HuntingNut
HuntingNut
   Login or Register
HomeCommunity ForumsPhoto AlbumsRegister
     
 

User Info

Welcome Anonymous


Membership:
Latest: RichardZ
New Today: 0
New Yesterday: 1
Overall: 13126

People Online:
Members: 0
Visitors: 332
BOT: 1
Total: 333
Who Is Where:
 Visitors:
01: Forums
02: Forums
03: Your Account
04: Forums
05: Home
06: Forums
07: Forums
08: Photo Albums
09: Forums
10: Forums
11: Forums
12: Forums
13: Forums
14: Forums
15: Forums
16: Forums
17: Photo Albums
18: Forums
19: Forums
20: Forums
21: Forums
22: Forums
23: Home
24: Your Account
25: Forums
26: Forums
27: Photo Albums
28: Forums
29: Forums
30: Photo Albums
31: Home
32: Forums
33: Home
34: Forums
35: Home
36: Forums
37: Forums
38: Forums
39: Forums
40: Forums
41: Forums
42: Forums
43: Photo Albums
44: Your Account
45: Home
46: Forums
47: Forums
48: Home
49: Your Account
50: Forums
51: Forums
52: Forums
53: Your Account
54: Your Account
55: Forums
56: Your Account
57: Forums
58: Forums
59: Your Account
60: Forums
61: Forums
62: Home
63: Forums
64: Photo Albums
65: Forums
66: Forums
67: Forums
68: Forums
69: Your Account
70: Home
71: Forums
72: Forums
73: Your Account
74: Forums
75: Photo Albums
76: Forums
77: Forums
78: Your Account
79: Forums
80: Forums
81: Photo Albums
82: Forums
83: Forums
84: Forums
85: Your Account
86: Forums
87: Forums
88: Forums
89: Home
90: Your Account
91: Forums
92: Your Account
93: Forums
94: Forums
95: Home
96: Forums
97: Forums
98: Forums
99: Forums
100: Your Account
101: Forums
102: Forums
103: Your Account
104: Forums
105: Forums
106: Forums
107: Forums
108: Your Account
109: Home
110: Forums
111: Forums
112: Forums
113: Forums
114: Forums
115: Forums
116: Forums
117: Forums
118: Home
119: Your Account
120: Home
121: Forums
122: Forums
123: Forums
124: Forums
125: Forums
126: Forums
127: Your Account
128: Forums
129: Forums
130: Home
131: Forums
132: Forums
133: Your Account
134: Forums
135: Forums
136: Forums
137: Forums
138: Forums
139: Your Account
140: Forums
141: Forums
142: Forums
143: Forums
144: Forums
145: Your Account
146: Forums
147: Photo Albums
148: Forums
149: Your Account
150: Forums
151: Your Account
152: Forums
153: Forums
154: Forums
155: Home
156: Home
157: Forums
158: Photo Albums
159: Forums
160: Forums
161: Photo Albums
162: Forums
163: Forums
164: Forums
165: Forums
166: Home
167: Your Account
168: Your Account
169: Forums
170: Home
171: Forums
172: Forums
173: Forums
174: Photo Albums
175: Forums
176: Forums
177: Photo Albums
178: Forums
179: Forums
180: Home
181: Forums
182: Photo Albums
183: Forums
184: Your Account
185: Forums
186: Forums
187: Forums
188: Forums
189: Photo Albums
190: Forums
191: Your Account
192: Forums
193: Forums
194: Forums
195: Forums
196: Home
197: Forums
198: Forums
199: Home
200: Forums
201: Forums
202: Forums
203: Forums
204: Photo Albums
205: Photo Albums
206: Forums
207: Forums
208: Forums
209: Photo Albums
210: Home
211: Your Account
212: Forums
213: Forums
214: Your Account
215: Forums
216: Your Account
217: Forums
218: Home
219: Your Account
220: Forums
221: Photo Albums
222: Forums
223: Photo Albums
224: Forums
225: Home
226: Forums
227: Forums
228: Photo Albums
229: Forums
230: Photo Albums
231: Forums
232: Forums
233: Forums
234: Forums
235: Forums
236: Forums
237: Forums
238: Your Account
239: Forums
240: Forums
241: Home
242: Forums
243: Forums
244: Forums
245: Forums
246: Photo Albums
247: Home
248: Forums
249: Photo Albums
250: Forums
251: Photo Albums
252: Your Account
253: Forums
254: Forums
255: Forums
256: Forums
257: Forums
258: Home
259: Forums
260: Forums
261: Your Account
262: Your Account
263: Forums
264: Forums
265: Your Account
266: Home
267: Forums
268: Home
269: Your Account
270: Forums
271: Photo Albums
272: Home
273: Your Account
274: Forums
275: Your Account
276: Forums
277: Forums
278: Forums
279: Forums
280: Forums
281: Photo Albums
282: Photo Albums
283: Forums
284: Your Account
285: Forums
286: Forums
287: Forums
288: Forums
289: Home
290: Home
291: Forums
292: Home
293: Forums
294: Forums
295: Forums
296: Forums
297: Forums
298: Forums
299: Photo Albums
300: Home
301: Forums
302: Home
303: Forums
304: Your Account
305: Your Account
306: Forums
307: Forums
308: Forums
309: Your Account
310: Forums
311: Forums
312: Forums
313: Forums
314: Forums
315: Forums
316: Forums
317: Home
318: Forums
319: Forums
320: Forums
321: Forums
322: Your Account
323: Forums
324: Forums
325: Forums
326: Your Account
327: Forums
328: Forums
329: Forums
330: Home
331: Forums
332: Forums
  BOT:
01: Forums

Staff Online:

No staff members are online!
 

Coppermine Stats
Photo Albums
 Albums: 308
 Pictures: 2451
  · Views: 820723
  · Votes: 1316
  · Comments: 86
 

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: 8314
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 Photo Gallery
Bushmaster
Super Member
Super Member


Joined: Jun 12, 2005
Posts: 11389
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: 5001
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: 4330
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: 8314
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 Photo Gallery
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: 1005
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: 1065
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: 8314
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 Photo Gallery
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


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* :.