Us Ftr chamber with scenar bullets

[Mtl74]

Hi,

Planning to order reamer for the above chamber. Berger bullets are not easily available here, but Scenars are and I will be using them. Max range is here is only 550 yards. So no 1000 yard range available.

Bullets that I am planning to use are Scenar155gr L bullets. I want to seat them long in the neck/shoulder junction. My question is the freebore. Has anybody done their chamber to this bullet seated long and if so what kind of freebore you have and performance? I have Shilen SM 10 twist ready for chambering.

The standard freebore is .170, but I think I need a bit less something from .140-.150 inches. But not quite sure about the exact amount, since its a bit difficult to calculate other that it needs to be less than .170. Maybe.

Would be nice to hear experience about this. Thank you.

 

[Laurie]

The 155gn Scenar is an exceptionally long bullet for its weight, also a near VLD shape so can benefit in some rifles from being seated into the lands. Put together these characteristics produce a need for far more freebore than other comparable weight models.

Back when F-TR was starting, 155s were the norm, at least here in the UK, and the Scenar was the obvious choice, high-BC and also Lapua bullets are usually well sourced and reasonably priced in this country. A friend seated one in a Lapua case optimally in relation to the shoulder / neck junction and sent it off to Dave Kiff to have a chamber reamer made. I can't tell you what its FB measurement is, but it's longish. When the 185 LRBT Juggernaut was introduced a few years later, we found our existing chambers suited it very well. It could also just be used with the since withdrawn 210gn Berger BT bullet, once a favourite here.

So, I'd suggest ascertaining the FB used on the US F-TR team reamer freebore back in the 2013 F-Class World Championship meeting at Raton and that era generally when the 185 Juggernaut was the norm, pre adoption of later and longer 200gn Hybrid types.

The 155gn Scenar can be a very finicky design in terms of seating / jump. As your maximum distance is 550 yards, I'd suggest you look instead at the 175gn Lapua Scenar-L, a bullet that performs much better than its paper BC figure would suggest and is capable of producing exceptional precision in a good barrel. A bunch of my former GB F-TR team mates including several times GB F-TR champion Adam Bagnall from the 101 Rifle Club formed a Nammo supported Team 101 Lapua a few years ago and did well in our various national F-TR team matches. The 175 Scenar-L was / is their standard bullet and it did very well for them indeed until 1,000 yards when it lost out to the higher BC Bergers. The 175 leans towards tangent ogive form and is very jump tolerant, so it performed very well for my friends in long FB chambers geared to the 200-20X and similar.

 

[Mtl74]

Thank you Laurie with this good info. What do think would the .170 freebore we good for the Scenar 175L bullet or do you know approximately what kind of freebore GB team uses with 175L Scenar bullet. Thank you.

 

[Ray123]

Hi,

Planning to order reamer for the above chamber. Berger bullets are not easily available here, but Scenars are and I will be using them. Max range is here is only 550 yards. So no 1000 yard range available.

Bullets that I am planning to use are Scenar155gr L bullets. I want to seat them long in the neck/shoulder junction. My question is the freebore. Has anybody done their chamber to this bullet seated long and if so what kind of freebore you have and performance? I have Shilen SM 10 twist ready for chambering.

The standard freebore is .170, but I think I need a bit less something from .140-.150 inches. But not quite sure about the exact amount, since its a bit difficult to calculate other that it needs to be less than .170. Maybe.

Would be nice to hear experience about this. Thank you.

I used to shoot out to 1400 yds, but mostly 1000 yds with 155 Lapua Scenar 308 bullets, with good results 17,000 of them back around 2004ish. So 500 yds is no problem. I used to keep notes so I looked it up..
I can give you the Cartridge OAL for the first barrel with a 155 308 Scenar bullets 2.943" to the lands, not my reamer. The last barrel for 155s is my own reamer, cartridge OAL is 2.910" to the lands, with several thousand rds on it. I used a 12 Twist Shilen on this build, shoots good with 155's. You can use a shorter throat finish chamber reamer and a 308 throating reamer to extend the throat, (as I do for the heavy 308 bullets) to your desired lenght,.. just go slow and clean and check. At 2.9" the 155 scenar boatail is in the neck /shoulder barley and half the bullet dia is in the neck...perfect for adding lots of Varget. I've been using 9 and 8 twist 308 barrels for the last 3 builds for 200 to 230 grain bullets. The 155s will shoot well in 308, they have been doing it for years.

 

[Longrange57]

I'm shooting 30-284 with .200 fb....not 308 ftr. However, my former 308 and current 30-284 shoot the 155 scenar L very well. with .200 fb I only have about .170 in the case and just kiss the lands. Shoots a node at 53.7 H4350 at 2855 and higher node at 2950 with 55.0 ...... 1/4 moa at 300 yds and right at .30 moa at 530 yards. I love this bullet. When 1,000-1,500 which we regularly do..... I shoot the 200.20x.
Once again, out to 530 yds I'll take the 155 sc any day. Very accurate even with a 9 twist.
These 30-284 combo's are very easy on brass for anything other than ftr. Thats the only reason I built them.
Good luck!

 

[CharlieNC]

Talk to your gunsmith. You should be able to make up a couple of dummy rounds, seating the bullet to the depth/protrusion you desire, and after chambering he can use a throating reamer just touch your dummy round.

 

[Ned Ludd]

The 155 Scenar [average] bullet BTO measurement is listed at 0.643" in Bryan Litz' Ballistic Performance of Rifle Bullets, 3rd Ed. He lists the 200.20X bullet BTO as 0.718", or ~.075" longer. The 0.170" fb cut by the US F-TR reamer is just about perfect for the 200.20X bullet, putting the boattail/bearing surface junction perhaps about 1/3 the length of the neck above the neck/shoulder junction, obviously dependent on the seating depth used. In my hands when seated at .009" to .012" off the lands, the boattail/bearing surface junction of the 200.20X is not halfway out the neck. As a rough guess, I'd think you could probably get away with using a freebore for the 155 Scenars of anywhere in the 0.100" to 0.150" range, or thereabouts.