Benchmark issue w/ 22-250 Need help

castnblast · August 23, 2009, 05:11 PM

I just chrono'd some loads, and discovered a problem - I did it because of strange shot patterns. May be the powder charge - please note I hand trickle each round to the exact weight.

Here's the issue. I've had excellent luck with this powder on 50gr. speer's. They scream - 3918 give or take a few either side. I noticed my shots were scattering on my 55 gr. Sierra BTSP's. Scope was fine, grooves fine, trigger good, mounts tight. So I borrowed a chrono, and here's what happened - first shot - 3606 fps. 2nd 3561. 3rd, 3548. As the barrel got hotter, velocity dropped like a rock. Don't have this problem w/ the 50's. Has anyone else had issues? Also, I had similar issue with IMR 4064. I'm looking for another powder - the gun is very capable of shooting tight groups - I need a powder for my 55grs. I will continue to use this for 50's but it's obviously not doing well with my 55 gr, which is a bummer, because it meters great. I'll buy some 50gr and continue to use, but what would be yoursuggestions for my 55 gr. dilema?

LHB1 · August 23, 2009, 06:31 PM

Have you checked the barrel/action bedding? The barrel/stock fit could be putting increased pressure on barrel as the barrel heats up. I've shot in CC and had to deal with the heat and constant SE wind up to 35 mph.

**Unclenick** · August 23, 2009, 07:25 PM

Did you keep the chrono at least 15 feet from the muzzle? Muzzle blast and powder can cause low and high readings, depending on the circumstance. Expelled powder or the muzzle blast can trip the first screen before the bullet gets there, but not trip the second screen that then waits for the bullet to arrive. The result is a low velocity number.

Also, what is your load and barrel length? QuickLOAD can't get a 24" barrel to move a 55 grain bullet at 3900 fps with Benchmark until the pressure is about 82,000 psi. Way above normal. At the normal peak pressure for the round the maximum velocity is just under 3700 fps. In the middle peak range of around 60,000 psi, it is another 100 fps slower than that.

If you overload a gun severely enough, you will find the steel starts to stretch elastically and velocities can actually drop. You most likely would, however, be getting sticky bolt lift and harder extraction at that point. The problem is that no single pressure sign is entirely reliable, so I can't say for sure you would see it. It is just probable that you would. As with low readings, being too close to the chronograph can also produce high velocity readings. So can some lighting conditions. Bright, but overcast is usually best for chronographs.

castnblast · August 23, 2009, 08:01 PM

No the 3900 was with 50 grain Speer bullet. I have a 22" Howa. The 3600 range is normal for my 55 gr. The charge is 33.5 gr, .1 under max. No excessive pressure signs. The chrono was approx. 20 ft from the gun, so close is not the issue. We chrono'd my 40S&W and the variance was only 3fps for the 5 shot test. The lousy group made me go w/ the chrono. The decrease with each shot was unusual, but give insight into the problem. I don't have an accuracy issue with my 50 gr. That charge is 36 gr if my memory is correct. COL is 2.355. SAMI Spec is 2.350. I don't believe the length is the issue.

**Unclenick** · August 23, 2009, 09:32 PM

Try knocking the load down about a grain and see if it still happens? Two causes occur to me. One is just ordinary barrel fouling. Different guns and loads and bullets react to it differently. The other is that you are near a maximum. As the gun heats, the powder burns faster, raising pressure. One of the common pressure signs is a load that levels or loses velocity with increase in charge. The same could happen due to heating a fixed charge that is OK when the gun is cold, but that was on the upper end of the line in your chamber.

The fact a manual's maximum load is higher means nothing to your gun. Your gun's maximum is what counts. I've even had a couple loads in the past where a manual's starting load was already at maximum in my particular gun. That's the reason a load range is usually given.

A_Gamehog · August 24, 2009, 01:17 AM

Howa/Weatherby's come with a "stock" 1-14 twist. Mine shoots 55 gr. anythings fine but it needs a tweak or two from my 50 loads. 55's are the max. 60's won't shoot..The speer TNT 50's have a very thin jacket and are not made for high speed above 3600+

Questions?
1). Has it ever shot 55's good? some soft points won't. if it did what were they and the length of the bullet?
2). What's the twist?
3). Changed primers from std. to mag? or vise versa?
4). Same make and sized brass?
5). temp at the time you were shooting?
6). Barrel temp also...too hot to handle for 5 sec.?

A_Gamehog · August 24, 2009, 01:25 AM

http://www.californiapredatorsclub.c...howtopic=14824

Quote from another boards shooter......

"I found Benchmark to be a very good powder in my 204 and my 223 AI. I also found it to be extremely accurate in my 22-250. The only problem I have is that it's extremely temperature sensitive. I loaded some 50 and 55 grain Nosler BT's with a max load of Benchmark and shot the best groups I've ever gotten from either of my 22-250's. Trouble is it was in the 50's when I did it. I loaded up some more in June and took them to the range and had trouble opening the bolt. "

**Mal H** · August 24, 2009, 09:32 AM

A Gamehog - the temperature observation made by the contributor in your post would appear to be the opposite effect castnblast is seeing. As the temp went up for castnblast, the velocities went down implying the pressure also went down. For your poster, as the temp went up (50* day to a much hotter day), the hard-to-open bolt implies a much higher pressure.

castnblast - You need to eliminate one of the variables, fouling and/or chamber temperature. The problem could be a little of both, but one of them probably more than the other. You should try cleaning the barrel after each shot with a quick run through of a patch or two, and see if that makes any difference in the velocity variations. If you do it quickly, the chamber temp will remain fairly high. Next you can try to wait about 5 to 10 minutes between shots (with the bolt open and the barrel pointed up) to see if cooling between shots makes any difference. Don't clean the barrel for the second experiment.

A bedding issue will certainly affect groupings as the barrel heats up, but generally not the actual velocity of the bullets within a narrow range.

**Unclenick** · August 24, 2009, 11:46 AM

Mal,

The pressure could go down with temperature rise due to changing expansion ratio caused by excess initial pressure expanding the chamber. That seems to be the most common explanation for why incrementing a near-maximum charge upward will often either fail to produce an increase in velocity or will actually cause a velocity drop when pressure limits for the gun are being exceeded. Sometimes two such velocity drop load ranges are observed in working up a load, with the first apparently caused by a bolt lug that has inadequate contact being forced down. That first velocity drop load range is then eliminated by lapping the bolt lugs.

I don't see a reason the same kind of velocity drop excess powder can cause would not also be caused by a temperature rise with a fixed charge that is near the upper limit for the gun? That's why I suggested he drop back a grain (or even two) and see if the phenomenon goes away? QuickLOAD had him running right up to the line on the SAAMI pressure limit (65 kpsi), though I don't know how accurate that estimate is without knowing his chamber's fired case water capacity or his bore's cross-sectional area. Most likely the QL calculation is a little high, but once in awhile I find a case smaller than the QL default, in which case pressure is likely even higher than predicted by the software.

castnblast · August 24, 2009, 08:17 PM

Thanks for all the replies - here's answers to a couple of questions about the loads.

These were loaded with new remington never fired brass - I resized all of them, and trimmed prior to loading - a practice I have always done with all the new brass I've purhcased.

The gun shot these very well in a work up a year ago when I loaded them. I went to the chrono when i suspected the problem. Benchmark is an extruded powder, and according to the manufacturer, it should not vary much within a 120 degree temp. I may contact Hodgdon about this as well, and see what they think. I may just need to change powders. I really like Benchmark because it meters great, and my 50 gr. loves it. I was considering H4350 just to see what it does. my 270 loves it, and may be the answer for the heavier bullet.

Gamehog, you are right on w/ the 55's. it is a 1:14. 60's are a no go. needs a 1:10 or better. It is a factory stock gun. Primers are the same, CCI 200 Large rifle. Outside temp was HOT. 101 actual temp. I bought b-m because it was supposed to be one of the most temp resistant powders. Based on everyone's comments, I'm thinking differently. I got really good results w/ IMR 4064, then had problems, but I discovered the problems were scope related, and most likely not the powder. I'm going to load some test loads w/ 4350 and IMR 4064, and see what the results are. I have a new Nikon scope, so that issue has been solved.

Since I have 40 of these rounds already loaded, I'm going to try the cleaning test and see what happens. If not, it may be the temp - These rounds shot a sub .5" group, but it was much cooler, in December when they were loaded. If I'm experiencing is an issue with temp, I will definitely try another powder - probably will anyway - so with that, I'd like some suggestions. I do not want to use ball powder, because it tends to be temp. sensitive as well.

Huge thanks for all the replies. I've been off the board for a while. Glad to be back.

hodaka · August 24, 2009, 08:51 PM

castnblast-If you want to shoot over my Ohler again I'll be there at dawn, or thereabout, on Sunday.

castnblast · August 24, 2009, 09:57 PM

Thanks, I really appreciate it. I was glad you were out there, because those groups really had me scratching my head. That gun shoots a lot better than that. My Chrono got shot a few years ago...I forgot to tell you that story...I bit my tounge, but man I was ticked...If you know bowden starlin, he's let me use his before. I ran into him today. Any suggestions on those powder charges? I really appreciate your help - w/out that chrono, I would have been wondering what was wrong with the gun.

**Unclenick** · August 24, 2009, 10:09 PM

Again, knock the load down a bit. The temperature immunity range for the Hodgdon Extreme powders is not unlimited. It seems to me they had 125 degrees as an upper number, but I don't entirely trust my memory, so check that. My point is just that a hot chamber wouldn't exactly have to try hard to take the powder from 101 to 125 inside the case. Knock the loads down one or two grains and see if you still see the symptom? If not, you've found a new maximum for your rifle in those conditions.

hodaka · August 25, 2009, 07:13 AM

One point is that you are attempting to draw conclusions from only 3 shots. A statistician would faint. Another is that the shots were fairly close together. I think that cooling 5 minutes between shots may shed some light on the issue. I don't know exactly what might happen to a barrel as it heats, but it does change. Heat does affect powders, but it should effect all of the loaded rounds the same on any given day. Also, as previously stated, pushing a patch or two between shots may eliminate the fouling/residue variable. Good luck.

Colorado Redneck · August 26, 2009, 10:03 PM

I like IMR 4064 for the 22-250. Have used it with 40 gr Noslers and 53 gr Sierras and 55 gr Hornadys with great success. Some people say it is dirty, but what the heck...I don't care.

Some combos just shoot bad in a certain gun. That is the fun of this sport. If you had used the same load previously and it was good, then suddenly it went bad, something would look really fishy. Maybe the gun just doesn't like this load.

August 23, 2009, 05:11 PM	#1
castnblast Senior Member Join Date: July 2, 2006 Location: Corpus Christi TX Posts: 1,148	Benchmark issue w/ 22-250 Need help I just chrono'd some loads, and discovered a problem - I did it because of strange shot patterns. May be the powder charge - please note I hand trickle each round to the exact weight. Here's the issue. I've had excellent luck with this powder on 50gr. speer's. They scream - 3918 give or take a few either side. I noticed my shots were scattering on my 55 gr. Sierra BTSP's. Scope was fine, grooves fine, trigger good, mounts tight. So I borrowed a chrono, and here's what happened - first shot - 3606 fps. 2nd 3561. 3rd, 3548. As the barrel got hotter, velocity dropped like a rock. Don't have this problem w/ the 50's. Has anyone else had issues? Also, I had similar issue with IMR 4064. I'm looking for another powder - the gun is very capable of shooting tight groups - I need a powder for my 55grs. I will continue to use this for 50's but it's obviously not doing well with my 55 gr, which is a bummer, because it meters great. I'll buy some 50gr and continue to use, but what would be yoursuggestions for my 55 gr. dilema?

August 23, 2009, 07:25 PM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,131	Did you keep the chrono at least 15 feet from the muzzle? Muzzle blast and powder can cause low and high readings, depending on the circumstance. Expelled powder or the muzzle blast can trip the first screen before the bullet gets there, but not trip the second screen that then waits for the bullet to arrive. The result is a low velocity number. Also, what is your load and barrel length? QuickLOAD can't get a 24" barrel to move a 55 grain bullet at 3900 fps with Benchmark until the pressure is about 82,000 psi. Way above normal. At the normal peak pressure for the round the maximum velocity is just under 3700 fps. In the middle peak range of around 60,000 psi, it is another 100 fps slower than that. If you overload a gun severely enough, you will find the steel starts to stretch elastically and velocities can actually drop. You most likely would, however, be getting sticky bolt lift and harder extraction at that point. The problem is that no single pressure sign is entirely reliable, so I can't say for sure you would see it. It is just probable that you would. As with low readings, being too close to the chronograph can also produce high velocity readings. So can some lighting conditions. Bright, but overcast is usually best for chronographs. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

August 23, 2009, 09:32 PM	#5
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,131	Try knocking the load down about a grain and see if it still happens? Two causes occur to me. One is just ordinary barrel fouling. Different guns and loads and bullets react to it differently. The other is that you are near a maximum. As the gun heats, the powder burns faster, raising pressure. One of the common pressure signs is a load that levels or loses velocity with increase in charge. The same could happen due to heating a fixed charge that is OK when the gun is cold, but that was on the upper end of the line in your chamber. The fact a manual's maximum load is higher means nothing to your gun. Your gun's maximum is what counts. I've even had a couple loads in the past where a manual's starting load was already at maximum in my particular gun. That's the reason a load range is usually given. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

August 24, 2009, 01:17 AM	#6
A_Gamehog Senior Member Join Date: February 9, 2009 Location: Central Oregun Posts: 563	What's the twist? Howa/Weatherby's come with a "stock" 1-14 twist. Mine shoots 55 gr. anythings fine but it needs a tweak or two from my 50 loads. 55's are the max. 60's won't shoot..The speer TNT 50's have a very thin jacket and are not made for high speed above 3600+ Questions? 1). Has it ever shot 55's good? some soft points won't. if it did what were they and the length of the bullet? 2). What's the twist? 3). Changed primers from std. to mag? or vise versa? 4). Same make and sized brass? 5). temp at the time you were shooting? 6). Barrel temp also...too hot to handle for 5 sec.?

August 24, 2009, 01:25 AM	#7
A_Gamehog Senior Member Join Date: February 9, 2009 Location: Central Oregun Posts: 563	Read this post, it speaks to the temp issues...with BM http://www.californiapredatorsclub.c...howtopic=14824 Quote from another boards shooter...... "I found Benchmark to be a very good powder in my 204 and my 223 AI. I also found it to be extremely accurate in my 22-250. The only problem I have is that it's extremely temperature sensitive. I loaded some 50 and 55 grain Nosler BT's with a max load of Benchmark and shot the best groups I've ever gotten from either of my 22-250's. Trouble is it was in the 50's when I did it. I loaded up some more in June and took them to the range and had trouble opening the bolt. "

August 23, 2009, 06:31 PM	#2
LHB1 Senior Member Join Date: March 25, 2005 Location: Houston, TX Posts: 1,545	Have you checked the barrel/action bedding? The barrel/stock fit could be putting increased pressure on barrel as the barrel heats up. I've shot in CC and had to deal with the heat and constant SE wind up to 35 mph.

August 23, 2009, 08:01 PM	#4
castnblast Senior Member Join Date: July 2, 2006 Location: Corpus Christi TX Posts: 1,148	No the 3900 was with 50 grain Speer bullet. I have a 22" Howa. The 3600 range is normal for my 55 gr. The charge is 33.5 gr, .1 under max. No excessive pressure signs. The chrono was approx. 20 ft from the gun, so close is not the issue. We chrono'd my 40S&W and the variance was only 3fps for the 5 shot test. The lousy group made me go w/ the chrono. The decrease with each shot was unusual, but give insight into the problem. I don't have an accuracy issue with my 50 gr. That charge is 36 gr if my memory is correct. COL is 2.355. SAMI Spec is 2.350. I don't believe the length is the issue.

August 24, 2009, 09:32 AM	#8
Mal H Staff Join Date: March 20, 1999 Location: Somewhere in the woods of Northern Virginia Posts: 16,972	A Gamehog - the temperature observation made by the contributor in your post would appear to be the opposite effect castnblast is seeing. As the temp went up for castnblast, the velocities went down implying the pressure also went down. For your poster, as the temp went up (50* day to a much hotter day), the hard-to-open bolt implies a much higher pressure. castnblast - You need to eliminate one of the variables, fouling and/or chamber temperature. The problem could be a little of both, but one of them probably more than the other. You should try cleaning the barrel after each shot with a quick run through of a patch or two, and see if that makes any difference in the velocity variations. If you do it quickly, the chamber temp will remain fairly high. Next you can try to wait about 5 to 10 minutes between shots (with the bolt open and the barrel pointed up) to see if cooling between shots makes any difference. Don't clean the barrel for the second experiment. A bedding issue will certainly affect groupings as the barrel heats up, but generally not the actual velocity of the bullets within a narrow range.

August 24, 2009, 11:46 AM	#9
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,131	Mal, The pressure could go down with temperature rise due to changing expansion ratio caused by excess initial pressure expanding the chamber. That seems to be the most common explanation for why incrementing a near-maximum charge upward will often either fail to produce an increase in velocity or will actually cause a velocity drop when pressure limits for the gun are being exceeded. Sometimes two such velocity drop load ranges are observed in working up a load, with the first apparently caused by a bolt lug that has inadequate contact being forced down. That first velocity drop load range is then eliminated by lapping the bolt lugs. I don't see a reason the same kind of velocity drop excess powder can cause would not also be caused by a temperature rise with a fixed charge that is near the upper limit for the gun? That's why I suggested he drop back a grain (or even two) and see if the phenomenon goes away? QuickLOAD had him running right up to the line on the SAAMI pressure limit (65 kpsi), though I don't know how accurate that estimate is without knowing his chamber's fired case water capacity or his bore's cross-sectional area. Most likely the QL calculation is a little high, but once in awhile I find a case smaller than the QL default, in which case pressure is likely even higher than predicted by the software. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

August 24, 2009, 08:17 PM	#10
castnblast Senior Member Join Date: July 2, 2006 Location: Corpus Christi TX Posts: 1,148	Thanks for all the replies - here's answers to a couple of questions about the loads. These were loaded with new remington never fired brass - I resized all of them, and trimmed prior to loading - a practice I have always done with all the new brass I've purhcased. The gun shot these very well in a work up a year ago when I loaded them. I went to the chrono when i suspected the problem. Benchmark is an extruded powder, and according to the manufacturer, it should not vary much within a 120 degree temp. I may contact Hodgdon about this as well, and see what they think. I may just need to change powders. I really like Benchmark because it meters great, and my 50 gr. loves it. I was considering H4350 just to see what it does. my 270 loves it, and may be the answer for the heavier bullet. Gamehog, you are right on w/ the 55's. it is a 1:14. 60's are a no go. needs a 1:10 or better. It is a factory stock gun. Primers are the same, CCI 200 Large rifle. Outside temp was HOT. 101 actual temp. I bought b-m because it was supposed to be one of the most temp resistant powders. Based on everyone's comments, I'm thinking differently. I got really good results w/ IMR 4064, then had problems, but I discovered the problems were scope related, and most likely not the powder. I'm going to load some test loads w/ 4350 and IMR 4064, and see what the results are. I have a new Nikon scope, so that issue has been solved. Since I have 40 of these rounds already loaded, I'm going to try the cleaning test and see what happens. If not, it may be the temp - These rounds shot a sub .5" group, but it was much cooler, in December when they were loaded. If I'm experiencing is an issue with temp, I will definitely try another powder - probably will anyway - so with that, I'd like some suggestions. I do not want to use ball powder, because it tends to be temp. sensitive as well. Huge thanks for all the replies. I've been off the board for a while. Glad to be back.

August 24, 2009, 08:51 PM	#11
hodaka Senior Member Join Date: April 23, 2006 Location: South Texas Posts: 2,010	castnblast-If you want to shoot over my Ohler again I'll be there at dawn, or thereabout, on Sunday.

August 24, 2009, 09:57 PM	#12
castnblast Senior Member Join Date: July 2, 2006 Location: Corpus Christi TX Posts: 1,148	Thanks, I really appreciate it. I was glad you were out there, because those groups really had me scratching my head. That gun shoots a lot better than that. My Chrono got shot a few years ago...I forgot to tell you that story...I bit my tounge, but man I was ticked...If you know bowden starlin, he's let me use his before. I ran into him today. Any suggestions on those powder charges? I really appreciate your help - w/out that chrono, I would have been wondering what was wrong with the gun.

August 24, 2009, 10:09 PM	#13
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,131	Again, knock the load down a bit. The temperature immunity range for the Hodgdon Extreme powders is not unlimited. It seems to me they had 125 degrees as an upper number, but I don't entirely trust my memory, so check that. My point is just that a hot chamber wouldn't exactly have to try hard to take the powder from 101 to 125 inside the case. Knock the loads down one or two grains and see if you still see the symptom? If not, you've found a new maximum for your rifle in those conditions. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

August 25, 2009, 07:13 AM	#14
hodaka Senior Member Join Date: April 23, 2006 Location: South Texas Posts: 2,010	One point is that you are attempting to draw conclusions from only 3 shots. A statistician would faint. Another is that the shots were fairly close together. I think that cooling 5 minutes between shots may shed some light on the issue. I don't know exactly what might happen to a barrel as it heats, but it does change. Heat does affect powders, but it should effect all of the loaded rounds the same on any given day. Also, as previously stated, pushing a patch or two between shots may eliminate the fouling/residue variable. Good luck.

August 26, 2009, 10:03 PM	#15
Colorado Redneck Senior Member Join Date: January 6, 2008 Location: Northeast Colorado Posts: 1,993	I like IMR 4064 for the 22-250. Have used it with 40 gr Noslers and 53 gr Sierras and 55 gr Hornadys with great success. Some people say it is dirty, but what the heck...I don't care. Some combos just shoot bad in a certain gun. That is the fun of this sport. If you had used the same load previously and it was good, then suddenly it went bad, something would look really fishy. Maybe the gun just doesn't like this load.