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3200 fps-300 smk

 
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  #1  
Old 04-05-2010, 01:52 PM
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3200 fps-300 smk

A couple weeks ago a guy was asking if it were possible to get 3200 fps out of a 300 smk without going to the chey-tac case. I can't find that thread and I reported you could not on a standard cartridge. But I shot an improved 338-378 wby last week that was easily clocking in the 3200's with a 300 grain smk. The case was blown out quite a bit more than my standard 338-378 case and the neck changed to 35 degrees. The neck length I think was .33. Other than that it was about straight walled. We worked it up to over 3300 fps shooting over two in line chrono's. This was the fastest I have ever seen the 300 pushed. So the answer to the guy who asked is yes but not with a standard cartridge. You have got to improve the huge 378 case. Also the guy had a 34 inch barrel. I am building one with a 32 inch barrel by elk season I hope. It was incredible to shoot.
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Old 04-05-2010, 05:41 PM
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Re: 3200 fps-300 smk

Better get you a primer pocket whacker smacker.
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Old 04-05-2010, 05:54 PM
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Re: 3200 fps-300 smk

Quote:
Originally Posted by Buffalobob View Post
Better get you a primer pocket whacker smacker.
LOL! True, but rather funny.
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Old 04-05-2010, 06:07 PM
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Re: 3200 fps-300 smk

I have worked with this round alot, especially before I started working with my 338 AX. Its called the 338 Kubla Kahn, basically a 338-378 with conventional 35 degree shoulder angle.

I shipped out several heavy rifles in this chamber and velocities varied from rifle to rifle but I would say that if your getting anywhere near 3200 fps, your pushing things pretty hard. I put a heavy rifle together for my Brother with a 36" Lilja and it would easily break 3150 fps but that was max and that was with a long throat.

My personal 338 Kahn with the same bullet would get 3050 fps and then primer pockets would loosen.

Now, these Lilja barrels were quite tight in bore diameter which does limit max velocity to some degree but to break 3200 fps with a 300 gr SMK I would say your really pushing the Wby case to hard.

I talked with Dick Cassull several years ago after hearing that he was getting 3200 fps with his 338-416 Rigby improved which is nearly identical to the round your using. We talked it over for a while and then I asked what his case life was. He asked what was case life, he shot his brass and threw it away after usually after the first firing but always after the second because the primer pockets were blown.

I would be curious how your primer pockets are doing, especially at +3200 fps.
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Old 04-05-2010, 06:39 PM
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Re: 3200 fps-300 smk

Kirby, I have no idea what it was or what it was called, or if he just had a special reamer built. I just looked at the case and measured the case and neck length. First one I have ever seen and the fastest I have ever seen a 300 smk shoot. From what I saw his 3200 fps loads were not extremely hot but I have no idea what his case life is. I just know it made my 338-378 wby look like a baby. He could have one of those barrels we all love to get that just outperforms the others. I don't know/ don't care really. I just remember some guy making a post a couple weeks back wanting 3200 fps and I told him it wasn't possible. Then low and behold I meet a guy on the range with this thing that proved me wrong. So I thought I would post back and let him know. I know the chrono was accurate because both had my velocities dead on. I have hit 3100 fps with some of my rifles, but never 3200 until this guy shot his. I decided I would build one and try it. Don't have anything better to do. I will report in later this year with what it does in a 32 inch barrel. Biggest reamer I could find was a 338 Big Baer or something like that which is everything you can get out of a 378 case. Have you ever heard of it?
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Old 04-05-2010, 09:41 PM
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Re: 3200 fps-300 smk

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Originally Posted by Long Time Long Ranger View Post
Biggest reamer I could find was a 338 Big Baer or something like that which is everything you can get out of a 378 case. Have you ever heard of it?
Long Time Long Ranger~

Just for clarification... The .338 Big Baer is based off of the .408 case. The .330 Baer is based off the .378 Wby case.

Both are improved versions with 35* shoulders and minimal taper.

The .330 Baer will not get you 3200 fps with the 300 SMK.
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Old 04-05-2010, 09:53 PM
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Re: 3200 fps-300 smk

I believe the 338 Big Baer is based on the 408 CT but I may be wrong about that, not sure.

The 338 Kahn was developed by Kenny Jarrett a long time ago. I got his reamer design. Only thing I do not like about his is that its a tight neck reamer and requires the neck to be turned. I do not particularly care for neck turning but on a rifle like this not a big deal.

Took a while to figure this need out. At first I was pressuring out at 2950 fps and could not figure out why as I COULD push a bullet through the fired case neck. Decided to take a thou off the neck thickness and was able to jump right up to 3050 in my personal rifle.

Again, all of my barrels have been very tight Lilja barrels. When I say tight, we are talking bore diameters in the 0.3282" to 0.3284" range which is well under nominal and WILL limit muzzle velocity. THey shoot so damn well though I never have decided to change barrels. Lilja current 338 barrels will run right at 0.3300" as they should but his 338 barrels from 5-6 years ago were running VERY tight.

Certainly there are barrels out there that are just plain fast, no question there. I have seen some barrels produce velocities I simply refuse to report on because I will be called a liar so that is a very real possibility.

My only concern is that Wby brass is not known to be overly strong and in fact quite soft. Several Kahns I have built for customers would have effortless bolt lift and extraction, but then have the primer fall out as the case was ejected from the rifle. This is one reason I went with the Lapua case for my 338 Allen Xpress. Brass is much stronger, much cleaper, much better quality and will damn near match or will match the big Wby with around 10 grains less powder. I am hitting 3000 fps with my AX and 300 gr SMK in 28" barrel lengths. I have never chambered a 34-36" barrel length but from my testing of other 338 magnums, you will see an average of around 15-18 fps per inch over 28" of barrel length so in a 36" barrel length, it would not be strange to expect to see 3100-3150 fps with this much smaller chambering.

IF, and its a big theoretical IF because its not true, but if the big Wby case could handle the chamber pressures that the 338 Lapua could, it would easily be capable of producing 3200 fps in a 34" barrel length.

That said, if the 408 CT parent cases could handle the same chamber pressures as the Lapua, it would easily push 3500 fps and in a 33" barrel length. In fact the old TTI 408 CT brass could handle this pressure and could indeed run up very close to 3500 fps. Different topic though.

Anyway, I am not saying its impossible to see the velocities your seeing with pressures that are not dangerous but I would say its very rare to get this level of performance without running pressures over what the Wby case will repeatably support. As you say, a special fast barrel could certainly be the reason.
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