Permitted enlargement of 1903 peep

[11mm]

While I don't intend to shoot my 1903 rifles in competition, I would like to enlarge the peeps in the sight leaves, as my eyes would like that. I believe I have seen that there is a maximum allowable size for peep enlargement that is accepted in competition for the military vintage matches. Could somebody pleas tell me what that size is? I would like to try that first, before going larger. Thanks.

[mhb]

I believe...

that the maximum permissible 1903 aperture diameter is .100" (the Marine slide aperture diameter). Standard-type 1903 slides were available with apertures in diameters from .040" to .090" in .010" increments.
I have enlarged the apertures of several of my 1903s to .100", and find that to be a great help for aging eyes, and it does not negatively impact accuracy or group size.

mhb - Mike

[clintonhater]

...find that to be a great help for aging eyes, and it does not negatively impact accuracy or group size.

mhb - Mike

I put Merit Iris disks in a couple of Lyman 48s I shoot regularly, and found that even in bright sun, when there should be some theoretical advantage to the smaller aperture, I always shot better with the wide-open orifice. And if you read William Lyman's earliest ads for his first tang sight, that was exactly the argument he was making--that better shooting could be done with a larger aperture, though this idea went against the thinking of his time.

Haven't drilled out any M1905 sights, but I have the pin-hole apertures on a couple of early Model 52s with the standard military-style leaf sights; big improvement.

[psteinmayer]

Although not a 1903, I enlarged the peep on my Krag 1902 sight (the Sgt peep) from 0.040 to 0.070 to help with sighting in the Vintage match. 0.070 was as large as I could go without risking damaging the plate. As mhb stated, you can enlarge to 0.100 and remain legal per CMP rules.

[PhillipM]

The CMP did away with all restrictions on aperture size a couple years ago.

Sights must be of the same types that were on rifles issued to regular
military personnel, except that the internal diameter of rear apertures
may be modified. Adjustable apertures, interchangeable inserts and
lens inserts of any type are prohibited. Special purpose sights designed
for sniping or competition are not permitted.

https://www.google.com/url?sa=t&source=web&rct=j&url=https://thecmp.org/wp-content/uploads/CMPGamesRules.pdf&ved=0ahUKEwj9rqzG8YvOAhUKLSYKHTkgA1cQFggbMAA&usg=AFQjCNEtX3Q-E0njXGIS7GG6ZbfAbZl_tA&sig2=KJ3PTigp61GC-3x2aTQhng

[11mm]

Thanks a lot guys. I now know where i can go with this modification.