Anybody know what the max velocity should be from an 18" 1:10 barrel in an AR/LR 10? before being "over pressured"?? 167gn bullets? 175gn??
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Anybody know what the max velocity should be from an 18" 1:10 barrel in an AR/LR 10? before being "over pressured"?? 167gn bullets? 175gn??
Not gonna lie...
With experience on this forum, I am very surprised t not have a SINGLE response....
I asked this question seriously... How fast is to fast... I was surprised by the chrono readings i got.... 2601 average for the 167gn Lapua 308, and for LC M118LR 2625fps average....
Your input is greatly apreciated!
Those numbers are close to what it should be. My only 308 is a much longer barrel, so I couldn't compare.
Do you gave any signs of overpressure on the case?
My hand loads for my 223 flatten primers pretty good, but I like it hot (26" barrel, 40gr, 3715fps)
My thoughts is to look up the loading data for that bullet / barrel combo. What style bullet?
> 175 smk
Most of the load data that I found indicate that is getting close to max pressure depending on the powder used.
That reminds me, I have a 'fresh' 308 barrel for my encore.
I will add my load for that barrel length and 175 SMK is 2534 FPS at 5660'.
I load for accuracy, so I am sure I pushed it faster, but I did not keep the data points. Off the cuff, I would think 2650 (+/-) would be a near the top of achievable FPS with an 18" AR and 175's. My $0.02.
You need to tell us. Every rifle, barrel, bullet and powder is different. We cannot tell you when you hit "pressure", let alone max pressure. If you are serious, you need to know what pressure and "over pressure" look like. There are plenty of signs to alert or warn you, heed them all. My load could blow your face off and vice-versa. If you want speed get a longer barrel. You (and everyone) should go for consistency rather than speed.Quote:
Originally Posted by normandinpatriot
Ten times the caliber (in mm) times the barrel length is your standard formula.
So for your rifle...
7.62 x 10= 76.2
76.2 x 18= 1,371.6 FPS
There you go. Anything over that and the rifle may explode killing everyone in a forty foot radius.
Thanks for responding!Quote:
Originally Posted by 00tec
Yes, i have flattened primers on the the Lapua ammo and a mild ejector mark that i understand to be common for the AR/LR 308 platform. The Lake City M118 LR has cratered primers, some popped and cratered primers and similar ejector marks as to the Lapua. The Lapua specs a 2600 fps rating and the M118LR specs 2559? 2595? I cant remember... I was surprised to see both ammo with readings so fast as most velocity testing seems to be done in barrels longer than 18", usually it seems 24 or 26" barrels are used.
As for my rifle... CMT matched billet upper and lower, JP High Pressure bolt, Lantac bolt carrier, Heavy Buffers 5.5oz. Buffer and matching spring, Odin Works ADJ gas block,Ballistic Advantage 18" 1:10 barrel...
Delfeugo, I am not looking for velocity as a target to hit, I am looking for what seems reasonably safe, I understand what you said. With factory loaded ammo, "overpressure" signs should not appear with out cause... I am trying to gain knowledge to eliminate looking in the wrong direction. I have shot Both Hornady and Sig ammo both also rated at 2600fps with absolutely ZERO signs of overpressure. I did not have a chrono at the time so I do not know what velocity actually was...
Bradbn4... I have the latest Hornady loading book. It shows a lower velocity for their 175gn projectile but makes no mention of barrel length.
the reloading info I looked at was for 24" barrel using generic 175 - 180 weight bullets - no reference on the shape of the bullet. That was online stuff - most of my reloading books are a bit dated. I have never setup for 308 reloading - got the equipment - but I never found a place I wanted to shoot at for distance.
You can?t mix metric & SAE. So that would be 1,371 MPS. The conversion factor is M X 3.281 = Feet. So, 1,371 x 3.281 = 4498.031 FPS.Quote:
Originally Posted by ray1970
At about the second shot, your barrel is spitting out molten Copper & lead....... [panic]
Hopefully you aren’t shooting tracers.......
Wait...you still have SAE in there with the 18 INCH barrel length?Quote:
Originally Posted by SideShow Bob
Quote:
Originally Posted by 20X11
Still havent got there yet... this weekend I chronoed Sig Sauer Elite performance 175gn OTM, Lake City M118LR 175 gr Sierra OTM , and Lapua 167gr Scenar OTM...
Temps were 88-91f relative humidity was near 50%, ... Yes i know that hotter temps equal faster velocity...
rifle: CMT matched upper/ lower DPMS patter LR308, Ballistic Advantage .308 18" 1:10 barrel about 200rds on this barrel, Odin Works ADJ gas block, SureFire brake/ adapter...
Distance to chrono.... 10 ft measured...
Sig ammo average is not comprehensive, as I got radically different readings from 2 boxes of the same lot.... first 20rds average about 2530... second box measures much higher... about 2625...
Lake City M118LR 175gn Sierra OTM average... 2695..10rds
Lapua 167grn Scenar OTM 2704..10 rds
best accuracy from the Sig ammo.in the 2600fps range..
All cases except the M118 looked acceptable.. the M118 had cratered and 2 popped primers...
groups were shot with a minimum of 5 minute cool down between each 5 shot group... and for some reason the photo of my painfully average 100yd target wont load...
As far as my shooting ability goes, I am able to generally shoot pretty well. I have never had any formal training, but have shot both pistol and rifle or about 35+ yearsAttachment 82645