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171 match burner for 7mm-08
- Thread starter Jskmtd
- Start date
I have experience with the 105gr match burner in .243win. I'm getting 2930ish fps and, using JBM with the published BC of .511 (G1), the data was perfect for shooting out to 1000 yards. 7.9 mils gets me to 1k using a 200 yard zero with a DA of ~1400.
I truly believe the BC of the 171 MB is overstated. In comparison to the 168SMK(.494) and 168VLD(.617) the 171MB(.695) is off the chart.
The Hornady 162 BTHP Match is only .610 and moving to 175/180 grain bullets the highest I know of is the Berger 180 Hybrid and it is only .674.
My only experiences with Barnes bullets have been they are too hard to tune and copper a barrel way too quickly.
I would be interested in how real world "dope" compares with what you get from a ballistic calculator with the stated BC on the MB bullets. Please post your velocities and actual vs. real yardage data ASAP.
The Hornady 162 BTHP Match is only .610 and moving to 175/180 grain bullets the highest I know of is the Berger 180 Hybrid and it is only .674.
My only experiences with Barnes bullets have been they are too hard to tune and copper a barrel way too quickly.
I would be interested in how real world "dope" compares with what you get from a ballistic calculator with the stated BC on the MB bullets. Please post your velocities and actual vs. real yardage data ASAP.
I am talking Bullet manufacturer's numbers here. You can check their websites and see for yourself.
Dia. (inches) Weight (grains) Sectional Density Ballistic Coefficients and Velocity Ranges
0.284 168 .298 .488 @ 2800 fps and above
.494 between 2800 and 2000 fps
.484 @ 2000 fps and below
From Sierra website. I am not knocking the SMK. I use them exclusively in my 7MM08.
0.284 168 .298 .488 @ 2800 fps and above
.494 between 2800 and 2000 fps
.484 @ 2000 fps and below
From Sierra website. I am not knocking the SMK. I use them exclusively in my 7MM08.
I know what it says. I've found this and litz book shows it at .565 there are also several other people out that have had this result. Advertised is awesome but like you are thinking can be inflated to an extent the BC might be correct but at what velocity. Another thing is Barnes are typically longer than other bullets by weight so it might likely be higher than other bullets in its weight class.
Yes, I know the Barnes are usually longer but I wouldn't have thought that little bit would make a huge difference. I mean even if the SMK is .560 that is still a helluva lot lower than the .695 claim from Barnes. Also, you are correct on speed. Sierra is the only manufacturer I know of that shows BC change with velocity change.
Sorry I didn't get back to this thread, been busy. Yes I'm trying them in a 24" barrel 7-08. Just found a load that is shooting in the high .3's at a 100 yards. I hope to be able to test it at longer range in the next week or so. I talked with Barnes about the advertised BC and the guy told me they checked it with a Doppler so the .645 should be accurate.
Jon
Jon
I have used the 140 MB's in my 260, and the BC published was is spot on. This 171 seems like an outstanding opportunity, I may try it myself in the SAUM.
Yes they have proven to be tough to find the sweet spot on seating depth. I worked my way out to 0.080 and it is shooting pretty good there. I will probably try 0.090 and 0.100 before I decide for sure. The further away from the lands I got the better it shot.
Jon
Jon
You may be surprised. I run the 140 in my 6.5 Creedmoor and the 105 in my 6 Creedmoor. The advertised BC is spot on. So much so that I was able to take top long range shooter with the 140 MB at the 2014 TBRC. Sure, lots of luck is involved, but I did it with the numbers provided.
If you look at the BC of the 140 and the 105, neither of these is out of line for the bullet classes. So it makes you wonder, if they are not inflating the numbers on the other bullets, why would they do it on the 7mm? Also, Barnes ballistic lab is the best in the country. Lots of other manufacturers will lease Barnes's lab from them to test their own stuff.
Ty
First off, Barnes advertises this bullet at .645 G1BC, and its sectional density is .303 lb/in*in
Secondly, a G1BC of .645 is essentially a G7BC of .330 (Litz's book, page 459 - JLK .284 caliber 180gr BTHP).
Form factor is equal to sectional density divided by G7BC...
Thus the form factor of the 171bmb assuming BARNE'S OWN published BC is: .303/.330 = .918
For reference, the FF of the Berger 7mm 175xld (wicked vld) is .923. The 180 hybrid is .924, and the 180vld is .946.
Does it seem "reasonable" this 171bmb is more streamlined than all of these other bullets (which are vlds)?
Thirdly, my magnetospeed clocks these right at 2700fps, and it takes me 8.8mrad up from 100 yard zero to smoke prairie dog steel @ 1000 yards. That translates to ~.62ish according to my calculator.
This is with a POINTED 171bmb, I don't have data for unpointed.
Secondly, a G1BC of .645 is essentially a G7BC of .330 (Litz's book, page 459 - JLK .284 caliber 180gr BTHP).
Form factor is equal to sectional density divided by G7BC...
Thus the form factor of the 171bmb assuming BARNE'S OWN published BC is: .303/.330 = .918
For reference, the FF of the Berger 7mm 175xld (wicked vld) is .923. The 180 hybrid is .924, and the 180vld is .946.
Does it seem "reasonable" this 171bmb is more streamlined than all of these other bullets (which are vlds)?
Thirdly, my magnetospeed clocks these right at 2700fps, and it takes me 8.8mrad up from 100 yard zero to smoke prairie dog steel @ 1000 yards. That translates to ~.62ish according to my calculator.
This is with a POINTED 171bmb, I don't have data for unpointed.
[MENTION=96711]HodgdonExtreme[/MENTION] that is what I want to see. I have been a "doubting Thomas" on the Barnes BC for the 171MB but, after feeling a put up or shut up kinda moment, I ordered some today for my own testing. If you don't mind please PM me some load data so I will at least have a good starting point. BTW, are these bullets hitting higher pressure quicker than normal lead core BT?
These are not solid copper like other Barne's bullets; they are traditional jacketed lead.
Loading wise, treat them like 7mm 175smk: start around 43gr H4350 or 39.5gr Varget, probably winding up around 41gr Varget or 45.5gr H4350.
That said, these kiss in my chamber at ~2.955", and I'm loading them at ~2.925". If you're loading more like SAAMI (~2.800"), back off .5-1.0gr to start.
Loading wise, treat them like 7mm 175smk: start around 43gr H4350 or 39.5gr Varget, probably winding up around 41gr Varget or 45.5gr H4350.
That said, these kiss in my chamber at ~2.955", and I'm loading them at ~2.925". If you're loading more like SAAMI (~2.800"), back off .5-1.0gr to start.
I guess I don't see why it has to be a VLD to have a low form factor. Liz states the 162 Amax has one of the lowest form factors at .94 and it isn't a vld.
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In fact, the 162amax is indeed an aggressive secant-ogive VLD.
The long skinny ogive of a secant/VLD bullet helps make it long for is weight, streamlining it and decreasing drag - so the best form factors are pretty much always VLDs.
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Judging from the comparison pictures of the other match burner to other bullets, the match burners appear to have long scan ogives as well. (Complete eye measurement.)
So far from what I've been reading Barnes numbers on their other bullets are right on or near right on. So why would they lie about this one?
Edit:
I'll add accurate shooter has an article where James Mock tested the Match burners (albeit in the 6mm) and he calls the VLDs so I would wager they are secant-ogive bullets.
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To my eyes, the 171bmb does not look like a typical VLD - which have a very obvious joint/junction between ogive and bearing surface. Nor do they have the "church steeple" look to them as many VLDs do. These look like commercial airliner nose cones (like sierras), not F18 hornet nose cones (like Bergers and JLKs).
I've actually little experience shooting and tuning VLDs, but can definitely say these are seating depth sensitive and quite finicky - so maybe they are secant VLDs. Dunno.
As for the BC: All I can tell you is in my testing with these after pointing them, is I've clocked them @ 2700fps, and it took 8.8mrad to get dead nuts at 1000 yards. Strelok and JBM claim that means .62
I've actually little experience shooting and tuning VLDs, but can definitely say these are seating depth sensitive and quite finicky - so maybe they are secant VLDs. Dunno.
As for the BC: All I can tell you is in my testing with these after pointing them, is I've clocked them @ 2700fps, and it took 8.8mrad to get dead nuts at 1000 yards. Strelok and JBM claim that means .62
I should say I have no dog in this fight, tbh, I have no idea why I originally posted. Haha.
Their other bullets seem to be fairly long the 175 308 is a good bit longer then the smk and closer on length to the gp11. Actually looking back it's in between the two.
I'll be curious to see how they compare when shoot4fun get them.
If you are estimating .620 bc, that's still not bad better then the 175 smk, a little worse then the 162 Amax. And the .02 difference is still dang close, and could be the difference in testing methodology.
I'll be more curious to see how consistent the bearing lengths, overall lengths, and weight are, and if there's a lot of lot to lot variance.
I'm going to grab a box of the 140 for my 260, as for dumb reasons I don't like the look of amaxs. And they have minisculey more bc then the Hornady 140 bthp.
Their other bullets seem to be fairly long the 175 308 is a good bit longer then the smk and closer on length to the gp11. Actually looking back it's in between the two.
I'll be curious to see how they compare when shoot4fun get them.
If you are estimating .620 bc, that's still not bad better then the 175 smk, a little worse then the 162 Amax. And the .02 difference is still dang close, and could be the difference in testing methodology.
I'll be more curious to see how consistent the bearing lengths, overall lengths, and weight are, and if there's a lot of lot to lot variance.
I'm going to grab a box of the 140 for my 260, as for dumb reasons I don't like the look of amaxs. And they have minisculey more bc then the Hornady 140 bthp.
No worries, man. What forums of a technical nature are all about - hammering out and arguing over all the details!
Litz puts the 7mm 175smk @ .639; I always use .64 and have had excellent luck with it. In fact it's my favorite bullet because they're consistent, super easy to tune, transition well and have great form factor and BC.
By all rights, on paper, the 162amax is the pick of the medium power 7mm litter, but Hornady goatfucked us all last year. Plus as the F class guys at my club like to say:
"Hornady. There's a miss in every box!"
Litz puts the 7mm 175smk @ .639; I always use .64 and have had excellent luck with it. In fact it's my favorite bullet because they're consistent, super easy to tune, transition well and have great form factor and BC.
By all rights, on paper, the 162amax is the pick of the medium power 7mm litter, but Hornady goatfucked us all last year. Plus as the F class guys at my club like to say:
"Hornady. There's a miss in every box!"
This has not been a fight at all! I have really enjoyed [MENTION=96711]HodgdonExtreme[/MENTION] comments and observations. Since I don't shoot the 175s in my 7MM08 I am only looking at how the 171MB will stack up against my 168SMK. But I will be sure to measure up some bullets to see how they compare to other brands.
Post your results of testing up when you get a chance. I'm interested in how they stack up as well.
This is great guys, keep it up. I weighed quite a few of the 168SMK last night and they had more out of line for weight bullets than I would have thought. Is anybody else found this to be true with Sierra's? Just for kicks, I have some 168 Nosler custom competitions and they were spot on at 167.8 consistently. Has anybody tried the 168gr Noslers. I am going to give the 175 SMK this week. Thanks HodgenExtreme for the load data.
The Sierra stuff I've used has been within a .1 either way which has been better than hornady amaxs neitger were off enough to justify sorting. I've sorted for loads but when shot didn't notice a difference. The Nosler 168 are a bit lower in bc than the Sierra but I don't remember how much lower. Litz has them in his new book for verified bc. The 168 mk is a 565 g1 bc which is a good bit higher than advertised but has been spot on for me out to 1000.
Today was the first chance to get to the range with the 171MB bullets. I have load info, chrono data and real trajectory data; also will have pics of groups fired (even tho only 5 shot groups due to shoulder problem).
I will say up front that I got into this thread by posting disbelief in the Barnes posted BC for this bullet. Will I have to eat crow? Let you know when I get it all assimilated and posted.
171 Match Burner Observations
I wanted to not only see what the 171 MB was capable of but compare to my current load. Lots of chrono data from my Magneto Speed II and pics of groups.
I preface by saying load data is for my rifle only. Most loads are over current published data and I bear no responsibility for their use outside my rifle.
My main load for accuracy and long range is 45 grains H4350 behind the 168SMK, lit by GM210M primers. It is in either WW or, in the case of these numbers, Lapua 260 that has been turned down to .014" thickness.
SMK loads were fired in Lapua brass; Barne's MB were in WW brass.
Chrono data: (24" 1 in 9 Bartlien)
168SMK 45 gr H4350 .005 off lands
Avg 2659 FPS
ES 20
SD 10
171 Match Burner 45 gr H4350 .005 off lands
Avg 2618 FPS
ES 22
SD 8
171 MB 39.5 Varget .005 off lands
AVG 2554
ES 51
SD 19
All groups are five shot at 100 yards from a bipod.
Once accuracy had been established I corrected for true 100 yard zero and moved to my 500 plate. Using JBM, which showed a BC of .645 for the 171MB, I set my turret to 3.2 mils elevation and proceeded to fire three shots. There was a bit of wind but not to effect elevation. The first two rounds on the plate hit dead center within 3/4" from each other and the wind pushed the third up slightly and over by about 1". So, I am eating crow. The posted BC appears to be correct.
I wanted to not only see what the 171 MB was capable of but compare to my current load. Lots of chrono data from my Magneto Speed II and pics of groups.
I preface by saying load data is for my rifle only. Most loads are over current published data and I bear no responsibility for their use outside my rifle.
My main load for accuracy and long range is 45 grains H4350 behind the 168SMK, lit by GM210M primers. It is in either WW or, in the case of these numbers, Lapua 260 that has been turned down to .014" thickness.
SMK loads were fired in Lapua brass; Barne's MB were in WW brass.
Chrono data: (24" 1 in 9 Bartlien)
168SMK 45 gr H4350 .005 off lands
Avg 2659 FPS
ES 20
SD 10
171 Match Burner 45 gr H4350 .005 off lands
Avg 2618 FPS
ES 22
SD 8
171 MB 39.5 Varget .005 off lands
AVG 2554
ES 51
SD 19
All groups are five shot at 100 yards from a bipod.
Once accuracy had been established I corrected for true 100 yard zero and moved to my 500 plate. Using JBM, which showed a BC of .645 for the 171MB, I set my turret to 3.2 mils elevation and proceeded to fire three shots. There was a bit of wind but not to effect elevation. The first two rounds on the plate hit dead center within 3/4" from each other and the wind pushed the third up slightly and over by about 1". So, I am eating crow. The posted BC appears to be correct.
Attachments
[MENTION=1962]shoot4fun[/MENTION]
Thanks for taking the time to test and post up!
A note on BC, however.
The elevation difference between .62 and .645 @ 500 yards is less than 3/4", assuming your stated velocity of ~2550fps.
I always get out to 1000+ yards when confirming BC when dealing with high BC and/or high velocity bullets.
Thanks for taking the time to test and post up!
A note on BC, however.
The elevation difference between .62 and .645 @ 500 yards is less than 3/4", assuming your stated velocity of ~2550fps.
I always get out to 1000+ yards when confirming BC when dealing with high BC and/or high velocity bullets.
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I did my measurements on what I would call a small sample. The first 100 bullets were all measure base to ogive. 74% were +/- .0005 of a measure with my tools of .625" and weights for the entire 100 were 170.4 to max of 171.2 grains. This is a little better than Sierra SMK, although I don't remember what I came up with when I looked at them a while back. Still, if you look at my groups, the SMK is not a bad bullet in my gun. If I were betting I would say the 162 Amax is still the best bullet for long range 7MM-08 loads when pushed at 2800 FPS. But they are unobtainium and so I will shoot the SMK.
I was never saying my findings were scientific. Just appears to my eye that when you put in the right data, let JBM work its' magic, dial up the elevation, then make a perfectly dead centered hit that the .645 BC must be close enough that I won't argue with the ballistics experts at Barnes over it.
Gotcha. Wasn't trying to be a dick, just getting all technical-like in what has probably become the marquee thread on the internet for info/data on this bullet.
Again, thanks for taking the time to share your results!
Again, thanks for taking the time to share your results!
No problem [MENTION=96711]HodgdonExtreme[/MENTION]
At one point I was shooting the 168SMK behind 47.2 grains H4350. It was compressed as hell but they made 2800+ and shot great. It was a Badger action and 26" Bartlien.
That was the max load published by Hodgdon in 2010 but they have cut it back a bit now.
At one point I was shooting the 168SMK behind 47.2 grains H4350. It was compressed as hell but they made 2800+ and shot great. It was a Badger action and 26" Bartlien.
That was the max load published by Hodgdon in 2010 but they have cut it back a bit now.
I picked up a box or two of those 168 smk and really like them. The bc is decent and they are easy to load for compared to the amax.
What little bit I've played with them the Litz .56 bc has been spot on to 1000 which is nice since it's advertised at .48 by Sierra.
