Looking for info on ballistics from a 20 incher. I chopped my 24 stainless 375 and now am going to lighten the whole setup and was wondering if anyone chronoed out of a 20” probably mostly 270 ttsx type bullets. Is there a noticible velocity gain? I would rechamber at the same time

You LOSE ≈90-100 fs give or take from whatever original load you used.

Good Hunting

Ok guessing no one has actually done this. So I might go ahead and do it to see what happens. Not 100 percent on being a straight dropoff but if 100 FPS drop from 375 weatherby in a 24” bbl that would still put it 100 FPS over 375 h+h velocity. Lots of muzzle blast I’m sure but if If can get the speed up there that would be worth it

I would have it at more than 100 f/s.

Two guaranteed, it will be faster than the H&H in normal barrel and it will be LOUD.

You could get some good estimates by searching around for 30/06 with 180 grain bullets.

I would take a look at the .375 Ruger. The Hornady manual lists their loads using a 20" bbl. I'm sure you can find loads using a 24incher to compare.

Hip

With my 21-1/4" barrel Sako 85 Kodiak .375 H&H Magnum following Barnes #3 data with the 270gr TSX and IMR4064 I get 2465 fps vs. 2545 fps listed for a 24" barrel. Only 80 fps less, not a huge speed loss. For sure a bigger loss with the larger capacity .375 Wby case in a short barrel.

.375 Wby: Going from 26" to 24" you will lose about 50 fps MV with the 300-grain Nosler factory ammo for the .375 WBY.
That is about 25 fps per inch of barrel shortening.
Below 24" length you are going to lose more per inch.
Loss ought to be in the 100 to 150 fps range for 24-incher shortened to 20-incher.
The smaller case-capacity of the .375 Ruger will not lose quite so much.
But a 20" .375 Ruger is about like a 24-25" .375 H&H.
So too might a 20" .375 Wby be about like a 25-26" .375 H&H.

Worse case, .378 Wby:
I have actually shot a 22" .378 Wby made by re-chambering a .375 H&H BRNO ZKK 602,
and compared it to a 25" .378 Wby made by re-chambering a CZ 550 Magnum.
Similar barrels but not as good as shooting the same barrel long then short.

Nevertheless, 5-yard instrumental velocities at different temperatures, different barrels, .378 Wby:
A 300-grain Swift handload gave 2780 fps in the 22" barrel at 85*F.
Same load gave 2878 fps in the 25" barrel at 60*F.
The powder was IMR-7828, 111.0 grains.
If that load had been shot at 85*F in the 25" barrel (25*F warmer),
velocity would have been at least 25 fps faster.
Let us just say that a 3" chop from 25" to 22" in the .378 Wby caused over 100 fps velocity loss.
That is over 33 fps per inch.
Shorter than 22" would be even greater loss per inch.

There was no .375/270-grain TTSX last time I checked.
There is a .375/250-grain TTSX.
There is a .375/270-grain TSX.
I wonder what QuickLOAD says about barrel shortening with that bullet in a .375 Wby?

Rip ...

You will always lose more per inch as the barrel is shortened because the bullet is going slower and so if acceleration was a constant it will gain more velocity per inch.

An extreme as an example. Acceleration due to gravity (1g) is an increase in speed of about 32 f/s every second. So speed increases by about 22 mph every second.

However, coming back from the moon or some meteorite coming to earth gets to about escape velocity before hitting the atmosphere. Escape velocity is about 25,000 mph or 7 miles a second. So at that velocity 1 g increases its speed by 22 mph in a second but it will travel 7 miles to get that increase of 22 mph.

Here is what QuickLOAD says about the 270-grain TSX (1.372" bullet length) in the .375 Wby Magnum at 3.600" COL, with 88.5 grains of H4350:

63,583 PSI (CIP max is 63,817 Piezo PSI or 4400 bar)

MV versus barrel length
26": 2965 fps
24": 2915 fps
22": 2857 fps
20": 2792 fps

That is a whopping 173 fps loss for 6" shortening.
From 24" to 20" the loss is 123 fps for 4" shortening.

From 26" to 24" averages -25 fps per inch.
From 24" to 22" averages -29 fps per inch
From 22" to 20" averages -33 fps per inch

That is very close to what I was guessing.
In real life I have seen about 25 fps per inch loss with the 300-grain Nosler factory load fired in a 24" barrel instead of 26".

QuickLOAD predicts only 23 fps per inch loss with the 300-grain TSX in 26" barrel shortened to 24".
Very close to reality.
This is something QuickLOAD must be very good at,
unlike its total ignorance of throating effects.

Heavier bullets and faster powders will make for less MV loss with barrel shortening,
but that is usually trifling and also makes for lower-velocity, max-pressure loads to start with.
We know these things from work with the .458 WIN.

Rip ...

Ok very good RIP great info. Still over 375 H+H velocity I think....which is what I am getting at. Can you do a standard H+h vs weatherby conparison?

Looks like a weatherby in a 20 incher will out perform a standard H+H with 24? Or be close

A 20" .375 Weatherby is definitely better than a 20" .375 Ruger, which I put on par with a 24" .375 H&H.
Maybe by 50 fps, just my SWAG.
The .375 Weatherby has a bigger case capacity than the .375 Ruger, especially if you use the Norma, proper-head-stamped brass.
And the .375 Weatherby has some throating advantage over the .375 Ruger, which effectively increases the case capacity even more,
with no flies on accuracy.
Your 20" .375 Weatherby will definitely out-do a 20" .375 Ruger, or a 24" .375 H&H, at cost of only a 0.200" longer action versus the .375 Ruger,
but 4" overall length savings over the .375 H&H.

Rip ...

My thoughts exactly. Thanks RIP. Sounds like a plan (insert thumbs up here)

Not to get a hoo-haw going or some long winded hair splitting session but...

FROM MY QL...

375 H&H ≈95 gr H2O
375 Ruger ≈100 gr H2O
375 Weatherby Mag ≈105 gr H2O...5 gr or 10 gr...1.25% or 2.5% gain or loss de[ending on how you look at it...a simple calculation.

You can get WHATEVER amount of gain/loss YOU WANT depending on what powder you use and HOW you develop the load...but for all intents and purposes you're just basically splitting hairs and cherry picking.

I chopped my CHRONOED ≈2850 fs/270 gr bullet H&H from 26" to 21" CHRONOED ≈2740 and turned it into not much more than a 2600-2650 fs 375-06/Hawk Skovill.

We must have different QL's, RIP...the best I could do VELOCITY WISE was with 85 gr RL-17, TSX #37556, 1.368", COAL 3.60", 2903 fs/62,641 psi, 24"...and 2786 20", dif, 117 fs...85 gr 760 came in at 2863/2743 dif, 120 fs...neither of the 4350's got anywhere near RL-17 or 760 which is a bit strange as all four of those powders are close in burn rate.

My QL is the second iteration and I'v learned NOT TO TRUST IT for anything other than working up a beginning load.

The ONLY way to know for certain WHAT the velocity loss will be is to measure it first, chop it off then measure it again...the rest is just guessing PERIOD...I CAN tell you I wish I had left well enough alone...losing 5" didn't do anything more than loosing me that extra velo which translates into EXTRA energy or LOSS of energy...and I think that 5" of extra barrel length made it handle better or at least swing better whichever way you want to look at it, and really screwed up the apple pie.

GOOD HUNTING

Default brass case capacities in QuickLOAD are not always right.
Norma .375 WBY brass is a few grains bigger than the QuickLOAD default, of that I am certain.

My QuickLOAD is version 3.5.03 and I refuse to buy it again.
It has been very close to reality with H4350 in the .375 Weatherby.
I always take it with a grain of saltpeter.

Besides a 1.25% increase in velocity over the .375 Ruger based on larger case capacity,
the .375 Weatherby throat is a little longer than that of the .375 Ruger.
So instead of a mere 33.75 fps extra MV over the Ruger, the Weatherby might get that up to an extra 50 fps.
Free-bore is a way to increase the case capacity regarding internal ballistic effects.

You are right, you never know until you shoot the rifle with a long barrel and then shoot the same rifle with same barrel shortened.
Same lot of ammo and chronographed at same ambient temperature.
Otherwise, prepare to SWAG.

Rip ...

It appears that I can get at least 375 H+H 24” ballistics out of a 20” 375 WBY that is my original intent. Easy rechamber and go. Although I did kill my grizzly at 200 yards with the chopped 20” H+H so not sure it all really matters

Ruger offers the 375 in 20". Your Weatherby has almost the same capacity. You'll be fine

It’s not a weatherby yet. An H+H but considering rechamberibg to get more velocity

quote:

Originally posted by MileHighShooter:
Ruger offers the 375 in 20". Your Weatherby has almost the same capacity. You'll be fine

Yes, the .375 Weatherby is only a little bit bigger in case capacity than the .375 Ruger.
Even though the cartridge is about 0.2" longer, thus making effective barrel length 0.2" shorter in the .375 Weatherby,
I think the extra case capacity plus the extra-extra case capacity produced by slightly longer free-bore of the .375 Wby will more than compensate
for the lost 0.2" of barrel.
The .375 Wby free-bore is quite tight in diameter, 0.3756", only 0.0006" (6/10,000") over bullet diameter,
and that parallel-sided free-bore is 0.370" long, slightly less in length than bullet diameter.
It is a very accurate throat.

Rip ...

My real world experience with the 375 H&H and the 375 WBY shooting the 270 TSX is as follows. My 375 H&H with 23" barrel gave 2725 FPS with a max load of R15. My 375 WBY with 24" barrel and 88 gr H 4350 gives 2900. if RIP is correct and you loose at max 150 FPS by chopping the barrel to 20" you should still be in the 2750 FPS area making the rifle good for up close and 300 yards fairly easy with good shooting.

If I had my druthers though and had it to do over I'd put a 26" barrel on the 375 WBY and stick with 270 TSX or TTSX for everything . It could be a great do it all rifle.

Mark

Too late now but I got a hair and chopped it. I probably should of left it 24” but if I can get some ballistic improvement won’t hurt collectibility now.

I've got a set of 375 Wby dies in the classifieds if you're thinking of making the switch

quote:

.375 Wby: Going from 26" to 24" you will lose about 50 fps MV with the 300-grain Nosler factory ammo for the .375 WBY.
That is about 25 fps per inch of barrel shortening.
Below 24" length you are going to lose more per inch.
Loss ought to be in the 100 to 150 fps range for 24-incher shortened to 20-incher.
The smaller case-capacity of the .375 Ruger will not lose quite so much.
But a 20" .375 Ruger is about like a 24-25" .375 H&H.
So too might a 20" .375 Wby be about like a 25-26" .375 H&H.

Gotta agree with the RIP-ster dude on this one.

But not only will the velocity loss be huge, the recoil off a 20" .375 Weatherby will knock your jaw alignment into next week.

I had my .375 H&H rechambered to the Weatherby and love it! I get an extra 150-200 fps, depending on the bullet, and can still shoot the H&H in a pinch. Win, win!

quote:

Originally posted by gunslinger55:
Too late now but I got a hair and chopped it. I probably should of left it 24” but if I can get some ballistic improvement won’t hurt collectibility now.

Hello gunslinger55,

Let us know what it chronographs. I have a Custom 378 wby with a 20-1/4" barrel, and I still get 2800fps with a 300g bullet.

Wow! That is impressive!

Barnes does make a TTSX for the 270 grain .375, its in the LRX series and was developed for the 375 RUM. I got mine from Midway and use it in my H&H

OK went out and finally chronoed my 20" 375 today with my new Lab radar to see if I can figure out how to run it. Never bothered to chrono since I chopped it and was shooting 300 A frame out to 300 no problem. Killed a grizzly at 180. Well its pretty slow at 2420 FPS average, which is about the 100 fps you would expect with a 4" shorter barrel. Factory remington A frame (got a bulk deal cheaper than reloading). My 270 TSX reloads were 2550 FPS. Looks like the weatherby can spruce this up a bit. I'll see that the results are when completed. I think possibly beyond 24" H+H velocities?

quote:

Originally posted by Lee Woiteshek:
Barnes does make a TTSX for the 270 grain .375, its in the LRX series and was developed for the 375 RUM. I got mine from Midway and use it in my H&H

Thanks for that. I need to start looking at the LRX bullets I have been ignorant of.
The light came on and my cockroach of ignorance has scurried away:

http://www.barnesbullets.com/bullets/lrx/

Rip ...

quote:

Originally posted by gunslinger55:
... I think possibly beyond 24" H+H velocities?

Be sure to use a reamer with 2002 CIP specs,
not Roy's 1945 version.

Try the Weatherby factory ammo with 300-grain Nosler that is usually good for 2800 fps in a 26" barrel, .375 Wby headstamp.
That is a good benchmark/reference load.
You will probably get over 2600 fps with that in a 20" barreled .375 Wby.

Don't trust the Remington factory load of .375 H&H with Swift A-Frame 300-grainer.
2420 fps with that bullet in a 20" .375 H&H is great.
You must have a fast barrel. Good omen.
Remington downloaded that A-Frame load due to pierced primers on the earliest lots of it that would do the usual 2530 fps in my 24" barreled .375 H&H.
That is a tough, sticky bullet that jacks up pressures or lowers velocities, take your pick, depending on the powder charge.

Buckstix must not have been using 300-grain A-Frames in his short-barreled .378 Wby.

Rip ...

Ok thanks RIP good info. That will make a handy little blaster, more so than it already is!

ANYTIME you are futzing around with reloading you should ALWAYS H2O weigh the cases you are USING and not go by information found in other sources...AND weigh an unfired case, shoot it and weigh again. You are NOT USING some case data found on QL, you are using actual cases in hand and you need ACTUAL data YOU develop using information from components YOU are using.

QL did the best they could with what they were using but variation jumps up and bites everyone on the po-po if you DON'T READ AND HEED the fine print. All this variation IS addressed by QL IN THE FINE PRINT. After I saw just how far off QL can be at times and with certain cases/calibers I just started using it to find beginning loads, compare chrono'ed velos and checked any results against reloading manuals or other sources. It's no different than my blood testing meter...it uses a 15% +/- range and any one with diabetes know just how wide of a range that can be. We just depend on too much technology today and NEVER QUESTION IT...Probably the reason I get the cold shoulder...NO ONE LIKES THE MESSENGER ESPECIALLY IF THEY DON'T LIKE THE ANSWER...

You can see what I mean by looking at my comments on 40-65...THAT DIFFERENCE WAS ≈4%...64.5/67.2. Comparing before and after...all samo-samo...will include all the factors you mentioned, no need to extrapolate or guess, which should be well know by advanced reloaders and should be learned by ALL reloader but usually isn't. I have seen >10% difference in some of my day-mares...basically similar to Ackley's iterations.

The fact that there is such a variation in ALL aspects if this "sport" is the basis for many if not all dust-ups here on AR...everyone is so sure they are right that ALL individuals go to battle over things they SHOULD KNOW/LEARNED but have forgotten, don't know, just have to be right...or dont care.

It really shouldn't matter what the velo is between various barrel lengths...what should matter is what the actual resulting velo of THAT PARTICULAR RIFLE AND BARREL LENGTH so you have realistic expectations and some kind of way to calculate resulting energy. If a 20" barrel suits your pistol then WHO is to argue?

I STILL don't know why I chopped off my 375 H&H...loosing velo was something I was perfectly aware of but sometimes I just "loose my shi*" and go all Homer. I had to screw around with the stock regaining the balance...AT 21" it STILL will carry the freight and make T-Rex VERY SICK.

Good Hunting

I’ll try factory ammo then reload with alan proper precautions. I personally prefer short barrels for DG rifles so this should works out good. Almost 4000 ft/lbs with 300 grabbers out of 20” probably fine but very simple mod to get 200 FPS sounds pretty good