barrel length and burn times
- Thread starter David N
- Start date
Morning David N,
Re:-Ramshot X-Terminator & 53gn V-Max bullet (at OAL 0.830inch.) Rifle 1:12 twist rate; barrel length 20inch.
Even with a higher pressure Working Load with Ramshot X-terminator 25.25gns @ 48000psi. MV bullet speed is estimated 3060fps. At this slow speed with 1:12 twist J.B. Miller formula indicates it becoming unstable at just 30yards.
Bullet speed at 30 yards estimated at 2950fps
Link to JB.Miller gyroscopic/stability formula, where bullet tip type is included in calculations :- JBM - Calculations - Stability
Suggest 5 options.
Change to lower grain bullet.
Use different propellent to Increase bullet speed to over 3300fps (watch for over pressure signs)
Enlist the assistance of an experienced reloader.
Purchase QuickLoad at £135
Change rifle for 1:10 twist rate of faster.
Good luck.
Regards
RoyR
PS just seen your latest post - written while I was doing mine.
Powder charge /pressure depends on the case capacity. A used Form Fired 223 Lapua brass case will hold 30.7gns. (H20 measured) Standard measurement used in most calculations is for NEW cases at only 28.8gns capacity. The 1.9gns difference in case capacities is where PSI pressure with Grains of powder differ.
I stated that I was using 30grains case capacity as you were reloading USED Form Fired cases. You do NEED TO MEASURE your USED Form Fired case capacity to establish safe working loads.
QuickLoad is the reloading data program. If you enter all the relevant parameters correctly, I've found it to be pretty accurate in assessing any new proposed load.
Re:-Ramshot X-Terminator & 53gn V-Max bullet (at OAL 0.830inch.) Rifle 1:12 twist rate; barrel length 20inch.
Even with a higher pressure Working Load with Ramshot X-terminator 25.25gns @ 48000psi. MV bullet speed is estimated 3060fps. At this slow speed with 1:12 twist J.B. Miller formula indicates it becoming unstable at just 30yards.
Bullet speed at 30 yards estimated at 2950fps
Link to JB.Miller gyroscopic/stability formula, where bullet tip type is included in calculations :- JBM - Calculations - Stability
Suggest 5 options.
Change to lower grain bullet.
Use different propellent to Increase bullet speed to over 3300fps (watch for over pressure signs)
Enlist the assistance of an experienced reloader.
Purchase QuickLoad at £135
Change rifle for 1:10 twist rate of faster.
Good luck.
Regards
RoyR
PS just seen your latest post - written while I was doing mine.
Powder charge /pressure depends on the case capacity. A used Form Fired 223 Lapua brass case will hold 30.7gns. (H20 measured) Standard measurement used in most calculations is for NEW cases at only 28.8gns capacity. The 1.9gns difference in case capacities is where PSI pressure with Grains of powder differ.
I stated that I was using 30grains case capacity as you were reloading USED Form Fired cases. You do NEED TO MEASURE your USED Form Fired case capacity to establish safe working loads.
QuickLoad is the reloading data program. If you enter all the relevant parameters correctly, I've found it to be pretty accurate in assessing any new proposed load.
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Further reading. Looking at different powder at 55gr
N133 gives 2989 to 3278
N135 gives 3041 to 3283
H322 gives 2953 to 3083
X-terminator gives 2936 to 3209 fps
So treat me gently am I right your saying non are great for. 223 with 20" barrel? Taking the manufacturers min and max loads?
Just trying to understand. Thanks David
N133 gives 2989 to 3278
N135 gives 3041 to 3283
H322 gives 2953 to 3083
X-terminator gives 2936 to 3209 fps
So treat me gently am I right your saying non are great for. 223 with 20" barrel? Taking the manufacturers min and max loads?
Just trying to understand. Thanks David
HistoricBore
Well-Known Member
I would stick with Vihtavuori; much better than American powders. Use N120 if need be. N133 works brilliantly in my .222.
HB
HB
Morning David N
Only got a few minutes spare this morning.
I reiterate, SAMMI MAX Pressure for .223Rem is 55,000PSI. Loading a charge of powder/bullet to anywhere near this Max PSI figure is dangerous and foolish IMHO; especially when an alternative powder achieves a faster bullet MV speed at a lower pressure of sub 49,000PSI. Personally I like a 10% safety margin and load 223 to estimated Max of 49,000PSI.
Quoted Ramshot X-Terminator with 53gn bullet @ 54,700PSI, leaves no room for error: it is not *T (temperature stable/resistant) meaning any high temperature/humidity could easily see an increase in powder burn rate of 2% to 5%, thus exceeding the Max 55,000PSI.
Apart from being dangerous, using these near MAX PSI loads also accelerates throat wear/erosion and reduces brass-case life.
If you review my previous posts, I have stated the loads I use with Tikka T3 Super Varmint with 20inch barrel, 1:12 twist rate, using Vihtavuori N120.
My favourite is with the 40gn V-Max @ Chrono'd 3740fps.
Apologies, have to go out now.
Regards
Roy
Only got a few minutes spare this morning.
I reiterate, SAMMI MAX Pressure for .223Rem is 55,000PSI. Loading a charge of powder/bullet to anywhere near this Max PSI figure is dangerous and foolish IMHO; especially when an alternative powder achieves a faster bullet MV speed at a lower pressure of sub 49,000PSI. Personally I like a 10% safety margin and load 223 to estimated Max of 49,000PSI.
Quoted Ramshot X-Terminator with 53gn bullet @ 54,700PSI, leaves no room for error: it is not *T (temperature stable/resistant) meaning any high temperature/humidity could easily see an increase in powder burn rate of 2% to 5%, thus exceeding the Max 55,000PSI.
Apart from being dangerous, using these near MAX PSI loads also accelerates throat wear/erosion and reduces brass-case life.
If you review my previous posts, I have stated the loads I use with Tikka T3 Super Varmint with 20inch barrel, 1:12 twist rate, using Vihtavuori N120.
My favourite is with the 40gn V-Max @ Chrono'd 3740fps.
Apologies, have to go out now.
Regards
Roy
jthyttin
Well-Known Member
Velocity has minor role in stabilization. Bullet length and twist rate basically tell you if it stabilizes or not.
Weight of course gives some indication of length but blunt flatbase projectile is a lot shorter than sleek boattail.
Sako/Tikka are quite bass ackwards nowadays, you cannot e.g. find the old "rifles datatable" from web page. But T3 has been offered in 1-12" and 1-8" twist rate. If you have 1-12" (as has been implied) 53gr V-Max may be too long.
Weight of course gives some indication of length but blunt flatbase projectile is a lot shorter than sleek boattail.
Sako/Tikka are quite bass ackwards nowadays, you cannot e.g. find the old "rifles datatable" from web page. But T3 has been offered in 1-12" and 1-8" twist rate. If you have 1-12" (as has been implied) 53gr V-Max may be too long.
Roy
Thanks. In a nut shell
223 max pressure either psi or cup have a value as found in SAAMI. To propel a bullet it needs x fps to stabilise.
So find a powder with appropriate fps and pressure under the max.
Is this about right?
David
Afternoon David N.
I believe you are appreciating the basic details required to develop a decent safe load; capable of delivering an accurate bullet with the necessary lethal force for that quarry. It's the more precise details for YOUR SPECIFIC RIFLE, like OGIVE measurement (Freebore /"bullet jump"), and measured H20 Capacity of your USED Form Fired cases, that will give you the customised ammunition best suited for your specific rifle.
As you have seen from the online JBM calculations, giroscopic stability is a factor of many components:-
1. Rifle calibre.
2. Barrel twist rate
3. Bullet weight.
4. Bullet length.
5. Bullet speed:- from MV speed to the slower down range speeds where giroscopic stability will accordingly be less - do check this if you want to shoot foxes over 300yards! ****
6 . Humidity and Temperature.
****N.B. Many bullets become unstable after 200 yards, (wrong twist rate, long bullet length, slow speed; etc) this is why ragged holes sometimes appear on paper targets, because the bullet has entered sideways-on. Have a read up on bullet Yaw and Tumbling effects after it becomes unstable.
A picture speaks a thousand words:-
If you want to use a 50Gn V-max in your 223, 20inch barrel 1;12 twist rate, assumed Form fired case of 30.2gns H20 capacity, then I do use this load which I've mentioned before; you may find acceptable? ( I still prefer the 40gn V-max load!)
50gn V-MAX;-
Vihtavuori N120 *C - 91.6% case fill @ 21.3gns; Chron'd M.V. 20inch barrel 3330fps; 100.% powder burnt at 15inches (a snipers dream); pressure sub 48000psi.
JB.Miller figure at MV 3330fps @ 1.595. At 300 yards bullet speed is estimated at 2200fps, JBM figure of 1.389 (still good). 50gn V-Max bullet becoming marginally unstable after 430yards with JBM figure of 1.29.
If you had a 24" barrel, bullet speed would be accordingly higher at estimated 3435fps.
Regards
RoyR
Thanks. In a nut shell
223 max pressure either psi or cup have a value as found in SAAMI. To propel a bullet it needs x fps to stabilise.
So find a powder with appropriate fps and pressure under the max.
Is this about right?
David
Afternoon David N.
I believe you are appreciating the basic details required to develop a decent safe load; capable of delivering an accurate bullet with the necessary lethal force for that quarry. It's the more precise details for YOUR SPECIFIC RIFLE, like OGIVE measurement (Freebore /"bullet jump"), and measured H20 Capacity of your USED Form Fired cases, that will give you the customised ammunition best suited for your specific rifle.
As you have seen from the online JBM calculations, giroscopic stability is a factor of many components:-
1. Rifle calibre.
2. Barrel twist rate
3. Bullet weight.
4. Bullet length.
5. Bullet speed:- from MV speed to the slower down range speeds where giroscopic stability will accordingly be less - do check this if you want to shoot foxes over 300yards! ****
6 . Humidity and Temperature.
****N.B. Many bullets become unstable after 200 yards, (wrong twist rate, long bullet length, slow speed; etc) this is why ragged holes sometimes appear on paper targets, because the bullet has entered sideways-on. Have a read up on bullet Yaw and Tumbling effects after it becomes unstable.
A picture speaks a thousand words:-
If you want to use a 50Gn V-max in your 223, 20inch barrel 1;12 twist rate, assumed Form fired case of 30.2gns H20 capacity, then I do use this load which I've mentioned before; you may find acceptable? ( I still prefer the 40gn V-max load!)
50gn V-MAX;-
Vihtavuori N120 *C - 91.6% case fill @ 21.3gns; Chron'd M.V. 20inch barrel 3330fps; 100.% powder burnt at 15inches (a snipers dream); pressure sub 48000psi.
JB.Miller figure at MV 3330fps @ 1.595. At 300 yards bullet speed is estimated at 2200fps, JBM figure of 1.389 (still good). 50gn V-Max bullet becoming marginally unstable after 430yards with JBM figure of 1.29.
If you had a 24" barrel, bullet speed would be accordingly higher at estimated 3435fps.
Regards
RoyR
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