.270 Win.
- Thread starter Blackrider
- Start date
My first Stalking rifle was a Browning A-Bolt in .270. Not had the pleasure of shooting any deer with it yet but i am confident in it's abilities and will also be confident that when i do finally put a deer in my crosshairs, whether that be muntjac or red then the rifle will do its job as designed.
Brithunter
Well-Known Member
Calibre yes as in English that is size of bore however the bullet measures 7.03mm in diameter.
Just like the .308 Winchester is a .30 calibre but uses bullets that measure 0.308" which is where Winchester grabbed the market name from.
This is why the 6mm/.243 is actually too small to be legal until the recent law change as the bore of them is 0.236" and as such did not meet the minimum of .240" calibre
.
bewsher500
Well-Known Member
All mine are 7.07mm
Bought my first 270 in 1988, now, as my user name suggests 270wsm with T8, throwing 130gr Sierra pro hunters and the occasional 150gr Hornady interlock.
Used to see more meat damage from .243's when I was game dealing. Two noteable carcasses were two roebucks shot by the same stalker on the same day with 100gr Norma sp's. Bullet placement was ok, but in both cases the round had disintergrated and mashed the shoulders and loins.
Used to see more meat damage from .243's when I was game dealing. Two noteable carcasses were two roebucks shot by the same stalker on the same day with 100gr Norma sp's. Bullet placement was ok, but in both cases the round had disintergrated and mashed the shoulders and loins.
Brithunter
Well-Known Member
I just converted .277" on the pocket calculator, which is the nominal size, I have no bullets here which I can actually measure due to the stupidity of the expanding projectile nonsense.
In line with our American friends theory the bullet should be 0.001" larger than groove size however as Ken Waters noted in his Pet Loads series that many .270 Winchester barrels are actually cut in the groove to 0.278" or larger and all his bullets measured 0.277" or LESS.
When I have measured bullets with a micrometer it was often noticed that many are in fact undersized in comparison to their claimed size. I have a feeling that with metal patched or jacketed if you like
that a bullet being several thousandths under size is not a problem. Cast lead is another matter entirely.
bewsher500
Well-Known Member
I just converted .277" on the pocket calculator, which is the nominal size, I have no bullets here which I can actually measure due to the stupidity of the expanding projectile nonsense.
In line with our American friends theory the bullet should be 0.001" larger than groove size however as Ken Waters noted in his Pet Loads series that many .270 Winchester barrels are actually cut in the groove to 0.278" or larger and all his bullets measured 0.277" or LESS.
When I have measured bullets with a micrometer it was often noticed that many are in fact undersized in comparison to their claimed size. I have a feeling that with metal patched or jacketed if you like
not sure I understand what you mean. mine measure OVER size
if the barrels are cut to 0.278" or larger you surely would need a bullet with a OD of at least that to seal? no?
0.278" = 7.0612mm
my bullets behind me here are all 7.07mm which makes sense
a 7.03mm bullet going down a barrel with a 7.06mm groove diameter would have gas blow by would it not? (assuming the crushing effect of the pressure behind and the swaging of the rifling does not force a larger OD once in the barrel
interestingly I just measured the cup aspect of the same bullets on a fired recovered bullet and it measures 7.09-7.10mm!! (0.2791" - 0.2795")
Brithunter
Well-Known Member
This gas blow by is just what Ken Waters was talking about when he discovered that a lot of barrels for the 270 Win have grooves of 0.278" or more in diameter. All the bullets he measured were under 0.277" in diameter BTW. have not got time right now but I will try to look out the article later.
The reason he discovered this is that he slugged the barrel in preparation to preparing some cast lead bullet loads and gas blow by on cast lead bullets is bad news as one then gets gas cutting of the bullet which ruins any precision and badly fouls the bore. I seem to recall he even went to a machinist friend and used his box of slips to check his micrometer for accuracy.
This all brings to mind the 6.5mm Mannlichers that I owned, I made a brass plug gauge up graduated in 0.001" steps and both barrels came in with 0.256" bores however as best I could measure with calipers the groove diameter is 0.268" which is 0.004" oversize according to our American friends who seem to think that rifling should only have 0.004 deep grooves. Interestingly there is many years between the manufacture of both barrels the one on the Rigby built rifle dating to 1893 yet the one now fitted to my Model 1903 Schoenauer was made over half a century later if we can go by the wrapping it came in which bore the logo used during the 1960's by Steyr.
As 6.5mm bullets are of a nominal size of 0.264" then then are under size for these barrels however it does not seem to have any real effect. I never measured the bullets but I doubt if all are really of a full 0.264" in diameter.
As the Schoenauer is scoped we could at least get a comparison with "modern" rifles. In initial testing before my move to this "god forsaken county" we found that it shot the Speer 120 Grain bullet well. However all load development was halted after the move as the FLO refused to allow the rifle to be shot and insisted it be "for collection only" hence the whole rebuild and restoration project was put on hold.
Of course the Rigby has found a new home now along with the nice 303 BSA made sporting rifle I had.
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