User Panel
User Panel
User Panel
|
Posted: 7/24/2013 9:55:14 AM EDT
[#1]
There seems to be a lot more misinformation, half-truths, and general guessing going on in this forum as of late.
|
|
|
|
Posted: 7/24/2013 9:59:30 AM EDT
[#2]
He was probably speaking along the lines of taking the bullet off of the lands of the rifling.
If a bullet is loaded right on the lands, it will generally have higher pressure than one that is loaded so there is a gap. All generally speaking of course. |
|
|
|
Posted: 7/24/2013 10:06:00 AM EDT
[#3]
Quote HistoryQuoted:
He was probably speaking along the lines of taking the bullet off of the lands of the rifling. If a bullet is loaded right on the lands, it will generally have higher pressure than one that is loaded so there is a gap. All generally speaking of course. Yup. THIS! Typically a non issue in most factory barrels with a 5.56 chamber.... there's a lot of leade already... so going shorter would give a little more pressure, I'd guess. |
|
|
|
Posted: 7/24/2013 10:13:46 AM EDT
[#4]
Quote HistoryQuoted:
He was probably speaking along the lines of taking the bullet off of the lands of the rifling. If a bullet is loaded right on the lands, it will generally have higher pressure than one that is loaded so there is a gap. All generally speaking of course. |
|
|
|
Posted: 7/24/2013 10:23:45 AM EDT
[#5]
Just look at the freebore in a Weatherby, that's how they can get such higher velocities. Freebore = longer throat.
Pressure goes down with a longer throat IN RIFLE ONLY Try that with a shorter freebore, and you have problems. Look up freebore |
|
|
|
Posted: 7/24/2013 10:32:18 AM EDT
[#6]
You are confusing straight sided pistol rounds and bottle neck rifle rounds as acting the same. The rules are different for each. Generally, with straight wall pistol rounds, pressure increases with a shorter OAL. Bottle neck rifle rounds with much greater internal capacity will be the opposite. |
|
|
|
Posted: 7/24/2013 2:06:54 PM EDT
[#7]
Quote HistoryQuoted:
You are confusing straight sided pistol rounds and bottle neck rifle rounds as acting the same. The rules are different for each. Generally, with straight wall pistol rounds, pressure increases with a shorter OAL. Bottle neck rifle rounds with much greater internal capacity will be the opposite. And This from John Barsness of Rifle/Handloader Magazine. It decreases peak pressure, for two reasons. The longer "jump" of the bullet to the rifling results in a lower peak pressure, since the bullet engraves more easily the faster it's going when it hits the rifling. Also involved is the "progressive" burning of almost all modern rifle powders. This means the pressure increases relatively slowly from the time of ignition. Thus peak pressure occurs when the bullet beyond the barrel throat, with very slow-burning powders as much as 3-4 inches. Here are a couple graphs as well. 
|
|
|
|
Posted: 7/24/2013 2:38:28 PM EDT
[#8]
Read the last few paragraphs on Hornday's internal ballistics page.
Freebore I have a manual of theirs from the 70's with the same pictures, guess the concept hasn't changed. In general, the deeper the oal on pistol rounds the more pressure, the opposite is true with rifle rounds to an extent. |
|
|
|
Posted: 7/25/2013 7:21:44 AM EDT
[#9]
Great info, thanks everyone. Now I understand the OAL/ leade/pressure relationship.
|
|
|
|
Posted: 7/25/2013 7:48:50 AM EDT
[#10]
Quote HistoryQuoted:
Great info, thanks everyone. Now I understand the OAL/ leade/pressure relationship. Remember, this "relationship" pertains to Bottle Necked rifle rounds and not straight walled pistol rounds. |
|
|
|
Posted: 7/25/2013 10:33:25 AM EDT
[#11]
Quoted:
In a different thread, writer stated going from 2.26" OAL to 2.24" would actually REDUCE pressure. How can this be? Shorter OAL equals lower capacity, which I understand to mean higher pressure with same load. Isn't lower capacity the reason we reduce load with mil spec brass, especially in 7.62? It depends on who you talk to. For a constant jump to land distance (free bore flight distance) the smaller the case volume for a given amount of powder, the higher the chamber pressure. For a constant boltface-to-land distance the smaller case volume translates into a longer free bore flight or jump to land and may translate into a lower pressure because there is no rifling resistance in the free bore travel of the projectile. |
|
|
Win a FREE Membership!
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.
