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| One of Us |
I'm off to Sweden soon in search of the lonesome moose. The new mousetrap is a M700 Titanium (old unfluted) in 308. 18" barrel and suppressor. Great rifle. Light = hot - really hot. Initial loads showed pressure signs as the rifle heated up. Not talking great long strings of 5 but 3 shot strings and cooling after the string but not inbetween shots. I've downgraded as I want to be able to shoot a couple of follow ups without pressure signs (and I like my eyes etc!)No pressure signs after 3 shots now. It's hotter here - 20C or so, Sweden will be low single figures. I'm now on 43gr Varget in RWS case (weighs the same as lapua and winchester) WLR primer and COL of 2.8 for the 180gr partition. MV 2,430fps and about 0.6moa. 3 shots no problem, moose practice - 6/7shots with some cooling but ending up unpleasant to hold the barrel when moving the rifle - ejector marks on shot 7 and hard bolt lift (yes they were greased - the lugs that is) Same with factory (privi partisan 145gr FMJ). So does one go lower (I really don't want to go below 2,400fps MV) or use it as a hunting load in colder weather where 4 shots max will be taken? | ||
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I did some quick research for you and think something is amiss . Your short barrel is surely limiting your velocity, but damn. I would suggest you go over to 6mmbr.com and look at the info on the 308. They are getting ALOT more speed than you are w/ several powders, including Varget. Just a thought. If velocity is your main concern, shoot the 165g Partition and call it good. | |||
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| one of us |
Adam: Here we are, two Texas boys advising a Limey on moose hunting in Sweden. Not sure we should carry much credibility, but here goes: I agree that it may strain a .308 with a short barrel to get the 180 grainer up to the speeds you might want. I also agree that the 165 Partition is a better match for the .308 and carries plenty of mass to give you the penetration you need on Alg. What I don't understand is the phenomenon of increasing pressure as the barrel heats. Since heat should expand the diameter of the bore slightly, this would seem backward. It may well have to do with your suppressor, which holds a lot of heat (all of the energy of that noise had to go somewhere!) Is it possible that the dynamics of the heating suppressor is creating a "squeeze" at the muzzle? This, too, seems backward, but I'm finding it difficult to explain otherwise. The only other reason that subsequent shots should exhibit higher pressure would be if you chambered them in a hot barrel and left them there long enough to substantially raise the temperature of the powder in the cartridge. And this itself is counter the the claim of Varget being particularly temperature insensitive. Or maybe it is simply that the Rifle Gods that are punishing you for shooting something besides one of your beloved Sakos? | |||
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| One of Us |
The rounds definately spend long enough to get hot! The barrel is the diameter of a knitting needle and the action gets pretty warm too. Factory ammunition getting pressure signs after 6-7shots says chamber temperature to me! 180s are pretty much standard in Sweden. Velocity - hornady gets 2,500fps from 43.2gr Varget, Nosler 2576fps with 44.5gr (and they always lie!) so I thought I was about right for a 4-6" shorter barrel.... | |||
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| One of Us |
If you're getting 3 shots from a cold barrel without pressure signs, I'd leave it alone. If you can't hit him with three, throw the rifle at him.  You don't want to get caught at time to go whilst still scrambling around. Once you're back will be time enought to start exploring other options. Aim for the exit hole | |||
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| One of Us |
I'm still a month off and have a bit of time to fine tune in cooler temps. | |||
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one of us |
Heating expands the metal in all directions, the bore gets tighter just as the OD of the barrel gets larger. The hot chamber also heats the powder in the cartridge, brass is an excellent heat exchange, and causes changes in the burn rate which can cause pressure to spike if high enough. Varmint hunters keep their ammo shaded on hot sunny days to prevent this. ------------------------------------ The trouble with the Internet is that it's replacing masturbation as a leisure activity. ~Patrick Murray "Why shouldn`t truth be stranger then fiction? Fiction after all has to make sense." (Samual Clemens) "Saepe errans, numquam dubitans --Frequently in error, never in doubt". | |||
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One of Us |
Can you seat the bullet out any farther? The Remington mag box should be able to allow you to get to at least 2.825. I would also back of .3 grains. See if that removes any of the pressure signs. Even if you drop 40 fps in velocity...the moose ain't going to know the difference. Mike Legistine actu quod scripsi? Never under estimate the internet community's ability to reply to your post with their personal rant about their tangentially related, single occurrence issue.  What I have learned on AR, since 2001: 1. The proper answer to: Where is the best place in town to get a steak dinner? is…You should go to Mel's Diner and get the fried chicken. 2. Big game animals can tell the difference between .015 of an inch in diameter, 15 grains of bullet weight, and 150 fps. 3. There is a difference in the performance of two identical projectiles launched at the same velocity if they came from different cartridges. 4. While a double rifle is the perfect DGR, every 375HH bolt gun needs to be modified to carry at least 5 down. 5. While a floor plate and detachable box magazine both use a mechanical latch, only the floor plate latch is reliable. Disregard the fact that every modern military rifle uses a detachable box magazine. 6. The Remington 700 is unreliable regardless of the fact it is the basis of the USMC M40 sniper rifle for 40+ years with no changes to the receiver or extractor and is the choice of more military and law enforcement sniper units than any other rifle. 7. PF actions are not suitable for a DGR and it is irrelevant that the M1, M14, M16, & AK47 which were designed for hunting men that can shoot back are all PF actions. 8. 95 deg F in Africa is different than 95 deg F in TX or CA and that is why you must worry about ammunition temperature in Africa (even though most safaris take place in winter) but not in TX or in CA. 9. The size of a ding in a gun's finish doesn't matter, what matters is whether it’s a safe ding or not. 10. 1 in a row is a trend, 2 in a row is statistically significant, and 3 in a row is an irrefutable fact. 11. Never buy a WSM or RCM cartridge for a safari rifle or your go to rifle in the USA because if they lose your ammo you can't find replacement ammo but don't worry 280 Rem, 338-06, 35 Whelen, and all Weatherby cartridges abound in Africa and back country stores. 12. A well hit animal can run 75 yds. in the open and suddenly drop with no initial blood trail, but the one I shot from 200 yds. away that ran 10 yds. and disappeared into a thicket and was not found was lost because the bullet penciled thru. I am 100% certain of this even though I have no physical evidence. 13. A 300 Win Mag is a 500 yard elk cartridge but a 308 Win is not a 300 yard elk cartridge even though the same bullet is travelling at the same velocity at those respective distances. | |||
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We usually start slaughtering or tracking after three shots this side of the border, I believe they do the same thing in Sweden. I think your MV is right up as high as you can expect with 180 grainers and that barrel, and I also prefer slow bullets over pressuresigns. Looking at the calendar I would leave it for this time if I were you and use some lighter premiumbullet next time. Moosehunting is'nt a lot of shooting. | |||
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| One of Us |
The issue is how hot the rifle gets - barrel is .55" for a good length. Downloaded to 42.5gr and better but still ejector mark on shot 4 when little or no cooling. Will go down to 2,375fps. I really don't think it's a good idea to have a 4 shot magazine and not be able to shoot them for fear of a pressure related incident  | |||
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| One of Us |
How long are the rounds staying in the hot chamber?? I had a load for the 7mag that was fine in cold weather but flatted the primer in hot. I have also seen this with ammo left in the sun. | |||
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Perhaps a silly idea Adam but..... Put the ammo and rifle in the chest freezer you no doubt have in the garage, transport it in a nice insulated rifle slip to the range and take a few shots. Ok, now that i've read it back again it does sound silly.... | |||
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| one of us |
Joe The molicules get further apart when heated, for the bore to get smaller they would have to get closer together. Ever use a torch to heat a jammed nut, your expanding the ID of the nut. | |||
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