7mm-08 with heavies for 1000yds

Discussion in 'Big Stuff--7mm, 30 Cal, .338+' started by Willyqbc, Jul 19, 2019.

  1. Willyqbc

    Willyqbc

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    Hello all, long time lurker in need of some opinions from you knowledgeable folk. I am looking to lengthen my target shooting out to 1000 yds, have a couple different rifles im working with. The one im asking about is a 7-08 (jc customs barrel). Have developed a few good loads with lighter bullets but was playing with h4350 and 171 match burners. The rifle loved this combo with 4 out of 6 charges tried going under 1/2"....best was .336". However, as you can imagine, they are SLOW!! lower node was around 2450fps.....if the bc's are reasonably accurate i "think" i will still be super sonic at 1000 but will have to test further. So, the question....any inherent problems or difficulties when shooting a slow combo like this out to 1000yds??

    Thanks all!
    Chris
     
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  2. JEFFPPC

    JEFFPPC Silver $$ Contributor

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    Wind will be a killer. Will need lots of available elevation to get there.
     
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  3. spclark

    spclark Gold $$ Contributor

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    2016 saw me playing with a 7mm wildcat based on an almost-neckless 308WIN case using Berger’s 180 Hybrid. Conceived by Robert Chombart, his 284 INCH. (There’s a 260INCH too, same idea for 6.5mm bullets.) Case has shoulder blown forward 3mm beyond where the 7-08 has it, in fact you can use 7-08 dies if you wish.

    Load settled on was north of 45 grains H4350 in the 1:9, 30” barrel I’d had chambered. Found a consistent node right at 2,800 fps after a lot of powder testing. Seated long, back edge of these bullets’ bearing surface is above the body/shoulder transition while the ~ 3mm neck length is enough for workable neck tension. The minimal throat vs. bullet dia. of this chamber’s design goes a long way to keeping bullet centered when chambered.

    Considering that I shoot match sights pretty much exclusively I was pleasantly surprised with the 200-15x @ 1,000 yds. I fired with this cartridge in its very first match late in June that year. Sufficient to tie the existing NRA Senior Open Sight National Record with two other shooters for a couple of seasons until D. Tubb passed it with 16X at the Nationals at Camp Atterbury last year.

    I have a 1:8.5 barrel out being chambered right now, intend to see if the faster twist permits a bit more velocity over that 1:9.

    Might even mount a scope....
     
    Last edited: Jul 21, 2019
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  4. dminn1

    dminn1

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    If you don't get the info you need from responses to this thread, type in 7-08 in the search feature and in the posted by member box type in Laurie. He has a lot of experience with this cartridge at this distance. Hope this helps.
     
  5. Mulligan

    Mulligan Gold $$ Contributor

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  6. Laurie

    Laurie

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    As stated in the link to the topic posted on the previous post by Mulligan, I settled on the 160gn Sierra TMK as a good compromise. The 162gn Hornady ELD-M may work as well or better. I';ve finally managed to get hold of a couple of hundred, but heavier 264 and 284 ELD-Ms are as rare as hen's teeth in the UK and expensive, almost at Berger price levels. Although I don't use my 7-08 rifle in F-Class beyond 600 yards, it will shoot well at 1,000. I tested it at this distance in a 1,000 BR match and the smallest of the four by five-round groups was somewhere around the half-MOA mark. It'll happily shoot under half-MOA in our winter series 600 yard BR matches, but prevailing (very windy) weather conditions hardly ever allow for really small groups.

    For heavier bullets, you do need generous throating to get them seated out enough to pack a bit more powder in. The other and/or complementary route may be some of the recent generation of very high energy powders. Alliant Re16 may be a possibility. I have done some limited testing with the Viht N500 series powders, both 550 and 560, with the 175gn SMK but wasn't over-impressed with the groups and ES values. Moreover, the whole idea behind adopting 7mm-08 was to get somewhere near the 260 Rem's potential performance but with a 50-100% longer barrel life. Burning Re17 or N550 for another 100 fps MV rather defeats the object of the exercise.

    For shorter distance matches I have a mild load that produces near BR precision using the 150gn Lapua Scenar-L and Czech Lovex SO65 powder in standard but batched and prepped a bit Winchester brass and the mild Murom KVB-7 primer. MV is also around 2,830 fps.

    (SO65 is now available in the US as Shooters World 'Long Rifle' a propellant that suits mid-size 6.5s and 7mm cartridges very well. In the UK it was originally touted as a substitute for H. VarGet as its manufacturer Explosia showed the pair as level in its burning rate chart. This is very misleading and it is a slower burning, bulkier powder with less energy than the Hodgdon product so is poor in cartridges like 308 Win, 6BR etc where VarGet is optimal. It has struggled to recover here from this poor start but is an excellent performer in suitable cartridges matching its characteristics. It should work well in the 7-08 too with 160/162s, but I've not tried it.)

    https://shootersworldpowder.com/long-rifle/
     
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  7. spclark

    spclark Gold $$ Contributor

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  8. Ggmac

    Ggmac Gold $$ Contributor

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    If you have the desire to rechamber , go to the 7 mm mauser Ackley , it should clean up the 7-08 chamber and give more room for powder .
     
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  9. murray brook

    murray brook Silver $$ Contributor

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    What twist are you using. I also have a 7mm/08 heavy barreled rifle with a JC custom barrel 1/8.5 twist installed. I was toying with the idea of trying the 171 MB from Barnes. Right now I am using the 160 gr Sierra TMK with 760/414 and RL-15. What powders have you tried with the 171 Barnes. Would you mind sharing your loads. TKS
     
  10. Mulligan

    Mulligan Gold $$ Contributor

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    Isn’t that the same as a 275 Rigby?
    CW
     
  11. Laurie

    Laurie

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    No, the 275 Rigby was just a lighter bullet / higher speed loading for the 7X57 Mauser which at that time was based on the 173gn RNFMJ at 2,300 fps from the M93 / M95's 29.3-inch barrel. I have seen it said it has a few changes from the standard German 7X57mm chamber - Rigby may have put a few 'tweaks' in to allow the company to claim it as a proprietary cartridge and it likely has a shorter leade as the 275 Rigby was based on a 150gn bullet. (Rigby did do an alternative heavier bullet load too IIRC.) In any event, it is in essence an upmarket 7X57 for 'gentlemen' (and a few ladies), as opposed to Boer farmers and other common folks who used their as issued service rifles and carbines for everything from small antelope to lions and large plains beasts.

    The 7X57 Ackley is a seriously 'improved' variant based like other AIs purely on fireforming in the improved chamber which also accepts and fires the base cartridge safely and efficiently. Because the long 7X57 case is heavily tapered and has a shallow shoulder, AI improvement gives it a substantial MV boost. It used to see some use in match shooting but is rare nowadays thanks to the 284 Winchester and its offshoots, 7mm SAUM and WSM etc. It's an excellent match round nevertheless.
     
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  12. Willyqbc

    Willyqbc

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    Thanks very much for the responses folks! I'll try and respond to some of the comments, and provide a bit more info

    Currently not interested in a rechamber as this is sort of a "trainer" rifle to get me started on long range shooting while I wait for a more appropriate build which is coming from my smith soon.

    I have worked a bit with RL17 and velocity topped out about 2650fps....but like laurie commented on above, the accuracy just wasn't there. As far as his comment about long throating, i could get it reamed a little deeper, currently running 2.945" to touch the lands with the 171, but it would make my hunting bullets WAY off the lands when i revert this rifle back to a hunting rig.

    Murray Brook - mine is a 9 twist, #4 contour IIRC from JC, i have worked with

    139 lrx (.050" off) & RL17 accuracy was around 45 grns 2850fps-2900fps, hit pressure at 48 grns 3018fps, hunting load ended up being 45.6grns 2878fps

    150 eld x (.020" off) & H4350 tested from 42.3 grns 2616fps up to 45.5 grns 2789fps, best load was 45.2 grns 2720fps with single digit SD, it is a repeatable 3/4 MOA load at 330yds

    171 Match Burner (.020" off) & RL17 tested 41.9grns 2553fps to 43.4 grns 2670fps, showed some promise at 100 yds but could only muster a little over MOA at 330 yds with assorted testing

    171 Match Burner (.020" off) & H4350 tested 40.7 grns 2421fps to 42.5 grns 2503fps, initial testing had 4 out of 6 groups under 1/2" at 100 yds. running my data through quickload I still have some room for more powder with the predicted higher node showing up at 42.9 grns 2552 fps 59500psi.....next time out i will be creeping up the powder .2 at a time and see what I can find

    As always, these were safe in my rifle...start low, work up etc...standard disclaimer!! HaHa!

    From what I can tell using JBM Ballistics if i'm stuck at 2450fps I will need 31 MOA adjustment for drop and should have 7.1 MOA drift in a full value 10mph wind. Having no frame of reference of my own....is that a lot of drift? If it is, is it so much so that it will hurt my efforts to learn long range shooting? I should say, this is strictly for myself, There is perhaps only 1000yd competition a year near me up here in Northern British Columbia....hoping to attend next year, just because it seems like it would be fun!

    Again, thanks for any insight/advice around this long range game!
    Chris
     
  13. murray brook

    murray brook Silver $$ Contributor

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    @Willyqbc
    Thanks for the info. I guess I'll get some match burners and give them a try. I have some H-4350 on hand. TKS
     
  14. shoot4fun

    shoot4fun Gold $$ Contributor

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    I shot the 7MM08 with 168 grain bullets, both SMK and Berger VLD, with a great deal of success a few years back. The advent of the, heaven forbid, 6.5 Creedmoor put my 7MM08 out to pasture. You really need a 26" barrel with an 8.5-8.75 twist rate for best results. The 168 Amax/ELDM can get the deal done too but you'll have to work on getting velocity up above where you are now.
     
  15. McFred

    McFred

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    I've used Superformance in a 7mm Wildcat whose capacity's between the 7mm-08 AI and the .284 Win. With a 28" Bartlein barrel it drives 162 Amax at 2950fps, 180 Berger Hybs at 2820, 183 Matchkings at 2800, 185 Noslers approaching 2800fps. Superformanace is dense and a relatively slow powder so it shines in longer barrels. It is somewhat temperature sensitive and seems to give better ES/SDs when it gets the pressure up.

    I have one datapoint for a friends 28" 7mm-08 (SAAMI chamber) with superformance and got 2950fps with a full case behind a 162 Amax which was pushing the pressure limit (Brux SS HV countour on a Pierce Engineering action).
     
  16. Willyqbc

    Willyqbc

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    Have definately considered that for more oomph, i am a bit of a fanboy for the old classics. Current build at the smiths is a heavy barrel fast twist 6mm rem to push 112 match burners or 125 matrix out to a thousand, following that my smith is currently sourcing a reamers and redding custom shop dies for a 6.5x55 BJ ackley! Will run fast twist heavy barrel to hopefully run the 156 EOL or 160 matrix!

    I just cant get excited for a creedmoor or PRC.....however wonderful and capable they are....something about the older classic cartridges and their variants gets me pumped to shoot them!! HaHa!! Just taking my first tenative steps into the world of long range, i can allready feel how addictive it could be!!
     
  17. murray brook

    murray brook Silver $$ Contributor

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    @Willyqbc
    Took your advice and tried the 171 MB. GREAT bullet. Best so far in my rifle and I've tried most Sierra"s and Berger's.. Got my best accuracy so far with WW760. Tried H4350, good but not great. Where do you buy your M B's from and price. TKS MB
     
  18. Zero333

    Zero333 Silver $$ Contributor

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    Good to hear you guys are getting good results with the 7mm 171gr matchburners.
    I've tried 30 cal 175 matchburners in a 308win and 6mm 105 MB's in a 243win (8" twist) and was not impressed.
     
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  19. Joe R

    Joe R Silver $$ Contributor

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    Chris,
    I shoot F-Open matches every month in Houston and I've never seen anyone using a 7-08. I have a 260 and a 308 so I understand the attraction. Many people have tried that route to no avail.

    If you want to shoot 1K yards, the most common caliber used there (with great success) is the 284 Winchester, H4350 and the Berger 180s or 184s. If you start with that, you get a winning combination, the rest is up to you.

    Joe
     
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  20. Longrange57

    Longrange57

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    Absolutely agree! I have done well with 6.5 x 47 and 6.5 x 284, but with any wind Joe is right! I have a great 7-08 bench gun that shoots 162 eldm but cannot match accuracy of those mentioned!
     
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