338 SIN Testing

[Long Time Long Ranger]

The other thread was getting so long I thought I would start another and list my data as I shot it. Had a great shoot this morning with the 225 grain cutting edge bullet .640 bc. Best accuracy out of my 24" barrel seems to be between 3100-3150 fps. I had one hole 100 yard groups in this velocity range with four different powders. Magpro, Winchester WMR, IMR 4831 and RE-19. From my limited testing so far it seems this cartridge is going to be very easy to load for. About anything shoots well in it. When I got near 3200 fps the groups began to spread so I backed off and started fine tuning in the accuracy range.

So far the most accurate loads are 95.5 grains Magpro, 93 grains winchester wmr, 87 grains imr 4831 and 86 grains RE-19. 4831 and re-19 retained the best accuracy at the highest velocities around 3170 fps. I expected that the faster burn powders would turn out best in my short barrel. The beauty of this efficient design is that it does very well in short barrels with faster burning powder than most big magnums. By utilizing the faster powders excellent velocities and accuracy can be had with a short barrel. This allows short barrel light carry rifles that can achieve great accuracy since there is no fireball of turbulence when the bullet exits the barrel as experienced with the RUM and larger class 338's in short barrel versions.

My rifle weighs just over six pounds so I stopped testing the 300 SMK in it. I shot a few and it was brutal. Winchester WMR shot great with the 300 smk but I stopped at a little over 2700 fps because of the massive recoil. I could have gone well into the 2700's which I thought was very good considering the 24" tube. My 340 wby shoots the 300 SMK 2730 fps and my two 338-300 RUM's shoot 2830-2850 fps all with 28" barrels. Basically there is 120 fps difference on average between the 340 wby and 338-300 RUM. The 338 SIN powder capacity is exactly half way between these two so it figures to hit right in there. With a 28-30 inch barrel I think 2800 fps is possible with less powder than the RUM's plus fit on any standard magnum action without modifications. This with plenty of room to load the 300's out to the lands since the case is about the same length as a 338 winchester.

Because of recoil in my light rifle I am only going to test bullets 225 grains and lighter in this gun. When Devin first showed me the diagram of this cartridge I immediately thought it was the answer to a light carry rifle for long range at large big game. I saw the extremely efficient design and so far it has done everything I thought it would. A 225 grain bullet with a .640 bc at 3170 fps out of a 24" barrel that weighs just over six pounds is my answer to long range backpack style hunting. I am going to test some 185 and 200 grain bullets over the next couple days but I expect to end up with the high bc of the cutting edge bullet. I am going to load the 4831 and Re-19 loads now and stretch the range out some this evening. I seated the bullets like recommended by CE and have no reason to change that right now with one hole groups at 100 yards with these two loads. If the accuracy is good at long range and the bc tests out to be around .64 then I plan on trying this combination in Alaska in August.

I will report back in as I get more data.

 

[Senderofan]

Really glad to hear the accuracy potential of this round. Also glad to hear of the velocities you're getting with the 24" barrel. I don't blame you for not pushing the envelope trying to develop a load for the 300 gr. bullet.....way too much punishment since you've designed your rig to be a lighter weight hunting rifle with the plan to shoot light to middle weight bullets.

Please keep us posted on your progress...when you have time. Great info.!

Thanks for posting results.

Wayne

 

[sinarms]

Thanks for the load and accuracy info Don, I will be working with mainly the 250 and 300gr bullets for everyone that wants to know about how they perform.

 

[jskmtd]

Can't wait to see what the 250-300 grain bullets will do. I have a savage long action waiting for the results. Keep us posted.

 

[Long Time Long Ranger]

Real close to having what I want with 85 grains of RE-19 and the 225 CE bullet. A five shot group had 9 fps velocity spread from 3157-3166 fps using federal 215 match primers. The group was under 3" at 600 yards. Extreme wind today so hope to shoot in the morning and stretch it out a little further. I haven't played with bullet seating yet. The bc on the bullet seems to be accurate so far. I will get some drop tests when I push it on out toward 1000 and check the bc. The 1000 yard drops with my 338-378 wby showed a .653 bc on JBM. It may be a little different with the 300 fps velocity difference. The 338-378 wby is incredible with this bullet at 3460 fps. But can't do it in a 6 pound rifle and 24" barrel which is why I like the 338 SIN.

jskmtd, So far the 300 grainers have shown to hit in the 2700's out of a 24" barrel. This is a very efficient cartridge design so I doubt you will gain much with a long barrel. My guess would be 15-20 fps per inch. At that a 30 inch barrel should come close to 2800 fps. The big plus of this cartridge is that it does extremely well in short barrels because of utilizing faster burn powders that get more complete burn in the short barrels. You do not get the big fireball muzzle blast of turbulence out the end of the barrel therefore increasing accuracy in a short barrel. As you go up through the RUM, lapua, and 378 wby cases slower burning powders are needed for velocity performance in these larger cases. With the slow powders you need barrel length for optimum performance. With the 338 SIN utilizing smaller charges of faster burning powders you can still maintain top velocity and accuracy in a short barrel lighter rifle. A stiff 24-26 inch barrel shooting 300 grainers in the 2700's with great accuracy would be a nice rifle. I think a 26" #5 barrel would be extremely accurate with an accuracy load in the 2700's. You would need no modifications to your savage action for it to be a repeater since it is such a short case.

 

[Bob L.]

Hope this isn't a silly question, but say you made a 338wsm would that have any advantages or disadvantages over the 338SIN? If you could use a rem short action to make it a pack rifle.
Thanks
Bob

 

[Long Time Long Ranger]

There is really no comparison between a 338 SIN and a 338wsm. The SIN is about 300 fps faster and just in a completely different league. The 338 wsm is a good cartridge for a short range lightweight carry rifle about 100 fps slower than a 338 winchester. They do not do well in short actions because the long 338 bullets must be seated so deep for proper feeding costing performance.

 

[geargrinder]

Hope this isn't a silly question, but say you made a 338wsm would that have any advantages or disadvantages over the 338SIN? If you could use a rem short action to make it a pack rifle.
Thanks
Bob

The Sin is taking advantage of a long action like the WSM takes advantage of a short action.

Maximized powder charge given the limited magazine length and action limitations.

 

[5280yotes]

So what case is the sin off of? Dakota?

 

[Long Time Long Ranger]

Devin based it off a shortenned RUM case however I am using 330 Dakota brass made by Norma. It is good brass. The only thing is I have a slightly short neck that resembles the gibbs cartridges. That has not affected performance or accuracy in mine. I listed the case capacities of all of them over on the other thread if you want to look it up. I think the 340 wby is 6 grains more than the dakota and the sin is 6 grains more than the 340 wby. Not exactly sure but I think that is right. Then the 338 RUM is 6 grains more than the sin. 120 fps difference between the 340 wby and the 338-300 RUM so on average probably 60 fps between the sin and the RUM's. All of them are right in there. I can tell you from shooting a 340 wby for 35 years I can not tell the difference hitting an animal with it or the RUM's. Just no difference in a hunting situation. Taken elk over 1000 yards with both. 120 fps is just not enough to make a determination over other than clicks.

 

[jskmtd]

Thanks for the info LTLR.

 

[sinarms]

Shot the 338 Sin today, figured out that my rings were a little loose, groups tightened to under 3/4" once I figured that out.

Used some R19 with 250gr SMK bullets. I worked up to just under 3050fps. I would say that is pretty much max with that powder as groups opened a little. At around 2950-2975fps I was shooting right around 1/2" groups. Low ES of 7-15fps on most loads I tried. As Don stated this is pretty easy to get a load for. Dump powder in and load bullet and you can pretty much shoot 1" or under. I plan on shooting some 300smks later this week. More to come.

 

[Long Time Long Ranger]

Went out this morning to do some more testing. It seems with the lighter bullets this rifle likes the faster burning powders. I tried some new loads for the 185 grain Barnes ttsx. H-414 was the clear winner over several powders. 89 grains with a fed 215 match primer averaged 3515 fps and was by far the best load with accuracy, velocity, and velocity spread. I have had extremely good performance out of this powder shooting light bullets in the 338 winchester, 338-300 wsm and the 300 wsm along with a few others.

I shot a 3 shot 100 yard group for zero and all three shots were touching. I carried it out to 800 yards and shot a 8 3/8" group. The BC on this bullet still amazes me. Last year I did quite a bit of shooting with this bullet in my 338 winchester and had to plug in bc's around .5 for it to match my drops. I know this bullet should not have this high of a bc but it did the same thing today. Later I am shooting it over two calibrated chrono's and get it down instead of doing drop tests. I just haven't had time to do that yet.

The rifle is a 24" barrel 1-10 twist. I also shot some 225 CE bullets with several different powders. 93 grains of Wichester WMR averaged 3121 fps, 96 grains of Magpro averaged 3114 fps, 86 grains of I-4831 averaged 3153 fps and 85 grains of RE-19 averaged 3160 fps. All of these loads are max in this rifle. This rifle shoots best with max loads. Velocity spreads got smaller and accuracy got better as the powder got faster. They improved exactly with the powder burn rates. So in my rifle the faster the powder the better to RE-19 with this bullet. I may try something faster later like H-414 that did outstanding with the 185 grain bullet.

The best accuracy and least velocity spread (8 fps) was with 85 grains RE-19. The 100 yard group was all touching and the 800 yard group was 7 1/4".

What I am finding is this cartridge performs very well with faster burning powders than what you would normaly see in a 338 cartridge with this level of performance. This is due to the efficient design of the cartridge similar to the wsm cartridges. Because of utilizing faster burning powders this cartridge does great in short barrels which is what I was looking for in a lightweight backpack style rifle. A 225 grain .65 or so bc going 3160 fps out of a 24" barrel lightweight rifle that weighs a little over six pounds is pretty amazing.

 

[HRstretch]

Devin,
What length barrel is your test gun?