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Short Barrel 7mm-08 Powders

This is a discussion on Short Barrel 7mm-08 Powders within the Reloading forums, part of the Firearm Forum category; I've been loading for a short 18" barreled 7mm-08 for a very long time. As is customary, the loading manual results were derived from standard ...


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Old November 18th, 2012, 07:18 PM   #1
 
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Short Barrel 7mm-08 Powders

I've been loading for a short 18" barreled 7mm-08 for a very long time. As is customary, the loading manual results were derived from standard length rifle barrels, with shorter barrels always expected to deliver lower velocities, which I accepted as a norm for that little gun. Some years ago, just running some tests with all the powders I had on hand, I unexpectedly discovered a pattern of results with my chronograph that actually went contrary to the data suggested for highest velocity in the manuals, in favor of the carbine barrel length. As anyone knows, the 7mm-08 is very generous when it comes to delivering accuracy with any powder, so it requires no commentary on that. But by a fluke one day, I loaded a batch of Accurate 2015 loads, as it was the only powder I had left on the shelf. According to my records dated 10-25-91, it was from Accurate's data, which is not one of the powders they list for the cartridge these days, and probably isn't there because it generally wouldn't give respectable velocity in standard barrels. It may not be the same powder now; I don't know. But it was the results that turned my head and got me looking at powders with similar burning rates.

In testing over the chronograph, I was pleasantly surprised to discover that with my 140 grain Sierra Spitzer, I was getting extremely uniform velocities that averaged 2746 fps. from that twig of a barrel with 39.0 grains, which was substantially greater than the standard powder results, and with wonderful accuracy. I'm please to say that my more recent tests with powders in the same section of the burning rate chart are performing likewise in the mid-to-high 2700s. Benchmark is the one I'm currently using, which is giving me spectacular accuracy, but more uniformity, without some of the fussiness the AA2015 gave if the charges went up or down 3 tenths. I have some H-322 on hand and will give that a try, expecting similar results.

My current hunting load that delivers consistent accuracy with metered charges is 38.8 grains Benchmark with WLR primers in Federal cases with 140 grain Sierra Spitzer (flat base), seated to touch rifling and given a moderate crimp with a Lee Factory Crimp Die. That load is not excessive in my gun and shows perfectly normal behavior, but it exceeds Hodgdon data by 1/2 grain, so proceed accordingly.

My theory is that, while powders in this burning range don't compare favorably to other powders velocity-wise in longer barrels, they may be affected negatively by friction after their burn is completed.

I did achieve greater velocities with a couple of other powders, but with nowhere near the accuracy and with very severe recoil in that small gun. H-414 was notable in this regard, as was now-obsolete H-205 which was discontinued due to irregular and reportedly dangerous pressure behavior.

As a matter of note, powder weight is the largest component of felt recoil, so it is great news to have relatively high velocity with low charge volume. We're talking as much as 6-8 grains difference, which substantially reduces a big kick in the shoulder.

Be mindful that this range of powder is producing velocities within less than 50 fps of factory advertised loads, which really permits a carbine user to take full advantage of the cartridge. The moral of the story is simply that while the higher velocity powders loose ground with shorter barrels, the lower velocity powders on the same data page seem to gain ground.




Last edited by GunBlue; November 19th, 2012 at 07:16 AM.
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Old November 18th, 2012, 08:15 PM   #2
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Sounds great! I am a big fan of the 7mm-08 and don't have a legitimate reason for not owning one. Another ball powder just faster than typically recommended but recommended for .308 and .223 is Ramshot TAC. It would make for an interesting combination. It is very fine and dense so metering is excellent. I bought it to load .308 but I bet it would work for your application as well. How effectively, I can't say.
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Old November 19th, 2012, 05:06 AM   #3
 
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I've used ball powders for many years very successfully, but have recently rediscovered single base extruded powders and their advantages. They burn extremely clean and cooler than ball powder, and my tests show they don't have dramatic accuracy swings when I deliberately vary charge weights. In other words, even if the charge isn't right on the money, the shot doesn't fly out of the group. They were always the darlings of the benchrest fraternity, such as IMR4895, IMR4198, and H322, and most of those guys, years ago, didn't even bother weighing charges but loaded on the road with drop measure on their tailgates! I've converted entirely to the Lee measures, which meter extruded powders reliably and with uncanny accuracy. The Lee Perfect Measure looks cheap as all getout, but works slick and doesn't crunch powder like my old reliable RCBS Uniflow. Good as it was, it was the reason I went to ball powders back in the late 70s.

I dug out some old records I kept from the 70's and was amazed at the groups I was getting with my .222 Rem with IMR4198 and with my '06 and IMR4064, and those two powders were the worst of the bunch when it came to being impossible to measure consistently, but according to my records, I was indeed throwing them, and getting great results. In fact, the only powders I used with my .270 Win loads were IMR4831 for 130 grain loads, and IMR4350 for 150s. Also IMR4831sc for the .300 Win. Mag. was awesome.

For some reason, I started using ball powders in the early 80s for many rifles, and perhaps lots had to do with how they measured nicely, but looking at the records I kept back then, I apparently didn't notice the wild group swings I was getting in incremental ladder tests that I never got with IMR powders, and it explains a lot of flyers and unpredictable results when temperatures became a factor. As I've said before, the biggest climate change is going from magazine to a hot chamber.

I think ball powders are terrific, but I think I'm sticking to extruded ones from now on, as it's really giving me consistent results.
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Old November 19th, 2012, 05:42 AM   #4
 
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Old November 19th, 2012, 06:58 AM   #5
 
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You'll be top on the list, Top Sargent.

Now I've got to head out to KTP over in Maine to find a pair of Johnson Mills trousers. Something got into my cedar closet and they shrunk from last year. If I have to drag a deer out at sunset wearing my cotton jeans, they'll be dragging me out in the morning. Getting a bit frosty these days. 12 this morning, and even Benny didn't want to stay out longer than duty required. Feels like something from out your way arrived. We'll be looking up at Zero pretty soon.
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Old November 19th, 2012, 07:58 AM   #6
 
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Quote:
Originally Posted by K57 View Post
Sounds great! I am a big fan of the 7mm-08 and don't have a legitimate reason for not owning one. Another ball powder just faster than typically recommended but recommended for .308 and .223 is Ramshot TAC. It would make for an interesting combination. It is very fine and dense so metering is excellent. I bought it to load .308 but I bet it would work for your application as well. How effectively, I can't say.
Go get yourself one, then! I went from a .308 in my old 660 Remington to the 7mm-08 with my Model Seven and never looked back. The 7mm bullet is just so efficient, grain for grain, compared to a .30. The 140 grain bullet has sectional density and ballistic coefficient on par with 165 grain .30 cals. Of course, the .308, being a larger bore, uses the case capacity more efficiently, and retains great energy with the 150 grain bullet down range, but has greater wind drift and is not as flat. That long slender 140 has tremendous sectional density that drives deep, too. Most have very generous magazines and long throats that permit loading any bullets without loss of efficiency. In most cases, it does slightly better than the old 7x57 Mauser all the way up to 175 grain bullets, and that cartridge has taken everything, including W.D. Bell's legendary elephants (though that would not be a recommended use for a 7mm by any stretch of the imagination!).

Being a fan of the .270 Winchester when I hauled out my long rifles, it really is in the same class minus 80 yards, just as the .308 Win. is to the .30-06. Of course, they're all great and most of it is academic stuff that means little at the end of the day when the buck is tagged. But if you want to play with a fun caliber that can drive tacks, I couldn't recommend a cartridge more highly. It's really a handloader's proposition, as the ammo companies have been very stingy about offering any bullet selections beyond 140 grains. There's no reason for that whatsoever. I suspect a marketing strategy behind that, I think, and I suspect it goes back to trying to keep the .280 Remington alive, which has finally breathed its last. Perhaps with that cartridge having finally surrendered to the .270 Winchester, someone will start offering a full variety of 7mm-08 factory loadings.
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Old November 19th, 2012, 10:57 AM   #7
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Well. I came real close back in the days of the Remington 788 and I'll always regret not getting the 788. Lately, I've been pondering another cartridge since Savage decided to make 6.5 X 284 a standard chambering. Good luck on the hunt this season.
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Old November 19th, 2012, 07:04 PM   #8
 
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If you can find an old hornady reloading manual #3. The data in that manual was developed using a Remington 788 18 1/2" barrel. It mentions that IMR 4320 and IMR 4064 worked good in that shorter barrel. You probably already know about this but I thought I would mention it just in case.
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Old November 19th, 2012, 07:56 PM   #9
 
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Originally Posted by montana View Post
If you can find an old hornady reloading manual #3. The data in that manual was developed using a Remington 788 18 1/2" barrel. It mentions that IMR 4320 and IMR 4064 worked good in that shorter barrel. You probably already know about this but I thought I would mention it just in case.
I recall that handbook, which is among the several that I either gave away or didn't pack when we moved 8 years ago. They might do well, and it would be worth giving them a try. They're on the slower end of the medium powders, and would likely do really well with heavier bullets in the short barrel.

With me, powders leave impressions from previous use that's hard to shake off. IMR-4064 was my favorite powder for my .30-06 with 150 grain bullets, but its stringy length was so annoying to deal with that I searched for a replacement, and it was about then that I got hooked on ball powder and replaced that load with either W-760 or H-414. I could never get a good load going with IMR-4320 for the life of me, except with my wife's 760 Remington pump .308 and 125 grain bullets... I've been reading my first old loading journal, and have been fascinated by the loads I shot back in the 70s and early 80s. I was overly fussy and traded off some fabulous guns! Fun reading. I'll have to run some of those loads up for folks to check out. Most are pretty traditional, like 20.0 grains of IMR-4198 and 50 grain Sierra for the .222 Remington. One load was unreal, 59 grains H-205 with 165 grain bullet with a Model 700 .30-06. That was a load.
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Old November 20th, 2012, 08:39 PM   #10
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Great thread! I have been shooting a 7mm08 Remington Model Seven (18 1/2" bbl) since 1987. I started loading for it with H414 powder and 140 grain bullets, and once I arrived on a good load combo (accuracy with decent velocity) using a chronograph, I've stuck with it for over 20 years. From the bench and sandbags, the rifle/load will easily place the first several shots in less than 1 inch at 100 yds. This is a 7 lb rifle; fully-loaded, scoped, and slung. The 140 gr Nosler BTs are travelling just under 2700 fps.

Simple logic would lead one to believe that a faster burning powder would produce better velocity with a shorter barrel, but that doesn't seem to be completely true with the 7-08.

Since I only load 20-40 rounds at a time, weighing each powder charge doesn't bother me.

Sometimes, I consider trying some other powders to see if I can get any better results, but it seems like I'm doing pretty well with the H414. Two other powders that get mentioned often for 140 gr bullets are Varget and RL17.

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Old November 21st, 2012, 02:53 AM   #11
 
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Originally Posted by firescout View Post
Great thread! I have been shooting a 7mm08 Remington Model Seven (18 1/2" bbl) since 1987. I started loading for it with H414 powder and 140 grain bullets, and once I arrived on a good load combo (accuracy with decent velocity) using a chronograph, I've stuck with it for over 20 years. From the bench and sandbags, the rifle/load will easily place the first several shots in less than 1 inch at 100 yds. This is a 7 lb rifle; fully-loaded, scoped, and slung. The 140 gr Nosler BTs are travelling just under 2700 fps.

Simple logic would lead one to believe that a faster burning powder would produce better velocity with a shorter barrel, but that doesn't seem to be completely true with the 7-08.

Since I only load 20-40 rounds at a time, weighing each powder charge doesn't bother me.

Sometimes, I consider trying some other powders to see if I can get any better results, but it seems like I'm doing pretty well with the H414. Two other powders that get mentioned often for 140 gr bullets are Varget and RL17.
That's my rig. We're going hunting right now. H-414 is a fabulous powder that I had great results with, but in fact my velocities were well above 2700, with wonderful accuracy. When I get back, I'll look up the data and my notes and send it along.
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