Suitable bullets?

[VarmLR]

Having had some success (surprisingly!) with 30 cal 190SMKs and N140, with the chrono seeing 2500 fps using 42.4gr seated at 2.865" (30 thou jump), I'm wondering if these might be ok for 1000 yds? (I'm shooting 900 in about a week and they should just be ok for precision up to 900)

 

I'm just a bit concerned that 2500fps isn't enough with the 190's for precision (ok for some fun though) as it looks pretty close to transonic at around 900 yds. The 190's though at least have a reputation for being stable through the transonic region.

 

Has anyone compared actual performance of something like the Lapua Scenars (150's driven fast) from a 24 inch barrel compared with the heavier bullets?

 

Another bullet on my radar is Berger's 185 Juggernaut.

 

I'd maybe settle for the 2156's driven hard except that they're not especially jump tolerant and my rifle has a pretty long chamber throat so I can't get them close enough to the lands. I doubt even if I did that I'd get the velocities needed from anything much under a 30 inch barrel for the lighter projectiles though.

 

Advice welcomed, even if it's "stick with the 190's" !

[That bald headed Geordie]

Many years ago I used the Sierra 190gr Matchking with about 45ish grains of N140 which I think gave about 2600 fps at 1000yd UKBRA benchrest comps at Diggle. Although I used that bullet/load in a bog standard Remington VSSF it was ok at that distance in the factory sport class it did pretty well. So although not the most accurate calibre on the firing point it did get to 1000yds without any problems. I did need 20 m.o.a. tapered scope bases to allow me to get on at 1000yds with about 40moa above 100yd zero. Hope that info helps.

[snakeman]

No advice Varm but intrigued about the results of your findings. Keep us posted and ATB at 900.. .

[The Gun Pimp]

Many years ago I used the Sierra 190gr Matchking with about 45ish grains of N140 which I think gave about 2600 fps at 1000yd UKBRA benchrest comps at Diggle. Although I used that bullet/load in a bog standard Remington VSSF it was ok at that distance in the factory sport class it did pretty well. So although not the most accurate calibre on the firing point it did get to 1000yds without any problems. I did need 20 m.o.a. tapered scope bases to allow me to get on at 1000yds with about 40moa above 100yd zero. Hope that info helps.

I remember that gun. What happened to it? It was one of those 'one in a million' Remmys. Half MOA at 1000 yds is good for ANY gun!

[VarmLR]

Many years ago I used the Sierra 190gr Matchking with about 45ish grains of N140 which I think gave about 2600 fps at 1000yd UKBRA benchrest comps at Diggle. Although I used that bullet/load in a bog standard Remington VSSF it was ok at that distance in the factory sport class it did pretty well. So although not the most accurate calibre on the firing point it did get to 1000yds without any problems. I did need 20 m.o.a. tapered scope bases to allow me to get on at 1000yds with about 40moa above 100yd zero. Hope that info helps.

 

Many thanks for that. I haven't got any pressure signs yet up to 43-ish grains N140, but on the chrono, every small fraction over 42.4 was giving less and less velocity gains, with peak velocity close to 2530fps (8 degrees C). Best groups at 100 yds were at 42.4grains, with the best being .3moa (almost a one hole group), so I stuck with the load that gave best accuracy, trusting to the inherent stability of the 190 to do the rest. That gets me to 900 ok-ish, but beyond that I'm looking for 2,600 fps for less pressure. N150 didn't seem to offer significant improvement but I'm informed that RS60 might, so perhaps what I need to do is stick to that bullet and try a more suitable propellant. I want, at all costs, to avoid the use of double base propellants in order to conserve barrel life. It's not for competitive shooting, but personal challenge, but I'd still like to do the best I can.

 

1/2 moa at 1000 yds, with any rifle, let alone a factory Remmy, is pretty impressive shooting! If there was a "bow down" smiley here, I'd be using it!

[snakeman]

[gbal]

Varm and Vince,I think I know where that 308Rem 700 VSSF may be resting.

 

The load was 43.6 V140 giving 2558 fps at 65Fwith sierra 190 HPBT Match King (Note-moly bullets powder load) This was 2531fps at 35F

Lapua 185 Scenar Moly 43.5 V140 gave 2595 at 42F ; 44g V140 gave 2610fps at 50F

 

Scope was 12-40 NF (expert Les) and 8-32 NF (1000y tyro). !/2 moa was on in benign conditions,seldom worse than 1.5 moa in Diggle challenges.

Recoil was uncomfortable in the standard light plastic factory stock,which didn't help at all (tyro's excuse).

 

I hear rumours that it might be brought out of retirement if a GRS fclass heavy laminate stock can be sourced in black/blue -no choice of colour,but an appropriate homage to the original recoil. :-)

 

gbal

[That bald headed Geordie]

Varm and Vince,I think I know where that 308Rem 700 VSSF may be resting.

 

The load was 43.6 V140 giving 2558 fps at 65Fwith sierra 190 HPBT Match King (Note-moly bullets powder load) This was 2531fps at 35F

Lapua 185 Scenar Moly 43.5 V140 gave 2595 at 42F ; 44g V140 gave 2610fps at 50F

 

Scope was 12-40 NF (expert Les) and 8-32 NF (1000y tyro). !/2 moa was on in benign conditions,seldom worse than 1.5 moa in Diggle challenges.

Recoil was uncomfortable in the standard light plastic factory stock,which didn't help at all (tyro's excuse).

 

I hear rumours that it might be brought out of retirement if a GRS fclass heavy laminate stock can be sourced in black/blue -no choice of colour,but an appropriate homage to the original recoil. :-)

 

gbal

 

Ah thanks for the update on my loads for the 190gr HPBT loads George I just made an guestimate of what the data was. And yes it was a bit of a kicker in the standard Remmy stock, but as long as I kept my distance from the scope I didn't get bitten (apart from once during an F class match).

 

Vince, as you can guess I sold it to George many years ago and he used it at Diggle, but wasn't too keen on recoil for that particular load set up.

The only reason I went for the Sierra 190 was that it was the only bullet that would allow me to have something left in the case mouth and get close to the rifling. I did try the 155gr but after pulling the trigger the bullet took 3 minutes to hit the rifling and the jump must have been horrendous (in my opinion).

But I must admit to preferring the recoil of my .284 and lately my 6BR which is a delight to shoot.

[Brillo]

I shot the 190 SMK through my Sako TRG with some success. Like TBHG I used it to get close to the lands due to the TRG long throat. I found it grouped best with N150 and the MV was much higher in reality than predicted by both Quickload and the Vhitavouri load data.

[VarmLR]

Thanks Brillo, that's exactly the sort of experience feedback I was after.

 

In the T3 barrel (their "long" version which is still only 24 inches, or to be precise, 23.7 inches), N140 starts to kick uncomfortably once up to 43 grains for really very little velocity gains over the lesser charge. I may stick with the 190 and simply use the N150. That means three different powders in the loading shed! I was using N140 for just about all my loads (223 & 308) but will reserve it for the 69TMKs and for the medium weight .308 bullets and perhaps switch to N150 with the 190 grain lumps, and push them tighter to the lands (probably at 10 thou) for greater case capacity.

 

I've found that the 2155's are extremely jump tolerant. I simply load those to mag length (2.800) and they happily jump the 53 thou to the lands remaining very accurate. The 2156's don't like it so much but I've found that the TmK's seem jump tolerant. The 168 TMK has been on the radar for a while but that's one that I haven't tried. Looking at the geometry, it doesn't look like a typical 600 yard design in that it has a longer boat tail with shallower angle than the HPBT, and a higher BC than the 190 SMK, but at a 30% cost premium over the 190's I don't know whether I'll bother.

[Laurie]

The 190 SMK was a favourite long-range bullet for many years with 'Match Rifle' competitors who shoot 308 out to 1,200 yards. It and the 200gn SMK had a fine reputation for being very transonic and subsonic-transition tolerant. However, nobody in MR uses the 190 today for the simple reason that bullets have moved on a far distance since the 190/200/220 SMKs were designed and introduced - competitors use today's 210gn Sierra MK and 200/215gn Berger Hybrids which are far more aerodynamic designs and are also very transonic etc tolerant.

 

The 190 has two benefits - it's relatively cheap compared to top of the range Bergers, and it is a good option for people who want to get a 308 factory rifle with a 24 or 26 inch barrel into doing a bit of long-range shooting. I used to advise people to give them a try maybe seven or eight years ago, but then Berger introduced the 185gn BT 'Juggernaut', a superior albeit more expensive design.

 

The key metric to compare the aerodynamic efficiency of different designs is the 'form factor'. It is a numeric representation of the average drag as seen in a bullet's drag curve and compares the design's drag to that of the reference projectile which for long-range match bullets is almost invariably the G7 model these days. The reference projectile is always given a form factor of 1.000 and the test bullet's efficiency is compared to that - a higher value means less efficient as the metric is drag related. (When combined with the bullet's sectional density which is weight/calibre generated, you get Ballistic Coefficient, but the form factor allows bullets of different weights and even calibres to be compared.)

 

The Form factors for the two SMKs and some equivalent Bergers are:

 

190gn SMK ............................ 1.070

200gn SMK ............................ 1.058

 

175gn Berger LRBT .............. 0.999

185gn Berger Juggernaut ..... 0.985

200gn Berger Hybrid ............. 0.944

210gn Berger LRBT .............. 0.988

 

The difference between the SMK's 1.070 and the Juggernaut's 0.985 is very significant in performance terms. The Juggernaut is an easy bullet to tune in most rifles and its COAL / ogive often suits factory rifle chambers.

 

The 200gn Hybrid's 0.944 is a stunning rating - a few years ago nobody believed that 30-cal bullets could be designed to give this level of efficiency (6.5s and 7s are a different matter with their much smaller cross-sections). However, it is a very long nosed bullet and there is much less chance of being able to get a satisfactory seating position / cartridge OAL with it set up just off the rifling lands in an out of the box factory rifle.

 

N150 is a better match to 185-200gn bullets in 308 than N140. N550 gives a serious hike to MVs in 24/26 inch barrels with these bullets - I used this powder years back to get a 24-inch barrel FN SPR 1,000 yard capable before I got my first 'proper' FTR rifle. It will wear the throat out faster of course.

[VarmLR]

Many thanks Laurie for such a comprehensive response. Yes, form factors do seem to have come a long way in modern bullet designs, but as you say, the 190 will get you there and do it quite a bit cheaper, but I can see, having read Brian Litz's Advanced Ballistics, just how important the FF is and how different designs can vary significantly due to aerodynamics and indeed partly due to CoG/attitude. I would love to try the Juggernaut as it seems a great design, and will try to develop a load for that one when shooting beyond 900. I'll also switch to N150 for anything over a 168gr in .308. I can't justify wearing out a barrel twice as fast for "fun" shooting, by the use of double base propellants, so will stick with single base.

 

Many thanks for the advice and feedback folks. I think that I now know where I need to go with this (190's up to 900 and perhaps to 1000 and 185 Bergers if I can get them for 1000 plus, switching to N150 for both).

[Laurie]

If using the 190gn SMK, check base to ogive measurements with a bullet comparator. These bullets used to have vast BTO variations and batching them made a big difference to L-R performance.

 

Current production may be OK. I've been very impressed by 6.5 and 7mm TMK consistency, and the new 183gn 7mm SMK is outstanding in both BTOs and weight, but as to the older .30" designs, I wouldn't know if Sierra has made the same production quality improvements.

[VarmLR]

If using the 190gn SMK, check base to ogive measurements with a bullet comparator. These bullets used to have vast BTO variations and batching them made a big difference to L-R performance.

 

Current production may be OK. I've been very impressed by 6.5 and 7mm TMK consistency, and the new 183gn 7mm SMK is outstanding in both BTOs and weight, but as to the older .30" designs, I wouldn't know if Sierra has made the same production quality improvements.

 

Funny you should mention that Laurie as that's exactly what I just discovered (yesterday in fact). I had a few hundred from a new batch and comparing them with the first batch I used several months back, there was a whopping 10 thou difference between COAL and ogive measurements. I thought it was just me, but when checking through the whole batch yesterday, the later batch was consistently shorter on COAL when loaded to the same Ogive seating depth checked using a comparator. My first batch measured 2.895" COAL to tip (averaged over 10 measurements) touching the lands, and were loaded to 2.865". This gave a measurement loaded using a comparator tool of 2.273" seated to Ogive.

 

The newer batch were loaded to the same 2.273" to Ogive but this resulted in a 10 thou shorter bullet overall. This was on average as some varied a little more than others. I was left scratching my head but I hadn't considered that it might be CBTO variations! That means that I've probably slightly compressed the latest batch. I may be talking myself into using a different bullet here...

 

I have found that in general, all of the TMK's that I've tried have been much better on consistency between batches. For the sake of 10p per round, it might be worth trying a batch of the 168 TMKs in 30 cal.