Barrel length?

[jebova2301]

Alright. The results are in....

Load:
55gr Hornady Soft Point
Virgin LC brass
27.0 grains WC-844
Fiocchi Small Rifle Magnum Primers
85.5 degrees F outside.

All three rifles were left outside for 2 hours to become the same temperature, and ammo was left outside for 1 hour to make sure it was the same ambient temperature as outdoors. Powder charges were NOT weighed individually. My RCBS uniflow was set to be roughly 27.0 grains, and generally throws within +/- 0.1 grains. I believe the tight charges in the first group were merely a fluke.

------------------------------------------------

Barrel 1: Daniel Defense 16" 1:7 CHF chrome lined
Shot number: Velocity
1: (forgot to push the button to start chronograph...oops)
2: 3035
3: 3016
4: 3011
5: 3009
6: 3020
7: 3003
8: 3003
9: 3016
10: 3010

Average 3013.75
Highest 3035.46
Lowest 3003.03
Ext. Spread 32.43
Std. Dev 9.91

------------------------------------------------

Barrel 2: Palmetto State Armory(FN stamped) 20" 1:7 CHF chrome lined
Shot number: Velocity
1: 3168
2: 3153
3: 3162
4: 3154
5: 3185
6: 3160
7: 3144
8: 3134
9: 3129
10: 3158

Average 3154.65
Highest 3185.1
Lowest 3129
Ext. Spread 56.11
Std. Dev 16.38

------------------------------------------------

Barrel 3: White Oak Precision(Krieger) 20" 1:7.7 Stainless Steel
Shot number: Velocity
1: 3234
2: 3206
3: 3222
4: 3212
5: 3219
6: 3194
7: 3181
8: 3209
9: 3166
10: 3205

Average 3204.82
Highest 3234.12
Lowest 3166.48
Ext. Spread 67.64
Std. Dev 19.99

------------------------------------------------

So what can we gather from all this? Not a whole lot, in my opinion. Obviously, a longer barrel increases velocity. The issue is the White Oak barrel compared to the PSA barrel. With there being multiple variables, it is impossible to isolate just one from this test. The White Oak barrel showed a 50FPS velocity gain over the PSA barrel. This could be from the White Oak being a precision made barrel, or from the slightly slower 1:7.7 twist instead of 1:7, or also the material the barrel is made of. Personally, I can't see the twist rate making that much of a difference. The PSA barrel has a few thousand rounds through it, where the White Oak barrel only has 500 or so through it.

The takeaway that I would look at would be more at the PSA vs DD barrels. They are both what I would consider more of a "typical" rifle barrel, they are both chrome lined, and they both have the same twist rate. Moving from the 16" barrel to the 20" barrel, there was an average gain of 140.9fps. With this specific powder, it looks like I was picking up about 35fps per inch of barrel length.

As far as pressure, and what is safe in regards to load data, it should be the same regardless of barrel length. The pressure will spike relatively quickly, and then taper off as the bullet is traveling down the bore. Remember, pressure is the result of the amount of gas inside a certain volume of space. As the volume increases, if there is not enough powder burning to create enough gas to maintain the pressure, the rate of acceleration slows down, and in the event of a barrel that is long enough, the bullet could actually lose velocity in the barrel assuming the friction from the bore is creating more resistance than the pressure is able to overcome(think of a low pressure cartridge with a long barrel). Having said all that, every barrel can be slightly different, and the powder charge to get to the SAAMI limits may be different between any two barrels, even if they are from the same manufacturer. Generally, you will not have to worry about this as long as you are in the middle of the load data. If you are running at the ragged edge and getting pressure signs from one barrel, I would not recommend that you test that load in a different barrel. Start a bit lower and work your way back up to find what is safe in that specific barrel.

Now, as for what load data to use for the best results, that is another issue all in itself. Every barrel will exhibit different barrel harmonics that can have an impact on the results downrange. If you are just shooting for 3 inch plates at 100 yards, these issues can mostly be ignored and you will be fine. The barrel harmonics issue typically comes into play when you are wanting to go into sub-moa territory. Nearly all barrels from a reputable manufacturer should be able to shoot 3 inch groups with minimal load development. Most should even be able to shoot 2 inch groups if a proper load has been developed for them. Some barrels might be able to shoot 1 inch groups, but that seems to be luck of the draw if you are buying a budget/mid-range barrel. Just because a load works phenomenally in one barrel does NOT mean it will work just as well in every other barrel. It can usually be used as a good reference point. Again, though, this goes back to "How good is good enough?" If you are just looking for hitting a 3 inch plate at 100 yards and you have a load that is shooting 1 or two inch groups, it is probably going to be just fine out of any barrel for the 3 inch plate.

 

[Bcwitt]

When it’s a formulaic regression, it certainly is.

Can you write the equasion? I'm hedging my bet that you cannot.

 

[Varminterror]

I’m not a Coder for QL. But it’s clear in your messages this afternoon, understanding the meaning of words like “hedging,” “interpolation,” “cartridge overall length,” “case length,” and “thespian” escape you.

 

[Varminterror]

So what can we gather from all this? Not a whole lot, in my opinion.

I’ve had 5 Bartlein barrels chambered by the same smith using the same reamer ~8mos apart, three bought and chambered together and the other two bought and chambered together. Heavy Palma, 6 creed, 26” finished, throated for the 105 Hybrid. All 5 barrels drew a node centered within +/-0.1grn of each other, and ALMOST all of them yielded velocity within +/-10fps... however, one barrel happened to run ~80fps faster than the other 4, including the two others with which it was originally purchased and chambered.

It’s fair to acknowledge that longer barrels should, for all intents and purposes, shoot faster than shorter barrels (again, longer barrel = longer dwell time under force), and it’s not particularly true to say every barrel is a law unto itself, because they’re not - but don’t sweat the small stuff. Linings, finishes, lapping, groove count, land geometry, cross-sectional bore area, twist rate... they all SHOULD have predictable influences, but at the end of the day, largely, they don’t. Longer barrels are typically faster than shorter barrels, or more predictably, cutting a barrel will typically reduce velocity by ~20-50fps/inch. Everything else is just academic pedantry.

 

[Blue68f100]

Alright. The results are in....

Load:
55gr Hornady Soft Point
Virgin LC brass
27.0 grains WC-844
Fiocchi Small Rifle Magnum Primers
85.5 degrees F outside.

All three rifles were left outside for 2 hours to become the same temperature, and ammo was left outside for 1 hour to make sure it was the same ambient temperature as outdoors. Powder charges were NOT weighed individually. My RCBS uniflow was set to be roughly 27.0 grains, and generally throws within +/- 0.1 grains. I believe the tight charges in the first group were merely a fluke.

------------------------------------------------

Barrel 1: Daniel Defense 16" 1:7 CHF chrome lined
Shot number: Velocity
1: (forgot to push the button to start chronograph...oops)
2: 3035
3: 3016
4: 3011
5: 3009
6: 3020
7: 3003
8: 3003
9: 3016
10: 3010

Average 3013.75
Highest 3035.46
Lowest 3003.03
Ext. Spread 32.43
Std. Dev 9.91

------------------------------------------------

Barrel 2: Palmetto State Armory(FN stamped) 20" 1:7 CHF chrome lined
Shot number: Velocity
1: 3168
2: 3153
3: 3162
4: 3154
5: 3185
6: 3160
7: 3144
8: 3134
9: 3129
10: 3158

Average 3154.65
Highest 3185.1
Lowest 3129
Ext. Spread 56.11
Std. Dev 16.38

------------------------------------------------

Barrel 3: White Oak Precision(Krieger) 20" 1:7.7 Stainless Steel
Shot number: Velocity
1: 3234
2: 3206
3: 3222
4: 3212
5: 3219
6: 3194
7: 3181
8: 3209
9: 3166
10: 3205

Average 3204.82
Highest 3234.12
Lowest 3166.48
Ext. Spread 67.64
Std. Dev 19.99

------------------------------------------------

So what can we gather from all this? Not a whole lot, in my opinion. Obviously, a longer barrel increases velocity. The issue is the White Oak barrel compared to the PSA barrel. With there being multiple variables, it is impossible to isolate just one from this test. The White Oak barrel showed a 50FPS velocity gain over the PSA barrel. This could be from the White Oak being a precision made barrel, or from the slightly slower 1:7.7 twist instead of 1:7, or also the material the barrel is made of. Personally, I can't see the twist rate making that much of a difference. The PSA barrel has a few thousand rounds through it, where the White Oak barrel only has 500 or so through it.

The takeaway that I would look at would be more at the PSA vs DD barrels. They are both what I would consider more of a "typical" rifle barrel, they are both chrome lined, and they both have the same twist rate. Moving from the 16" barrel to the 20" barrel, there was an average gain of 140.9fps. With this specific powder, it looks like I was picking up about 35fps per inch of barrel length.

As far as pressure, and what is safe in regards to load data, it should be the same regardless of barrel length. The pressure will spike relatively quickly, and then taper off as the bullet is traveling down the bore. Remember, pressure is the result of the amount of gas inside a certain volume of space. As the volume increases, if there is not enough powder burning to create enough gas to maintain the pressure, the rate of acceleration slows down, and in the event of a barrel that is long enough, the bullet could actually lose velocity in the barrel assuming the friction from the bore is creating more resistance than the pressure is able to overcome(think of a low pressure cartridge with a long barrel). Having said all that, every barrel can be slightly different, and the powder charge to get to the SAAMI limits may be different between any two barrels, even if they are from the same manufacturer. Generally, you will not have to worry about this as long as you are in the middle of the load data. If you are running at the ragged edge and getting pressure signs from one barrel, I would not recommend that you test that load in a different barrel. Start a bit lower and work your way back up to find what is safe in that specific barrel.

Now, as for what load data to use for the best results, that is another issue all in itself. Every barrel will exhibit different barrel harmonics that can have an impact on the results downrange. If you are just shooting for 3 inch plates at 100 yards, these issues can mostly be ignored and you will be fine. The barrel harmonics issue typically comes into play when you are wanting to go into sub-moa territory. Nearly all barrels from a reputable manufacturer should be able to shoot 3 inch groups with minimal load development. Most should even be able to shoot 2 inch groups if a proper load has been developed for them. Some barrels might be able to shoot 1 inch groups, but that seems to be luck of the draw if you are buying a budget/mid-range barrel. Just because a load works phenomenally in one barrel does NOT mean it will work just as well in every other barrel. It can usually be used as a good reference point. Again, though, this goes back to "How good is good enough?" If you are just looking for hitting a 3 inch plate at 100 yards and you have a load that is shooting 1 or two inch groups, it is probably going to be just fine out of any barrel for the 3 inch plate.

Tighter chamber, heavier (thicker brass) can increase pressure. I have 1 match barrel that is 100 fps faster than any of my others. All were cut with the same chamber reamer. The polish bore, tolerance in the bore can make a difference in lower friction with all else the same. Slower twist rate can impact it some but I have not seen hardly any differences. Except that the slower twist loves the lighter bullets.

 

[Bcwitt]

Technically, there is a formula to calculate the peak pressure, because that is EXACTLY what Quickload does.

Our pressure peak typically happens within the first three inches of bullet travel (read “typically” to mean “almost always, but I’m hedging my bet against one dumbass who wants to pontificate the few exceptions which exist”), such the peak pressure is completely oblivious to how much barrel remains in front of the bullet after the instance of peak pressure. So unless you’re cutting your 300 win mag to a 1.5” barrel, you don’t need to worry much about barrel length influencing peak pressure.

Are you saying anyone whom disagrees w you is a d_____s? It kinda looks that way.

 

[Bcwitt]

I’m not a Coder for QL. But it’s clear in your messages this afternoon, understanding the meaning of words like “hedging,” “interpolation,” “cartridge overall length,” “case length,” and “thespian” escape you.

I think you are being rather nasty. No shame in admitting a mistake.

 

[Varminterror]

Are you saying anyone whom disagrees w you is a d_____s? It kinda looks that way.

No. Only the dumbasses who use exceptions as evidence to attempt to nullify a largely applicable rule. I’m certain there are specific loads out there which do peak beyond 3” of bullet travel, but these are exceedingly rare, so I hedged my bet - meaning admitted less than 100% confidence in full truth to the claim being made - by acknowledging they do exist. However, an overwhelming majority of cartridges have their pressure peak somewhere between 1 and 2” of bullet travel, so there’s no difference between 4”, 40”, and 400” when it comes to peak pressure. But if I make the inflexible claim that all cartridges peak within 3”, someone can produce a QL curve depicting a 3.2” peak and throw the baby out with the bath water.

 

[Bcwitt]

Again, it isnt mathematically reliable if there is ANY exception. That is why we use equations. You program is purely theoretical. That defies the most basic rule of safety in handloading (use of pressure tested data) I think it is inappropriate to tell an inexperienced person (by his own admition) to throw caution to the wind & do what you say. That is not scientific @ all. Perhaps your baby was a miscarriage?

 

[Bcwitt]

No. Only the dumbasses who use exceptions as evidence to attempt to nullify a largely applicable rule. I’m certain there are specific loads out there which do peak beyond 3” of bullet travel, but these are exceedingly rare, so I hedged my bet - meaning admitted less than 100% confidence in full truth to the claim being made - by acknowledging they do exist. However, an overwhelming majority of cartridges have their pressure peak somewhere between 1 and 2” of bullet travel, so there’s no difference between 4”, 40”, and 400” when it comes to peak pressure. But if I make the inflexible claim that all cartridges peak within 3”, someone can produce a QL curve depicting a 3.2” peak and throw the baby out with the bath water.

"Only the d_______s who use exceptions as evidence" are you joking?? Look @ what you said.