Oddball pressure

multistage · March 8, 2007, 03:00 AM

Hello to all, this is my first post. I was breaking in a 22-250 today. I used a fairly mild load of a 55 grain Ballistic Tip and 38 grains of 760. Sticky bolt, shaved head brass, the works. Velocity, however, was low at 3350 fps, average. I think I may have seated the bullets out too far, but shouldn't a spike in pressure give a higher velocity? I used to run the same bullet and 39 grains in another rifle I had. Speed was 3550 fps, cases lasted forever. If my speed was higher I could understand it, but pressure with low speed has me scratching my head. Any suggestions would be appreciated.

Foxman · March 8, 2007, 03:31 AM

Newer tighter barrel, chamber etc, always start lower and work up. the load Winchester quote is for the speer bullet, the Nosler is a boattail which takes up more case room. It sure is telling you things are too hot.
Nosler dont give a load for 760 with this bullet only for the 40gr maybe they know something.
The most accurate load they quote is for H380 start load 31.5 and max ( most accurate) 35.5grs, win wlr primer, win case.
Give it a go may turn out a tack driver.

Scorch · March 9, 2007, 12:54 PM

Sounds like you may have seated the bullet too far out, or you have too little powder and are getting detonation. With that load, you are getting very good velocity, probably due to whatever is causing the high pressure problem. I load the same bullet, use very close to the max load out of Hornady's reloading manual (several grains above your load), seat the bullets to max OAL, and never have pressure problems. And it is an accurate load, on top of all that.

I have found that most of my .22 centerfire rifles shoot best at just below maximum load. Don't know why or how. Don't care why or how. I just enjoy it.

Ruger4570 · March 9, 2007, 10:40 PM

If you think you seated the bullets out too far, you just might have. In a gun, thing happen very fast, and a bullet lodged against the rifling can raise pressure very quickly, at least til it overcomes the resistance. I generally give my bullets a .10 of freebore and some require a bit more. If you were using lead bullets, it probably wouldn't make much difference due to the softness of the lead. You certainly need to figure out what is wrong as you seem to be getting some REALLY high pressure signals. There is always the possibility it is simply the gun not liking the loads but I have a feeling it is more from no "run up" room for the bullet.

**Unclenick** · March 10, 2007, 03:54 PM

A really common cause of pressure is a component change. If you worked your original load up with Winchester brass, which is typically light on brass and roomy, then switched to almost any other brand, you will need less powder to hit the same pressure, but will get less velocity.

Note that a tighter chamber will do the same thing. Peak pressure in guns firing above around 30,000 PSI, will depend on chamber dimensions rather than re-sized brass dimensions. Compare the water capacity of a fired case from the new gun with one from the old gun. If it is lower, then less powder is needed to hit the same pressure numbers.

QuickLOAD shows a case with 43.5 grains of water capacity is 98.1% filled with your 760 load when that Nosler bullet is seated to an OAL of 2.350". Peak pressure is just below 50.000 PSI. Muzzle velocity is predicted to be 3523 fps from a 24" barrel and 3597 fps from a 26" barrel. It also shows a lot of unburned powder (8% and 7%, for the respective barrel lengths), and high muzzle pressure (10,000 PSI range). Ballistic efficency is 21.5% and 22.4%, respectively.

Calculations show the same peak pressure will actually give you 10 or 15 fps more velocity and over 25% efficiency using 32.0 grains of IMR 3031.
A more newly identified phenomenon, secondary muzzle pressure, can occur when too slow a powder is paired with too light a bullet. Unlike detonation, which is hard to reproduce, Texas gunsmith Charlie Sisk had been able to blow muzzles off barrels with regularity deomonstrating this pheonomenon. It often is undetected at the breech, but RSI's web site has pressure traces that show it on a strain gauge at the rear of the barrel, so apparently it can show up there. Moreover, since faster 3031 will actually do better in your gun with that bullet, there is no point in taking the risk.

Trapper L · March 11, 2007, 12:37 PM

I'm with Unclenick on this on. I have had issues with pressure spikes using 760 powder and relatively light bullets. In my 6.5x 06, my middle of the road loads will show primers with the same load from showing rounded edges and normal to flat and falling out of the primer pocket. The 760 powder is not a favorite at my house. I would suggest a different powder.

multistage · March 12, 2007, 02:59 PM

This is my fifth 22-250, and I have always used Winchester brass, Federal 210 primers, 55 grain Nolser BT's, and 760. A load I am fond of is 39 grains of 760. 3550 fps, cases lasted forever. This is also a virgin rifle. The books say a guy can go up to 40-41 grains of powder, but I don't like to hotrod my rifles. I believe I have seated the bullets out too far. I used a Stoney Point gauge and took off about .020. However, the books seat bullets quite a bit deeper than 2.500. They go with 2.37. I reseated the test loads to 2.410 and will give them a try.

Scorch · March 12, 2007, 07:00 PM

I have used 760 in my 22-250 for over 20 years. I used to load IMR3031, but switched due to the issues loading rod-shaped powders. In my rifle, 40.4 gr of WW760 with a 55 gr bullet is accurate and shows no pressure signs.

March 8, 2007, 03:00 AM	#1
multistage Member Join Date: March 8, 2007 Location: Wyoming Posts: 25	Oddball pressure Hello to all, this is my first post. I was breaking in a 22-250 today. I used a fairly mild load of a 55 grain Ballistic Tip and 38 grains of 760. Sticky bolt, shaved head brass, the works. Velocity, however, was low at 3350 fps, average. I think I may have seated the bullets out too far, but shouldn't a spike in pressure give a higher velocity? I used to run the same bullet and 39 grains in another rifle I had. Speed was 3550 fps, cases lasted forever. If my speed was higher I could understand it, but pressure with low speed has me scratching my head. Any suggestions would be appreciated.

March 8, 2007, 03:31 AM	#2
Foxman Senior Member Join Date: August 13, 2005 Posts: 466	Newer tighter barrel, chamber etc, always start lower and work up. the load Winchester quote is for the speer bullet, the Nosler is a boattail which takes up more case room. It sure is telling you things are too hot. Nosler dont give a load for 760 with this bullet only for the 40gr maybe they know something. The most accurate load they quote is for H380 start load 31.5 and max ( most accurate) 35.5grs, win wlr primer, win case. Give it a go may turn out a tack driver. __________________ Better the man suspected of being a fool keep his mouth shut, than to open it and remove all doubt.

March 9, 2007, 12:54 PM	#3
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	Sounds like you may have seated the bullet too far out, or you have too little powder and are getting detonation. With that load, you are getting very good velocity, probably due to whatever is causing the high pressure problem. I load the same bullet, use very close to the max load out of Hornady's reloading manual (several grains above your load), seat the bullets to max OAL, and never have pressure problems. And it is an accurate load, on top of all that. I have found that most of my .22 centerfire rifles shoot best at just below maximum load. Don't know why or how. Don't care why or how. I just enjoy it. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

March 10, 2007, 03:54 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	A really common cause of pressure is a component change. If you worked your original load up with Winchester brass, which is typically light on brass and roomy, then switched to almost any other brand, you will need less powder to hit the same pressure, but will get less velocity. Note that a tighter chamber will do the same thing. Peak pressure in guns firing above around 30,000 PSI, will depend on chamber dimensions rather than re-sized brass dimensions. Compare the water capacity of a fired case from the new gun with one from the old gun. If it is lower, then less powder is needed to hit the same pressure numbers. QuickLOAD shows a case with 43.5 grains of water capacity is 98.1% filled with your 760 load when that Nosler bullet is seated to an OAL of 2.350". Peak pressure is just below 50.000 PSI. Muzzle velocity is predicted to be 3523 fps from a 24" barrel and 3597 fps from a 26" barrel. It also shows a lot of unburned powder (8% and 7%, for the respective barrel lengths), and high muzzle pressure (10,000 PSI range). Ballistic efficency is 21.5% and 22.4%, respectively. Calculations show the same peak pressure will actually give you 10 or 15 fps more velocity and over 25% efficiency using 32.0 grains of IMR 3031. A more newly identified phenomenon, secondary muzzle pressure, can occur when too slow a powder is paired with too light a bullet. Unlike detonation, which is hard to reproduce, Texas gunsmith Charlie Sisk had been able to blow muzzles off barrels with regularity deomonstrating this pheonomenon. It often is undetected at the breech, but RSI's web site has pressure traces that show it on a strain gauge at the rear of the barrel, so apparently it can show up there. Moreover, since faster 3031 will actually do better in your gun with that bullet, there is no point in taking the risk. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 12, 2007, 07:00 PM	#8
Scorch Senior Member Join Date: February 13, 2006 Location: Washington state Posts: 15,248	I have used 760 in my 22-250 for over 20 years. I used to load IMR3031, but switched due to the issues loading rod-shaped powders. In my rifle, 40.4 gr of WW760 with a 55 gr bullet is accurate and shows no pressure signs. __________________ Never try to educate someone who resists knowledge at all costs. But what do I know? Summit Arms Services

March 9, 2007, 10:40 PM	#4
Ruger4570 Senior Member Join Date: April 3, 2005 Location: Rochester, New York Posts: 2,136	If you think you seated the bullets out too far, you just might have. In a gun, thing happen very fast, and a bullet lodged against the rifling can raise pressure very quickly, at least til it overcomes the resistance. I generally give my bullets a .10 of freebore and some require a bit more. If you were using lead bullets, it probably wouldn't make much difference due to the softness of the lead. You certainly need to figure out what is wrong as you seem to be getting some REALLY high pressure signals. There is always the possibility it is simply the gun not liking the loads but I have a feeling it is more from no "run up" room for the bullet.

March 11, 2007, 12:37 PM	#6
Trapper L Senior Member Join Date: November 20, 2006 Location: South Texas Posts: 804	I'm with Unclenick on this on. I have had issues with pressure spikes using 760 powder and relatively light bullets. In my 6.5x 06, my middle of the road loads will show primers with the same load from showing rounded edges and normal to flat and falling out of the primer pocket. The 760 powder is not a favorite at my house. I would suggest a different powder.

March 12, 2007, 02:59 PM	#7
multistage Member Join Date: March 8, 2007 Location: Wyoming Posts: 25	This is my fifth 22-250, and I have always used Winchester brass, Federal 210 primers, 55 grain Nolser BT's, and 760. A load I am fond of is 39 grains of 760. 3550 fps, cases lasted forever. This is also a virgin rifle. The books say a guy can go up to 40-41 grains of powder, but I don't like to hotrod my rifles. I believe I have seated the bullets out too far. I used a Stoney Point gauge and took off about .020. However, the books seat bullets quite a bit deeper than 2.500. They go with 2.37. I reseated the test loads to 2.410 and will give them a try.