Projectile weight, 1:10, 20", .308

klink1983

klink1983

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I have a rem 700AACSD with the shorter barrel, but it has 1:10 rifling.

I've been playing with 168, 178, and 175gr projectiles although I don't have time presently to do more in depth load development.

I've been told because of the 1:10 I will have better luck with heavier bullets, which for the most part is true.

I've thought about a lighter projectile to achieve faster velocity, and was told from someone to be cautious of over stabilization of the projectile. I'm not exactly sure what they meant by that.

Is 155gr too light of a projectile? My goal is to work on something to shoot to 1km.... is lighter but more wind drift better, or heavier but more drop better? :(
 
I find 150gr good for 400yards and less there has been reports of it reaching 800 yards but not in my experience. Also I have gone to 208 at the heaviest, this limits my scope for distance due to bullet drop. I have had success with smk 168 & 175 out to 800yards but anything past that is nibinized due to windage and other small factors. I have hit past 800 but not consectively enough to say"hey watch this". I have used varget, benchmark, blc2, imr 4166, and a few other powders but I find 4166 and varget the best for the long rge shots.
 
Was shooting 1200 yards this winter with 178 Amax and varget this winter. 1:10 barrel 22inch. Amazed with the results. Wasn't as happy with the 175 smk's I tried.
 
Stabilizing bullets is quite important. One thing you need to know is that there are an awful lot of unproven rumors out there. The one in ten twist that is so common in 30 caliber rifles dates back to just before the turn of the twentieth century. Back in those heady days long, heavy bullets for diameter were the flavor of the day. As the century crept forward it was found along with the advent of slower powders that were more stable and of course the development of bullets that lighter bullets were more than acceptable for the needs of both the military and firearms enthusiasts. This led to all sorts of new developments in twist rates and cartridge forms as well.

There is a formula that hopefully someone will post for you that gives an equation to calculate the ideal twist rate for any particular bullet. A good rule of thumb is a bullet of 3 calibers in length will do well with a 1-10 twist rate and as the length increases twist rate should get tighter.

Many 308 and 30-06 shooters that don't intend to shoot bullets heavier than 150 grains will install 1-12 twist rate barrels on their rifles. This decreases the pressure curves/recoil and increases velocities and is often leads to extreme accuracy. The 1-10 twist will stabilize 220 grain bullets very well with great accuracy as well.

Hunter Bench Rest shooters will have 1-14/15 twist barrels installed to shoot their specially made 110-125 grain bullets. These are about 2 calibers in length.

If you go to the hand loading manuals they all include 110 grain round nose bullets in their profiles. Just like girl friends, some will and some won't.

I often shoot the 125 grain bullets intended for the 7.62x39 cartridge through my 303 Brit/30-06/308 rifles. The military fmjs give very good accuracy and the commercial offerings give better accuracy. All of these rifles have a 1-10 twist barrel. The only loads I have had any issues with are the 110 grain round nose that are intended for the 30Carbine cartridge. The 1-10 twist barrels will over stabilize them if you push them to fast. The 1-12 twist barrels usually shoot them very well at higher velocities and the 1-15 twist barrels can be loaded to the nuts with these light bullets.

The 150 grain bullets you want to shoot will do just fine in your 1-10 twist barrel. It's to bad the old Western 135 grain/.308 dia bullets aren't still available. Those were fantastic bullets and held together well on bear and deer sized game.

Go ahead and load the lighter bullets. If you are concerned they will over stabilize then purchase boat tail bullets which are longer.
 
IMO, 150-190gr would work...and if shooting groups at distance I'd go on the heavier side of 168. Some of the really heavy ones may not seat far enough without over compressing powder charges.

It also depends on how fast you're pushing the bullet.

I'm not sure what "over-stabilization" means...but I had a fast twist barrel setup for shooting 80gr .22cal for a really fast 22-250 setup. I was warned that shooting light varmit bullets i.e light jacket v-max style would potentially see the bullets spin so fast that they may come apart in mid-air. We definitely tried...lol
 
"Over-stabilization" is a term that is thrown around regarding some light varmint bullets that have extremely thin jackets , which can , on occasion literally spin apart and disintegrate in the air. (if pushed fast in fast twist barrels) , this will not be a concern in any .308 caliber bullet. Shoot away with the smallest bullets you can find. You may just find that they don't hold the velocity at extreme distances. While the bigger bullets start out slower, they lose less speed during travel and actually end up at the finish line sooner.
Maybe look at a box of the 110gr x bullets as they are longer than some 150gr bullets.
 
As a Target Rifle shooter we are limited to 156 gr bullets in our .308's. The 156 gr rule is just in case any 155 grain bullet ends up being a little over 155 gr. We shoot from 300 yards to 1000 yards. I have seen guys shoot everything from a 1:10 twist to a 1:14 twist and all shoot very well.
I have heard that down in the southern states, some F'ers are shooting 220 gr bullets out of 1:7 or 1:8 barrels and spanking the 6.5-.285 shooters.
 
Confirm throat length. Recently helped a gent with a new Rem tactical. Throat was so long, the only bullet that would fit properly and still mag feed was the 178gr Amax.

If the throat is "standard", then any of the bullets you have listed will work. BUT what the barrel likes is a whole different story and only testing solves that.

Remember, not every factory barrel will shoot so....

Jerry
 
1 in 10 is the standard for .30 calibre rifles and has been for eons. Works well for heavy bullets, but the barrel length matters. Your 20 incher very likely will not maintain adequate velocity with a 155 to even get to 1,000 meters.
Read the 'Things that won't work' paragraph near the bottom. Add the W's. .6mmbr.com/palmabasics.html
 
If you want to shoot accurately at long range, wind drift is a big issue, in addition to the size of the group.

Testing will determine what bullets will group well in your rifle, and what velocity they achieve. I suggest the groups be shot at a moderate distance like 500 yards. I have not found 100 yards groups to be very indicative of long range performance.

A 1:10 will handle long bullets, like the Amax 208. I suggest you start with the heavy match bullets, because a superior BC beats high velocity, every time.

Here is the wind drift at 1100 yards, assuming 208 gr @ 2400 fps; 178 gr @ 2500 fps; 155 gr @ 2800 fps (out of a 20' barrel)

Drift inches - minutes

155 204 - 18

178 182 - 16

208 148 - 13


That is, the heavy bullet drifts about 4 1/2 feet less than a 155.

I suggest you buy a selection of heavy match bullets and start load development.

I have shot competition at 1100 and 1200 yards using both the light and the heavy bullets. With the 155 type bullet a moderate shift in wind angle or strength would take me way out of the bull, and maybe be right off the target.

By the way, SunShine said "Your 20 incher very likely will not maintain adequate velocity with a 155 to even get to 1,000 meters." I don't how much long range loading/shooting he has, but I would estimate that your 20 incher could do it. I use a 32" barrel, myself (only because I can't get a 34'). I have a 20" heavy barrel rifle, but have never tried it at long range. However, I have shot 155s at reduced velocity. 155s at 2,850 worked well at 1000 yards.
 
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