338 RUM project

John J

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I came across a used Remington 700 in 338 Ultra mag with a VX II 3×9 scope. I couldnt resist, so I bought it. The barrel was 26", I like short barrels for hunting. First step was to chrono and trim the barrel an inch at a time. The rifle was magna ported, at 10' from the muzzle velocity was 2794 fps. I used factory Barnes 250 gr LRX BT at 2910 fps advertised. Cutting 1" off the barrel removed 2 of the 4 ports and velocity increased to 2854 fps. The next cut removed the other 2 ports and velocity was 2815 fps. The next two cuts velocity was 2846 and 2822 fps. I was looking for about 20-21" barrel length and/ or 2700 fps or better. At 2822 fps I trimmed a half inch off. Things went goofy from there. The next 3 shots with a 21.5" barrel were 3356, 3355, 3378. After the 3356 shot I inspected the rifle, ammo and chronograph as I had stiff bolt lift. I let the rifle cool and the chrono sit turned off for a while. The next shot was 2742 fps, more velocity loss than I expected in a half inch. So the cutting was done. The next 3 shots averaged 2723 fps. I did lightly chamfer the muzzle after each cut with a stone bit to clean up burrs and break the edge. Need to square up the muzzle face, crown it, and test fire for accuracy. 4.5" cut off the total barrel length and 92 fps total velocity loss, using the higher 2854 fps as my start velocity. After this, providing good accuracy I plan on adding a 3 position safety, new trigger and iron sights. Change the stock, probably guncoat or cera coat the barrel and action. She should make a handy elk rifle to carry in the mountains.
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131 fps velocity loss not 92.
 
@John J , new nickname is "Hacksaw" :V Chainsaw:

Agree that the chrony results are a bit strange.
 
Yup, that's what I did. It was a brand new blade too!
 
You and Larry Potterfield :)

 
The good thing about the RUM cartridges are the magnum actions they come with.
In the event you are unhappy with the 338RUM, you can always rebarrel to a 404J.
They even have the same case head diameter.

Yes, a proper DG caliber I see in your future.
 
A magnum needs a long barrel for optimum velocity. The muzzle blast must be horrendous!
Gotta be better than it was with the Mag-na-port.
 
I really mean the question respectfully, but what does taking a .338 RUM 250 gr 2,900 fps load down to 2,700 fps by chopping the barrel from 26" to 21.5" accomplish, other than downgrading it to an hear splitting (I would bet far worse than the previous Mag-na-ported 26" pipe) and 30% greater recoil .338 Win?
Not to mention cost and availability of ammo, but this is likely alleviated by hand loading, I suppose.
What am I missing in the rationale for the exercise?
No disrespect intended, God knows I love a fast .33 (my personal medicine is the .340 Wby) but I am really perplexed :E Hmmm:
 
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I really mean the question respectfully, but what does taking a .338 RUM 250 gr 2,900 fps load down to 2,700 fps by chopping the barrel from 26" to 21.5" accomplish, other than downgrading it to an hear splitting (I would bet far worse than the previous Mag-na-ported 26" pipe) and 30% greater recoil .338 Win?
Not to mention cost and availability of ammo, but this is likely alleviated by hand loading, I suppose.
What am I missing in the rationale for the exercise?
No disrespect intended, God knows I love a fast .33 (my personal medicine is the .340 Wby) but I am really perplexed :E Hmmm:

Me too!!!
 
A magnum needs a long barrel for optimum velocity. The muzzle blast must be horrendous!
I haven't noticed any extra blast. I like shorter barrels on my hunting rifles. I'm not opposed to standard length either. I hunt alot with a Ruger 16.25" scout rifle in 308 Win and used a 20" barrel 500 MDM this year in Zimbabwe. On the ruger the blast is horrible, so I put a linear comp on it. All the blast is directed out the front with the bullet. As far as the cartridge and loosing performance in was willing to loose some but not all. The cartridge was just what was there on the used rack so I gave it a whirl. I thought it would be an interesting project. Worst case I can put a new barrel in and know about where the velocity really took a nose dive. Yes would prefer that last half inch back for 2800 fps. Any normal hunting distance for me and then some I still have plenty of power for elk. I hunted them for a long while with a 45 70 and iron sights. So having a :slower" 338 in a handy package is not seen as a disadvantage to me. I am full in with the B&M line up of cartridges/rifles and the reasons behind them. They were designed to perform in a shorter barrel from the beginning. I have 2 actions waiting on some spare cash to turn them into 458 B&M's for my son an I. No offense taken at all gentlemen. Why not have some fun and learn something I think. Maybe my hack saw job will inform another what not to do, or how much to push his project rifle? John
 
I agree with some of the others John. Doesn't make sense to shoot all that powder to accomplish what you want. But I'm assuming you picked this up used and it was worth the downgrade in performance for you. I would need to do some math but I'm pretty sure you could have got those velocities out of a short barreled 300wsm. Same bullet as well. But again the hell with it. If you picked that up at a decent price. And can do the barrel work yourself. Then what the hell. Your the one paying for the ammo lol.

Your accuracy will be effected at that length though. The bullet needs time to stabilize and your barrel twist will be off for a barrel of that length. Can you glue 1" back on???? Lmao.

One thing you can do after you shoot out that barrel. Get it re barreled in 300wsm. The bolt face would be the same size as the rum. Yes the WSM belongs in a short action from factory. But I have one built in a Long action. It allows me to seat my bullets very shallow. And load it with a little more sauce. Just my two cents.
 
Stability is one thing I did not take into account. Checking some twist rate calculators shows a 1:11 would be optimal. The factory barrel should be a 1:10. How much that matters I have no idea. The Berger twist calculator shows stability will be fine. I did get the rifle at a decent price with the thought if it all went south I would rebarrel with no worries. I never intended to buy that rifle or cartridge but when I came across it she came home with me. Burning the extra powder doesn't bother me and the rifle balances well. Slightly muzzle heavy. Just need some spare time to take it to a smith and have the cut squared up and we will see how it worked out.
 
JohnJ........great thread.... Learned something.......would have thought that vel would have dropped a lot more than that, so interesting to hear. The 338 UM is my favorite of all the big 33's. There are some with more power, but not by too much for standard bbls...........interesting project....thanks for posting...................FWB
 

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