175 tmk vs 175 scenar

[Phys86]

Have enough people here tried both of these bullets for there to be a general consensus on which is easier to get an accurate load for? In pictures, they look to me to have the same shape ogive

 

[Laurie]

In pictures, they look to me to have the same shape ogive

Not according to Bryan Litz's measurements and drawings in Ballistic Performance of Rifle Bullets 3rd edition. The TMK has a much longer nose section with a more gently radiused profile at 14.94 calibres radius and Rt/R aspect of 0.55 (nearly true VLD which rates 0.5). The Scenar-L is very much closer to a traditional tangent ogive form with a shorter, blunter 8-cal radius nose and 0.83 Rt/R value (true tangent is 1.0).

The TMK gains in BC as a result - 0.266 v the Scenar's 0.247. The former is pretty well the same as the very efficient Berger 168gn Hybrid; the latter only marginally higher than the ancient 175gn SMK. The TMK also has a significantly shorter bearing section of 0.377" v the Scenar's 0.446", so should be capable of being driven a bit faster without pressure appearing. (The Scenar's BSL is also much longer than that of the old 175gn SMK.)

I have some friends who are among the UK's best FTR competitors who gained some Lapua sponsorship a year or two back and shot the 175 Scenar-L. They did reasonably well with it to 800/900 yards and found it an easy design to 'tune'. At 900 yards and even more so 1,000, it became hopelessly uncompetitive against the 200gn Berger Hybrid in any sort of wind. So, think of it as a newer and supremely well/consistently made equivalent to the old Sierra 175 MK. (Not that today's Sierras aren't well or consistently made!)

 

[Ned Ludd]

As Laurie noted, the ogive radius and other dimensional properties of these two bullets are not really very similar at all. Both can be made to shoot well. For those that follows a well-regimented reloading/testing approach, there really shouldn't be all that much difference in the total amount of effort it takes to initially find what each bullet wants/needs for optimal precision. However, it is very possible that one or the other may be more forgiving with respect to how wide the optimal charge weight/seating depth windows are. In other words, if you carry out a standardized load development procedure with two new bullets, you should [usually] be able to find where they both want to shoot initially with about the same amount of effort. But if one bullet tolerates noticeably wider windows in terms of optimal charge weight and/or seating depth, it will likely maintain precision for a noticeably longer time (higher number of fired rounds) before the load needs to be re-tuned, meaning potentially less effort over the long term. Generally, tangent ogive bullets are more forgiving with regard to seating depth optimum and maintaining optimal precision over time than are secant ogive bullets.

 

[Bill Norris]

The 175 gr. Sierra TMK was very easy to develop a load for in my Custom Rem 700 .308.

 

[Phys86]

Not according to Bryan Litz's measurements and drawings in Ballistic Performance of Rifle Bullets 3rd edition. The TMK has a much longer nose section with a more gently radiused profile at 14.94 calibres radius and Rt/R aspect of 0.55 (nearly true VLD which rates 0.5). The Scenar-L is very much closer to a traditional tangent ogive form with a shorter, blunter 8-cal radius nose and 0.83 Rt/R value (true tangent is 1.0).

The TMK gains in BC as a result - 0.266 v the Scenar's 0.247. The former is pretty well the same as the very efficient Berger 168gn Hybrid; the latter only marginally higher than the ancient 175gn SMK. The TMK also has a significantly shorter bearing section of 0.377" v the Scenar's 0.446", so should be capable of being driven a bit faster without pressure appearing. (The Scenar's BSL is also much longer than that of the old 175gn SMK.)

I have some friends who are among the UK's best FTR competitors who gained some Lapua sponsorship a year or two back and shot the 175 Scenar-L. They did reasonably well with it to 800/900 yards and found it an easy design to 'tune'. At 900 yards and even more so 1,000, it became hopelessly uncompetitive against the 200gn Berger Hybrid in any sort of wind. So, think of it as a newer and supremely well/consistently made equivalent to the old Sierra 175 MK. (Not that today's Sierras aren't well or consistently made!)

As Laurie noted, the ogive radius and other dimensional properties of these two bullets are not really very similar at all. Both can be made to shoot well. For those that follows a well-regimented reloading/testing approach, there really shouldn't be all that much difference in the total amount of effort it takes to initially find what each bullet wants/needs for optimal precision. However, it is very possible that one or the other may be more forgiving with respect to how wide the optimal charge weight/seating depth windows are. In other words, if you carry out a standardized load development procedure with two new bullets, you should [usually] be able to find where they both want to shoot initially with about the same amount of effort. But if one bullet tolerates noticeably wider windows in terms of optimal charge weight and/or seating depth, it will likely maintain precision for a noticeably longer time (higher number of fired rounds) before the load needs to be re-tuned, meaning potentially less effort over the long term. Generally, tangent ogive bullets are more forgiving with regard to seating depth optimum and maintaining optimal precision over time than are secant ogive bullets.

Thank you both!

I do not have the extensive knowledge on bullet design that you both obviously have... I was only going off of pictures. My knowledge only extends to secant gives being a little more picky on seating depth.

My question on which bullet being easier to load accurately was meant to say that I'd like one that gives me a wide window of an accuracy node so that I don't have to return often. I'm no great reloader and occasionally chase my tail a bit, so the more forgiving bullets help me out.

That's great to hear the scenarL is more similar to a 175smk. I've gotten great results with that bullet somewhat easily.

Thanks!

 

[Phys86]

Also, I'll have to look that book up. I've heard Brian's name, but didn't know he had published a book. It sounds very interesting and something I'd like to read.

 

[Ned Ludd]

FWIW - Bryan has a number of different volumes that pertain to long range shooting. The Ballistic Performance of Rifle Bullets 3rd ed. book is a resource focused primarily on various bullet designs, providing specific information for individual bullets such as external dimensions, ogive radius, twist rates, etc. I find a very useful tool from the perspective of reloading. However, some of Bryan's other volumes contain substantial additional information with regard to external ballistics, wind reading, shooting techniques, etc., and are also worth having:

Books & Media

 

[dttheliman]

On the 175gr TMK , when they first came out I got a couple of thousand - and thats all I use in a 20"AR10 (over IMR4064 in a1.10 twist Bartlien running at 2665fps) they are accurate out to 800 yards and hog hammers (only after 100+ yards, any closer they dont seem to do as much insta-damage) Worked up a bolt gun load but never really "got there" as I had a 178gr load that just plain worked - so kinda didnt try very hard , I'm sure with some perseverance and a spare 30 minutes I could get them to shoot very well - like them a lot.

 

[Phys86]

On the 175gr TMK , when they first came out I got a couple of thousand - and thats all I use in a 20"AR10 (over IMR4064 in a1.10 twist Bartlien running at 2665fps) they are accurate out to 800 yards and hog hammers (only after 100+ yards, any closer they dont seem to do as much insta-damage) Worked up a bolt gun load but never really "got there" as I had a 178gr load that just plain worked - so kinda didnt try very hard , I'm sure with some perseverance and a spare 30 minutes I could get them to shoot very well - like them a lot.

I'm kind of leaning towards the tmk. I'm sierra fan. These are going to be for elk also and I've seen more on game reports of the 175tmk and none of the scenar (other than the 155). The tmk sounds very reliable, but I worry about doing too much meat damage with it even though I'm not a shoulder shooter.

How do they do on hogs? Any deer or elk with that bullet?

 

[dttheliman]

On hogs - in the right place on the shoulder breaks the bone and turns the heart and lungs to pulp - never had a runner , (again over 100 yards range), I did take a shot at one medium size sow at around 40 yards , placement was ok bullet entered chest from the front and went out through the ribs , the ba$tard run into the bush and we spent about 2 hours trying to find it - when we did it had run about 400 yards and dropped , when we hung and peeled it the damage was minimal , looked like it bled out internally - bearing in mind this is essentially a target bullet so probably speed and placement v expansion had a lot to do with it, YMMV, just a sh1tty experience crawling around in the cedar trying to follow blood track at dusk, worrying about getting my old ass stomped by a pissed pig so I give them a bit of distance now before I light them up with the AR10 - only deer I have taken with that rifle and the TMK are Texas whitetail's always around 150 to 200 yards range - instadeadrightthere - and no through and throughs, next to zero waste , very effective bullet.

 

[Phys86]

On hogs - in the right place on the shoulder breaks the bone and turns the heart and lungs to pulp - never had a runner , (again over 100 yards range), I did take a shot at one medium size sow at around 40 yards , placement was ok bullet entered chest from the front and went out through the ribs , the ba$tard run into the bush and we spent about 2 hours trying to find it - when we did it had run about 400 yards and dropped , when we hung and peeled it the damage was minimal , looked like it bled out internally - bearing in mind this is essentially a target bullet so probably speed and placement v expansion had a lot to do with it, YMMV, just a sh1tty experience crawling around in the cedar trying to follow blood track at dusk, worrying about getting my old ass stomped by a pissed pig so I give them a bit of distance now before I light them up with the AR10 - only deer I have taken with that rifle and the TMK are Texas whitetail's always around 150 to 200 yards range - instadeadrightthere - and no through and throughs, next to zero waste , very effective bullet.

No that doesn't sound like a fun tracking experience!

I found a box locally, so maybe I'll try them out to see how they do in my gun.

 

[dthomas]

I don't have any first hand experience hunting with the tmk but hear they work like a Berger on game.

 

[Phys86]

I've read that they're a little less messy than Bergers (caliber dependent). The scenars are supposed to be less messy still and create pretty clean but good size holes despite being a match bullet. The only issues with those is that the 155 is hard to find for a reasonable price right now, and there's not any documented success with the 175