BSA CF2 in .243

[RufusRover]

Hi!

Does anyone here shoot a BSA CF2 in .243 and if so what the heaviest round you load that it will stabilise?

I've worked out a load it likes in 75grn and have loaded a few batches of 90grn to try at 200 yards next time I'm out. I'd like to try some 100 or 105 but if it won't group there's no point.

[AL8]

I have a stutzen one that shoots 95 grn ok at 100 yards. Less than 1/2 " group.

[RufusRover]

Ooh I like the Stutzen but couldn't find one!

Sounds like our group sizes are similar - albeit mine are using 75grn so that's encouraging. I'll have to get to the range and try my 90's.

[AL8]

let us know how you get on

[RufusRover]

Finally got out with the .243. And I'm more than happy with the groups I got using 90grn (8 inside an inch at 100 yard with 2 just over an inch - but it's windy....or I pulled them). However, I had twenty 105grn to try and at 100 yards they were starting to keyhole and by 200 they were all over the place. So I'll do some more load testing with the 90's and the 200 x 87grn Hornady soft points I've just ordered. I'll get some pictures up when I can.

[Oddbod]

My friend's Stutzen is OK with 100's but as you've found out, can't stabilise 105's.
It's absolutely nails with 55gr Sierra Blitzkings - half an inch or less for five shot groups @100yds.

[Laurie]

With the standard SAAMI 1 turn in 10-inch twist rate which is most likely what BSA gave its CF2s, 100gn PSP type deer bullets usually mark the stability watershed. Flat base models are just fine, but boat-tail types are often marginal to the point of failing to group even at short ranges.

This is partly down to bullet length, as stability requirements are mostly determined by that factor as measured in calibres, but also because the boat-tail form in itself requires a higher rate of spin for stabilisation than a same weight / same length flat-base model, one point in barrel twist rate as a guide. So, if a 100gn BTSP needs a 9.5" twist rate just to group at all, the flat-base equivalent model manages on 10.5" if the same OAL, and maybe even 11" if it has a shorter OAL.

For those who know about and use the Millers Twist Rule spreadsheet, note that it is designed for BT designs and it understates the Sg (coefficient of stability) value for flat-base models.

All 105gn HPBT bullets need faster twists than 10". The shortest models might just stabilise enough at short range to make round holes and apparently group after a fashion, but it is so marginal that one is in the situation that the load will work under one set of weather conditions and not another as air density affects rotational speed / stability requirements. (Those who shoot on hot, high desert plateaus in the USA or the NRA Whittington Center ranges in Raton, New Mexico some 6,500 ft ASL and with summer temperatures in the 80s/90s can get away with what would be a roughly one to two inch twist rate 'deficit' on a cold day at sea level.)

Most 105s though need 9-twist for marginal stabilisation and 8-twist for the full amount. That's why 8-twist barrels are the norm for long-range custom match 6mm rifles where use of this bullet type and weight is the norm. With recent designs of long-range match bullets having become ever longer for a given weight, even 8-twist is sometimes no longer sufficient for full stabilisation. The 105gn Berger 'Hybrid' needs 7.5" to achieve the desired 1.5 Sg value in most UK range conditions.

It was to allow use of 100gn BTSP deer bullets in all normal weather conditions that saw Remington Arms adopt a faster twist rate than the US SAAMI 10-inch norm for its Remington 700 models, 9.25" IIRC.

[DW58]

I used to shoot with a .243 Stutzen (my first fullbore rifle). I shot 100gr RWS factory and 100gr Nosler SBBT reloads with it with excellent accuracy.

The only thing essential on these rifles is to remove the barrel band so that the barrel floats - simply re-attach the front swivel to the stock without the barrel band.

[RufusRover]

My friend's Stutzen is OK with 100's but as you've found out, can't stabilise 105's.
It's absolutely nails with 55gr Sierra Blitzkings - half an inch or less for five shot groups @100yds.

OOh I'll add some of these to my next order!

Interesting that such a small increase in weight can have such a profound effect to the accuracy!