69SMKs in a 12 Twist

[Rickhem]

Last weekend, I loaded up some 69 SMK bullets over Varget to use in an older .223 flat top with a 1-8 twist barrel, that was intended to be a match rifle back over a decade ago. Freshly loaded ammo, but the bullets and powder are that old too. Turns out there were optics troubles on the flat top, so didn’t get to fire very many through that upper.
I did shoot a 5 shot group with that ammo through a very old 700 Varmint rifle, which has a 12 twist barrel. That rifle was bone stock. Was expecting to see keyholes at 100, and it ended up printing a group of about a half inch. All 5 shots touching in a diagonal line. That’s not supposed to happen.

Anyone else find those 69 SMKs worked in a 12 twist?

 

[jpretle]

Not sure I would call 1 group a definitive answer.

 

[mike mccormick]

Never tried that combination, always got my best 12 twist groups with 52 or 53 gainers. Common wisdom says the 69s shouldn't work. Odd

 

[bpd459]

Years ago, I tried my service rifle load of 24.5 Varget/69gr SMK in my 1-12“ REM varmint rifle and it shot knots. I was truly surprised. Loaded same powder charge and tried the Hornady 68’s and I’ve shot tighter groups with a full choke 12ga…
John

 

[Rickhem]

Years ago, I tried my service rifle load of 24.5 Varget/69gr SMK in my 1-12“ REM varmint rifle and it shot knots. I was truly surprised. Loaded same powder charge and tried the Hornady 68’s and I’ve shot tighter groups with a full choke 12ga…
John

Yes, exactly. I'm a half grain up from you with my load, and that has been a great load in 7 and 8 twist service rifle barrels, more than a few of them. That's why I loaded it for the match upper too. I have some of the Hornady 68s, but strangely enough, that is a much longer bullet. My 700V usually gets loads with 52-53 match bullets, or the 50TNT, which shoots very well from that rifle. I had both at the bench, so when my turret wouldn't adjust on the match upper, I decided to fire 5 shots through the bolt gun. I've heard internet tales of how speeding up a marginal bullet could give good results, and benchrest guys tend towards the lower side of bullet stability, so why not? I figured I'd see a shotgun pattern, but that isn't what happened.

Granted, a single 5 shot group isn't definitive, but if that combination wasn't enough to stabilize the bullet, I'd never see a group, at least that has been my experience with other combinations that were outside of the stability parameters. So follow-up groups will be tried, and probably stretching it out to 200 or 300 as well.
And I tightened up the set screws on the turret on the match upper, so that'll see some of this ammo too.

 

[SteveOak]

I am well known at work for the mantra, "Declare success and move on". My meaning there is to not get bogged down unecessarly in the why if it is not useful, better to make progress.

In this case I would encourage you to try longer distances, at least 300, before you declare success.

 

[Turkeytider]

Don`t know about a 12 twist, but the 69 SMK out of my 7 twist Savage Model 12 is money at 500 when I`m not screwing up the shot. Sub-MOA group into a 5" gong is more than feasible. And that`s with a factory load ( ADI ). From personal experience and from what I`ve read, the 69SMK has to be one of the very best .223 bullets ever produced.

 

[Laurie]

Years back I borrowed a newly introduced .223 Cz527 'Varmint Match' from the UK importer for review. This was a heavy-barrel model with an alleged 9-inch twist, in an HS-Precision kevlar stock and aluminium bedding block.

Off I went to the range with 50 newly loaded rounds half each of the 69gn SMK and the longer, as @bpd459 notes, 68gn Hornady HPBTM. The 69gn bullets held the old UK NRA 'black' at 300 yards, most in the 3-MOA 4-ring - not exactly precision rifle performance. That was on a range at around 175 ft ASL on a cool day barely in the 60s. The twist rate was of course NOT 1 turn in 9-inches, and was CZ's version of the standard 12 twist after a disagreement between the company and the European firearms / ammunition standards agency the CIP. I'd regard that performance as typical and exactly as expected in this twist and environmental mix - ie barely stabilised and certainly not properly stabilised. The longer 68gn Hornadys barely held the 6ft square target frame and unlike the SMKs produced elongated holes.

The same rifle later shot quarter to half -MOA groups with 53gn Hornady AMaxes on the same range and similar conditions. The UK importer (who was unaware of the specification change until the complaints rolled in) offered 9-twist equivalent Remington 700 PSS models to unhappy buyers, and later once CZ and CIP had come to an agreement rebarreled the early 12 twist examples with the proper spec CZ barrel.

On a range situated at a significantly higher altitude and/or in warmer air, many users would have been unaware of any issue here. However, note that Berger's stability calculator says this combination (0.900-inch OAL BT bullet at 3,000 fps in 12-twist) is actually unstable and you need 11-twist to be even marginally stable. Since factory rifle barrels' actual twists can vary significantly from the specified nominal value, playing with barely adequate twists is frequently a lottery.

 

[Rickhem]

Got some time after mowing today to shoot a little. Since I fixed the turrets on the match upper, I got that hitting my 400 yard plate. Wind was a puzzle at first, but not enough to cause misses if I held for it. So with a few rounds of that same ammo left, I got out the Rem 700V again, and decided to try stretching out to 200. Unfortunately, the grass in the field blocked my view of my target frame at 200, so I moved it back out to 300. I added 5 minutes of elevation and took three shots. Those are the 3 on the backer above the target in the picture. Took 4 clicks off and fired 5 more rounds. They're still a little high, but all down on the target. That group is about 2¼" left to right, and that was on a pretty windy afternoon. I'll have to chronograph this load, since it seems to need a minute less elevation to get to 300 than most other cartridges do. Task for another day.

So again, not definitive, but it held under MOA at 300 on a pretty breezy afternoon. I'm also going to have to check that barrel and see what I get for twist rate on it.