I'm thinking of having a 308 barrel spun up for my match rifle to switch out. Curious what velocities everybody is getting with 18-22" barrels with 155-185gr bullets?
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Shorty 308 velocities?
- Thread starter DynamicAccuracy
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that would depend on the particular ammo or load, but this article will provide some examples of different ammo and barrel lengths.
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The Truth About Barrel Length, Muzzle Velocity and Accuracy
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It takes some work and experimentation but you can get decent velocities out of a 308 w/20 inch barrel.
I using Lapua brass, 210m, RL-15, Hornady 178 ELD-M @ 2740 FPS with ES 15 and SD 7 out of my AX.
I using Lapua brass, 210m, RL-15, Hornady 178 ELD-M @ 2740 FPS with ES 15 and SD 7 out of my AX.
My old 17.5” barreled Surgeon was consistently running reloads (43.8 Varget,210,178 bthp) at 2575-2580.
Running it suppressed did boost my velocities to 2620-2640.
Running it suppressed did boost my velocities to 2620-2640.
must be awesome to be able to tailor your ammo for the sweet spot of your rifle, whatever the length of barrel.
for a lot of common .308 or 7.62x51mm ammo (military ball to Federal GMM) the 20" barrel seems to be the sweet spot as far as dropping velocity compared to a longer barrel. in real world testing, going from 20" down to 19" steps down more than from 21" to 20".
perhaps that is why it is the length chosen for some of those military applications like the M40A6 or my Scar 20S.
308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″)
308 Winchester / 7.62x51mm NATO: Barrel Length versus Velocity (28″ to 16.5″) Introduction Released by Winchester in 1952 (and adopted by NATO in 1954 as the 7.62x51mm NATO), the 308 Wi…
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There is always one that can't get the velocities and accuracy, so they doubt what others can do with a little work and patience.
There's no work and patience involved in loading a case to excess pressure. Just add too much powder...
I've loaded for more than a few 20" barreled 308s. IF you are getting 2740 fps with a 178 ELD-M in Lapua brass, using RL-15 you have a unicorn. 99+% of the 20" barreled 308s out there are not going to see 2740 fps w/178 & RL-15 w/o trashing brass. Nominally, 2580 to 2620 is the velocity one sees with 178 from a 20" barrel. You are blessed with an exceptionally fast barrel, a special lot# of RL-15 and a perfect combination of components; enjoy it while it lasts as it is unlikely to be reliably repeated with new barrel, new lot # of powder.
Nada to do with work and patience. You are 120ish fps above what is achieved with a fairly warm load from a 20" barreled 308. Chamber, barrel, burn rate of that lot # of powder, etc are allowing something special. 2740 is pretty warm from a 26" barreled rifle, much less a 20" barrel.
918v's calling BS is valid, you are claiming something that 99+% of the time is going to yield excessive pressure, blown primer pockets or worse.
The barrel is a Bartlein 5R 1-10 standard 308 chamber. I too was seeing 2550-2610 velocities with the standard 308 powders (4064, Varget, 2000-MR) What I have found after much tinkering and trial is that with the shorter barrels (18-20) in many different calibers (308,338LM, 260) is that you have to look to powders that are faster burning than what the typical rated powders for caliber are.
This approach has work for me on most bolt actions that I have had with exception of the AR styles.
I have a 338LM with a 20 factory barrel that I am shooting the 285 ELD-M moly, Peterson, 215m, H4831sc, with an average velocity of 2747 with ES of 20 and SD 9
I went through the standard powders here also (H1000, R33, Retumbo) all with the same results of a velocity that is low (2485 to 2574)
Case in point is that if you try different powders until you find one that gives you low ES and SD with good velocity is what I am looking for.
I guess that I am the 1% : )
This approach has work for me on most bolt actions that I have had with exception of the AR styles.
I have a 338LM with a 20 factory barrel that I am shooting the 285 ELD-M moly, Peterson, 215m, H4831sc, with an average velocity of 2747 with ES of 20 and SD 9
I went through the standard powders here also (H1000, R33, Retumbo) all with the same results of a velocity that is low (2485 to 2574)
Case in point is that if you try different powders until you find one that gives you low ES and SD with good velocity is what I am looking for.
I guess that I am the 1% : )
Both of your loads are likely 70k PSI or higher per Quickload, and well above SAAMI pressure max specs. Just because they have good SD/ES doesn't mean they are reasonable and safe pressures.
Generally speaking, going to a faster powder will result in higher pressures for any given velocity. Yes you have the potential to make more pressure because you can fit more powder in the case and have more total energy potential, but going to a faster power to make better speed is not usually the recommended approach.
Generally speaking, going to a faster powder will result in higher pressures for any given velocity. Yes you have the potential to make more pressure because you can fit more powder in the case and have more total energy potential, but going to a faster power to make better speed is not usually the recommended approach.
What’s BS about that? He didn’t say it was a SAMMI spec load or even if it was within recommend book pressure. People have been running hot loads in weapons for years. Comes down to knowing your weapons capabilities, loading capabilities and weather conditions in which both operate.
My 17.5” barrel suppressed Surgeon was 2620-2640 with a middle of the road load. 2.5” of more barrel should be roughly 2700 FPS if you figure 25 FPS per inch of barrel which is common with hand lapped after market barrels.
That’s another factor is how “fast” your particular barrel is. I’ve seen two consecutive barrels from the same maker chambered the same day consistently shoot 70-80 FPS different from each other with the same exact load ??
and they maintained that difference through out their life. While the 2740 he claims isn’t on average what is experienced or seen it’s not BS. If he claimed 2850 then I would call BS or have to see that for myself.
15 FPS per inch. 25 for magnums.
I said BS because he’s claiming a velocity typically gotten from 26” hand lapped match barrels.
I understand that powder lots vary in burning rate and generate higher or lower velocity but with that comes a change in pressure.
Running loads that hot is beyond stupid.
I said BS because he’s claiming a velocity typically gotten from 26” hand lapped match barrels.
I understand that powder lots vary in burning rate and generate higher or lower velocity but with that comes a change in pressure.
Running loads that hot is beyond stupid.
Area under curve.
Peak pressure.
Physics is physics.
You might be the 1%, higher probability is you got the 1% barrel, chamber, ideal RL-15 burn rate, winning lottery ticket.
2740 from a 20" barreled 308 is a fluke, essentially a blind luck lottery win. I'm saying it is not commonly going to happen.
I agree with finding powder that gives you low ES and SD with good velocity. Only way you are getting the velocities stated in a 20" barreled 308 is by running higher pressures. RL-15 is NOT a faster burn rate than typically used for 308 w/175 bullet, right in the middle unless you happen to have gotten a much faster than typical burn rate lot #. Effective burn rate of powder varies by cartridge used in, by bore size, by lot #, by land / groove ratio, by land / groove diameter.
H4831sc in a 338LM with a moly 285 Hornady isn't really what I'd consider to be a faster burn rate for caliber either. H1000 (not so much), RL-33 and Retumbo are all really geared more for 300 gr bullet than the 285. H4831sc is smack in the middle of burn rate for what I'd expect to work with moly 285, which would be closer to a bare 250 gr bullet.
I tailor fit ammo to customer rifles, have done a LOT of this kind of tinkering to find ideal combinations. Telling somebody that he can get 2740 fps with a 178 from a 20" barrel is unrealistic at best. I've probably played with more combinations of powder, bullet, brass, primer, barrel, chamber and temperature range than the average person. 2740 with a 178 from a 20" barrel is an unsafe load in 99+% of the 308 bolt rifles and 100% of the gas guns operating as a gas gun.
I'm all for getting as much performance as possible. Promoting an unsafe load, unrealistic velocity expectation because you happen to have a <1% solution for a shorter barreled 308 and justifying by stating "There is always one that can't get the velocities and accuracy, so they doubt what others can do with a little work and patience." is unacceptable. More like there is ONE who has made this work, managed to not damage brass, rifle or himself. Least you can do is make it clear to OP, thread readers that your load is an anomoly. Unless you've done this for 10+ rifles with 20" barrel, ran that load from -10 F to 110 F w/o pressure issues, you really can't say it is "safe, commonly occurring" load. IF you've done this for 10 + rifles, >3 lot #s of RL-15/primers/brass/bullets then that is different and you are clearly the <1%; you are THE internal ballistics god.
RL15 is not faster burning than Varget or 4064. RL15 is middle of the road burn rate powder for 308. Slightly slower than Varget and 4064 and faster than 2000MR.
18" SAC built rifle with Bartlien barrel runs 185 Juggernauts at 2570.
Shorter barrels, heavier bullets are your friend as they lose less performance.
I do not have data for lighter bullets, I'm an admitted heavier bullet aficionado.
Well this goes to show the amount of ignorance and narrow mindedness that people have. You are stating that Quickload is saying 70k of pressure. Well that is all well and good but I did not mention the powder charge only the powder being used, as for the amount of chamber pressure it can be decreased by using a coating on the bullet to a certain extent.
Bottom line, is if you are satisfied with your short barreled 308 shooting @2550-2600 then do what you have been doing.
If you want to gain the edge on pushing the 178's to higher velocities and .50 groups with low ES an SD then you have to think out side the box and experiment in a safe manor.
I have spent a lot of time and effort on load development, and have found a combination that is providing me with a stable, repeatable and above all SAFE load for my rifles.
I’m curious, what pressure are you running? How did you determine this is a safe load?
My 20” factory AI barrel was getting ~2500 with 4064 @ 41.8. I was able to get ~2600 with 42.5gr but was over pressured...
Got a bit over 2600 with Varget @ 43.5, no pressure signs!
Edit: this was with LC brass
Got a bit over 2600 with Varget @ 43.5, no pressure signs!
Edit: this was with LC brass
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I don't have any way of determining the amount of pressure a give load has. Shooting this load in my 308 using Lapua brass I am on my 7th reload on the brass, and still tight primer pockets, no heavy bolt lift or excessive case stretching. No doubt it is a stout load but not over pressured as this would Pierce or blow primers and eventually split the cases.
I have a SR25 APC 16" factory kac gun, with their 7.62QDC suppressor that slings the factory fgmm 175 gr ammo at 2610 fps. Exact same round from the same box of ammo out of my 20 inch rem 700 is only 5-10 fps faster at 2615-2620. When I had the Fix with 16 inch 308 barrel, I could only get 2525 with the 178 eldx and that was right at pressure with varget. With a suppressor. That same 178gr varget load in the rem 700 was just about 2600 in that 20 inch gun with a suppressor.
Pretty sure Lowlight was getting some pretty impressive numbers with a short .308 and 2000MR...might check out of some of his podcasts for details...
