so I put together a new Norma dasher on a 9-1/4 twist 8 groove barrel I had laying about. I went to the range today and at 100yd grouping would not be the right word. I ladder tested in .3 gr increments from 30-32.6gr varget over a br4 primer several were over 6" for 3 shots I got one group of 1.5" at the 32.3 increment all were set at .005 jump. My crowning wasn't completely cooperating but when it did read velocities were 2800-3040fps ES around 30fps usually Any ideas on what to try next? Id like to at least enjoy burning these bullets up. Can't enjoy buckshot groups Thanks (I know this scenario has thousands of variables but I'm not after bugholes, MOA will make me smile)
Completely humbled by 95gr tmk
- Thread starter Shawnba67
- Start date
Just wondering if you have enough twist. Those are some pretty big groups.
Paul
Paul
I double checked the scope mounting bolts, the scope itself is a known quantity. The barrel is not, but it looks fine, LOL. I've got some 95gr nosler bt's to try. And I guess I'll try the tmk jammed up in there and backed off .030. I did notice the tmk is one long bugger my oal too give was longer with the 95tmk than it was with a 105nosler. Nosler was just to see I knew it was not gonna fly in a 9 twist
It seems that the twist rate is the likeliest causal. the first 3 shots were so all over the place I thought I'd forgottren to torque the barrrl down lol The crown was recently recut on my lathe plenty of room for that to have been botched but it looks good to the eye. I'm gonna try some lighter bullets next trip to range. It seems from what I've learned that the 9 recommended twist is for stabilization and not bc optimization
Did your target so any signs of bullet key-holing ?? These are several programs on the net that will give you a close Est. on the twist needed . This jbm program allows for tipped bullets
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi
Ive shot the 6mm 95gr TMK recently in a 6mmAR with an 8 twist barrel. I had not issues with stabilization, or grouping. In fact I would be using this bullet for this rifle from now on if the accuracy node would have been in the velocity band that I needed it to be in, so I am sticking with 107 SMK's. I don't think barrel twist is your problem.
Big difference between a 8 twist and a 9 1/4. Look at how the 244 REM shot with the bigger bullets. They made it work by a faster twist and called it 6mm REM. Matt
Those bullets are not being stabilized correctly out of his barrel. If you go on Burgers twist calculator and put the dimensions in a 1:8 is about perfect for those bullets. I shoot them out of a 243 with a 1:8 twist and they're fine. I wouldn't waste my time with load development any further with them.
WyleWD
Silver $$ Contributor
I've tried those bullets in an 8 twist 6br, a 9 twist 6br, and a 9 twist 6xc. I could get them to shoot consistently under an inch but never under 1/2" with any consistency..... and that's about it. Stabilization was not an issue as they shot similarly to 300yds in all 3 rifles.
But if I read your post correctly you got an amazing 6"group.
It was time to stop right there and find the issue. Without looking at your groups we're at a disadvantage, but a bad lot or box of bullets, crown condition or scope would be high on my list to check. Good idea to check with some 95gr BT's or Sierra 95gr match bullets (non tipped) Good luck and let us know what (all) you find. WDI've tried those bullets in an 8 twist 6br, a 9 twist 6br, and a 9 twist 6xc. I could get them to shoot consistently under an inch but never under 1/2" with any consistency..... and that's about it. Stabilization was not an issue as they shot similarly to 300yds in all 3 rifles.
But if I read your post correctly you got an amazing 6"group.
I've used H4350, H4831 SC, and H1000 with a 243 and all got sub 1/2" groups with this bullet at 100 yards. The H1000 was the most consistent and accurate with this bullet and groups around 1/4 inch. Maybe you have the wrong caliber for this bullet. And this is a varmint rifle not a bench gun and I've killed Woodchucks with it out to 600 yards not an issue.
Put my bet in for too slow of a twist. My 1:9 gives me fits from time to time, let us know how the shorter Nosler's work.
I just started working with these in a Kreiger 4 groove 1-9t 6x47L, running them from 3125-3180, shooting 2 shot groups just to get a feel for what might be worth pursuing but here's the groups so far (heavy wind) and I'll post what I find out in a session this afternoon.
Oops looks like I misread the OP. Thought it said 8 twist, but just realized it said 8 groove (crazy) and 9.25 twist. I change my thought then to this very possibly being a stability issue.
Funny story....My brother was working on his 22 250 AI and 55 gr Btips. He shot 3 shots at 25 to get the new setup on paper and then began testing at 100. Major frustration after a day of shooting. 1 - 2 MOA Tore the gun down, checked it over, and put it back together with a new scope. Day two was turning out just like the first.....HORRABLE groups. Just as he was leaving the range he decided to pick up the 25 yard target from the day before since it wasn't being used any more. ALL 3 HOLES WERE KEYHOLED....... PERFECT BULLET SILLOWETS.......but at 100 no sign of tumbling at all...or , at least very very little sign. The 55 grainers would not stabilize in a 14 twist tube. I checked the Berger twist calculator and it gave a .79 or some thing like that....way under stabilized. My thought was how many hundreds million 55 grain BTip's had been shot over the years in factory 14 twist bbls with ZERO problems?
My point, you can't always tell by looking at the bullet hole shape if the bullets are unstable.
shoot4fun
Gold $$ Contributor
I can tell you from experience the stamp on the shank isn't 100% certain.
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.