Hot barrel affect velocity?

MightyMO1911 · May 23, 2015, 07:24 PM

I had an excellent day of procurement today. I found some things I haven't seen in several years. 22 ammo for one. I got some Unique, Green Dot, Varget, some Nosler bullets and a really sweet deal on skme Barnes 30 caliber bullets. But I digress.

So now that I have Varget and more bullets, I am going to work up a deer hunting load for my 30-06. Here is my question.

Does a hot barrel have any effect on velocity? I am going to be running quite a few of these downrange and I am curious if I need to allow the barrel to cool down between shots.

603Country · May 23, 2015, 08:01 PM

Let it cool. If it's too hot to hold your hand on it, it's too hot.

olddav · May 23, 2015, 08:15 PM

If your goal is to develop a hunting round you need to keep the barrel cool. After all when you take a shot at game the barrel will be cold. Does a hot barrel effect velocity? I would think it would but I have no idea how.

1100 tac · May 23, 2015, 09:42 PM

Some of our men that have to really reach out and kill someone over in the sandbox, leave their ammunition sitting in the sun for a period of time to get it hot for a little more chamber pressure=a little more velocity=a little more range.

Yes a hot bbl affects velocity, esp if a round has been in the chamber of the hot bbl long enough to heat it up.

For a quick follow up shot while hunting, will not have much effect on velocity.

Unless you are being attacked by a whole bunch of well armed bunny rabbits you shouldn't have to do a mag dump, which might get your bbl hot enough to change things...

However, if I found myself at a really "busy" dog town, I would probably let my bbl cool a little after five or so shots...YMMV.

**Unclenick** · May 23, 2015, 09:48 PM

Yes, except that Varget is one of the Hodgdon Extreme powders that is temperature compensated so the pre-baking trick shouldn't have any effect on it. Hot barrels do, however, get beyond that temperature compensation range and tend to make primers run warmer, to boot, so yes, it can increase velocity.

This article by board member Denton Bramwell illustrates the effect and limitations of powder burn rate stability in preventing it.

skizzums · May 23, 2015, 09:59 PM

I have only one large rifle caliber, 54r, so I don't have a wealth of knowledge. but even after 10-15 rounds I start to vertical string unless I let it set for a few. it's immediately noticeable when the heat starts to affet accuracy. velocity? I am not sure it would be significant, but I think you are speaking in terms of working up an accurate load.

MightyMO1911 · May 23, 2015, 10:21 PM

Fantastic article. Thank younfor sharing that.

So it appears that while I am running these rounds over my chronograph to see which charge is the most consistent, I need to shoot rather slowly and allow the bbl to cool between shots. I will not be able to maintain a constant bbl temperature variation as tight as those in the aforementioned article, but I certainly can prevent the bbl from getting "hot" and increasing the velocity appreciably. I am looking for the most consistent velocities and when that is discovered, I will more seriously put that load on paper for sighting in and accuracy.

I have a stock, standard hunting rifle and while I do want the load to be as consistent and accurate as possible, I will be quite happy with MOA groups, and slightly sub-MOA would just tickle me to no end. My rifle simply isn't capable, I don't believe, of half MOA so I need to keep this realistic. And MOA groups I believe, are.

Thank you for the replies thus far. All very informative.

May 23, 2015, 07:24 PM	#1
MightyMO1911 Senior Member Join Date: February 8, 2014 Posts: 122	Hot barrel affect velocity? I had an excellent day of procurement today. I found some things I haven't seen in several years. 22 ammo for one. I got some Unique, Green Dot, Varget, some Nosler bullets and a really sweet deal on skme Barnes 30 caliber bullets. But I digress. So now that I have Varget and more bullets, I am going to work up a deer hunting load for my 30-06. Here is my question. Does a hot barrel have any effect on velocity? I am going to be running quite a few of these downrange and I am curious if I need to allow the barrel to cool down between shots.

May 23, 2015, 08:15 PM	#3
olddav Senior Member Join Date: December 21, 2008 Location: Lower Alabama Posts: 727	If your goal is to develop a hunting round you need to keep the barrel cool. After all when you take a shot at game the barrel will be cold. Does a hot barrel effect velocity? I would think it would but I have no idea how. __________________ Never beat your head against the wall with out a helmet

May 23, 2015, 09:48 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,057	Yes, except that Varget is one of the Hodgdon Extreme powders that is temperature compensated so the pre-baking trick shouldn't have any effect on it. Hot barrels do, however, get beyond that temperature compensation range and tend to make primers run warmer, to boot, so yes, it can increase velocity. This article by board member Denton Bramwell illustrates the effect and limitations of powder burn rate stability in preventing it. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

May 23, 2015, 09:59 PM	#6
skizzums Senior Member Join Date: July 1, 2013 Location: Douglasville, Ga Posts: 4,615	I have only one large rifle caliber, 54r, so I don't have a wealth of knowledge. but even after 10-15 rounds I start to vertical string unless I let it set for a few. it's immediately noticeable when the heat starts to affet accuracy. velocity? I am not sure it would be significant, but I think you are speaking in terms of working up an accurate load. __________________ My head is bloody, but unbowed

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May 23, 2015, 08:01 PM	#2
603Country Senior Member Join Date: January 6, 2011 Location: Thornton, Texas Posts: 3,996	Let it cool. If it's too hot to hold your hand on it, it's too hot.

May 23, 2015, 09:42 PM	#4
1100 tac Senior Member Join Date: February 7, 2012 Posts: 299	Some of our men that have to really reach out and kill someone over in the sandbox, leave their ammunition sitting in the sun for a period of time to get it hot for a little more chamber pressure=a little more velocity=a little more range. Yes a hot bbl affects velocity, esp if a round has been in the chamber of the hot bbl long enough to heat it up. For a quick follow up shot while hunting, will not have much effect on velocity. Unless you are being attacked by a whole bunch of well armed bunny rabbits you shouldn't have to do a mag dump, which might get your bbl hot enough to change things... However, if I found myself at a really "busy" dog town, I would probably let my bbl cool a little after five or so shots...YMMV.

May 23, 2015, 10:21 PM	#7
MightyMO1911 Senior Member Join Date: February 8, 2014 Posts: 122	Fantastic article. Thank younfor sharing that. So it appears that while I am running these rounds over my chronograph to see which charge is the most consistent, I need to shoot rather slowly and allow the bbl to cool between shots. I will not be able to maintain a constant bbl temperature variation as tight as those in the aforementioned article, but I certainly can prevent the bbl from getting "hot" and increasing the velocity appreciably. I am looking for the most consistent velocities and when that is discovered, I will more seriously put that load on paper for sighting in and accuracy. I have a stock, standard hunting rifle and while I do want the load to be as consistent and accurate as possible, I will be quite happy with MOA groups, and slightly sub-MOA would just tickle me to no end. My rifle simply isn't capable, I don't believe, of half MOA so I need to keep this realistic. And MOA groups I believe, are. Thank you for the replies thus far. All very informative.