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#6177773 - 02/10/16 01:09 PM Burn rate and barrel length
Cleric Offline
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Registered: 03/11/12
Posts: 2579
Question... If you have a shorter barrel does the saying of xx fps per inch go down if you select a faster burning powder.

So if I had a handful of powders that could get approx the same velocity. Would the faster burning one have a higher chance of getting that velocity out of a shorter barrel?

Thanks

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#6177783 - 02/10/16 01:22 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
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Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
Nope.
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Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6177787 - 02/10/16 01:26 PM Re: Burn rate and barrel length [Re: Cleric]
ChadTRG42 Online   happy
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Registered: 09/16/09
Posts: 9397
Loc: Lewisville, TX
Yes. It's a close trade off. Take a 308 Win. Varget is a great 308 powder for the 168-178 grain weight bullets. If you were to run the Varget in a longer barrel (26"), you will get more speed than a faster burning powder, like 4895. And you will get a complete powder burn longer down the barrel. Opposite goes for the shorter barrel. The faster burning powder will reach pressure sooner, and have a more complete burn in a shorter length time and barrel length. So, you will get slightly more speed in a shorter barrel with a faster powder than you will with a slower powder. This is why I recommend a faster burning powder for your shorter barrels.

Also, if it's a gas gun, the gas port is about 9" to 11" away from the chamber. A slower burning powder will have much more port pressure than a faster burning powder will, since the faster burning powder will reach peak pressure much sooner, and bleed off pressure more quickly, and reduce port pressures. Something in the 8208 and 4895 area is about ideal for a gas gun with an 18" to 20" barrel length. But Varget does perform excellent in an Armalite AR-10T with a 175 SMK, and gets great speed.
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#6177793 - 02/10/16 01:33 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
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Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
I guess that deserves an explanation.

Using the larger cartridges and the slowest burning powders, the powder is as consumed as it can be by the time the bullet has moved about ten inches. With more typical cartridges like .30-06, all the powder that is going to burn will do so in about four inches of bullet travel.

Some cartridge and powder combinations won't achieve 100% burn no matter what the barrel length.
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Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6177795 - 02/10/16 01:33 PM Re: Burn rate and barrel length [Re: Cleric]
Cleric Offline
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Registered: 03/11/12
Posts: 2579
So for a 7mm-08 with an 18in barrel what type of powder speed am I looking for? Ideally I could use something in the 162 grain area

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#6177796 - 02/10/16 01:35 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
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Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
Not so Chad. Powder burn ceases when pressure falls to a certain point.
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Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6177798 - 02/10/16 01:40 PM Re: Burn rate and barrel length [Re: RiverRider]
ChadTRG42 Online   happy
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Registered: 09/16/09
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Loc: Lewisville, TX
Originally Posted By: RiverRider
Not so Chad. Powder burn ceases when pressure falls to a certain point.

At what point is that?
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#6177814 - 02/10/16 01:55 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
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Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
I wouldn't know *exactly.* What I DO know is that sometimes you'll have to push a load harder with a given powder to achieve 100% burn.

Pressure falls rapidly as the bullet moves down the bore. Since modern smokeless is progressive burning, the burn requires high pressure be maintained long enough to complete. I picture that as a surfer trying to stay up high on the face of a wave to get a good ride.

Higher velocity with slower burning powders has more to do with the amount of gas generated than how long the powder burns. The burn rate only determines the speed at which that volume of gas is generated.
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Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6177824 - 02/10/16 02:04 PM Re: Burn rate and barrel length [Re: Cleric]
ChadTRG42 Online   happy
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Registered: 09/16/09
Posts: 9397
Loc: Lewisville, TX
Yeah, I'm scratching my head right now. I'm running some numbers in QuickLoad, and they are not showing me what I'm thinking. But the more pressure I have, the more complete burn is achieved. I know that from playing with subsonic loads.
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#6177842 - 02/10/16 02:12 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
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Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
Exactly. I've been paying more attention to burn percentages lately, and one of the powders I was interested in showed about a 97% burn, IIRC. With an increased charge and the resulting higher pressure peak, consumption jumped to 100%.

Not to derail the OP...but, I got to thinking about it and it stands to reason that if you can get consistently high enough pressure to always achieve 100% burn, then all that carefully metered powder will yield the most consistent volume of gas, and therefore the most consistent velocities. Kinda falls together nicely, doesn't it?
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Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6177856 - 02/10/16 02:22 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
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Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
Chad, since you are running QL, try running a powder profile on something like .308 and set barrel length to 18 inches, then run it again with a 26-inch barrel. You'll see that the results show a very consistent order of powders sorted by velocity.
_________________________


Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6178038 - 02/10/16 04:31 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
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Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
For the OP...

First, with a 26-inch barrel:


Code:
Cartridge          : 7 mm-08 Rem.
Bullet             : .284, 162, Hornady A-MAX 28402
Useable Case Capaci: 45.033 grain H2O = 2.924 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length      : 26.0 inch = 660.4 mm

Predicted Data for Indicated Charges of the Following Powders.
Matching Maximum Pressure: 61641 psi, or 425 MPa
or a maximum loading ratio or filling of 106 %
These calculations refer to your specified settings in QuickLOAD 'Cartridge Dimensions' window.
C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

58 loads produced a Loading Ratio below user-defined minimum of 86%. These powders have been skipped.
Powder type          Filling/Loading Ratio  Charge    Charge   Vel. Prop.Burnt P max  P muzz  B_Time
                                      %     Grains    Gramm   fps     %       psi     psi    ms
---------------------------------  -----------------------------------------------------------------
Alliant Reloder-17                 102.9     44.8     2.90    2840   100.0    61641    7866   1.227  
Winchester 760                     101.7     44.7     2.89    2793    98.9    61641    8021   1.244  
Hodgdon H414                       101.7     44.7     2.89    2793    98.9    61641    8021   1.244  
Vihtavuori N550                    104.2     44.2     2.86    2786    99.9    61641    7850   1.252  
Accurate 4350                      106.0     44.0     2.85    2765    99.9    60070    7679   1.274  
Hodgdon CFE223                      91.6     42.3     2.74    2758   100.0    61641    7321   1.252  
Ramshot Big Game                    97.0     42.9     2.78    2758   100.0    61641    7336   1.251  
Ramshot Hunter                     106.0     45.4     2.94    2757    99.1    58160    7980   1.269  
Norma 204                          106.0     45.4     2.94    2756    97.1    61240    7933   1.245  
Norma URP                          106.0     43.5     2.82    2753    99.9    59065    7691   1.269  
IMR 4895                            96.5     40.1     2.60    2749   100.0    61641    7335   1.262  
Alliant Reloder-15                  97.3     40.4     2.62    2740   100.0    61641    7309   1.263  
Norma 203B                          97.8     40.6     2.63    2739   100.0    61641    7252   1.264  
Hodgdon BL-C2                       92.0     41.7     2.70    2736   100.0    61641    7168   1.265  
Norma 203 old                       99.4     41.7     2.70    2734   100.0    61641    7147   1.273  
Hodgdon H380                        98.6     41.8     2.71    2732    99.8    61641    7421   1.266  
Winchester 748                      89.5     40.0     2.59    2724   100.0    61641    6875   1.260  
Ramshot Wild Boar                   92.3     40.9     2.65    2724   100.0    61641    7145   1.261  
IMR 4320                            99.2     40.5     2.63    2721   100.0    61641    7030   1.250  
Hodgdon H4895                       93.8     38.9     2.52    2721   100.0    61641    7064   1.266  
Ramshot TAC                         92.1     41.2     2.67    2701    99.6    61641    7244   1.264  
Hodgdon VARGET                      99.8     40.1     2.60    2701   100.0    61641    7055   1.259  
IMR 4007 SSC                       100.1     42.1     2.73    2700    98.3    61641    7401   1.268  
IMR 3031                            96.9     37.6     2.44    2700   100.0    61641    6508   1.269  
IMR 4350                           106.0     43.8     2.84    2699    98.1    59794    7464   1.270  
Accurate 2520                       92.1     40.3     2.61    2698   100.0    61641    6672   1.280  
Accurate 4064                       99.2     40.3     2.61    2697   100.0    61641    6670   1.297  
IMR 4064                           100.5     39.4     2.55    2691   100.0    61641    6888   1.264  
Vihtavuori N530                     90.5     37.8     2.45    2689   100.0    61641    6757   1.267  
Alliant Reloder-26                 106.0     47.3     3.07    2683    98.6    46294    8635   1.379
IMR 8208 XBR                        92.5     38.4     2.49    2682   100.0    61641    6685   1.267  
Norma 201                           95.2     38.7     2.51    2682   100.0    61641    6750   1.281  
Vihtavuori N540                     96.9     40.7     2.63    2680   100.0    61641    6692   1.273  
Norma 202                           94.6     38.6     2.50    2674   100.0    61641    6529   1.276  
Ramshot X-Terminator                89.8     39.8     2.58    2674   100.0    61641    6788   1.270  




Then, with an 18-inch barrel:


Code:
Cartridge          : 7 mm-08 Rem.
Bullet             : .284, 162, Hornady A-MAX 28402
Useable Case Capaci: 45.033 grain H2O = 2.924 cm³
Cartridge O.A.L. L6: 2.800 inch = 71.12 mm
Barrel Length      : 18.0 inch = 457.2 mm

Predicted Data for Indicated Charges of the Following Powders.
Matching Maximum Pressure: 61641 psi, or 425 MPa
or a maximum loading ratio or filling of 106 %
These calculations refer to your specified settings in QuickLOAD 'Cartridge Dimensions' window.
C A U T I O N : any load listed can result in a powder charge that falls below minimum suggested
loads or exceeds maximum suggested loads as presented in current handloading manuals. Understand
that all of the listed powders can be unsuitable for the given combination of cartridge, bullet
and gun. Actual load order can vary, depending upon lot-to-lot powder and component variations.
USE ONLY FOR COMPARISON !

58 loads produced a Loading Ratio below user-defined minimum of 86%. These powders have been skipped.
Powder type          Filling/Loading Ratio  Charge    Charge   Vel. Prop.Burnt P max  P muzz  B_Time
                                      %     Grains    Gramm   fps     %       psi     psi    ms
---------------------------------  -----------------------------------------------------------------
Alliant Reloder-17                 102.9     44.8     2.90    2631    99.9    61641   12425   0.984  
Winchester 760                     101.7     44.7     2.89    2580    96.8    61641   12326   0.996  
Hodgdon H414                       101.7     44.7     2.89    2580    96.8    61641   12326   0.996  
Vihtavuori N550                    104.2     44.2     2.86    2576    98.9    61641   12169   1.004  
Hodgdon CFE223                      91.6     42.3     2.74    2558    99.8    61641   11520   1.001  
Ramshot Big Game                    97.0     42.9     2.78    2558    99.6    61641   11543   1.000  
Accurate 4350                      106.0     44.0     2.85    2557    98.8    60070   12004   1.024  
IMR 4895                            96.5     40.1     2.60    2549    99.7    61641   11522   1.011  
Norma URP                          106.0     43.5     2.82    2545    98.7    59065   11936   1.019  
Norma 204                          106.0     45.4     2.94    2544    94.3    61240   12018   0.994  
Ramshot Hunter                     106.0     45.4     2.94    2542    97.0    58160   12217   1.019  
Alliant Reloder-15                  97.3     40.4     2.62    2540    99.5    61641   11453   1.011  
Norma 203B                          97.8     40.6     2.63    2540    99.7    61641   11392   1.012  
Hodgdon BL-C2                       92.0     41.7     2.70    2539   100.0    61641   11267   1.013  
Norma 203 old                       99.4     41.7     2.70    2538    99.9    61641   11274   1.021  
Winchester 748                      89.5     40.0     2.59    2535   100.0    61641   10869   1.007  
Hodgdon H380                        98.6     41.8     2.71    2530    98.7    61641   11507   1.014  
IMR 4320                            99.2     40.5     2.63    2527    99.6    61641   11045   0.997  
Ramshot Wild Boar                   92.3     40.9     2.65    2527    99.7    61641   11199   1.007  
Hodgdon H4895                       93.8     38.9     2.52    2525    99.9    61641   11112   1.012  
IMR 3031                            96.9     37.6     2.44    2519   100.0    61641   10287   1.014  
Accurate 2520                       92.1     40.3     2.61    2512   100.0    61641   10567   1.025  
Accurate 4064                       99.2     40.3     2.61    2511   100.0    61641   10564   1.042  
Hodgdon VARGET                      99.8     40.1     2.60    2506    99.4    61641   10976   1.003  
Ramshot TAC                         92.1     41.2     2.67    2502    98.2    61641   11165   1.009  
Vihtavuori N530                     90.5     37.8     2.45    2501   100.0    61641   10624   1.011  
IMR 4064                           100.5     39.4     2.55    2500    99.5    61641   10796   1.008  
IMR 4007 SSC                       100.1     42.1     2.73    2497    96.1    61641   11297   1.012  
IMR 4350                           106.0     43.8     2.84    2495    95.7    59794   11388   1.014  
IMR 8208 XBR                        92.5     38.4     2.49    2495   100.0    61641   10534   1.010  
Vihtavuori N540                     96.9     40.7     2.63    2494   100.0    61641   10433   1.016  
Norma 201                           95.2     38.7     2.51    2493   100.0    61641   10624   1.024  
Norma 202                           94.6     38.6     2.50    2491   100.0    61641   10256   1.018  
Accurate 2495                       93.3     37.9     2.46    2490   100.0    61641   10120   1.049  
Ramshot X-Terminator                89.8     39.8     2.58    2483    99.6    61641   10626   1.012  




The order of the powders, sorted by velocity, generally does not change. There are a few exceptions, but it can be said that generally speaking the powder that yields the highest velocity in a given barrel length will also yield the highest velocity in a shorter barrel.

There is a little difference in the completion of the burn (between the two barrel lengths), but that small amount of additional burn in the longer barrel cannot contribute to higher velocity because by the time it occurs, the volume of the gas behind the bullet in the bore is so great that the small additional percentage of the charge burning cannot contribute to the time-pressure curve sufficiently to make any real difference.
_________________________


Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6178072 - 02/10/16 04:48 PM Re: Burn rate and barrel length [Re: Cleric]
Cleric Offline
Veteran Tracker

Registered: 03/11/12
Posts: 2579
Awesome info. Surprised 4451 is not on there


Btw... Just realized I am in your sig banana

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#6178123 - 02/10/16 05:10 PM Re: Burn rate and barrel length [Re: Cleric]
RiverRider Offline
THF Trophy Hunter

Registered: 11/11/07
Posts: 6199
Loc: Wise Co.
I wish it was!! The QL database for powder is not up to the latest developments. I've been waiting for LT-32 to be added for several years now. And Ramshot Wild Boar?? I don't believe I've ever heard of it...but, CRS, ya know.

Yes, I thought your post in a recent thread that turned horribly ugly would make a good sig line. cheers
_________________________


Originally Posted By: Cleric
God I am hating caliber threads more and more

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#6178175 - 02/10/16 05:57 PM Re: Burn rate and barrel length [Re: Cleric]
Sneaky Offline
The "Grouch"

Registered: 10/22/12
Posts: 15874
Loc: Winters
I've learned quite a bit since I started paying attention to RiverRider.
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