HuntingNut
HuntingNut
   Login or Register
HomeCommunity ForumsPhoto AlbumsRegister
     
 

User Info

Welcome Anonymous


Membership:
Latest: Sarvo
New Today: 0
New Yesterday: 0
Overall: 12586

People Online:
Members: 1
Visitors: 60
BOT: 2
Total: 63
Who Is Where:
 Members:
01: Bushmaster > Home
 Visitors:
01: Forums
02: Forums
03: Forums
04: Forums
05: Forums
06: Forums
07: Forums
08: Home
09: Forums
10: Forums
11: Forums
12: Forums
13: Forums
14: Forums
15: Forums
16: Forums
17: Forums
18: Forums
19: Forums
20: Forums
21: Forums
22: Forums
23: Home
24: Forums
25: Forums
26: Forums
27: Forums
28: Forums
29: Forums
30: Forums
31: Forums
32: Forums
33: Forums
34: Forums
35: Forums
36: Forums
37: Forums
38: Forums
39: Forums
40: Home
41: Forums
42: Forums
43: Forums
44: Forums
45: Forums
46: Forums
47: Forums
48: Home
49: Forums
50: Forums
51: Forums
52: Forums
53: Forums
54: Forums
55: Forums
56: Home
57: Forums
58: Forums
59: Forums
60: Forums
  BOT:
01: Forums
02: Forums

Staff Online:

No staff members are online!
 

Coppermine Stats
Photo Albums
 Albums: 305
 Pictures: 2358
  · Views: 358003
  · Votes: 1306
  · Comments: 85
 

Support our Advertisers

Bullet Jump vs Pressure vs Velocity?
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
Post new topic   Reply to topic   Printer Friendly Page    Forum Index » Reloading Ammunition

View previous topic :: View next topic  
Author Message
Victorian
Member
Member


Joined: Jul 07, 2014
Posts: 29
Location: Melbourne

PostPosted: Sun Jul 06, 2014 7:46 pm    Post subject: Bullet Jump vs Pressure vs Velocity? Reply with quote

I hope someone with a chonograph can help clear something up for me. I have a 7.62x51 ex-Israeli 98k Mauser (sporterised) that was showing pressure signs with some (not all) Winchester factory ammo (slightly stiff bolt lift, bright extractor mark on head). Doing some investigation it turns out this rifle has a short throat and factory ammo in/on the lands. (Headspace is also on the long side of 308W spec, but in spec)

So I have seated my factory ammo 100 thou deeper and I have been making my reloads about 100 thou off the lands and all is OK with compressed loads of Varget (AR2208) and 150gn Hornady SPBT.

I'm curious what this will this do to velocity (not that a fallow deer will care)? I read some places velocity can drop by 100fps or more. Other references show negligible drop in velocity. Not having a chronograph myself, when I get a chance I was thinking of comparing point of impacts at 100yds & 300yds to get an estimate of velocity variations.

Has anyone already tested velocity & seating depth?

I'm not too worried about extreme accuracy (getting about 1 moa @ 100yds - again a fallow deer won't care). Would seating say 50 thou off the lands (and not crunching my powder so much) get better velocity without too much more pressure? How close to the lands does pressure start increasing?

(attached pic is Win factory Power Point 150 gn)

_________________
Ne Obliviscarus
Never Forget (1996)
Back to top
View user's profile
tikkat3
Super Member
Super Member


Joined: Jul 30, 2006
Posts: 709

PostPosted: Sun Jul 06, 2014 8:53 pm    Post subject: Re: Bullet Jump vs Pressure vs Velocity? Reply with quote

I've just started playing around with one and have some averages for a 375H&H
3.5" 2856fps
3.6" 2885fps
3.7" 2887fps
Lands 3.8"
Back to top
View user's profile
slimjim
Super Member
Super Member


Joined: May 16, 2009
Posts: 7471
Location: Fort Worth TX

PostPosted: Sun Jul 06, 2014 8:55 pm    Post subject: Re: Bullet Jump vs Pressure vs Velocity? Reply with quote

www.huntingnut.com/ind...c&start=15

Victorian, I usually run my lead-core bullets about 0.015" off the lands and my monolithic copper bullets about 0.050" off the lands. At the bottom of the page in the link above you will find some testing I did on changes in seating depth and the impact to pressure and velocity. This was for my 6.8mm SPC II. Pressure did increase getting closer to the land for most of the bullets. I also found situations were pressure increased with a shorter COAL. And the bullets from GS Custom didn't change pressure with COAL. From this experience, I would postulate that there is a COAL where pressure is lowest and, if COAL is decreased or increased, pressure with increase.

_________________
"To anger a conservative, lie to him. To anger a liberal, tell him the truth." - Theodore Roosevelt

"The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it." - Albert Einstein
Back to top
View user's profile
Victorian
Member
Member


Joined: Jul 07, 2014
Posts: 29
Location: Melbourne

PostPosted: Sun Jul 06, 2014 9:40 pm    Post subject: Re: Bullet Jump vs Pressure vs Velocity? Reply with quote

Thanks Slimjim,

With your 120g Hornady SST's what is the COAL touching the lands?

_________________
Ne Obliviscarus
Never Forget (1996)
Back to top
View user's profile
slimjim
Super Member
Super Member


Joined: May 16, 2009
Posts: 7471
Location: Fort Worth TX

PostPosted: Mon Jul 07, 2014 6:43 am    Post subject: Re: Bullet Jump vs Pressure vs Velocity? Reply with quote

Victorian, this is for my 6.8mm 18" ARP barrel with has less freebore than the standard SAAMI chamber.

120 Hornady SST__2.358”

95 Barnes TTSX___2.375”
110 Barnes TSX___2.438”
110 Hornady BTHP_2.335”
115 Nosler Custom_2.325”
120 Fusion MSR____2.475”
130 Nosler Partition_2.450"
130 Berger VLD_____2.475”
130 Hornady SST___2.485”
130 Nosler BT______2.505”
150 Nosler AB LR___2.560”

_________________
"To anger a conservative, lie to him. To anger a liberal, tell him the truth." - Theodore Roosevelt

"The world is a dangerous place to live; not because of the people who are evil, but because of the people who don't do anything about it." - Albert Einstein
Back to top
View user's profile
Display posts from previous:   
Post new topic   Reply to topic   Printer Friendly Page    Forum Index » Reloading Ammunition
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 :.