what twist on 6.5

[jim dab]

Building 6.5 to shoot only 160gr bullets between 2900 and 3000ft/sec what twist should I be looking at. I know it's a heavy bullet but doesn't the velocity also have to be considered?

Jim
Alberta

[Luckyducker]

You will need a barrel with a 1/8" twist to stabilize those heavy bullets.  I had a custom Mauser rebarreled to 264WinMag last year and in my ignorance had my smith put a Shilen 1/9" barrel on it and I can only shoot the 129 grain bullets accurately.  I tried several different 140's and a variety of powders/loads but they just wouldn't stabilize in the slower twist barrel.  Had I taken the time to look at Shilen's website I would have seen the correct rate of twist for the heavier slugs.  Sooooo, you can learn from my mistake and do it right.  Good luck.

[Lone Star]

My .260 M700 shoots Speer 140s just fine with its 9" twist - but the 120s and 107s shoot slightly better.  Get the 1:8" rate.


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[kombi1976]

From memory the twist on a M96 and M38 is about 1:7.8" or similar.
I'd be making 1:8" at least.
That way you'll be able to load it up with heavy bullets.
The same reason why you want to ensure the throat isn't too short.
Since 6.5s really like heavy-for-calibre bullets and give superb penetration it's silly to take that away from them but not giving them the capability to do it.

[Mikey]

Twist on the 6.5 Swede military carbines is 1:7.5.  Since the carbines were just shortened rifles, at first, I would expect the twist to be the same in the M96 Mausers in 6.5.  I haven't loaded the 160 grainers in the Swede yet but shot a lot of them through my M38 Carcano years ago and they were nice and accurate.  Mikey.

[Don Fischer]

My 6.5x06 also has a 1-9" Shilen barrel and a had a terrible time getting 140's to shoot well. They ran about 1 1/4 to 1 1/2". Dropped to 129 gr and no problem but, talked to Sierra and they said their 140 gr Match king would but the 142 wouldn't. The 140 gr do shoot really really well. Have shot a number of group's at 200 yds under 1/2" with them. I get another 6.5 and it'll definatelly have a 1-8" barrel.

3000fps sounds a bit optimistic for a 160 gr 6.5. What are you shooting it in?

[jim dab]

So general consenus is that velocity is really not to be considered at all for rate of twist, A 1- 8" twist will be fine?

Jim
Alberta

P.S. Thanks GUYS

I was writing this before you posted yours Don,so I should address your comments. First I'm hearing that 130 and smaller shoot in 1-9" but you need 1-8" for 140's so with that im mind should I not be looking for an even faster rate of twist?

Don I've been considering this project for two months now. I started with the idea of shortening a RUM case because I didn't think I needed that much case. The work involved in shortening the case may be more than I want to do so I looked at the Dakota case. Then this 375 Ruger shows up. I'm thinking it should be just right. What do you think?

[Slamfire]

Actually velocity does count. It is rpm that stabilizes the bullet, so the faster it travels the more rpm is developed. My rebored Savage has an 8.5" twist, although I've no use for 160s in a .260, as the 140s and 129s do everything I ever needed.

[6.5BR]

Wow, 160 at those speeds, careful.

Fast twist, long bearing surfaced bullets add up to PRESSURE.  Slow powders in order.  You might do as well or better with a 7mm bore, a 7mag with get you there, and with good bullets, I am not sure you are gaining much using 160 6.5 bullets.  There are many controlled expanding premium 140's out there and I think some may do as well or better for hunting.  I assume that is your purpose.

Good luck, Be safe!  Anything over '06 or 284 case is overbore no doubt.  Some have used 300 weatherby cases I believe, check out what shooters who hunt game in Pennslyvania use for their 1000 yd shots or so.  Crazy distances, and they use 140-142's.  These are the elite guys, not that I would attempt it.

[jim dab]

6.5BR  I'm not really looking for longrange shooting. Just a very deep penitration round. The 3000ft/sec because most of my rifles, except the 30-30 are flat shooters and I don't want to mix up the old brain top much. I'll probally take this to Africa with me I'm thinking it would be awsome out to 300 yards. Your thinking I may be asking way to much velocity with that weight of bullet? I would rather give up velocity than change caliber or weight. As any one knows when it comes to toys need has nothing to do with it, It's all want!

But this still doesn't give me a definitive answer on rate of twist. It sounds like what came first the chicken or the egg. Rate depends on velocity, velocity depends on pressure caused by rate of twist.

OK let me ask this question. When it comes to letting someone make this dicision who would you trust?  The dicision could cost as little as dollars and at most my head. Someonr had mentioned Huntingtons has computer software that figures this stuff out would you trust it.

Jim
Alberta

[Slamfire]

Jim I don't know of a 6.5 that'll drive 160s at those speeds. And it isn't the powder capacity that's the hold up, its the size of the bore. Read P. O. Ackleys 'Handbook for Shooter's and Reloaders. Bore capacity is explained in a manner that most folks can grasp. As for penetration I once put a 140 Partition right between the hams of a cow elk, we found it in her brisket. That was from a 6.5-.257 the equivalent of the 6.5x55. The 160s have a place in the smaller 6.5s like the 6.5x52, 6.5x53 and 6.5x54 where the velocity is quite low, like your .30-30, momentum takes the place of velocity in those cartridges. 

[jim dab]

Well lets have a best guess as to top velocity with 160's. Not to be disrespectful but I think I heard this same discussion about bore capacity in regards to both the 25 cal and 30 cals. Now lets see what those Lazzeroni's will do or some of the even faster 30 cals. Yes I maybe I can get the same penatration from a 140 TB or Swift with a little more velocity but thats not what I " want ".

Jim
Alberta

[Slamfire]

Well I guess you'd better look up the .264 Win Mag to get a good idea of what is just about the most velocity, or possibly the 6.5x68.

[jim dab]

Slamfire I think this new ruger case is awful close to the 6.5 X 68, just blown out.
Thanks
Jim
Alberta

[Doesniper]

I shoot a 260 Ackley with a 1:9 twist, and it shoots a 147g Clinch River very good. Best to date is 3 shots @ 500yds in 1.5". The BC is around .624, and leaves the bore at 2900 fps. I use a long action so the bullets can be seated out as far as needed.