Sierra MK for 7mm-08...

[x_wolf]

I've read this .pdf file: www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA554683 and I'm wondering if somebody used the Sierra HPBT MK 168gr. or 175gr. in 7mm-08. Because B. Litz data in the table on 7th page looks very promising. I saw there relatively high BC numbers for 7mm Sierra MK's.
Any experience and load recommendation for these two bullets would be very appreciated.

Thanks

 

[XTR]

I have a 7-08 that is throated long for the 162s. This is a hunting rifle, not a target rifle. I gave the 162s with H4350 a shot in my first testing but found that I just couldn't get enough in there to get the MV up where I wanted it. If this is for competition you are really giving up a lot of MV to the bigger sevens.

I found for my application that the 140s at a tad over 2900 were the ticket.

I don't know what your planned application is, but I've pondered and discussed it several times, and for a competition rifle the 7-08 just can't seem to fit unless maybe it's in silhouette shooting where you can get a somewhat reduced recoil, better ballistics than a 30, and the weight to knock over rams.

In F class it has to compete in Open. At mid range the 6s will do as well or better with less recoil, at long range it lacks the boiler to get the heavy for class bullets up to speed with the 284s.

I'm getting 140s out the tube at 2900, the big 7s are running almost that with 180s. You just can't get the horsepower.

All of that said, it is my go to rifle for hunting pretty much anything east of the Front Range.

 

[shoot4fun]

I've sent a lot of 168SMK down range from a 7MM08 and had a fair amount of success. The first barrel was a 26" and I compressed H4350 hard to get that barrel making 2850 FPS. The second (present) barrel I went to a 24" and that was a mistake for best results to 1000 yards. I am about 100 FPS short of what I had before and it shows. So, in summary, I would get at least 1 in 9 twist (more likely 8.75), 26" minimum barrel length and find a good stout load for the 7MM08 to get the most from it.

 

[alf]

I've read this .pdf file: www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA554683 and I'm wondering if somebody used the Sierra HPBT MK 168gr. or 175gr. in 7mm-08. Because B. Litz data in the table on 7th page looks very promising. I saw there relatively high BC numbers for 7mm Sierra MK's.
Any experience and load recommendation for these two bullets would be very appreciated.

No experience with either of those two, but I did work up loads in mine with 162 Amaxes and 168 Bergers. My 700 has a Wyatts mag, so I could seat the bullets out to touch the lands and still fit in the magazine.

I could run either bullet to 2800 in a 23" Rock barrel, but have since settled on 140 Noslers instead, either Ballistic Tips or Accubonds interchangeably, same load, same velocity, same POI at 2940.

 

[Laurie]

As shootforfun and XTR say, it's hard to get velocities up to competitive levels. Bear in mind that the better 140gn 6.5s have the same G7 BCs as the 168gn Berger VLD and that in turn has a considerably higher BC than the 168gn Sierra MK (0.316 v 0.289, source Bryan Litz). IME it is much easier to get the 260 Rem / 6.5mm Creedmoor to give 140s MVs above 2,800 fps (in a 30-inch barrel) with good accuracy than to achieve the same performance with the 7-08 and the Berger 168. (That's with a long-throat chamber too which sees the bullet seated at 2.96" COAL.)

The 308 Win based case is really a bit short of capacity for 7mm in the long-range target role. 284 Win in long-throat form is a much better competition cartridge for mid and long range.

If you want to really push MVs in the 7-08 with heavier bullets, you need to go to double-based or high-energy powders, both of which incorporate nitroglycerin making them denser and also increasing their specific energy ratings. So, we're talking powders like Alliant Re17, Viht N550 and N560, Ramshot Hunter, Hodgdon H414 and suchlike. The cost of using these powders is two-fold: greater temperature sensitivity; hotter burning which reduces barrel life.

As a nice, accurate short/mid-range cartridge, there is nothing at all wrong with the 7mm-08 paired with the 168gn Sierra MK. It is pleasant to shoot and gives longer barrel life than the mid size 6.5s, but it is ballistically challenged compared to equivalent 6.5s and sixes. In the hunting role, it's at its best with 140-150gn bullets - there are no factory rounds with anything heavier than 140gn bullets last time I looked.

The 4350 / 4831s' burning rates are very well suited to the cartridge with heavier bullets, but you can't stuff enough of them in to get full pressures and velocities. So, you generally need something like H. VarGet, IMR-4320, Re15. IMR-4350 can be used at a pinch (with a compressed charge), H414 or Ramshot Hunter (for hotter burning loads with higher MVs). Some 7-08 shooters like IMR-4007 ssc, but this powder was withdrawn a year or two back - there may still be some tubs in the shops as it wasn't a big seller.

 

[x_wolf]

Thank you guys for every post.
Let me present my point of view. The rifle is upgraded Howa short action, there is 26" tube in with 9" twist. Until last weekend I was completely happy with A-Max 162. I was pushing it around 2790fps with no big effort (Lapua brass, CCI BR2, Reload Swiss RS60 powder). But then it was all wrong. Same lot of powder, bullets and primers, the nice groups were gone, I was hardly able to hold 1 MOA at 300 meters. So I completely re-done the load development with A-Max and I also made few cartridges with Sierra 168 just to be sure. Nothing with A-Max but Sierra showed nice 0,3 MOA group at 300 meters. Now I am little bit confused because A-Max was my universal target/hunting bullet. The hunt was only small part of it maybe 10% of all shooting. Now what? Should I wait for the ELD bullets? Hunting with 7mm-08 is not so important for me I have other hunting rifles. And I don't feel further work with A-Max...
When I look to the offerings here in Europe the Berger bullets are really pricey. They cost almost twice as much Sierra. But if I will find some good load for the Berger I'll go for it.
I think I can push the Berger 168 also up to 2800fps with the swiss powder. Second option is the Sierra 175, here is the my speed limit somewhere at 2740-2750 fps according to Quick Load.
Of course I'm bit limited with my case capacity compared to the overpowered 6,5 a or big sevens. But I think it can work for me as good as the A-Max did until now.
Maybe is here someone who tried heavier bullets in small 7mm-08 case...

Click on preview for bigger pics

 

[Zero333]

Consider the 160 Tippedkings.

My only 7mm08 is a light hunting rifle but made me think twice and am pondering a 7mm08 Improved for f-class in the future. Mainly for the extended barrel life.

 

[normmatzen]

I use a 7X57 for hunting and a 284 WIN for F Class and heavy gun long range bench rest. Both guns shoot best with RL-17. Temp sensitivity has not been a problem as I take ammo to the range in an insulated bag. For hunting, mostly morning, temp is not a strong factor especially as a hunting load has more tolerance for MV than a competition gun.

My QL says RL-17 is the most efficient powder for both my 7mm rifles
and the muzzle velocity is higher than I can get in either gun with 4831sc or H4350 and with less chamber pressure.

 

[jsthntn247]

My hunting rifle is a 7-08 shooting 168 Berger's or 162 Amax. 45.7gr for Berger's and 45.4gr for the Amax's of H4350 yield 2750 in the summer and 2720 in the winter. The gun has taken 9 deer from 70 yards to 510 yards in the last 2 years and none has taken a step. Recoil is very manageable without a brake also. It needs a long action or single shot short action to take advantage of these bullets.

 

[Laurie]

For those in the States, Reload Swiss RS60 and Alliant Reloder 17 are one and the same thing in different packaging. I'm not surprised the OP got the 162 AMAX up to 2,800 fps with it - it really is the best velocity generator around in its burning rate group. Equally, though I'm not surprised that something suddenly changed and the groups went belly-up. I've seen it so often with RS60 / Re17 - fantastic groups then one day the heavens fall in for no apparent reason. (284 Win is very prone to Re17/RS60 collapse syndrome IME.)

I've deliberately kept away from this powder in my 7-08, partly because of the inconsistency factor, also because if its performance if fully used it is a barrel killer par excellence.

So far as European powders go and for the 168gn SMK, you'll likely find it hard to beat Reload Swiss RS62, same general burning rate as RS60, but single-based and longer grained. It is a very good performer in the mid-size 6.5s and 7s combining higher MVs than H or IMR 4350 can provide and usually good groups and MV consistency (although nothing in this world is certain and especially not in handloading). You won't get the same MVs as with RS60, but it'll match all but a few other 'high-energy' types such as the Viht N500 series and won't give much away to them anyway. It is a much more tolerant propellant than RS60 in my experience to date.

So far, I've found QuickLOAD to be fairly reliable with this powder, unlike some in the Reload Swiss range where I'm very cautious indeed as to its computations, finding that actual pressures turn out to be much higher than predicted. (That reliability / accuracy from the program is for other cartridges though as I've yet to try RS62 in the 7-08.)

If you're happy with an easy to tune but relatively low BC bullet like the SMK, have a look at the very similar 168gn Nosler Custom Competition HPBT Match which is if anything likely to be cheaper than the Sierra where you are. (Many people in the UK order Nosler CCs from the big west European bullet suppliers online as they're cheaper than anything we can get here through the UK trade distributors. Also, Nosler's presence here is heavily weighted towards the expanding hunting bullets. I've no experience with the 7mm CC version, but its .30 and 6.5mm equivalents have a reputation (as with SMKs) for being very jump tolerant and easy to tune bullets which I can certainly support in 6.5mm through personal experience.

 

[x_wolf]

Very informative post Laurie. Thank you. I will try both bullets from Sierra and also the Berger VLD 168gr.

 

[x_wolf]

I've checked the website of Reload Swiss, all the powders from RS36 up to RS80 are declared as single-based powders.

 

[Laurie]

Nitrochemie is being a little disingenuous here, even if factually accurate. Most users call any powder which includes nitroglycerin 'double-based'. RS40, RS52, RS60, RS70 and some others most assuredly contain nitroglycerin and therefore are what shooters know as double-based.

Nitrochemie manufactured these grades as single-base (nitrocellulose only) kernels, then added nitroglycerin using an infusion process. Technically, these are 'high-energy' propellants. These RS grades use the same technology and production methods as applied to the Vihtavuori N500 series 'high-energy' propellants (in fact Nitrochemie sold the process to Viht, but says it has since developed it to a superior form to that used by Viht).

Being pedantic as in chemical engineer pedantic a 'double-based' (or triple-based') propellant is one that has the extra energetic components mixed in at the very beginning of the production process before it is turned into a colloid and then rolled / cut up into kernels and given other treatments. All Winchester / Hodgdon / Ramshot etc ball / spherical powders are double-based as nitroglycerin is a base ingredient of this type and is mixed in with nitrocellulose when the initial slurry is created. In such a form and other multi-based propellants, the nitroglycerin and other energetics are fully mixed into the base material and their molecules spread throughout the entire material. In the high-energy types, the nitroglycerin is infused so isn't mixed throughout the powder kernel's material.

So Nitrochemie is factually accurate in describing all its powders as single-base as the the base material was nitrocellulose alone. However, around half of its grades contain nitroglycerin, and that's what matters to the user in that the use of this ingredient produces pros and cons - more energy / velocity v higher temperatures / reduced barrel life.

RS50 and RS62 do not contain any nitroglycerin in any form.