6.5 150g SMK

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macguru
Posts: 1206
Joined: Wed Aug 05, 2009 9:49 am

Re: 6.5 150g SMK

#16 Postby macguru » Wed Jun 13, 2018 7:34 am

The other alternative would be 6.5x55 AI. Then you could wear out the barrel fireforming, but at least you start with good brass (lapua). I guess you need at least 2 barrels done at the same time or at least with the same reamer... I never want to get another 6.5x284, too much stress on that case head.

RDavies
Posts: 1865
Joined: Sun Feb 12, 2006 7:23 pm
Location: Singleton NSW

Re: 6.5 150g SMK

#17 Postby RDavies » Wed Jun 13, 2018 9:50 am

macguru wrote:The other alternative would be 6.5x55 AI. Then you could wear out the barrel fireforming, but at least you start with good brass (lapua). I guess you need at least 2 barrels done at the same time or at least with the same reamer... I never want to get another 6.5x284, too much stress on that case head.

A 6.5x55AI would be my choice for running the 150s (or upcoming Bergers). It wont be pushing them fast enough for them to start coming apart. For fire forming without chewing up barrel, you could just use Trail Boss powder and have a plinking session out bush with them. Ive been able to shoot off a lot of rounds pretty quickly with Trail Boss without the barrel getting hot, and getting surprisingly good plinking accuracy.

BRETT B
Posts: 183
Joined: Fri Sep 30, 2005 2:37 pm
Location: PERTH

Re: 6.5 150g SMK

#18 Postby BRETT B » Wed Jun 13, 2018 9:57 am

Waiting to get my hands on some and put the through my 260AI
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

Frank Green
Posts: 188
Joined: Wed May 28, 2014 11:48 pm

Re: 6.5 150g SMK

#19 Postby Frank Green » Fri Jun 15, 2018 11:26 pm

RDavies wrote:
Frank Green wrote:
RDavies wrote:Is this in a canted land (5T) barrel?


Yes it's the 5R style rifling.

The posts I read on the U.S forum seemed to indicate that the 5R type barrels didn’t have the same bullet blow up problem as the regular barrels. In your position you would know a lot more about this than myself (and most others) so do you think there is any validity to the notion that the canted land barrels are gentler on bullet jackets when bullets are spun very quickly.


Rod, I don't think it's got anymore to do with the angles on the sides of the lands (although it's not hurting anything) but more to do with the odd number of lands and grooves. With the lands not directly opposing one another I feel this helps in distorting/upsetting the bullet jacket less and in conjunction with the angles on the sides I feel this will help fight bullet failure. Not all odd number groove barrels give you the benefit I feel though. Look at some of the 3 groove barrels. The lands are typically really wide. So a portion of one land still opposes the other land. I don't feel this is a benefit at all.

Bullet failure is a higher problem in calibers under 6.5mm typically. With the newer heavier 6.5's etc...and spinning them hard with faster twist rates and possibly higher velocities. Might work against you.

At 2700fps in 1-7 twist barrel the bullet is spinning at 277,714 rpm. At 3000fps. in the same twist barrel that bullet is going to spin at 308,571 rpm. Those are some heavy numbers and we all take bullets for granted and expect a lot out of them. I feel we all push the envelope!

Later, Frank

Frank Green
Posts: 188
Joined: Wed May 28, 2014 11:48 pm

Re: 6.5 150g SMK

#20 Postby Frank Green » Sat Jun 16, 2018 12:12 am

For comparison sake....look at a .308win. bullet at 2700fps in a 1-12 twist barrel. The rpm of that bullet is only 162,000.


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