What is the correct O & E barrel Block mount hole distance

OK, another potentially stoopid question to the MilSurps community. What is the correct mount hole distance of the O & E barrel Block?

I have a number of O & E blocks I bought from Steve Earle Products recently and a few years ago, and from one other supplier that I used a few years back. The mount hole distances on the receiver and barrel blocks are 0.860" and 0.560" respectively.

I have a barreled receiver drill and tap fixture for the 1903 Springfield that I bought years ago thru Liberty Tree. There has always been an issue with the center to center distance of the bushings to guide the mount holes for the barrel block. They sent me a drawing and they make the fixture with the center to center distance of the bushings to 0.500".

Ive never seen a O & E Block for the barrel with a center to center distance of the bushings to 0.500". Liberty Tree says that if I want an OVER-ARM made with the center to center distance of the bushings to 0.560" it is non-standard and will have to be custom made at my request.

What am I missing here? Was the original center to center distance of the barrel block mount holes 0.500"?

the rear holes, are exactly the same as Redfield, Burris, Leupold ect.. not the same as Weaver bases.. the only drill and tap fixture that works, is the one made by Forester.. unless you plan on doing a few, it may not be worth spending 350.00 on one. every other fixture iv tried was a failure, i made a special fixture to do the holes on the barrel.

O&E Blocks are for the 1903 and 1903A1 USGI scoped rifles (e.g., for Win A5, B5, or Lyman 5A scopes). I am not sure who the original manufacturers were.
Rear holes???? Are you referring to an A3 scope base or the one piece non-USGI base for the '03.

In any case I need an actual dimension of the hole center distance of the two mount holes of the barrel block (so that may perhaps referred to as the "front" holes) to answer my question (cant remember if that is the O, or the E block).

My initial post may have been a little misleading about the fixture I have. Though I seem to remember that I bought it thru Liberty Tree (memory could be wrong), but it is made by Forester. That is who I am in contact with.
It is designed for a barreled '03 or '03A1 with the drill and tap for both receiver and barrel on the one "Over-Arm" as Forester calls it. I think it will work on other rifle types with the corresponding Over-Arm, but I may be wrong.
Just curious, what other fixtures are there that you have tried?

no.. you asked what the dems in the holes on the receiver ring are.. my response was... they are exactly the same, as any standard Redfield , burris, leupold modern base, the 2 holes on the ring.. and not the 1903A3, this is the fixture, Universal Sight Mounting Fixture Forster Products
if thats what you have, thats what works. so,
the 2 front holes in the guide are the right dems. this fixture was made to drill and tap for standard scope bases, Redfield ect. use a level bubble set up, and make sure everything is square in your drill press.. your welcome to call, and ill walk you through this.. if your not careful, you can do alot of damage you cant fix..

Thanks, I checked out your link. That is in fact the fixture I have. I appreciate the efforts you have made and the time you have taken to try and help me.
Am I correct in thinking that it may be used on a number of barreled receivers and not just the '03? (just curious)

If I seem dense or slow to understand your answer, I need to point out that referencing other mount manufacturers and simply saying they are the same does not provide me the actual dim I was looking for.
The fact is that Forester has showed me their drawing of the over-arm and the hole to hole center distance between the two closer bushings is 0.500" (which is for the block for the barrel) on the over-arm (Forester's name for it), yet everyone of the blocks I have bought recently and in the past years measure 0.560". It has caused me no few difficulties. I have had to drill and tap the first hole, then move the Over-Arm 0.06" for the second hole in order to achieve the 0.560" hole distance between the mount hole centers on the barrel needed for the blocks I have. I drill 7.2" distant from the receiver ring block (distance between the centers of each block).

I cant remember who I sourced the blocks from years ago, but the most recent were sourced from Steve Earle Products and are listed as O & E blocks for the '03 rifle.
scope blocks (sorry, I was unable to make this an active link).
I have a number of sets of these blocks bought over the past 15 years from more than one vendor and the center to center mount hole distance of the short/tall barrel blocks are all 0.560".

I am sorry if my initial post may have been confusing, but if you re-read my initial post, I made no mention of the receiver ring and clearly stated (or so I thought) that I was asking about the block for the barrel.

You never mention O & E blocks, so I got confused and didnt understand your references to Redfield, Burris, Leupold modern base. However, may I assume from your replies that Redfield, Burris and Leupold make or made O&E or similar bases? (I am going to google them in a moment) For the record, I have tried to get my answer about this hole center dim from the internet with no success.

If the name O&E is specific to only one manufacturer (Unertl?) and they are called something else by others? I am simply unaware as it is one of many areas I am still learning to know.

most likely you got the 1903 Bases, that he started building for me, and they worked better then the copy of O E bases. and yes, they are the same, if you used the front holes, on the arm that the drill guide goes through, you shouldnt have had to move it, i have 2 number 31 drill guides., and once it is set up, i drill the rear hole first, so i can see how deap i need to go , then move to the front hole, drill the same amount, then, use the 7.64 drill guide as a tap guide, {not moving the arm} and tap the 2 holes, the base should attach with no issue, as long as you have squared and leveled it. the block for the barrel is a bit of a pain in the butt, i made some fixtures for drilling them, the 2 closest holes should be the correct holes..{in theory}
have to be careful not to go all the way into the bore, of that trashes the barrel.. lived that a few times.

Attachment 138548 heres the fixture i made

WOW! That is WELL DONE! Im impressed. I like acquiring good tools and fixtures, but there is nothing like the feeling when a DIY project like this ends with good results!

LOL, Ive never drilled the barrel mount holes beyond the correct depth, but over the years, Ive ruined the headspace of almost a dozen '03 and A3 short chambered NOS barrels by making mistakes, using the wrong gage, being too aggressive with the reamer, etc.! Each time just made me embarrassed but also ****ed me off that I did that. You'd think that after the first few Id learn to pay close attention and not repeat the same mistakes! :-(

For the record I have now verified that the mount holes of the Unertl E Blocks are 0.560" - 0.562" apart, but similar blocks by Weaver are set at 0.500" apart. The original Unertl O and E block spec chart show the mount hole spacing of the E Block is .560. An except from Lt. Brophy's book on the '03 Springfield also confirms the 0.560" spacing. I have confirmed with Forester that their over-arm is designed for Weaver Blocks with a 0.500" - 0.504" spacing. The distance between what you refer to as the rear bushing holes (for the E Block mounted to the barrel) is therefore not compatible for Unertl O & E Blocks. They consider 0.560" spaving to be non-standard, but that is a Forester spec. The bushing hole spacing between what you call the front holes on the Forester Overarm is 0.860 +/- 0.002" (Forester sent me their drawing). These holes are for guiding the drill and tap for the O Block mount holes that mounts to the receiver ring. Fortunately, the spacing of the mount holes for the blocks mounted on the receiver ring is the same for all suppliers.

Below is a link to an old thread about the Unertl Blocks.
Rifle Scopes - Unertl bases | Snipers Hide Forum

So...mystery solved!

have built well over 200 of these over the last few years.