Length of Sierra .270 175gn Game King?
- Thread starter ww111
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Darkker
Well-Known Member
Sierra .270 175gn Tipped Game King
I was perusing the Sierra website when I came across these. Anyone seen or tried these? It said they need a 1-8" twist. Now we're getting somewhere!
I just measured 7of them and got an average of 1.645"
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The Sierra 175 is not in here but many other bullets are from JBM. Handy to have around.
www.jbmballistics.com
JBM - Bullet Length List
Matrix was the first to develop the 175g .277 cal, which requires 1:8' or faster. I built my .270 AI in 2012 with a 30" Lilja 3G barrel primarily to propel the 165/175 Matrix VLDs.
Darkker
Well-Known Member
Remember that bullet weight is mostly irrelevant to stability, it's length that needs stabilization through RPM.
Use the JBM link given above, they have a stability calculator on the left. Plug in the length given to you by poor choices, and you'll have an idea of there's any hope of stability.
Remember that JBM's calc isn't perfect, so RPM dependant, yellow might work. This is because while velocity decay happens rather quickly, rotational decay happens quite slowly. So relative to the linear velocity, RPM increases as the bullet travels down range.
not necessarily, but in most cases length does matter more on stability. velocity can matter also. twist gets to stability faster than upping velocity. i run numbers thru berger and jbm. if you think that length is the GREATEST factor, drop velocity by 500, 1,000 or to half.
lancetkenyon
Well-Known Member
While this is technically true, bullet length is directly related to bullet weight in any given caliber as long as we are talking same bullet design (cup and core HPBT for example).
With a fixed diameter, higher weight can only be had with longer bullets.
There are some variable factors that come into play with ogive shape, and base shape. When you want higher BC boattails and long ogives, these only exaggerate the lengths.
A 175 flat base round nose will be much shorter than a 175 boattail high BC match bullets.
