HuntingNut
HuntingNut
   Login or Register
HomeCommunity ForumsPhoto AlbumsRegister
     
 

User Info

Welcome Anonymous


Membership:
Latest: Matt47
New Today: 0
New Yesterday: 1
Overall: 12785

People Online:
Members: 1
Visitors: 201
BOT: 1
Total: 203
Who Is Where:
 Members:
01: Bushmaster > Forums
 Visitors:
01: Forums
02: Home
03: Forums
04: Forums
05: Forums
06: Forums
07: Forums
08: Forums
09: Forums
10: Forums
11: Forums
12: Forums
13: Forums
14: Statistics
15: Home
16: Forums
17: Forums
18: Your Account
19: Statistics
20: Forums
21: Forums
22: Your Account
23: Home
24: Forums
25: Photo Albums
26: Forums
27: Forums
28: Forums
29: Forums
30: Forums
31: Forums
32: Home
33: Forums
34: Home
35: Forums
36: Forums
37: Forums
38: Forums
39: Statistics
40: Home
41: Photo Albums
42: Forums
43: Photo Albums
44: Forums
45: Home
46: Forums
47: Forums
48: Forums
49: Forums
50: Forums
51: Photo Albums
52: Forums
53: Home
54: Photo Albums
55: Home
56: Forums
57: Forums
58: Photo Albums
59: Forums
60: Forums
61: Forums
62: Forums
63: Your Account
64: Forums
65: Forums
66: Home
67: Forums
68: Home
69: Forums
70: Forums
71: Forums
72: Home
73: Home
74: Forums
75: Forums
76: Forums
77: Home
78: Forums
79: Forums
80: Your Account
81: Home
82: Home
83: Forums
84: Forums
85: Forums
86: Home
87: Home
88: Forums
89: Forums
90: Photo Albums
91: Forums
92: Home
93: Forums
94: Forums
95: Forums
96: Home
97: Forums
98: Your Account
99: Forums
100: Forums
101: Forums
102: Forums
103: Photo Albums
104: Forums
105: Forums
106: Forums
107: Forums
108: Forums
109: Forums
110: Forums
111: Forums
112: Photo Albums
113: Forums
114: Forums
115: Home
116: Forums
117: Forums
118: Forums
119: Forums
120: Forums
121: Forums
122: Forums
123: Forums
124: News
125: Forums
126: Forums
127: Forums
128: Photo Albums
129: Forums
130: Home
131: Forums
132: Forums
133: Forums
134: Forums
135: Photo Albums
136: Photo Albums
137: Forums
138: Forums
139: Forums
140: Photo Albums
141: Forums
142: Forums
143: Your Account
144: Photo Albums
145: Forums
146: Home
147: Forums
148: Forums
149: Forums
150: Forums
151: Home
152: Forums
153: Forums
154: Forums
155: Forums
156: Forums
157: Home
158: Forums
159: Forums
160: Forums
161: Home
162: Your Account
163: Forums
164: Forums
165: Forums
166: Forums
167: Photo Albums
168: Forums
169: Home
170: Forums
171: Forums
172: Forums
173: Forums
174: Forums
175: Forums
176: Forums
177: Forums
178: Forums
179: Forums
180: Home
181: Forums
182: Forums
183: Forums
184: Forums
185: Forums
186: Forums
187: Home
188: Forums
189: Forums
190: Forums
191: Home
192: Photo Albums
193: Forums
194: Forums
195: Home
196: Forums
197: Forums
198: Home
199: Forums
200: Forums
201: Forums
  BOT:
01: Forums

Staff Online:

No staff members are online!
 

Coppermine Stats
Photo Albums
 Albums: 307
 Pictures: 2392
  · Views: 621811
  · Votes: 1312
  · Comments: 86
 

Support our Advertisers

Bullet Velocity vs barrel clean or dirty
Discussions related to Guns and Firearms

View previous topic :: View next topic  
Author Message
slimjim
Super Member
Super Member


Joined: May 16, 2009
Posts: 8016
Location: Fort Worth TX

PostPosted: Fri Sep 11, 2009 5:07 am    Post subject: Bullet Velocity vs barrel clean or dirty Reply with quote

I have been trying to determine my bullet velocity for my 270 Win. I'm loading Barnes copper banded 110gr TTSX in front of 60.5 grains of IMR 4350. I don't have a chronograph yet so have been doing velocity estimation by shooting at 100 yards then deriving velocity from bullet drop at a longer range like 250 or 325 depending on the range I'm at. My first derived velocity was 3450 fps which is within a few feet of load manual data. Then one day while at the range, a shooter next to me let me use his chronograph. The first shot was 3410 fps and the next 3 were very close together at 3700 fps (I'm not showing signs of overpressure). The only difference between these shots were the first one was through a clean, unfouled barrel. I was skeptical of the higher velocities until I shot a few weeks later at 410 yards and 550 yards and my impacts were high. If I went back into the ballistic calculator with 3700 fps, the differences at both ranges were accounted for. Then last week I had the chance to do a derived velocity check at 100 and 325 yards and the group average was 3375. This time, however, the barrel hadn't been cleaned in 60 some rounds. I have not been getting much fouling at all with the Barnes bullets and a cleaning after this shooting session still showed little fouling (longest I have gone so far with this rifle). Thanks for getting through the background.

Has anyone experienced velocity changes based on a clean or fouled barrel? Other suggestions besides try another chronograph? I hope to be going back to the 325 yard range next week to repeat with a clean barrel.
Back to top
View user's profile
Bushmaster
Super Member
Super Member


Joined: Jun 12, 2005
Posts: 10837
Location: Ava, Missouri

PostPosted: Fri Sep 11, 2009 7:03 am    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

I do have a chronograph and see little difference in fps from a clean dry barrel or a several shot fouled barrel. Maybe +/- 50 to 100 fps difference. I do, however, notice that some of my rifles shoot better clean and some don't. Of course I don't clean after every shot so this is a flawed statement too.

_________________
I have one nerve left and yer standin' on it...

DEMOCRACY Two wolves and one sheep voting on what to have for lunch...
LIBERTY A well armed sheep contesting the outcome of the vote...
Back to top
View user's profile
chambered221
Super Member
Super Member


Joined: Aug 17, 2007
Posts: 3455
Location: Lost for good !!!

PostPosted: Fri Sep 11, 2009 8:32 am    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

Did you account for any head or tail winds that could affect POI ???
I find the 250-300fps jump to be odd regardless of a clean/dirty barrel!!!

_________________
Ask as many people needed, sooner or later your question will be answered the way you want it answered !!!

A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.
~George Washington
Back to top
View user's profile Photo Gallery
Pumpkinslinger
Super Member
Super Member


Joined: Sep 22, 2007
Posts: 4618
Location: NC foothills

PostPosted: Fri Sep 11, 2009 8:45 am    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

How many rounds are you firing at each distance? How are you measuring the changes in drop? If I understand correctly I don't think this method could give you much more that a ballpark figure because there are too many variables. Chronographs aren't all that expensive... Wink

_________________
Mike

"I ain't no better than anybody else, and there ain't nobody better than me!" Ma Kettle
Back to top
View user's profile AIM Address Yahoo Messenger Photo Gallery
stovepipe
Super Member
Super Member


Joined: Sep 25, 2008
Posts: 4877
Location: Pine, Az.

PostPosted: Fri Sep 11, 2009 11:00 am    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

I've read some barrles can "shoot into a sweet spot" improving or affecting accruacy and consistency. (kinda off topic, I know....)

It made sense to me. Just as some barrels/guns like a particular load over others.

Anyone else read this or something like it?
Back to top
View user's profile
PaulS
Super Member
Super Member


Joined: Feb 18, 2006
Posts: 3913
Location: South-Eastern Washington - the State

PostPosted: Fri Sep 11, 2009 2:00 pm    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

All gun barrels undergo a resonant vibration when shooting. This means the barrel is whipping - sometimes in a rotary motion - on each shot. If the bullet exits the barrel closer to the Peak (high or low and right or left) then small variations don't change your point of impact. If they exit in the middle of the whip - when the barrel is moving faster then even small variations can change the point of impact a lot.

When I work up a load I find the most consistent round over a few months of testing and tuning the loads. Then I get the chronograph out and check the velocity so I can work up ballistics tables. That is how I get sub MOA groups (sometimes sub-caliber) consistently.

_________________
Paul
__________________
Speer, Lyman, Hodgdon, Sierra, and Hornady = reliable loading data
So and So's pages on the internet = NOT reliable loading data
Always check data against manuals
NEVER exceed maximum listed loads
Back to top
View user's profile Send e-mail
chambered221
Super Member
Super Member


Joined: Aug 17, 2007
Posts: 3455
Location: Lost for good !!!

PostPosted: Fri Sep 11, 2009 2:16 pm    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

Good point Paul!!! I believe we had a discussion on this a long time ago???

_________________
Ask as many people needed, sooner or later your question will be answered the way you want it answered !!!

A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.
~George Washington
Back to top
View user's profile Photo Gallery
stovepipe
Super Member
Super Member


Joined: Sep 25, 2008
Posts: 4877
Location: Pine, Az.

PostPosted: Fri Sep 11, 2009 2:27 pm    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

Those are really cool fine points and I've only read about them....
Back to top
View user's profile
slimjim
Super Member
Super Member


Joined: May 16, 2009
Posts: 8016
Location: Fort Worth TX

PostPosted: Fri Sep 11, 2009 3:12 pm    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

Pumpkinslinger wrote:
How many rounds are you firing at each distance? How are you measuring the changes in drop? If I understand correctly I don't think this method could give you much more that a ballpark figure because there are too many variables.

Sight your rifle in for 100 yards and verify with a 3-shot group. Reposition to 325 yards (max distance at the range I shot) and shoot at least 3 shots and measure bullet drop. Bullet drop was -10.9 inches. Go to your ballistic program and change velocity to match bullet drop. If you BC is good, there is no reason that this should not be an effective way to measure velocity.


Wind only changes left-right impact with any significance which doesn't affect a velocity measurement. The rifle/load is shooting about a 1/2 MOA so there isn't much variation in impact. Last 3-shot group at 325 yards was an inch. One of the groups had a vertical variation of only 0.25 inches which should be an indication of consistent velocity. I'm suspect of the chronograph I used. I definitely need to collect more data at longer distances.

Chronographs have gotten fairly inexpensive though I'm not sure I have room for one more thing in my garage.
Back to top
View user's profile
fnuser
Super Member
Super Member


Joined: Dec 23, 2008
Posts: 914
Location: S.W. Missouri, U.S.A.

PostPosted: Sat Sep 12, 2009 3:07 pm    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

Pumpkins right, 325 fps difference isn't where it is. I've chrony'd new barrels that have never been fired from hart, and virgin clean to dirty you could account for maybe 100 but even that is stretching. if you like doing math recalculate the difference in velocity as it is related to pressure and see how much pressure would be required to gain that 325 f.p.s. As you probably know since this is a diminishing return it would take quite a bit.

_________________
N.R.A. Endowment Member
Back to top
View user's profile Photo Gallery
Donut Slayer
Super Member
Super Member


Joined: Jun 27, 2007
Posts: 594
Location: Pensacola, Florida

PostPosted: Sun Sep 13, 2009 9:30 am    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

PaulS wrote:
All gun barrels undergo a resonant vibration when shooting. This means the barrel is whipping - sometimes in a rotary motion - on each shot. If the bullet exits the barrel closer to the Peak (high or low and right or left) then small variations don't change your point of impact. If they exit in the middle of the whip - when the barrel is moving faster then even small variations can change the point of impact a lot.

When I work up a load I find the most consistent round over a few months of testing and tuning the loads. Then I get the chronograph out and check the velocity so I can work up ballistics tables. That is how I get sub MOA groups (sometimes sub-caliber) consistently.
Thats how i do it too. Work for accuracy first then get the tables for the velocity later.

_________________
Browning X-Bolt in 30'06. The work for a pet load starts again. Wink The more people I meet, the more I like my dog.
Back to top
View user's profile Send e-mail
chambered221
Super Member
Super Member


Joined: Aug 17, 2007
Posts: 3455
Location: Lost for good !!!

PostPosted: Sun Sep 13, 2009 4:17 pm    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

Been thinking about them 3700fps readings!!!

It is entirely possible that a shadow has caused the second pickup to trip early giving you false readings!!!
One thing that I learned early on with chronographs is that any time you get a reading that don’t seem right or no reading at all it can usually be tracked down to a lighting issue. That’s one of the reasons light kits are available for the better units.
If the sun was low and angling in from the back it could cause a shadow that trips the unit before the bullet actually passes over. I’ve personally had this happen while shooting a 9mm.
wtf I was getting velocities just over 1200fps with a 147gr bullet. It wasn’t until a cloud covered the sun and velocity showed 850fps that I realized what was going on. I moved the unit to another shooting bench and proceeded with my testing.

When using a chrono it’s best to obtain data over multiple shot strings and even multiple days to get a true average.

_________________
Ask as many people needed, sooner or later your question will be answered the way you want it answered !!!

A free people ought not only to be armed and disciplined, but they should have sufficient arms and ammunition to maintain a status of independence from any who might attempt to abuse them, which would include their own government.
~George Washington
Back to top
View user's profile Photo Gallery
SingleShotLover
Super Member
Super Member


Joined: Dec 26, 2007
Posts: 999
Location: Illinois

PostPosted: Mon Sep 14, 2009 5:00 am    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

It stands to reason that shots from a fouled barrel might be slightly higher than from clean barrels simply because of the fouling causing slightly higher pressure...but the differences should only be in the statistical range and certainly not around 300 fps difference. I agree with 221 that you need a wider range of results before relying on your original readings.

_________________
If you can't hit it with one, you probably can't with two either!

The biggest problem with a closed mind is that it never seems to come with a closed mouth.

SSL
Back to top
View user's profile Photo Gallery
Dawgdad
Super Member
Super Member


Joined: Feb 08, 2006
Posts: 1059
Location: On the Prairie

PostPosted: Mon Sep 14, 2009 6:48 am    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

chambered221 wrote:
Good point Paul!!! I believe we had a discussion on this a long time ago???

still fresh in my mind... Shocked

_________________
Alcohol, Tobacco and Firearms should be a convenience store, not a government agency...
Back to top
View user's profile Photo Gallery
slimjim
Super Member
Super Member


Joined: May 16, 2009
Posts: 8016
Location: Fort Worth TX

PostPosted: Sat Sep 19, 2009 2:47 pm    Post subject: Re: Bullet Velocity vs barrel clean or dirty Reply with quote

I went out yesterday and refired at 325 yards with a clean barrel. There was no noticeable change in impact point, thus no difference in velocity. The new groups printed exactly over the old. Thanks for the feedback.
Back to top
View user's profile
Display posts from previous:   
Post new topic   Reply to topic   Printer Friendly Page    Forum Index » Gun & Firearm Discussions
Page 1 of 1
All times are GMT - 7 Hours



Jump to:  


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


Advertisements
 


Valid CSS! Valid HTML 4.01!
Click to check if this page is realy HTML 4.01 compliant for speed :)

All logos and trademarks in this site are property of HuntingNut.com.
The comments are property of their posters, all the rest © 2011 by HuntingNut.com
Interactive software released under GNU GPL, Code Credits, Privacy Policy

.: Upgraded to DragonFly 9.2 by Dizfunkshunal :.