estimating short barrel velocities with no chrony?

[Gallahad]

I realize im getting out on a limb here, but I havent had a chrony for a few years now. most load data for 243 win is for a 24" barrel. I have a 20" barrel. I know that even if I had a 24" barrel, my velocities would most likely vary a bit from load data, and I know I should get a nother chrony, but for the time being is there an average fps I can take off to get an approx. velocity?

[DDZ]

The general rule of thumb is 50fps per inch of barrel. Depending on the caliber and velocity, the change in velocity lost per inch of barrel reduction can be more or less. I think the slower velocity calibers like 45/70, the loss of velocity per inch of barrel is not as great. The faster moving ones like a .220 swift or a .22-250 the loss of velocity per barrel inch is greater.
I remember seeing a test done with a .308. They started with a 24 inch tube and cut off 2" of barrel at a time and recorded velocity for each length. they went down to a 18 tube. I think the loss of velocity per every 2" inches of barrel cut was around 150fps.

[Luckyducker]

I have a model 600 Remington in 6mmRem w/18.5" barrel that I shoot a starting load of IMR 4350 under a Nosler 70 grain Ballistic Tip bullet.  This load runs about 3020 ft/sec over my chronograph at muzzle +10' while the Nosler manual gives a velocity of 3312 ft/sec from their 24" tube.  That figures about 50 ft/sec velocity loss per 1" of barrel length.  This number will vary from one cartridge to another but should be close IMO for a 243W.  The gurus say about 30 ft/sec for the 30 cal rifles, but without the aid of chrono that is sheer speculation.

[Blackhawk44]

The real problem is that without a chronograph, you don't know what velocity to take that 50fps per inch from...   Have a .308 BLR that gives sticky extraction with fast powders showing velocities of 2400 to 2500fps while max loads of slower powders easily exceed 2800fps and let it feed and extract like a .22LR.  Judging by extraction without the chrono, you likely would imagine opposite results.

[PawPaw]

Without a chronograph, you won't know for sure, but how important is that data?

If it's for hunting and you can hit what you're shooting at with a good bullet, will the game know the difference between 2800 fps and 2900 fps?  I doubt it. 

Lots of us hobbyists love to accumulate data, but sometimes I question how important it is to know such things.

[kevinsmith5]

My 32" BC (45-70) gets faster MV's with slower powders than the load manuals for 22-24" barrels by around 250 FPS. With faster powders it sometimes gets the same or slower.  Hornady's LeverEvolutions (pretty sure their designed for 18" guide guns) get 150 fps SLOWER than the company advertises. I'd say if you wanna know your MV your gonna need a chrony. I got mine by ordering online form Walmart and picking up at the store, no shipping.

[R.W.Dale]

Without a chronograph, you won't know for sure, but how important is that data?

If it's for hunting and you can hit what you're shooting at with a good bullet, will the game know the difference between 2800 fps and 2900 fps?  I doubt it.  

Lots of us hobbyists love to accumulate data, but sometimes I question how important it is to know such things.

If shooting game beyond 30-30 ranges you absolutely need to know the MV to make accurate calculations for come ups to put that bullet where it needs to go.

The problem with such guestimations is they can be off by a large margin.

Generally the more overbore a cartridge is the harder MV's are hit as bbl length decreases. As an example I recently chronographed factory 100g 243 rem loads at only 2670fps from an 18.5" 788

[necchi]

you absolutely need to know the MV to make accurate calculations for come ups to put that bullet where it needs to go.

Only as it apply's to the mathmatical calculations made with pen and paper.

Nothing quite beats actually shooting at longer ranges within the limits of you, your gun and your game.

[R.W.Dale]

you absolutely need to know the MV to make accurate calculations for come ups to put that bullet where it needs to go.

Only as it apply's to the mathmatical calculations made with pen and paper.

Nothing quite beats actually shooting at longer ranges within the limits of you, your gun and your game.

I agree but not completely,    Most don't bother actually shooting at those oddball in between ranges animals like to present themselves at, folks range time is almost exclusively in 100yd increments. A mathimatical bullet drop chart tuned to match range results can bean the difference between good and poor placement when an animal is halfway between 100yd incrementation

[Sweetwater]

Got my Chrony for my 55th birthday. Don't think I had any problems with the Wyoming antelope at varying distances from in my face to over 400 yards before I got it. I have yet to meet anyone with a field calculator in hand working on a "long shot". You know what you are doing, or you don't.

Necci - couldn't agree with you more!! Well stated!!

[kevinsmith5]

I've mostly used mine to determine if accurate loads are also going to be lethal at a given range. If I know the MV, BC and weight of the bullet I can figure the foot pounds at a given range to know if the load is good for causing expansion/damage at that range.

[huntswithdogs]

Sometimes, I think we're out doing ourselves where technology is concerned.
 I've been loading since back in the eighties with no Chrono and haven't EVER missed a game animal with my reloads. Ranges from "in your face" to "should I shoot?". All of my loads have been "book listed" and I took the time to go to the range and learn my rifle and cartridge combo. Heck! We all should be doing it!
Find a load that's accurate(again, range time) then shoot a bunch of them.


HWD

[huntswithdogs]

 What? Nobody had anything to say about having a wind meter to measure wind velocities...?

JUST KIDDING!!!!!!!!!!!!!!!!!!!!!

HWD