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October 23, 2017 ...

Topic: 18” ballistic advantage 6.5 CM barrel (Read 209 times) previous topic - next topic

18” ballistic advantage 6.5 CM barrel
I got a 18" ballistic advantage barrel (premium series) on my diamondback AR10. I broke it in with hornady whitetail using BA's suggested break in. I then started loading the 143 eld-x's with H4350/federal match primers @ mag length 2.805". Shot 5-5 shots groups at 40, 40.5, 41, 41.5, 42g. Best group was 1.4" at 100 yds. Other 4 groups were 2"+. I received my hornady modified 6.5 cm case and measured. To the lands was 2.892" so in the mag 87thou jump. I read these bullets are jump tolerant. Should I try seating even further to see if the grouping improves. A friend suggested shooting 139g Lapua Scenars. Any others using these in a ballistic advantage barrel.

  • rardoin
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Re: 18” ballistic advantage 6.5 CM barrel
Reply #1
Don't be afraid to try more jump.  Test perhaps 0.100 and 0.120" jump.

  • dadajack
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Re: 18” ballistic advantage 6.5 CM barrel
Reply #2
There's an old saying, something like, "If you throw enough jump at the wall, one jump will stick out more than the others." Something like that...

Seriously though, @rardoin is absolutely right, and that is the secret to the SMK success as one of the most accurate loads for the 308 ever devised by a manufacturer. I mean, 90% of the guns in the world can't be wrong, and 95% of the guys shooting Federal Match are not shooting "match" chambers with -0.005" jam, you know?

I'd also suggest you drop your powder charge steps to 0.3 grains at a max. I prefer to go 0.2 once I've gotten to within a grain of my preceived/calculated maximum based on my knowledge of how the gun handles max charges with that particular bullet construction. You might find a window in there where you get all the resonant bunnies to jump together and point the pointy thing in the same direction every time it leaves the tube. Good luck!

One more thing, are you sure you can't get those to load out to 2.820"? I get good reliability at that mag length with my Magpul, Lancer, and GI mags.
Silence is golden. Duct tape is silver.
I have a lot of guns... There, I said it.

Re: 18” ballistic advantage 6.5 CM barrel
Reply #3
Did you keep info on boxed ammo accuracy or were you just burning bullets down the pipe?

Re: 18” ballistic advantage 6.5 CM barrel
Reply #4
Did you keep info on boxed ammo accuracy or were you just burning bullets down the pipe?

Single shot and cleans for 10 rounds. Then one three shot and clean then 5 shots and cleaned through 40 total rounds. I was trying to sight in at the same time and do a little grouping. The factory Hornady Whitetails actually shot a little better when I did the 3 and 5 shot groups. 1.5"-2". But still not good.

Re: 18” ballistic advantage 6.5 CM barrel
Reply #5
There's an old saying, something like, "If you throw enough jump at the wall, one jump will stick out more than the others." Something like

Seriously though, @rardoin is absolutely right, and that is the secret to the SMK success as one of the most accurate loads for the 308 ever devised by a manufacturer. I mean, 90% of the guns in the world can't be wrong, and 95% of the guys shooting Federal Match are not shooting "match" chambers with -0.005" jam, you know?

I'd also suggest you drop your powder charge steps to 0.3 grains at a max. I prefer to go 0.2 once I've gotten to within a grain of my preceived/calculated maximum based on my knowledge of how the gun handles max charges with that particular bullet construction. You might find a window in there where you get all the resonant bunnies to jump together and point the pointy thing in the same direction every time it leaves the tube. Good luck!

One more thing, are you sure you can't get those to load out to 2.820"? I get good reliability at that mag length with my Magpul, Lancer, and GI mags.


I will try them at 2.820" That would get me to around 65 thou jump. Which Ibe read a few times was good. I am running magpul magazines. If that doesn't work I will try deeper. I run the the 178's in my .308 savage fcp (factory) at .015" jump and get great results consistently around .75" groups. Thats why the big jump to lands in my AR had me worried.

Re: 18” ballistic advantage 6.5 CM barrel
Reply #6
You might have a bad barrel, but probably not. My 18" BA is very accurate...if it shoots outside of 1 MOA it's usually my fault. I won't go so far as to say it's MOA all day, but I have made several .75 ish groups with factory loads. A few even better than that.

It *definitely* prefers 140 eld-m and 143 eld-x factory ammo...but I haven't tried reloads yet do I can't really speak to that.

I hope yours isn't a lemon, but if it is I'm sure BA would make it right.

Re: 18” ballistic advantage 6.5 CM barrel
Reply #7
You might have a bad barrel, but probably not. My 18" BA is very accurate...if it shoots outside of 1 MOA it's usually my fault. I won't go so far as to say it's MOA all day, but I have made several .75 ish groups with factory loads. A few even better than that.

It *definitely* prefers 140 eld-m and 143 eld-x factory ammo...but I haven't tried reloads yet do I can't really speak to that.

I hope yours isn't a lemon, but if it is I'm sure BA would make it right.

same here with the same barrel just on the other side of the pond. I would give them a buzz if it persists.

I am currently struggling with powders, hope not to highjack this too much but refers to the same barrel.
Here H4350 is a real myth and as Loch Ness monster dust has been on order for the last 10 months or so. Who knows. In the meanwhile I got some light local bullets (http://windcutbullets.com/) and I picked up some 125 gr tactical for the 6.5 cm. I was looking for data to start with using what I have in the drawer, some N150. Is it a big risk using Scenars 123 data from VV? Any word of wisdome on that? Will share the results with all BA owners...N150 seems to be a little bit faster than H4350, but might be palatable for a short (18") barrel like ours. Opinions?

  • dadajack
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Re: 18” ballistic advantage 6.5 CM barrel
Reply #8
@gnatmm A rule of thumb I use is: starting charges for cup and core bullets is pretty much interchangeable with one caveat - you must know you are not changing the internal capacity of the case more than 10%, and that you are not jamming the lands at your chosen OAL. Bullet construction, for the most part, allows for some liberties to be taken when substituting one mfg bullet for another. You cannot do the same with powder. Even swapping primers should cause you to back off your load data 3-5% and work back up to make sure you are not introducing a dangerous variable. Hope this helps.
Silence is golden. Duct tape is silver.
I have a lot of guns... There, I said it.

Re: 18” ballistic advantage 6.5 CM barrel
Reply #9
@gnatmm A rule of thumb I use is: starting charges for cup and core bullets is pretty much interchangeable with one caveat - you must know you are not changing the internal capacity of the case more than 10%, and that you are not jamming the lands at your chosen OAL. Bullet construction, for the most part, allows for some liberties to be taken when substituting one mfg bullet for another. You cannot do the same with powder. Even swapping primers should cause you to back off your load data 3-5% and work back up to make sure you are not introducing a dangerous variable. Hope this helps.
very useful thank you. my original plan was to add another level of uncertainty, named Peterson palma brass...What could possibly go wrong? :D Correct me if I am wrong, another good reason to back off load data, as using a 'premium' case with small rifle primer definitely is :D Now I am more on adding one degree of uncertainty at a time starting with good ole Hornady brass and Federal primers, and then change gradually and develop step by step. As far as bullet seating is concerned, I am using the lock n load stuff and the bullet should jump 0.080" off the lands. There is always time to get it closer... I seated one bullet, no powder or primer and chambered and it comes out extracted the right way. I was also checking neck tension and I can confirm that no crimp is needed (I use Forster FL sizing die). The bullet does not move through the cycle, as it is light enough.

Re: 18” ballistic advantage 6.5 CM barrel
Reply #10
I have an upper with the same barrel.  I broke it in with American Eagle 140 grain rounds.  The rifle was MOA and sub MOA at 100-500 yards.  Reloading with 143 ELD X and IMR 4451 is getting sub MOA groups.  I have moved to Berger 130 grain AR hybrids and have had great success from 100-750 yards on steel.  Keep at it and don't over clean between firings.