There is not difference in appearance from the outside, The lug is on the underside of the rear, sometimes called the heal, of the receiver. Where the serial number is. It makes a stiffer set up and keeps the receiver from moving due to recoil. With older bedded stocks it helps. I have a rear lugged super match in the for sale section if you would like to find out first hand the benefit.
Rear lugged is the best way to go if fiberglass bedding the barreled action into the stock is what you are looking for. It provides more surface contact between the receiver and the bedding. The only difference in appearance is the lug on the receiver, which isn't visible once it's bedded.
The benefits are as stated in the above posts. There are a few rear AND front lugged receivers out there. A friend of mine has 2 LRB M25 dual lugged receivers. I feel a single rear lug is sufficient if you plan to bed the rifle. If you're looking for a "battle" rifle, a rear lug is not necessary. HTH
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1Bolt</div><div class="ubbcode-body">Rear lugged vs. non M1A?
Tried to search this subject, what's the benefit, what's the difference in appearance? </div></div>
There is also a qualitative difference, depending on the manufacturer. I have heard of ARMSCORPS rear lugged receivers having their lug break off at the joint. Have not heard the same for Springfield Armory receivers. LRB is a high quality product, and should not be a problem.
I have put a few (thousand) rounds thru rifles with and without lugs. The unlugged rifles will shoot just as well as a single or double lugged rifle if it is correctly bedded into the stock.
That being said, a single lugged rifle (what the Navy used for DMRs) will maintain the accuracy of the bedding job longer. No more skim bedding after 3-5000 rounds. More like re-bedding with a re-barrel.
The double lug rifles (the Navy Match Grade A) could be (carefully) removed and replaced in the stock without a significant loss of zero. When bedding double lugged rifles, you wouldn't put tension on the front ferrule. With the stiffer McMillan stocks, the barrel/gas cyl assembly was almost free-floating.
Remember, with both single and double lugged rifles, the lugs have screws that are pillar bedded into the stock, just like a bolt gun.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1Bolt</div><div class="ubbcode-body">Can you describe skim bedding.. It that related to filling gaps created over time? </div></div>
Skim bedding is done when the bedding relaxes over time, or more likely gets the crap beaten out of it over time. You merely remove a small amount of the bedding top surface then re-bed the action into the stock as you would when you first bed it in.
I also skim-bedded my R700 into the B&C light tactical stock with the aluminum bedding block by roughing the aluminum surface a little and applying the Devcon just like a regular bedding job, just a thinner coat.
I shoot my standard (non-lugged) more than my Super Match because it shoots really well. At 100 yards on a 100 yard SR-1 NRA target I can keep my shots all in the black (9, 10 & X ring) using surplus 147 Gr. ammo from a bench. My Super Match rifles (lugged and non-lugged) will shoot exceptionally tight groups at 100 and 200 yards with Sierra 168 SMK's from a bench, but they are built to be approx. 3 pounds heavier than a standard weight rifle, mainly due to the heavier barrel and thicker forearm. Hell, you can't go wrong with shooting any M1A. PAT.
I was told by a well known Marine Armorer, if you have access to an Armorer double lug is the way to go. If not, front single lugged is the only option. The reason being, if the rear lug breaks, you’re out of the game. If the front breaks, remove the broken pieces and keep going! My M1A is single lugged front with Hart 1-10 and its hell on the 1000 yard line even with Federal 168 Gold Cups, especially 168 Hornady with 41.2 grains of IMR4895!