Strange hole in upper handguard of early 1903

I have an early Rock Island...1908... and there is a strange slot in the upper handguard....it looks original to the handguard...it is about 1/4" wide and 3/4" long and sits just about 5/8" forward of the rear sight base..... my sight base has been milled flat as my rifle has a cocking piece peep sight.

What would this slot be for ?? any ideas ?

Thanks
Joel

Joel, that is known as a Fixturing Slot. Its purpose was to aid in holding the hand guard steady while cutting it to form on the machine.

If memory serves, there was no fixturing slot in a RIA handguard so you may have a Springfield handguard.

i think its the other way around.. RIA has a slot...SA no slot..

Quote:

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Originally Posted by chuckindenver

i think its the other way around.. RIA has a slot...SA no slot..

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Nope -- SA has the slot. If you look at Remington high hump handguards, they don't have a fixturing slot, either - a carryover from the RIA machinery they used.