Barrel length vs Bullet weight

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Savagehawg

New member
Loading for a 7mm-08 which is new Caliber for me, new rifle with a 1:9 1/2 twist 20inch barrel. Loaded 140gn Accubonds with 46gn of IMR 4350 groups are consistent but tightest group is 1 inch, trying to figure out do i want to play with the powder load, seating depth , or bullet weight . I could try different powder but would probably have to purchase some new powders, I have other powders but none for what loading books are recommending , since most of our reloading is for magnum style rifles.

So my main question is for shorter barrels do i go heavier or lighter weight or do you think that it makes no difference. Would like to stick with the Accubonds since i have 2 boxes of them and nothing do do with them, but also know some barrels just don't like some bullets.

Thanks in advance for any help
 
Don't let barrel length determine anything about your bullet and powder choices. I don't have a 7-08, but I do have 5 rifles in 308 and the 2 are very similar. I have barrels of 18, 20,and 22" I load and shoot 125-180 gr bullets for all of them and have even experimented some with 200 gr bullets.

The same powder that would give you the best speeds from a 26" barrel will also be the fastest with a 20" barrel. A lot of folks mistakenly believe they need a faster burning powder with a shorter barrel. Even the slowest powders burn within 6-8". The faster powders in 4-6". This might matter with a handgun, but not a rifle.

Experiment and use the bullets that shoot best for you and do what you need them to do.

If you start with a longer barrel, measure velocity, then start cutting the barrel shorter you will note less speed as the barrel gets shorter. But even from the same length barrel 2 different rifles can have significantly different speeds. I've seen 130+ fps from the same length barrel.

Of my rifles the one with the 20" barrel consistently has more speed than all of the others, even the ones with 22" barrels. And there is 50 fps difference between the fastest 22" gun and the slowest 22" gun. The 18" gun is the slowest, but isn't very far behind one of the 22" rifles. About 65-70 fps slower than the one with the 20" barrel, the fastest one.
 
jmr40 wrote:

Don't let barrel length determine anything about your bullet and powder choices. .....

Experiment and use the bullets that shoot best for you. .....
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Yeah. This is my thinking also.

Savagehawg, If me, depending on how much experimenting you've done with he ABs,
my next step would probably be to pick and try a different bullet.

Now, I've read where many reloaders have had some accuracy improvements with the ABs by increasing the jump to lands, i.e. loading to a shorter COL. This is not intuitive, but has worked many times with the ABs so not to be ignored.

So...What COLs and jumps have you tried with the ABs ?
 
When the 7-08 was popular in the '90's for rifle matches, IMR4064 and similar speed stick powders were popular.

https://www.accurateshooter.com/featured/7mm/

While IMR4350 will produce higher velocities, it was never popular when best accuracy is the objective.

Accuracy, to me, is best defined by the largest groups fired, that's what can be counted on. They show what happens when all the variables add up.

Smallest groups happen when one of two situations exist; all the variables are minimum or they cancel each other out, difficult to repeat. If you shoot enough groups with any load, one will be very small.
 
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Loading for a 7mm-08 which is new Caliber for me, new rifle with a 1:9 1/2 twist 20inch barrel. Loaded 140gn Accubonds with 46gn of IMR 4350 groups are consistent but tightest group is 1 inch,
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And is the rifle a light weight hunting rifle, or a heavier bench/match type gun??

1 inch groups are good for a big game rifle, and despite that "everyone" on the Internet seems to shoot half that or more real hunting guns are doing well to shoot 1" groups.

Try different bullets and powders in various loads, you might find a sweet spot where the gun/ammo combination groups significantly better. Just be aware, that you also might NOT.

Every rifle and ammo combination can be different. Its not unheard of for the same ammo to shoot different size groups and different velocities fried from "identical" barrels.

Just because someone else got less than an inch with a certain load in their rifle doesn't mean you will in yours.
 
Pretty sure barrel length has any effect other than velocity. You may have to tweak the load a tad one way or the other to get it to perform to your liking though. I had a 69 grain SMK load that shot great in a AR but I had to tweak the charge to get it to shoot in my 26" barrel bolt gun. Took it down .2 gn and even with the same COL it shot great

Never shot the Accubonds but I have shot a lot of Nosler CC's in various calibers and in general the Noslers have always liked about a .040 to .050 jump

edit - what primer ? Different primers can cause some pretty dramatic changes. My rifles like Remington primers with 4350. Other powders they might like CCI or Federal
 
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Shadow9mm said:
my understanding it bullet weight and barrel length have no correlation. The important part is to match the bullet length to the twist rate. as far as powders with a 20in barrel i wouldn't worry about it too much. 16 or 18 in I would steer towards the faster burning side.
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There is the situation in the British Empire shooting 7.62 M80 ammo's 147 grain FMJBT bullets in fullbore matches up to 1000 yards. The bullet velocities leaving 22 inch or shorter barrels wasn't enough to keep them supersonic that far.

They used 30 inch barrels so bullets stayed supersonic with 1:14"`twist for best accuracy leaving about 3000 fps.
 
Thanks for the advice guys, working up some loads with less/more and see what we come up with, i understand what people say about a hunting rifles and accuracy, well i don't really believe that in this day and time, My main rifle is a savage 25-06 shooting a 120 gn hornady BTHP and 5 rounds at a 100 yards and will all be touching with some through the same holes, my Dads A-bolt in 7mm Rem Mag almost the same, Now the BLR is different because you cant play with the seating depth as much because the Mag is so short and if you get to long you will have feeding problems. If 1 inch is all it will do then i can live with it since its primarily a deer and hog gun. I love this Rifle just got to tweak it some more :)
 
hounddawg said:
Pretty sure barrel length has any effect other than velocity. You may have to tweak the load a tad one way or the other to get it to perform to your liking though. I had a 69 grain SMK load that shot great in a AR but I had to tweak the charge to get it to shoot in my 26" barrel bolt gun. Took it down .2 gn and even with the same COL it shot great

Never shot the Accubonds but I have shot a lot of Nosler CC's in various calibers and in general the Noslers have always liked about a .040 to .050 jump

edit - what primer ? Different primers can cause some pretty dramatic changes. My rifles like Remington primers with 4350. Other powders they might like CCI or Federal
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We started with WLR and going to switch it to CCI on the next loads and also going to slow it down and speed it up and do some loads with some 150 gn and see what happens, also going to play with some new powder just haven't decided witch ones yet
 
hounddawg said:
Pretty sure barrel length has any effect other than velocity.
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Changing only barrel length for a given load will cause more or less vertical shot stringing because the line of fire axis spread will change. So will the average point of impact on target. Muzzle velocity will also change.

The one resonant and several harmonic frequencies it vibrates at will change. They'll be lower if the barrel's longer, higher if shorter.
 
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If your looking at group size, play with seating depth.

As for the regular Accubond, i've found that either your rifle likes them or it doesn't.
I've gone from seating them touching the lands to 0.060" off. And everywhere in between.
Gave up on them.

ABLR, no issues.
 
44 AMP said:
And is the rifle a light weight hunting rifle, or a heavier bench/match type gun??

1 inch groups are good for a big game rifle, and despite that "everyone" on the Internet seems to shoot half that or more real hunting guns are doing well to shoot 1" groups.

Try different bullets and powders in various loads, you might find a sweet spot where the gun/ammo combination groups significantly better. Just be aware, that you also might NOT.

Every rifle and ammo combination can be different. Its not unheard of for the same ammo to shoot different size groups and different velocities fried from "identical" barrels.

Just because someone else got less than an inch with a certain load in their rifle doesn't mean you will in yours.
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The Rifle is a Browning BLR lever action, 6.5 lbs right at 7.5 lbs with scope
 
I'd play with the seating depth at least before tossing the towel on them. A lot of times it only takes a .005-.010" change one way or the other. Granted your limited going out, but it could improve going in.

Most all of my loads start at the max magazine length and go shorter. I hunt with them all and they have to feed reliably. I usually work up to around 2800- 2900fps and once there adjust seating depth in .005 increments. I have gone as far as .120" to hit a sweet spot but that was an extreme case. Usually it comes together within. 020-.075" at most depending upon caliber.

As for barrel length and bullets, my 7/30 Waters Contender barrel is 14" and the most accurate bullets are 140grs. It has put up a multitude of 1" five shot groups at 200yds and is almost boring to shoot at 100.
 
Mike / Tx said:
As for barrel length and bullets, my 7/30 Waters Contender barrel is 14" and the most accurate bullets are 140grs. It has put up a multitude of 1" five shot groups at 200yds and is almost boring to shoot at 100.
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What are all the other group's sizes?

How many is a multitude?

Are they consecutive?

I suspect those are the smallest groups occasionally shot.
 
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Bart, I did have groups that were bigger. I worked for a month or three with several powders, bullets, cases and primers to dial in the very best possible load i could develop.

The end result however will shoot better than I can, day in and out, and has turned plenty of consistent clover leaf groups at 100 and 200. It is an awesome combination and I'm proud to own it. I also have a .223 AI barrel that has made just as impressive a track record.
 
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