I know it's been asked but: What does the x39 or x54 mean when it follows 7.62?
- Thread starter Skippy
- Start date
I read through this topic in eager anticipation somebody would point out that 7.62mm (.30") is the bore diameter of both the Russian and the US rifles. It's the groove diameters that are different (.310" and .308", respectively). Put as simply as possible, Russian grooves are nominally .005" deep and the US standard is .004". That's why they use bullets of different diameters. The .303 British has a bore diameter of .303" (7.7mm), grooves .005" deep, and a normal groove diameter of .313".
Now none of these numbers are absolutes - manufactured items have tolerances and it's costly in time and money to hold them tighter than necessary for the intended purpose. In military rifle barrels, it's not uncommon to see tolerances of .002" or more in bore and groove dimensions, especially on wartime products where it was more important to churn out plenty of weapons than to hold them to the last .001".
Now none of these numbers are absolutes - manufactured items have tolerances and it's costly in time and money to hold them tighter than necessary for the intended purpose. In military rifle barrels, it's not uncommon to see tolerances of .002" or more in bore and groove dimensions, especially on wartime products where it was more important to churn out plenty of weapons than to hold them to the last .001".
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Well I just learned something new from Parashooter.
I was not aware of the groove depth difference. I just assumed that the barrel blank was 2 thou. different. Actually, I thought the Russian was .311, but as you say, what is .0001 (1 thou.) in war?
Thanks
I was not aware of the groove depth difference. I just assumed that the barrel blank was 2 thou. different. Actually, I thought the Russian was .311, but as you say, what is .0001 (1 thou.) in war?
Thanks
Well just for fun i will take some info i posted on another board & post it here:
I am starting to play with cast loads & I decided to slug my bores. I got some suprising results, the ones that looked horrible didn't slug too bad. I wonder how much accuracy comes from diameter & how much comes from sharpness of land. You can really tell which have the rough bores & which don't. I am going to try it again after shooting some of the rougher ones to see if they smoothen out. For reference
1947 ishy m44 refurb, mint bore, never shot it .301 land, .312groove, never shot
1953 Polish m44 mint painted black by the Poles, mint bore .300, .314, scary accurate
1917 rem 91 Finn used, beat on the outside, bore looks slightly frosted but sharp .301, .313, never shot for group
1936 ishy 91/30 spanish civil war cut down sporter, shot with corrosive ammo & not cleaned, bore rough .303, 313, never shot
1939 ishy 91/30 refurb laminate, outside mint, bore is a little worn & frosted, .301, .313, accurate
Fin m-28 well used outside, bore was rusty & lands rounded, .301, .3105 (da made them real tight)never shot
1943 ishy 91/30 refurb, most beatiful stock & shellac job I have ever seen, bore shot with corrosive ammo & not cleaned,bore rough .303, .314(I don't think it was all that tight to begin with), never shot
1895 steyr long rifle 8x56r refurb many times, bore looks good with some frost, .316, .330, never shot
1945 dou Iraeli used k98, well used, bore look good with frost, .314, .326, very accurate(scary)
1904/39 virgueiro 8x57, outside looks good, bore will blind you, .312, .324, very accurate
Notice two things: 1 I have no tula mosins yet, 2 I have way too many guns
I have never shot. thats not all of them but I ran out of sinkers.
And I just measured a bullet pulled from 150gr hungarian surplus 7.62x54r .3095 & a hornady 308 cal .308, I used a micrometer. Ever wonder why most Finn mosins shoot so good? Tighter barrels helps.
I am starting to play with cast loads & I decided to slug my bores. I got some suprising results, the ones that looked horrible didn't slug too bad. I wonder how much accuracy comes from diameter & how much comes from sharpness of land. You can really tell which have the rough bores & which don't. I am going to try it again after shooting some of the rougher ones to see if they smoothen out. For reference
1947 ishy m44 refurb, mint bore, never shot it .301 land, .312groove, never shot
1953 Polish m44 mint painted black by the Poles, mint bore .300, .314, scary accurate
1917 rem 91 Finn used, beat on the outside, bore looks slightly frosted but sharp .301, .313, never shot for group
1936 ishy 91/30 spanish civil war cut down sporter, shot with corrosive ammo & not cleaned, bore rough .303, 313, never shot
1939 ishy 91/30 refurb laminate, outside mint, bore is a little worn & frosted, .301, .313, accurate
Fin m-28 well used outside, bore was rusty & lands rounded, .301, .3105 (da made them real tight)never shot
1943 ishy 91/30 refurb, most beatiful stock & shellac job I have ever seen, bore shot with corrosive ammo & not cleaned,bore rough .303, .314(I don't think it was all that tight to begin with), never shot
1895 steyr long rifle 8x56r refurb many times, bore looks good with some frost, .316, .330, never shot
1945 dou Iraeli used k98, well used, bore look good with frost, .314, .326, very accurate(scary)
1904/39 virgueiro 8x57, outside looks good, bore will blind you, .312, .324, very accurate
Notice two things: 1 I have no tula mosins yet, 2 I have way too many guns
I have never shot. thats not all of them but I ran out of sinkers.
And I just measured a bullet pulled from 150gr hungarian surplus 7.62x54r .3095 & a hornady 308 cal .308, I used a micrometer. Ever wonder why most Finn mosins shoot so good? Tighter barrels helps.
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