Bedding the Rifle

[motohead185]

I have a few question concerning improving accuracy through bedding compunds. I have done alot of research concerning bedding the action of bolt guns. but was wondering if anyone here has ever heard of using Silicone epoxy in the barrel channel, to reduce barrel harmonics? of course this would be applied after the action being bedded.

thx
casey

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[Spitpatch]

Howdy, Casey.

I am not familiar with silicone epoxy. As for "reducing" barrel harmonics, that is usually NOT the goal with barrel bedding techniques. The goal is to ALLOW barrel harmonics, and allow them freely. This is the reason most guns will shoot best with a "free-floated" barrel (the entire barrel is touching nothing ahead of the chamber portion). This allows the tuning fork characteristics of a fired barrel to do exactly what it wants with no interference: vibrate freely for its entire length. Outside contact results in the "tuning fork" to quit vibrating before it wants to.

Having said that, a few rifles shoot better if fully bedded all the way out: that is, bedding compound touching the barrel completely and with no gaps all the way to the forearm tip. Other guns may shoot better with moderate pressure just under the barrel at the forearm tip. This is the quickie technique employed by most bolt rifle manufacturers as a result of the prohibitive expense of a good glass-bedding/free-floating job. You can observe a small amount of additional wood left at the forearm tip in the barrel channel of the stock, creating moderate upward pressure on the barrel when the action is cinched down in the wood.

Winchester (post-64) employed an economical "glass-bedding" application on their Model 70's for awhile, that used a compound quite like "heat-gun" glue dropped into the recoil lug recess before the action was dropped in, and free-floated the barrel the rest of the way out. They were extremely generous in their free-floating, and in these '70's, the gap on either side of the barrel was literallly like a chasm. Complaints were that this allowed moisture and debris into those gaps, and the compound used in the lug recess was not durable: it would crumble after a few years, causing these rifles to shoot dismally poor when that happened, often unbeknownst to the average shooter that rarely took the action out of the stock. I recently re-bedded a Model 70 with just this problem, and the gun went from shooting 2-3" groups to less than a half-inch.

It is also possible, and a very good idea to glass-bed the entire barrel channel for the sole purpose of sealing the wood and adding some strength to the forearm, while still having the barrel free-floated. Electrical tape is attached to the barrel where it would rest in the stock, proper glass bedding is done to the recoil lug (and tang if necessary), and the action is dropped in, allowing the bedding compound to dry. When the action is removed, tape removed and gun re-assembled, the space occupied by the electrical tape has created a very nice free-float, and the stock channel is perfectly sealed.

I don't know under what reasoning changing to a different compound for this purpose would be beneficial.

More helpful hints can be supplied if you need them from me before you do your first glass-bed job. Some of them are not included in bedding kit instructions, but really help the process a lot. Learned by trial-and-error (sometimes severe error, especially in my first couple attempts) in over 35 years of doing this.

 

[Oohrah]

I'm not familiar with that compound either. However I agree with bedding the action, and if that doesn't improve it greatly, I usually end up full length bedding barrel and action. You can play with it by bedding the action, and shimming the barrel with material to put upward presure on the barrel. I have found usually if the upward pressure is needed to shrink the groups down, a full bedding job is in order, and corrects it.

 

[the4thshake]

Silicone spray can be used as a release agent so the bedding compound doesn't stick to the action an barrel.

 

[Oohrah]

Good tip. You only have to have it happen once, that not enough, or miss a spot with release agent to be be very aware not to do it again!!! Not many freezers to put an entire rifle in, and pull it out and give it a sharp rap to get the metal to release from the stock!

 

[motohead185]

Thanks for the info folks. I plan on doing a full bedding job from the tang to about 1" infront of the receiver, Also plan on installing steel pillars. I'm one of those people that measure 4 times cuts once. But i have heard if you use a silcone epoxy in the barrel channel it reduce the barrel vibrations so that it becomes more accurate. kinda like if you have a penny and drop it on the counter it bounces and reacts to the surface, but if you put a towel down it doesnt react.

 

[Oohrah]

Pillar or solid action bedding YES. Silicon in the barrel channel no. Free floating or solid barrel bedding only. Bonding of the material and heat would most likely cause some problem between the barrel channel and the barrel. Each barrel will differ in the spot of vibration, and is one reason actions are bedded with the barrel left free floating. Never used one, but I have seen a device that slides down the barrel until you find a honey spot, and you leave it on that position. A good barrel I have not ever considered vibration as creating an accuracy problem. I have a pre 64 Feather wt. Model 70, in a 30-06. When I bought it new back in the 60s, I thought the light weight barrel was the cause of horizontial stringing, as a dollar bill would slide down the barrel between it and the stock. Best it would group was 1 1/2 to 1 3/4" when hot. The cause was the barrel heat caused the forend wood to contact the barrel. It was no longer free floating. Removing a small bit of wood on the contact side cured that problem, and the rifle would shoot sub minute of angle groups.
If filling the barrel channel with silicon improved accuracy, all the tactical and military sniper rifles would be using it. I don't believe it will give you any kind of an edge, and most likely create more problems for you.

 

[usmc]

i use a compound called DEVCON, it is machinable ,can be polished to five microns, and so on. its like JB weld on steroids.i used it to lug bed my model 70 and it helped quite a bit.if the barrel isnt heavy enough like a bullbarrel , their is no reason to free float it.i have full length bedded my .308 with a sako barrel, and it will shoot through the same hole all day long.i have also had situations where it did not help either way, but there is alot of factors to consider when accuracy is at stake. all in all i think it helps with the right application.

 

[Spitpatch]

Casey,

You may not need to glass-bed the entire action. Most (often all) improvement is obtained with bedding the lug recess area and the chamber only. (Go a bit farther than an inch ahead of the lug.)

Bedding the tang region I usually reserve for heavy-recoiling guns, and guns that may already have some sort of wood-to-metal issue at the tang. (Poorly inletted guns, old guns, or damaged wood there.)

I will assume with your research that you know the lug is not bedded with contact anywhere but at the rear, and how to accomplish that.

I will assume that you know the value of your favorite girlfriend "PAM" in the process (one gent mentioned silicone spray for the same purpose). This is in addition to any release agent supplied by the glass bedding company.

I will assume that you know how indispensable modeling clay is for the process.

Heat Lamp, Dremel tool, bungee wrap, plastic knife, masking tape, newspaper, etc. All essential.

Be brave, be careful, and "measure SIX times".

 

[Celtic Armory]

After more than 20 years of working around a variety of adhesives, epoxies, resins, fiberglass, graphite, boron, kevlar and a crap ton of solvents and such I have never heard of "silicone epoxy". Silicone and Epoxy are two completely different chemical compounds.

As for glass bedding. Pillar bedding is great for strengthening the recoil lug/mounting bolt areas. Full action bedding is best to help tighten up a rifles action where it fits into the stock. As far as the barrel channel goes in the stock there are two things you can do; full glass bedding or free floating. What you intend to use the rifle for is what will determine what course you take.

If it's going to be an actual hunting weapon that will be out in the weather, full bedding is the way to go. This fills the whole barrel channel with glass resin or epoxy and conforms to the full shape of the rifle. It prevents most of the barrel flex and harmonics. You get improved accuracy over doing nothing but it also prevents water and dirt from getting under the action or barrel and causing pressure points and corrosion.

If you're only going to take it to the range on nice days and put it on a bench and shoot tiny little groups, free floating is the best. With this method you fully glass bed the action (perhaps even going as far as pillar bedding) and you relieve the barrel channel in the stock enough that when you shoot it the barrel can flex naturally without hitting the stock. This gets you your best accuracy possible, but only if you can keep debris out of the weapon.

 

[MountainBear]

Try MarineTex to bed your rifles. I have used it for about 90% of the rifles I've bedded (several hundred now). It is slightly more forgiving and easy to use. I have in my few years gunsmithing used MarineTex, Devcon (steelbed), AcraGlas, and AcraGel. MarineTex is still my favorite. When using most bedding compounds, I generally don't worry about pillar bedding as I'm not terribly worried about compression of the stock.

I agree with some of the above posts as to the full length bedding if its going to be a hunting rifle. Its easy to get crap into the barrel channel (like tree needles and dirt). I free float all my target rifles, generally by inletting the stock with the barrel covered in a piece of 10 mil tape and then bedding the rifle with the tape still in place. Synthetic stocks are a bit easier, as the stock will more than likely be painted after the fact anyway. Wood needs to be inletted more precisely to the metal with the tape on the barrel already...

 

[Oohrah]

Thanks for the tips! I think Marine Tex is about the only one that I haven't used, but shall on the next one. Like you, I haven't used the pillar bedding as
I have been able to get good results using old school methods.

 

[motohead185]

After more than 20 years of working around a variety of adhesives, epoxies, resins, fiberglass, graphite, boron, kevlar and a crap ton of solvents and such I have never heard of "silicone epoxy". Silicone and Epoxy are two completely different chemical compounds.

As for glass bedding. Pillar bedding is great for strengthening the recoil lug/mounting bolt areas. Full action bedding is best to help tighten up a rifles action where it fits into the stock. As far as the barrel channel goes in the stock there are two things you can do; full glass bedding or free floating. What you intend to use the rifle for is what will determine what course you take.

If it's going to be an actual hunting weapon that will be out in the weather, full bedding is the way to go. This fills the whole barrel channel with glass resin or epoxy and conforms to the full shape of the rifle. It prevents most of the barrel flex and harmonics. You get improved accuracy over doing nothing but it also prevents water and dirt from getting under the action or barrel and causing pressure points and corrosion.

If you're only going to take it to the range on nice days and put it on a bench and shoot tiny little groups, free floating is the best. With this method you fully glass bed the action (perhaps even going as far as pillar bedding) and you relieve the barrel channel in the stock enough that when you shoot it the barrel can flex naturally without hitting the stock. This gets you your best accuracy possible, but only if you can keep debris out of the weapon.

Sorry for the miss use of terms. There was another forum i had stumbled upon that talked about using a bedding compound called "Ultra-RVC" and in that thread one individual said that you could use RTV Silicone to reduce barrel harmonics, in order to increase accuracy. But i am not to worried about it anymore and plan on sticking to the tested methods.

 

[Celtic Armory]

Sorry for the miss use of terms. There was another forum i had stumbled upon that talked about using a bedding compound called "Ultra-RVC" and in that thread one individual said that you could use RTV Silicone to reduce barrel harmonics, in order to increase accuracy. But i am not to worried about it anymore and plan on sticking to the tested methods.

Good idea. I personally wouldn't use RTV as it's very soft and isn't really stopping any harmonics, though it would reduce some vibration. However because of the way it flexes it could cause an adverse wave effect down the length of the barrel as it shoots.

I've only used Acraglass, and wasn't that impressed at first. I'll have to look into MarineTex.