Is there a standard barrel length that is used when factories do their ballistics tests? My assumption would be the posted velocities are based on a 22" barrel, but I wanted to see if someone could confirm. Thanks.
Range Report Factory Ammo Muzzle Velocities?
- Thread starter Megahoser
- Start date
Re: Factory Ammo Muzzle Velocities?
i was all ways told its done on a 26" barrel but im no expert
i was all ways told its done on a 26" barrel but im no expert
Re: Factory Ammo Muzzle Velocities?
If they don't say, you don't know.
The one thing I'd suggest is that those published velocities be used as guidelines (maybe +/-100-200fps), and not as precise data. Barrel length is only one of several variables which determine MV.
Greg
If they don't say, you don't know.
The one thing I'd suggest is that those published velocities be used as guidelines (maybe +/-100-200fps), and not as precise data. Barrel length is only one of several variables which determine MV.
Greg
Re: Factory Ammo Muzzle Velocities?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">The one thing I'd suggest is that those published velocities be used as guidelines (maybe +/-100-200fps), and not as precise data. Barrel length is only one of several variables which determine MV.</div></div>
Understood, but I was just wondering if they all use a standard baseline when reporting their MV. I figured there has to be one, else they could all just use what ever gives their round the best performance.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">The one thing I'd suggest is that those published velocities be used as guidelines (maybe +/-100-200fps), and not as precise data. Barrel length is only one of several variables which determine MV.</div></div>
Understood, but I was just wondering if they all use a standard baseline when reporting their MV. I figured there has to be one, else they could all just use what ever gives their round the best performance.
Re: Factory Ammo Muzzle Velocities?
Typically, a 22" barrel is used on standard calibers (308 and 30-06 cases) and 24" for magnum calibers (300WM, 7 Rem Mag).
I've seen some will do 24" on standard and 26" on magnum, which bumps up their velocity claims by using an extra 2 inches of barrel.
Using their velocity will get you close, but you really need to chrono the load to know for sure.
Typically, a 22" barrel is used on standard calibers (308 and 30-06 cases) and 24" for magnum calibers (300WM, 7 Rem Mag).
I've seen some will do 24" on standard and 26" on magnum, which bumps up their velocity claims by using an extra 2 inches of barrel.
Using their velocity will get you close, but you really need to chrono the load to know for sure.
Re: Factory Ammo Muzzle Velocities?
Thanks for the info, I will definately be doing my own chrono...I just wanted to have an idea of what kind of deviance I am seeing when I test my 20" barrel.
Thanks for the info, I will definately be doing my own chrono...I just wanted to have an idea of what kind of deviance I am seeing when I test my 20" barrel.
Re: Factory Ammo Muzzle Velocities?
So far the only factory stuff I've chrono'ed is the Federal Fusion in .308, 150 grain. Out of a 20" SPS it averaged 2793, site list it as 2820. I was very consistent also, 2789 was low and 2799 high, 5 shots at 55 degree's I will try again at a warmer/cooler temp to see the difference.
Group was 1"
So far the only factory stuff I've chrono'ed is the Federal Fusion in .308, 150 grain. Out of a 20" SPS it averaged 2793, site list it as 2820. I was very consistent also, 2789 was low and 2799 high, 5 shots at 55 degree's I will try again at a warmer/cooler temp to see the difference.
Group was 1"
Re: Factory Ammo Muzzle Velocities?
I know Federal says a 24" barrel.
I know Federal says a 24" barrel.
Re: Factory Ammo Muzzle Velocities?
Here's the factory stuff I've chrono'd so far out of my 20" .308 SPS-T:
Win 150grn Power Point - 2790
Win 150grn PHP - 2738
Fed 150 grn SP - 2796
Chrono was a CED M2. Temps during testing was ~75-80F
Here's the factory stuff I've chrono'd so far out of my 20" .308 SPS-T:
Win 150grn Power Point - 2790
Win 150grn PHP - 2738
Fed 150 grn SP - 2796
Chrono was a CED M2. Temps during testing was ~75-80F
Re: Factory Ammo Muzzle Velocities?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">If they don't say, you don't know.
The one thing I'd suggest is that those published velocities be used as guidelines (maybe +/-100-200fps), and not as precise data. Barrel length is only one of several variables which determine MV.
Greg </div></div>
Once again Greg has hit it. Some companies use actual hunting rifles. But most testing departments use a universal receiver with untapered barrel blanks. These things are almost like an unlimited rifle in benchrest. Some of them weight as much as 50 pounds.
Use the numbers as a guideline only.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">If they don't say, you don't know.
The one thing I'd suggest is that those published velocities be used as guidelines (maybe +/-100-200fps), and not as precise data. Barrel length is only one of several variables which determine MV.
Greg </div></div>
Once again Greg has hit it. Some companies use actual hunting rifles. But most testing departments use a universal receiver with untapered barrel blanks. These things are almost like an unlimited rifle in benchrest. Some of them weight as much as 50 pounds.
Use the numbers as a guideline only.
Re: Factory Ammo Muzzle Velocities?
I mistrust chronos, as I have undoubtedly and boringly stated on numerous occasions.
I believe that the only real way to figure this stuff out is from observation and extrapolation using a reliable ballistic routine and accurate input data.
Even then, confirmation is essential.
Greg
I mistrust chronos, as I have undoubtedly and boringly stated on numerous occasions.
I believe that the only real way to figure this stuff out is from observation and extrapolation using a reliable ballistic routine and accurate input data.
Even then, confirmation is essential.
Greg
Re: Factory Ammo Muzzle Velocities?
So many variables, its difficult to make heads or tails.
So many variables, its difficult to make heads or tails.
Re: Factory Ammo Muzzle Velocities?
Do you really need the velocities? What are you giving up now by not having them?
If your stuck with factory ammo anyways, accuracy will be the deciding factor most likely. All thats left is to shoot for come-ups. I wouldn't get stuck on this...too many variables.
Do you really need the velocities? What are you giving up now by not having them?
If your stuck with factory ammo anyways, accuracy will be the deciding factor most likely. All thats left is to shoot for come-ups. I wouldn't get stuck on this...too many variables.
Re: Factory Ammo Muzzle Velocities?
Knowing velocities, combined with one or a few known POI's at known distances, can help one use a ballistic calculation to extrapolate dope for other distances, and/or use observed drops as a fudge to estimate actual ranges; as well as determining where imprecision and terminal energy drop-off may turn a contemplated shot into a bad bet.
Pejsa Spreadsheets have a 'stock table' feature which allows one to print out a small chart that can be laminated and mounted on a rifle stock. Shooting confirmations can help synchronize such computations with reality. Many of my practical rifles have such charts fastened on them.
Admittedly, no calculation is going to work perfectly in a real world, but knowing velocities and having ballpark data can be a useful hedge against uncertainty.
Greg
Knowing velocities, combined with one or a few known POI's at known distances, can help one use a ballistic calculation to extrapolate dope for other distances, and/or use observed drops as a fudge to estimate actual ranges; as well as determining where imprecision and terminal energy drop-off may turn a contemplated shot into a bad bet.
Pejsa Spreadsheets have a 'stock table' feature which allows one to print out a small chart that can be laminated and mounted on a rifle stock. Shooting confirmations can help synchronize such computations with reality. Many of my practical rifles have such charts fastened on them.
Admittedly, no calculation is going to work perfectly in a real world, but knowing velocities and having ballpark data can be a useful hedge against uncertainty.
Greg
Re: Factory Ammo Muzzle Velocities?
What I was getting at was that not knowing advertised velocities by the ammo manufacturers is no great handicap. Worrying about whether the test barrel was 24 or 26 is trivial. Just shoot for dope and then use the software to fill in the gaps for future use.
What I was getting at was that not knowing advertised velocities by the ammo manufacturers is no great handicap. Worrying about whether the test barrel was 24 or 26 is trivial. Just shoot for dope and then use the software to fill in the gaps for future use.
