40, then dust with talcum powder. Reassemble the action and trigger guard, and tighten up the king screw. Disassemble once more and observe how the action has imprinted into the talc dust:

dusted.jpg
Dust + reassemble to see the interface
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In my example, you can see a distinct area immediately behind the king screw that has made contact. Moving rearward (besides the draws), there is little observable contact. On the upside, my draws look to have equal distribution onto both recoil lugs; this is absolutely critical to accuracy. If your gun is not centered on the draws, stop here and address that issue first. Bedding the recoil lugs is beyond the scope of this guide.

Ideally the action should bed down all along the length of the action as shown in this diagram (in red):

bedProjected.jpg
And here is the goal; bed the action/barrel, free float the tip.
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So that defines the goal of PART 1; Acraglass Gel bed the action along the red areas.

In addition to where the action will sit, Wadham also suggests free floating then adding a small bed approximately 1" wide for the reinforce point just in front knox-form. This area can be masked using painter's tape.

Clean as much oil as you can from the timber. This can be ahieved with acetone, a toothbrush, a heat gun and some elbow grease! After the targeted area has been thoroughly cleaned and dried, roughen it up with a small file to give the epoxy somewhere to "grab".

cleaned.jpg
Forend has been cleaned and "roughened"
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Mask any areas of the forend you don't want the epoxy to bleed to. Thoroughly degrease and apply two-to-three coats of release agent to any areas of the action and knox form that are likely to make contact with the epoxy. Fill any problematic holes with air-drying modeling clay.

Mix the Acraglas Gel per instructions, then apply to the targeted areas of the timber. Reassemble the action and trigger guard and tighten the king screw. Let the epoxy harden for 24 hours. Remove the action from the forend, using a piece of timber and hammer to gently tap off any stuck forend.

set.jpg
Immediatley after "cracking" the bedded forend off
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Cleanup the bulging epoxy that has extruded to the sides of the bed; I do this carefully using a Dremel tool. Cut away the areas of the reinforce point bed over the masking tape, leaving just the little pad for the reinforce point to rest on.

cleanedUp.jpg
All the knobbly bits removed
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The action should now mate perfectly with the timber, leading into PART 2.

PART 2: RTV CENTER BEDDING

Wadham indicates two popular bedding methods for the no4; “central” bedding and “center” bedding.

Central bedding defines laying a stabilising bed on the second platform after the knox-form, nearest to the central barrel-band/sling attachment.

Center bedding is similar, but is done on the first platform after the knox form. He claims that center bedding yields possibly the best accuracy out of the two styles, which makes sense as it leaves the longest possible length of free-floating barrel beyond the bed. The only caveat of center bedding is the potential for droop / forend contact under recoil. Center bedding is better suited to the heavier no4 barrel.

Personally I went with the center bedding method, after all it will be possible to change the bedding to central down the track. Let’s just see how a large sample of my scores pan out.

Wadham talks about two possible barrel bedding materials; the modern epoxy bed, and more flexible and traditional cork-strips bedding. This is where I deviate, opting for a third option in the form of RTV gasket silicone (klnown as "Permatex Ultra Black"). I see RTV bedding as comparable to cork, yet much more concise and permanent.

Again, clean the timber thoroughly on the first platform using acetone/heat. Meanwhile mark and mask your barrel in the appropriate location. Degrease and apply two-to-three coats of release agent to the barrel around the circumference. Mask adjacent areas of timber with painter's tape on the forend to protect from any extrusion. Lay down a thick consistent bead of RTV silicone (not the acetic cure type!) onto the targeted timber platform.

rtv.jpg
A liberal bed of RTC silicone ready for reassembly
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Reassemble the barreled action and trigger guard and tighten the king screw. The silicone should extrude out either side of the barrel as it beds down as shown;

setting.jpg
RTV silicone should extrude out either side a little
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Wait 48 hours for the silicone to dry in cold climate, 24 hours in warm. Carefully cut away the extruded bead slightly lower than flush to break any mechanical lock. Clean up any overhang/extrusion with a scalpel leaving something like this:

RTVed.jpg
Cleaned up with a scalpel
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Now, do the exact same thing all over again, only this time for the top timber above the same spot. Once completed, the idea is once the top and bottom wood is reassembled, the RTV beds will gently clamp down around the barrel (above the targeted platform), providing support and rigidity, yet still allowing a little cushion room.

That concludes PART 2 and paves the way for PART 3.

PART 3: FREE FLOATING THE FOREND TIP

Part 3 is relatively straight forward; we just need to relieve the timber swell at the tip of the forend such that the barrel is completely free floating This can be achieved incrementally using some sort of bearing blue. I use matte red lipstick as a cheap and convenient alternative to machinist’s blue. Again, the Dremel can greatly speed up this step with care! Keep removing material until the barrel can noticeably flex up/down/left/right once reassembled; the last thing we want is for the barrel to whip against the forend under recoil.

freeFloated.jpg
Factory timber pad at tip of forend free-floated
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Wadham also talks about bedding the trigger guard, but that’s trivial and easily achieved if you’ve made it to this point.

A quick visit to the range yielded an encouraging result. Here's 10 SMKs over a full case of AR2209, with sling tension and a bag under my stabilising hand. I used the factory front blade sight with an original No4 micrometer arpeture sight:

10shot_.jpg
10-shots, 50m, No4 iron sights
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More or less, there's also shooter error there, particularly elevation, as that's the part I find hard to get super precise (using the front service rifle blade).

With 8/10 hovering on 1" @ 50m, I believe it would easily go south of 2-moa with a scope and say, a 5-shot sample size. Perhaps I will scope it one day, and see. :thumbsup:

This outcome is what I was hoping for, and noticebly better than how it shot prior to this work.

Wadham reflects upon service rifle shooters shooting 15” groups at 1000yds with the No4. I now think this might just be in the realms of possible...
Cheers,
In2anity.
Last edited by in2anity on 23 Jul 2020, 9:04 am, edited 31 times in total.
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Re: RTV Bedding a Lee-Enfield No4

Post by marksman » 16 Jul 2020, 4:33 pm

very interested in how it goes
cheers for all the effort you have gone to :thumbsup: :drinks:
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Re: RTV Bedding a Lee-Enfield No4

Post by bladeracer » 16 Jul 2020, 5:07 pm

Is any of this modification allowed in Service Rifle though, I thought you could only use rifles in "as issued" condition?
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Re: RTV Bedding a Lee-Enfield No4

Post by in2anity » 16 Jul 2020, 5:33 pm

bladeracer wrote:Is any of this modification allowed in Service Rifle though, I thought you could only use rifles in "as issued" condition?


Club level may seperate “modified” and “as issued”, our club just lumps them together. Modified still has its restrictions; in our club, bedding alteration is not one of them.

Higher level and championships probably enforce this distinction more strictly - I’m not exactly sure. Club level; it really varies from club to club - our club is big, and thus writes its own rules, based on what the members want, which is the smart way of maximizing membership and attendance, keeping things interesting :thumbsup:
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Re: RTV Bedding a Lee-Enfield No4

Post by in2anity » 20 Jul 2020, 9:59 pm

I made it to the 50m range to test my work; here's 10 SMKs over a full case of AR2209 shot in under 2 minutes, with sling tension and a bag under my stabilising hand. I used the factory front blade sight with an original No4 micrometer arpeture sight:

10shot_.jpg
10 shots, 50m, No4 iron sights
10shot_.jpg (735.89 KiB) Viewed 4177 times


More or less, there's also shooter error there, particularly elevation, as that's the part I find hard to get super precise (using the coarse old front blade).

With 8/10 hovering on 1" @ 50m, I believe it would easily go south of 2-moa scoped and sampling a smaller 5-shot size. Perhaps I will scope it one day, and see :thumbsup:

This outcome is what I was hoping for, and noticebly better than how it shot prior to carrying out this work.

Wadham reflects upon service rifle shooters shooting 15” groups at 1000yds with their No4s. I now think this might just be in the realms of possible...
At what point does lack of maintenance become patina?
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Re: RTV Bedding a Lee-Enfield No4

Post by Wm.Traynor » 21 Jul 2020, 1:01 pm

Very well done in2anity :thumbsup:
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Re: RTV Bedding a Lee-Enfield No4

Post by in2anity » 21 Jul 2020, 1:08 pm

Wm.Traynor wrote:Very well done in2anity :thumbsup:

Thanks WM, but tbh I'm still not satisfied :D I want to remove the verticality from my groups. Distributions should be homogenous on both axis. I'm currently investigating the length of the main-screw bushing - I think there may be a problem there :unknown:

What made/makes this whole process tricky is I still needed to be able to rock up to club events on Sats. It bit me on the ar$e the other day with a changed poi - not so forgiving on the 300m mound :lol: it bloody cost me 15 points!

To be continued...
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Re: RTV Bedding a Lee-Enfield No4

Post by in2anity » 12 Aug 2020, 10:24 am

PART 4: THE KING SCREW

After observing "verticality" in my groups (as somewhat shown in the OP target), I further investigated the potential cause. There a few things to consider. 1) King screw bushing length 2) Timber shrinkage 3) King screw washer / king screw length.

sub.jpg
11) king screw bushing 19) king screw 20) king screw washer
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Of all the accurizations, the relationship between the king screw and the forend is possibly the most critical, and warrants much investigation and experimentation. And because over time the forend can dry out (without the constent application of linseed oil), there's a good chance your timber has srunk away from the trigger guard. That's exactly what I found with my rifle, and what was causing the vertical stringing.

washer.jpg
Make sure a washer is present to prevent the king screw from bottoming out in its hole
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The king screw should not bottom out in its hole, hence the need for the king screw washer (20). The king screw bushing should not be tightly clamped between the trigger guard and the action (as was the case with my rifle). Shim the trigger guard until the king screw bushing is not binding, resulting on the clamping force instead being uniformely distributed onto the timber forend. This was actually a technique used on the L42 sniper.This can be done with pop can as I did:

shims.jpg
Mine took four pop-can shims to take the pressure off the bushing
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shims2.jpg
Trace the pop can with the guard for a precise fit
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Or better yet, a steel shim(s) or washer.

After these alterations, the shape of my groups are generally more concentric. More importantly, overall groups are now more consistent. Again that 8 ring shot is more than likely shooter error. Leaving 9/10 into 2moa from a hot barrel over service sights.

IMG_1785.jpg
Elbows 50m, front-blade, quick 10-shots, sling-tension, bag under the sling hand.
IMG_1785.jpg (503.73 KiB) Viewed 3944 times


Cheers,
in2.
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