Barrel Length and Chamber Pressure

[Allen Kitts]

Gents,
I got some load data to day for a new rifle and when the gentleman gave me the info he made a point of making sure I understood it was for a 26" barrel. I am not new to the game but by no means no anywhere near as much as I would like to know about reloading so I am posing the question. Does barrel length have anything to do with chamber pressure. If I use the load data in a rifle with a 24" barrel would there be any issues?

 

[Mikecr]

Not that I've ever heard of.
I don't see how, other than the possibility of a secondary pressure peak due to extreme muzzle pressures kicking back. This, an anomaly with barrels too short for load.
An example seen/described here: https://www.shootingsoftware.com/pressure.htm

 

[Orange Dust]

Gents,
I got some load data to day for a new rifle and when the gentleman gave me the info he made a point of making sure I understood it was for a 26" barrel. I am not new to the game but by no means no anywhere near as much as I would like to know about reloading so I am posing the question. Does barrel length have anything to do with chamber pressure. If I use the load data in a rifle with a 24" barrel would there be any issues?

You should never use load data from someone else's rifle. If someone has a pet load you would like to try, you can use the same components, a reloading book and work up to it. Throat length and condition, actual barrel diameter, type and twist of rifling all affect pressure. Barrel length usually affects velocity more than pressure unless the powder is too slow for the combination, then some nasty spikes can occur. If you are new to reloading stay with the book, and pick a powder in the middle of burning range of the powders listed.

 

[Allen Kitts]

You should never use load data from someone else's rifle. If someone has a pet load you would like to try, you can use the same components, a reloading book and work up to it. Throat length and condition, actual barrel diameter, type and twist of rifling all affect pressure. Barrel length usually affects velocity more than pressure unless the powder is too slow for the combination, then some nasty spikes can occur. If you are new to reloading stay with the book, and pick a powder in the middle of burning range of the powders listed.

Load Data was from Berger Bullets:

 

[lancetkenyon]

How about supplying the load data and we can help more. I have gotten some really weird responses from Berger when requesting load data.
They straight up told me last year, they had no load data for 6 Creed w. H4350 and 105 Hybrids.

 

[Allen Kitts]

The gentleman I got the info from was very helpful and offered up lots of great info. He did also give me some velocities for min load and max load so maybe that is the reason for stressing the barrel length. Just wanted to make sure that I did not go with the loading information and have an issue.

 

[Orange Dust]

The gentleman I got the info from was very helpful and offered up lots of great info. He did also give me some velocities for min load and max load so maybe that is the reason for stressing the barrel length. Just wanted to make sure that I did not go with the loading information and have an issue.

You should be golden. Be careful

 

[Allen Kitts]

300 PRC
Berger 215 Grain Hybrid
84.1 Grains of H1000 (Max Load)
COAL 3.700
The main reason for my questions is this is way over the max load put out by Hornady for the 212 Grain ELDX for H-1000 and after I loaded the rounds I had second thoughts. I know different bullets will react differently but I just wanted to get some outside knowledge before I pulled the trigger. The starting load was 80 grains so I loaded three each going up in half grain increments to see where the pressure signs will start.

 

[J E Custom]

Barrel length has the most effect on velocity. Pressure is at its max if all of the powder is consumed in the barrel. Added barrel length will increase the time the bullet spends with pressure applied but at some length the pressure has peeked and will not increase. Normally max pressure is reached at near 2/3 thirds to 3/5 of the barrel length if it is an efficient load.

If the barrel is to long the velocity gain per inch becomes less at some point because the powder has been consumed and pressure is starting to drop. Velocity will/can continue to increase, but at a lower rate. Theoretically, At some point the velocity will start to slow down if the barrel is long enough. This happens all the time on cartridges that have very small powder charges (Like the 22 LRs)

Depending on powder burn rates and volume this will occur at different barrel lengths. Go with the standard load data and start in the middle of the pressure range and you will be fine. The 2 extra inches will only increase the velocity listed if it was tested with a 24" barrel.

J E CUSTOM

 

[Allen Kitts]

JE , thanks for the info. I was wondering if you could tell me that if I cannot get the COAL of 3.700" that Berger specified, as it will not fit into my magazine, and my COAL is like 3.620 will that change the pressure?

 

[Orange Dust]

JE , thanks for the info. I was wondering if you could tell me that if I cannot get the COAL of 3.700" that Berger specified, as it will not fit into my magazine, and my COAL is like 3.620 will that change the pressure?

Yes it will. Most likely MAX will be lower. Start with the starting load and work up!!!

 

[cohunt]

A 215 hybrid is nothing like a 212 eldx-- they have different ogives, jacket thicknesses, lead hardness, and bearing length - all those things can/will affect engraving force which does affect pressure, brass and primers are a consideration also--- that is why the best load data usually comes from the bullet manufacture 1st, then powder manufacture 2nd. And you start low and work up, so you can see those pressure signs- as they develop in your particular firearm

 

[Allen Kitts]

Thanks guys I appreciate the input.

 

[cohunt]

FYI-- berger has full bullet specs on each bullet on their web page

the 215 had a OAL of 1.598 and a bearing length of .529 , Boat tail is .280 and nose is .859"

harder to find the dimensions of the Hornady bullets but the 212 is 1.61" oal, with a bearing length of .626 -- and the eld-x bullet has a thicker jacket IIRC in addition to the "internal locking band" which makes it have a greater engraving force than the bergers

that is one reason why those 215's are such a good option as the bearing length is quite a bit shorter than other brands in the same weight category-- so they can be driven as fast as a 200 grain bullet from other manufactures