[Marlin4570]

Has anyone bedded a rear lugged receiver? I have a Fulton rear lugged receiver with a Krieger heavy barrel. I inlet a heavy, GI, M14 stock to fit it and it was a pretty tight fit. This was prior to bedding. I shot it this way for a while and was able to shoot sub MOA groups at 100 yds. Even double tapping steel at 800 yards. One day shooting at 100 yds I started noting verticle stringing of my groups. Figured the stock was loosening and it was time to bed.
I only bedded the rear lug and I added a pillar and screw. 1st time out torqued the screw to about 30 inch pounds. 1st shot bullseye at 100 yds.
2nd to the right about 2 inches and then another and another. Made a scope adjustment. Same thing. Decided to loosen the screw. Same thing. Today I torqued it at 60 inch pounds. 2 shots bullseye, 3rd and 4th shot 2 inches right. Kept shooting and torqueing. Everytime I torqued the screw the 1st or 2nd shots were on then the next went right about 2 inches. Anyone have any advice as to what I've induced here? I put two cards under the barrel when I bedded the rear lug. When I torque the rear lug the barrel stays above the stock and the barrel band lip touches the bottom of the ferrule. Could this be the issue? Any advice will be appreciated.

 

[30Caliber]

You want the stock to pull down on the barrel at the ferrule. This helps dampen out all the odd harmonics you get from all the stuff that hangs off the barrel. It should take a really stiff grip (like a bone crushing handshake) to make a gap between the band and the ferrule.

I haven't dealt with screws. Have you tried pulling it out? There are a couple good articles here on bedding that might be useful for backtracking:
http://replay.waybackmachine.org/20000312011219/http://members.home.com/stuka/csptips.html

 

[Marlin4570]

30 Caliber,
Thanks for the advice. I have removed the action from the stock so I know it isn't stuck. I see what you mean about a stiff handshake. There is tension where the barrel band is in contact with the ferrule. I am not sure I have enough tension? Or maybe I have a really strong handshake! Someone said you can get away with bedding the rear lug only. Maybe I need to look at bedding up front as well? The rear lug seems to have the elevation stringing under control. I guess it is getting some sort of oscillations left and right causing the flyers to the right. Could be because of the twist of the barrel and the torque of the 175 grain bullets leaving the barrel?

 

[dighawaii]

Marlin,

Not sure if this is the case with your situation, but from what I understand about bedding, it is to eliminate the horizontal and vertical movement of the receiver when locked in with the trigger group. I have used the Kuhnhausen Shop Manual as a reference with Art's video to identify all of the locations of where and how the action should be bedded.

There should be a sufficient amount of "draw" pressure at the front band/ferrule contact point (like Ty said). I have used a fishing scale to measure the draw pressure by locking the rifle into a rifle cradle and attaching the fish scale to the barrel assembly at the gas cylinder and when drawing down, I could then meaure the downward draw pressure.

Books that I have read have indicated that 8# of draw was sufficient, but from my experience and tests, that 8# was insufficient. It's been my experience that about 24# yielded better results. But please experiment for yourself, I am only novice compared to the Guru's that we have on the forum.

But I am sure if you only bedded the lug area, that you may be getting some lateral or possibly vertical movement. It would take only a small amount of movement to cause accuracy problems.

Good luck on your endeavors.

Aloha,

Tom O.

 

[bd111]

With double-lugged receivers, heavy barrels, and McMillan stocks, guys have built accurate rifles with zero draw pressure. They just glue 'em and screw 'em like a free floated bolt gun.

 

[jpk1md]

With double-lugged receivers, heavy barrels, and McMillan stocks, guys have built accurate rifles with zero draw pressure. They just glue 'em and screw 'em like a free floated bolt gun.

Its not the same as a bolt action gun or even a free floated AR tube due to the mass of the gas piston/cylinder/spring and other parts.

Hanging this amount of weight off the front end of the M14 causes issues with harmonics etc which as I understand it is what tension on the stock tenon is meant to remedy

Increasing the mass/rigidity of the barrel helps to reduce the effect but it is still there nonetheless.

 

[ripsaw]

Are you putting a good layer of grease between the ferrel and barrel band lip ? The grease will allow it to slip back into the same position better after each shot and enhance the repeatability of it, once you have all the other issues corrected.

 

[ct_lynch]

It's a murky art...

I had the same idea a few months ago, and having bedded a couple of bolt guns, I thought that I'd be able to do it. The M1a is a complicated receiver with a lot of things going on, and a lot of ways to glue the action into the stock if you aren't careful. When it starts to get really dicey is the ferrule/front band/gas piston relationship (alignment and draw pressure) and the correct amount of draw on the trigger group. These are variable depending upon your barrel weight and whether you are using a pillar screw for the rear lug.

My limited understanding, and I am hoping that I'm correct, is that with heavy barrels like the Krieger you need less draw on the receiver. I'm also led to believe that if you use the pillar screw bedding then you don't need much draw with the trigger group as the screw ensures that the receiver is suitably locked into the bedded stock.

It is a very dark art and much more complicated than a bolt gun. After research and reflection I decided that I was better off paying a pro to do the work for me. I think it was a good decision.

 

[Phil “Murphy” McGrath]

Double lugs anchor the action into the bedded stock evenly F/R and keep the reciever from squirming the front lug helps keep the chamber area from lifting up and away when things get moving, as for the trigger group its just along for the ride theres no more clamping as the lugs do all the work. Removing the action takes more effort but they do come out for there bi-anual scrub down inbetween cleanings are done without braking the rifle down, the nice thing is that they don't need too settle back down after there cleanings

Double lugging was the best money I spent on my rifle.

Dark Art I don't think so after a while you get up too speed and figure things out with some help, now where did I leave my magic wrench and file?

 

[Ted Brown]

Rear Lug Bedding Methods

There are two types of rear lug set ups. One does not use a bedding screw which it what Springfield has on their Super Match rifle. This type of receiver should be bedded exactly the same method as a standard receiver. Clamping pressure from the trigger group is required.

When the lug is set up with a screw, the receiver and trigger group should be bedded without locking pressure from the guard. It's still a good idea to maintain clearance between the stock and receiver just behind the receiver legs. This system takes all the stress off the receiver while still firmly securing it in the bedding. The screw should be through a pillar and torqued to 65 inch pounds. Front band presure from the stock ferrule is still required to stabilize the barrel.

The inaccuracy sited is probably related to the lack of complete bedding and inadequate torque on the bedding screw.

 

[gwolf]

The rear lug is on the m25 is tapered would it be worthwhile to put a thin spacer like tape on the bottom of the lug to give it room to suck up and wedge itself when the screw is torqued? This is assuming the front of the lug is epoxied as well.

 

[Gus Fisher]

I only bedded the rear lug and I added a pillar and screw.

This is almost certainly your problem. Now the rear lug fits better and therefore the receiver is looser and most likely is causing the stringing.

When you bed a lugged receiver, you have to bed the whole receiver and lug at the same time. Otherwise, the lug takes more pressure than the front end.

The first thing I would suggest is bed the reeceiver AND skim glass the rear lug at the same time so the bedded surface is balanced.