Stability?

[MrMajestic]

Savage 10 CFM, 7.62X39, 20" 1in10" twist barrel, Lapua case, 168 gr. Berger Hunting VLD, BR2 primer, Undisclosed amount of 1680 due to being in excess of standard load data available however deemed safe in firearm using standard pressure detection methods, estimated velocity of 2200 fps.
Range-23 yds while checking velocities at my in-house range.
I would have never guessed there would have been a problem but pictures speak louder than words! I am no expert however I am thinking this will not make for a longer range load in this rifle. What do you guys think? :

 

[bheadboy]

you do not have the velocity or twith to stabalize that long a bullet.

Bob

 

[rcw3]

Some 7.62 x 39 bores are .310" and .308" bullets don't fare so well in them. I don't know if that's what you have going on, but a 1:10" twist, if that's also what you have, should be fine for that bullet, even at somewhat anemic speeds.
Robert

 

[MrMajestic]

Robert, It's a .308 bore and that's what I thought. JBM's stability even gives the 208 gr. A-Max a 1.2(memory?) at 1900 and 0 degrees. I have shot the 208's with N130 at 1989 fps and they weren't the best(Minute of Deer) but didn't go in sideways at 200 yds. By the way the 110 grain V-Max at 2700+ fps are 3/4 MOA!

 

[Keith Glasscock]

German Salazar recently had a mis-marked barrel. It was marked as an 11 twist but when he checked it was an 18!

Have you verified the barrel twist?

 

[TonyR]

German Salazar recently had a mis-marked barrel. It was marked as an 11 twist but when he checked it was an 18!

Have you verified the barrel twist?

There were a bunch of those. The manufacturer knew the serial numbers and the vendor called me about mine. It is definitely worth checking.

 

[fullersson]

MrMajestic,
You have taken keyholing to a whole new level. I don't think I've ever seen a bullet hit completely side ways. Keep us updated on this I would be very interested to hear what was the problem. Brian Brown.

 

[MrMajestic]

I checked the twist immediately after noting the entrance angle. With a tight patch and cleaning rod it appeared to be 1in10". Leaving a 1/4" margin for error there shouldn't be a problem from all I have read. I will try to duplicate however at an outdoor range to protect my mechanicals located behind my backstop. I too have never seen a bullet go in at 90 degrees!

 

[6BRinNZ]

23 yards - it just hasn't gone to sleep yet

Seriously - good luck, it looks like an odd one to figure out...

 

[mikecr]

Gyroscopically unstable bullets tumble immediately.
This was just beyond my chrono:

 

[MrMajestic]

mikecr, are you trying to make me feel bad or good? I stopped after one! ;D

 

[mikecr]

I don't know the actual problem. I guess I'm just suggesting that bullets tumbling so close are typical of gyroscopic instability, rather than dynamic instability.

I knew the bullets fired toward that plate would be unstable, and found that I could not hit anything with them by 100yds.
Often I read someone suggest sideways impacts out at 300, or 500yds.. I don't think so. I don't see how they would ever get there.

Anyway, it's hard to believe your twist is actually 1:10

 

[Heavies]

How is the crown, any recent damage?

 

[MrMajestic]

No, but good suggestion and I will verify with known loads.

 

[jonbearman]

I just built one of these myself and used a mcgowen .310 bore.I loaded some sierra 125 soft points with 29.0 grains of benchmark.It shoots .290 groups at 200 yards.If you have a .308 barrel for sure,why are you shooting such heavy bullets? Is there a reason for shooting a 200 plus grain bullet versus a 120 to 150 grain bullet like it was intended originally.Without the muzzle velocity above 2400fps,I dont think you can stabilize them .Try something a bit lighter.Let us know how you make out. I love the little rifle I built and wouldnt trade it for anything.SPECIAL NOTE TO MR MAJESTIC::::::: LOOK AT THE SIERRA ACCURACY LOADS FOR EACH BULLET. That is how I found the load I am currently using.

 

[MrMajestic]

Jon, it is a .308 bore and a 1in10" twist. It is throated very long and the 208 gr. A-Max into the rifling puts the BT and major diameter junction at the base of the neck, perfect fit. It shoots these Minute of Deer at 200 yds with a MV of 1989 fps. Even with the long jump to the rifling it shoots the 110 gr. V-Max sub-MOA. To answer your question why, because we can and its why we do what we do. The .30-30 shoots a 170 gr. at 2200 fps and the 168 gr. at the same velocity mimics it. Also due to the high BC extends its range considerably. I really like what the 208 does to the terminal energy at extended ranges with making it a viable 500 yd. Deer cartridge although with a lot of drop! Basically I am just experimenting, came across an odd occurrence, and thought it made an interesting post. Thanks for the advice with the load data and I have experimented with Bench Mark and the heavier weight bullets.