With all the interest in the XM25 i'm reintroducing this post in the hopes that someone can shed light on this question,someone has had to of seen them,someone had to of marked them,but the question is what did they actually stamp on them
(see pic in post 73)
http://m14forum.com/m14/121347-toki-s-xm25-project-5.html
I presume Toki's barrel is a US Army barrel that was from an XM25 kit.
"
4 GR 1 10 7.62 MM 4 88" = 4 groove, 1:10 twist, 7.62 NATO caliber, made April, 1988. This seems typical of Barnett prepped military barrels of that era.
My Navy M14 team barrel is a heavy Douglass/Barnett and is similarly marked:
"
1 10 7 62 MM 4 93 4 SPL USN" = 1:10 twist, 7.62 NATO caliber, made April, 1993, 4 groove, SPL = unknown (match/heavy barrel perhaps?) and USN is obviously US Navy.
http://i289.photobucket.com/albums/... 2017/M14_USN_barrel_markings_zpseikniioj.jpg
So here's what I would say about markings on military M14 Douglass/Barnett barrels presumably used on XM25 and M25 rifles:
4 groove marked
1:10 twist marked
7 62 MM marked
month + 2 digit year marked
"USN" mark on Navy barrels (no equivalent marking on US Army barrels)
"SPL" not sure about this on the heavy profile barrel, could refer to chambering or heavy barrel profile.
According to Different's research/book, the XM25 designation occurred in 1988, and the M25 designation occurred three years later in 1991. (I don't know what month). My understanding is that medium weights were used on the XM25 and that heavy barrels were used on the M25s. I think the M14 team rifles also made the switch from medium to heavy barrels around the 1990/91 period or there abouts, but I need to review the source of that recollection)
Hope that info helps.