1 in 10 twist only ?
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J E Custom
Well-Known Member
Badaboom
We need more info, Caliber, Velocity ,Brand ETC !!!
J E CUSTOM
We need more info, Caliber, Velocity ,Brand ETC !!!
J E CUSTOM
Ballistic64
Well-Known Member
Typically,oblong holes in the target.A friend and I just went through this lately.Not with a big bore but with a 22-250.He bought a Savage LRPV with an incorrectly marked barrel/box.It was marked 1-9" but was actually 1-12".With anything heavier than 60gr the target was keyholed.Being the smart guys we are,we went through a pile of 69-75gr bullets before common sense clobbered us over the head and we finally checked the twist with a cleaning rod.light bulb
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J E Custom
Well-Known Member
The 1 in 12 twist is recomended for 225gr- bullets in the 338
and a 1 in 10 for 250gr+ .
But with the velocity of the 338 LM you may be ok.
Bench rest shooters like slower twist if they can make them
shoot because if the bullets center of gravity is not perfict
the faster it spins the imbalance has more effect on it.
I would try it and see. The big 300gr 338 bullet is very forgiving
and you might be pleasantly surprised.
Good Luck
J E CUSTOM
and a 1 in 10 for 250gr+ .
But with the velocity of the 338 LM you may be ok.
Bench rest shooters like slower twist if they can make them
shoot because if the bullets center of gravity is not perfict
the faster it spins the imbalance has more effect on it.
I would try it and see. The big 300gr 338 bullet is very forgiving
and you might be pleasantly surprised.
Good Luck
J E CUSTOM
Dexters LAB
I have just made up some stew and will be going out to see the results.
210 Grain Nosler partition H4350 84gr
250 Sierra Spire point 7828 SCC 86 gr
250 grain Nosler partition 7828 85 gr
300 Grain Sierra Rutumbo 92 gr
It's Chrony Time
I have already tried the 250 grain Nosler partition 7828 they travel @ MV 30XX FPS 3100
and the target appeared just fine regarding the style of puncture hole in paper.
I have just made up some stew and will be going out to see the results.
210 Grain Nosler partition H4350 84gr
250 Sierra Spire point 7828 SCC 86 gr
250 grain Nosler partition 7828 85 gr
300 Grain Sierra Rutumbo 92 gr
It's Chrony Time
I have already tried the 250 grain Nosler partition 7828 they travel @ MV 30XX FPS 3100
and the target appeared just fine regarding the style of puncture hole in paper.
davewilson
Well-Known Member
one of the better gun smiths in the 1k game told me that some were shooting an 11 twist and a couple with 11.5 using the 300smk. haven't heard of anyone using a 12 though. only one way to find out. please let us know what you find out.
Results
Results:
210 Grain Nosler partition H4350 84gr
2975 FPS @Muzzle
250 Grain Lapua Scenar 85 grain IMR 7828
2860 FPS @Muzzle
250 Sierra Spire point 7828 SCC 86 gr
2790 FPS @Muzzle
250 grain Nosler partition 7828 85 gr
2840 FPS @Muzzle
300 Grain Sierra Rutumbo 92 gr
2750 FPS @Muzzle
Stabilized fine @ 100 yards
90 degree day @ the range
Most of these loads are in the lower 30% end
of the scale for being HOT except the Rutumbo
Still doing alot of load testing - on - going
need to try some H-1000 and a bit more powder
Results:
210 Grain Nosler partition H4350 84gr
2975 FPS @Muzzle
250 Grain Lapua Scenar 85 grain IMR 7828
2860 FPS @Muzzle
250 Sierra Spire point 7828 SCC 86 gr
2790 FPS @Muzzle
250 grain Nosler partition 7828 85 gr
2840 FPS @Muzzle
300 Grain Sierra Rutumbo 92 gr
2750 FPS @Muzzle
Stabilized fine @ 100 yards
90 degree day @ the range
Most of these loads are in the lower 30% end
of the scale for being HOT except the Rutumbo
Still doing alot of load testing - on - going
need to try some H-1000 and a bit more powder
NesikaChad
Well-Known Member
338 Lapua Magnums and 300 Grain Sierra bullets
I've made a lot of these guns. By a lot I mean over 200 in a range of different configurations. Sporting, Competitive, and Tactical.
The 1-10 twist barrel gets the job done reasonably well with 300 grainers. A 1-9.7 twist does it even better.
Personally, I encourage you to use 225-250 grain bullets if your shooting anything slower than a 1-10 for a twist rate.
The throat becomes an issue as well.
To get the velocity from a 300 takes some aggressive loading. This means a high load density if done properly. The 300 is not a magazine tolerant bullet when seated with the boat tail/bearing surface junction just above the neck/shoulder junction on the case. Not in a TRG magazine anyways.
These are the same magazines used in the Dakota Arms, Inc "Scimitar" sniper rifle. A gun I played a significant role in developing and producing for the Royal Jordanian Special Operations Command in 2004-2005 when I worked for Nesika/Dakota as a production manager.
The throat will more than likely become your limiting factor because the bullets will jam into the lands long before the case is shouldered up against the chamber; making for sticky bolts and high pressures. Not good on an already high pressure (62,000 cup) magnum cartridge already stoked up to the high side of a reloading manual. This condition will force you to back off the load and seat the bullet deeper into the case. All counter productive to the advantages of the 300 grain SMK. This is why I advocate the 250's. They run in the gun better and still shoot extremely well.
I found best accuracy by jumping the bullets. Not much, only .005-.010. This was on a gun chambered with a PTG reamer set up with a 1*30" throat angle specific to the 300 grain sierras. Loading them with the bullets sticking out a ways also puts the bearing surface in contact with the bore, right where it should be.
The 250's were also chambered reamer specific and the load used there was factory loaded Black Hills red box with Lapua and (in the early days) Norma brass.
Now, the exception to some of this is when we had another reamer made for the 300's set at a magazine tolerant depth just to try it out. The guns were "ok" but because the velocity was down a bit and (my personal opinion) because the barrel's twist rate was 1-10 instead of 1-9.7 the accuracy just wasn't quite as good as when we stoked up the loads and ran them further out.
Expect recoil to increase a bit also. The sniper rifles didn't have muzzle brakes or any other type of recoil reduction device. A few rounds are more than tolerable on a 12-15lb gun but go prone supporting the rifle only with two hands, a sling, and a shoulder and it'll wear you out after a couple magazines.
As far as accuracy goes, I was able to hold a rock solid 1/2 of a minute on a 10 shot string supporting the rifle from a slung in prone. I never shot them off bags or a rest. This was at a distance of 800 yards. Some of the guys shot them from rests/bags and the groups dropped down into the 1/4 to 1/3rd range. Competitive type heavy bag guns shot about the same with the big advantage being when having to be on the wind. Keep in mind we didn't devote the long hours to perfecting the loads for all these guns, once they shot well enough (under a half minute) we shipped them out the door. Customers routinely got better groups after fussing with the loads more.
Hope this helped.
Chad
I've made a lot of these guns. By a lot I mean over 200 in a range of different configurations. Sporting, Competitive, and Tactical.
The 1-10 twist barrel gets the job done reasonably well with 300 grainers. A 1-9.7 twist does it even better.
Personally, I encourage you to use 225-250 grain bullets if your shooting anything slower than a 1-10 for a twist rate.
The throat becomes an issue as well.
To get the velocity from a 300 takes some aggressive loading. This means a high load density if done properly. The 300 is not a magazine tolerant bullet when seated with the boat tail/bearing surface junction just above the neck/shoulder junction on the case. Not in a TRG magazine anyways.
These are the same magazines used in the Dakota Arms, Inc "Scimitar" sniper rifle. A gun I played a significant role in developing and producing for the Royal Jordanian Special Operations Command in 2004-2005 when I worked for Nesika/Dakota as a production manager.
The throat will more than likely become your limiting factor because the bullets will jam into the lands long before the case is shouldered up against the chamber; making for sticky bolts and high pressures. Not good on an already high pressure (62,000 cup) magnum cartridge already stoked up to the high side of a reloading manual. This condition will force you to back off the load and seat the bullet deeper into the case. All counter productive to the advantages of the 300 grain SMK. This is why I advocate the 250's. They run in the gun better and still shoot extremely well.
I found best accuracy by jumping the bullets. Not much, only .005-.010. This was on a gun chambered with a PTG reamer set up with a 1*30" throat angle specific to the 300 grain sierras. Loading them with the bullets sticking out a ways also puts the bearing surface in contact with the bore, right where it should be.
The 250's were also chambered reamer specific and the load used there was factory loaded Black Hills red box with Lapua and (in the early days) Norma brass.
Now, the exception to some of this is when we had another reamer made for the 300's set at a magazine tolerant depth just to try it out. The guns were "ok" but because the velocity was down a bit and (my personal opinion) because the barrel's twist rate was 1-10 instead of 1-9.7 the accuracy just wasn't quite as good as when we stoked up the loads and ran them further out.
Expect recoil to increase a bit also. The sniper rifles didn't have muzzle brakes or any other type of recoil reduction device. A few rounds are more than tolerable on a 12-15lb gun but go prone supporting the rifle only with two hands, a sling, and a shoulder and it'll wear you out after a couple magazines.
As far as accuracy goes, I was able to hold a rock solid 1/2 of a minute on a 10 shot string supporting the rifle from a slung in prone. I never shot them off bags or a rest. This was at a distance of 800 yards. Some of the guys shot them from rests/bags and the groups dropped down into the 1/4 to 1/3rd range. Competitive type heavy bag guns shot about the same with the big advantage being when having to be on the wind. Keep in mind we didn't devote the long hours to perfecting the loads for all these guns, once they shot well enough (under a half minute) we shipped them out the door. Customers routinely got better groups after fussing with the loads more.
Hope this helped.
Chad
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NesikaChad
Well-Known Member
My BIG mouth.
I get too long winded sometimes. . .
I get too long winded sometimes. . .
James Jones
Well-Known Member
- Joined
- Jul 1, 2002
- Messages
- 2,854
I have heard that the Sako TRG-42 in 338 Lapua (1-12 twist) doesen't like them to much when loaded from BlackHills , the 250gs SMK's are said to shoot alot better.
Only one way to find out , try it
Only one way to find out , try it
