Fiftydriver
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Found out something interesting about RL33 over the past couple days. In the 7mm AM and 300 AX.
Now I have tested my 338 AX with this new powder and velocity gains were quite good but velocity gains per grain of powder increased extremely consistently from quite low pressure loads right up until red line pressures. Very impressed. Velocity consistency was pretty darn good as well over the entire range of pressures.
That was with a 300 gr Berger seated 10 thou off the lands.
That brings us to this weekend. Trying to get my old 7mm AM set up with the Berger 180 gr Hybrid so I decided to test RL33 in that as well. Velocity was great but I noticed that as my load increased, I started seeing more velocity spreads. In fact up 125 fps with same load in velocity spreads. I thought this was quite strange so I looked into the issue a bit more.
Well, long story short, this barrel on my 7mm AM is VERY long in the tooth, in fact I have had a replacement barrel sitting here on the rack for three years expecting a need to replace the barrel. Well, that time came. After checking the throat length in 7mm AM, I found that its length had increased by 170 thou over the original length. Severe erosion!!! Expected. At 100 yards, surprisingly, the rifle is still consistently in the 3/4 moa range for three shot group size. At long range however, the velocity spreads have started to show up in pretty noticeable vertical stringing.
That is where the interesting part comes in. With Retumbo, I can drive the 180 gr Berger Hybrid to 3308 fps with comfortable loads and extreme spreads run in the mid to upper 30 fps range. At long range, the rifle holds 1 moa pretty easily out to 1/2 mile.
With RL33 however, using an OAL of 3.670" to fit in the HS Precision DM. I can drive the same bullet to an average velocity of 3397 fps with what appears to be very similar pressure but with extreme spreads in the 125 fps range...... Again, this is with roughly a 170 thou jump to whats left of the lands, same as for the load with Retumbo.
So, with the same bullet, with the same jump to the lands, Retumbo will get 3308 fps and 3/4 moa 100 yard groups and sub 1 moa 800 yard groups. RL33 will get same 3/4 moa 100 yard groups but at 800 yards its closer to 3 moa and nearly 100% vertical stringing.
Now for the interesting part. IF I seat the bullets out very long to JUST touch whats left of the lands, the OAL is 3.840". Had to drop a grain of powder off each load as pressures increased significantly removing the bullet jump, now with Retumbo, seating the 180 gr Berger to the lands produced and average of 3318 fps. Seated to the same OAL, RL33 averged 3411 fps. Close to the average velocities before but with a grain less powder. The Extreme Spread of Retumbo was similar at 36 fps, but now with the bullets seated to the lands, RL33 had an Extreme Spread of 29 fps.
Goes from 125 fps seated off the lands to 29 fps seated to touch the lands....... Unfortunately, I have the HS Precision DM on this rifle. If the Seekins 3.900" DM system was available, I would just order one of those in and keep this a 7mm AM. But with the current rush on custom gun parts, those are hard to come by so need to stay with the HS.
Decided it was time. Saturday, I pulled old green apart and replaced the barrel. I decided this time however to go with my 300 AX as I had a #4 contour, fluted SS barrel blank from Lilja with a 1-10 twist. Finish length was 26.5" with finished with a small PK brake installed.
I had wanted to use the Berger 215 and 230 gr in the freshly barreled rifle but their Ogives are to long for the HS Precision DM system. So I went with the 200 gr Barnes LRX just to see what it would do. Again, I did a load work up using RL33 to see what it would do with this bullet. Velocities increased consistently and predictably until I got close to upper pressures and then velocity spreads really started to jump again. Top load was 104.0 gr RL 33 with the 200 gr LRX which averaged 3375 fps but had an extreme spread of 100 fps. At 100 yards, it was shooting right at 1/2 moa for three shots. I was very happy with the accuracy but again at longer ranges, 700 yards today in the wind!!! It was showing pretty noticeable vertical stringing again with the 100 fps level ES numbers....
Now, I seated these 70 thou off the lands as recommended. Accuracy was great but velocity spreads were quite poor.
Could it be that RL33 simply NEEDS the bullets seated close to the lands for proper powder ignition and therefor consistant muzzle velocities.......
To test this, I headed back to the shop, grabbed some 220 gr SMKs off the shelf. I used these bullets simply because I knew I could seat them to the lands and still fit in the mag box. Worked up the load with RL33 and topped out at 3250 fps and extreme spreads of 18 fps......
Next took the same load but seated the bullets 50 thou deeper. Also added one more grain of powder to bring the velocity back up similar to the first load at 3239 fps. However, ES numbers increased to 68 fps........
Seated the bullets another 50 thou so now 100 off the lands. Left the powder charge where it was. Average velocity dropped to 3202 fps. ES numbers rose to 103 fps.......
Then I took some Retumbo and did the same thing. Seated to the lands, Retumbo averaged 3148 fps and had an ES of 21 fps.
Seated 50 thou off the lands and increased one grain of powder for an average of 3141 fps, ES number was 26 fps.
Seated another 50 thou off the lands, velocity dropped to 3118 fps and ES numbers were 31 fps. All of which are totally acceptable for me.
So, I have to deduce from this that RL33 really likes to have some resistance on ignition to get consistant ignition. You do not see this a lot with stick powders. I have seen it ALOT using the ultra slow burning ball surplus powders as they can be a bit hard to ignite so seating the bullets just baring touching the lands produces a steeper pressure spike which seems to improve powder ignition and in turn improves velocity spreads.
My brother tested RL33 in his Warbird today as well, this was with the 180 gr Accubond and he topped out at 3518 fps. His velocities were very consistant throughout testing with no high ES numbers at all but he was also seating to the lands. In his rifle however, Retumbo averaged 3511 fps with about 6 grains less powder so we decided that Retumbo was probably a better match to the 180 gr bullet weight in the Warbird. There just is no real sense to burn an extra 6 grains of powder simply to match the velocity of Retumbo.
I feel with heavier bullet weights, RL33 may start to show its velocity advantages over Retumbo but with the relatively light 180 gr bullet, it tops out very similar to Retumbo.
So, back to my testing, I have loaded up a batch of test loads using the 200 gr Accubond. This bullet allows me to seat to the lands which I have seated them roughly 5 thou into the lands with an OAL of 3.650" which easily fits in the HS DM system. They also offer a BC that is a bit higher then the 200 gr LRX and should be a bit easier expanding at extended ranges. This is all on paper, until I prove them its all a theory.
Again, it seems that RL33 DOES NOT like a lot of bullet jump to the lands so for bullets such as the barnes what need 50-70 thou jump, you may see your ES numbers increase. With bullets that you can seat right up to the lands and even into the lands, ES numbers have been quite impressive so for the Accubonds, SMK and Bergers or any other conventional cup jacketed bullet, I believe you will see very good quality ES numbers.
Hope to get these 300 AX test loads sent down range tomorrow when I test a couple customer rifles. If things hold out, ES numbers should be tight and I am expecting to see the 300 AX be able to drive the 200 gr Accubond to +3400 fps in the 26.5" barrel length. Will report what happens.
Now I have tested my 338 AX with this new powder and velocity gains were quite good but velocity gains per grain of powder increased extremely consistently from quite low pressure loads right up until red line pressures. Very impressed. Velocity consistency was pretty darn good as well over the entire range of pressures.
That was with a 300 gr Berger seated 10 thou off the lands.
That brings us to this weekend. Trying to get my old 7mm AM set up with the Berger 180 gr Hybrid so I decided to test RL33 in that as well. Velocity was great but I noticed that as my load increased, I started seeing more velocity spreads. In fact up 125 fps with same load in velocity spreads. I thought this was quite strange so I looked into the issue a bit more.
Well, long story short, this barrel on my 7mm AM is VERY long in the tooth, in fact I have had a replacement barrel sitting here on the rack for three years expecting a need to replace the barrel. Well, that time came. After checking the throat length in 7mm AM, I found that its length had increased by 170 thou over the original length. Severe erosion!!! Expected. At 100 yards, surprisingly, the rifle is still consistently in the 3/4 moa range for three shot group size. At long range however, the velocity spreads have started to show up in pretty noticeable vertical stringing.
That is where the interesting part comes in. With Retumbo, I can drive the 180 gr Berger Hybrid to 3308 fps with comfortable loads and extreme spreads run in the mid to upper 30 fps range. At long range, the rifle holds 1 moa pretty easily out to 1/2 mile.
With RL33 however, using an OAL of 3.670" to fit in the HS Precision DM. I can drive the same bullet to an average velocity of 3397 fps with what appears to be very similar pressure but with extreme spreads in the 125 fps range...... Again, this is with roughly a 170 thou jump to whats left of the lands, same as for the load with Retumbo.
So, with the same bullet, with the same jump to the lands, Retumbo will get 3308 fps and 3/4 moa 100 yard groups and sub 1 moa 800 yard groups. RL33 will get same 3/4 moa 100 yard groups but at 800 yards its closer to 3 moa and nearly 100% vertical stringing.
Now for the interesting part. IF I seat the bullets out very long to JUST touch whats left of the lands, the OAL is 3.840". Had to drop a grain of powder off each load as pressures increased significantly removing the bullet jump, now with Retumbo, seating the 180 gr Berger to the lands produced and average of 3318 fps. Seated to the same OAL, RL33 averged 3411 fps. Close to the average velocities before but with a grain less powder. The Extreme Spread of Retumbo was similar at 36 fps, but now with the bullets seated to the lands, RL33 had an Extreme Spread of 29 fps.
Goes from 125 fps seated off the lands to 29 fps seated to touch the lands....... Unfortunately, I have the HS Precision DM on this rifle. If the Seekins 3.900" DM system was available, I would just order one of those in and keep this a 7mm AM. But with the current rush on custom gun parts, those are hard to come by so need to stay with the HS.
Decided it was time. Saturday, I pulled old green apart and replaced the barrel. I decided this time however to go with my 300 AX as I had a #4 contour, fluted SS barrel blank from Lilja with a 1-10 twist. Finish length was 26.5" with finished with a small PK brake installed.
I had wanted to use the Berger 215 and 230 gr in the freshly barreled rifle but their Ogives are to long for the HS Precision DM system. So I went with the 200 gr Barnes LRX just to see what it would do. Again, I did a load work up using RL33 to see what it would do with this bullet. Velocities increased consistently and predictably until I got close to upper pressures and then velocity spreads really started to jump again. Top load was 104.0 gr RL 33 with the 200 gr LRX which averaged 3375 fps but had an extreme spread of 100 fps. At 100 yards, it was shooting right at 1/2 moa for three shots. I was very happy with the accuracy but again at longer ranges, 700 yards today in the wind!!! It was showing pretty noticeable vertical stringing again with the 100 fps level ES numbers....
Now, I seated these 70 thou off the lands as recommended. Accuracy was great but velocity spreads were quite poor.
Could it be that RL33 simply NEEDS the bullets seated close to the lands for proper powder ignition and therefor consistant muzzle velocities.......
To test this, I headed back to the shop, grabbed some 220 gr SMKs off the shelf. I used these bullets simply because I knew I could seat them to the lands and still fit in the mag box. Worked up the load with RL33 and topped out at 3250 fps and extreme spreads of 18 fps......
Next took the same load but seated the bullets 50 thou deeper. Also added one more grain of powder to bring the velocity back up similar to the first load at 3239 fps. However, ES numbers increased to 68 fps........
Seated the bullets another 50 thou so now 100 off the lands. Left the powder charge where it was. Average velocity dropped to 3202 fps. ES numbers rose to 103 fps.......
Then I took some Retumbo and did the same thing. Seated to the lands, Retumbo averaged 3148 fps and had an ES of 21 fps.
Seated 50 thou off the lands and increased one grain of powder for an average of 3141 fps, ES number was 26 fps.
Seated another 50 thou off the lands, velocity dropped to 3118 fps and ES numbers were 31 fps. All of which are totally acceptable for me.
So, I have to deduce from this that RL33 really likes to have some resistance on ignition to get consistant ignition. You do not see this a lot with stick powders. I have seen it ALOT using the ultra slow burning ball surplus powders as they can be a bit hard to ignite so seating the bullets just baring touching the lands produces a steeper pressure spike which seems to improve powder ignition and in turn improves velocity spreads.
My brother tested RL33 in his Warbird today as well, this was with the 180 gr Accubond and he topped out at 3518 fps. His velocities were very consistant throughout testing with no high ES numbers at all but he was also seating to the lands. In his rifle however, Retumbo averaged 3511 fps with about 6 grains less powder so we decided that Retumbo was probably a better match to the 180 gr bullet weight in the Warbird. There just is no real sense to burn an extra 6 grains of powder simply to match the velocity of Retumbo.
I feel with heavier bullet weights, RL33 may start to show its velocity advantages over Retumbo but with the relatively light 180 gr bullet, it tops out very similar to Retumbo.
So, back to my testing, I have loaded up a batch of test loads using the 200 gr Accubond. This bullet allows me to seat to the lands which I have seated them roughly 5 thou into the lands with an OAL of 3.650" which easily fits in the HS DM system. They also offer a BC that is a bit higher then the 200 gr LRX and should be a bit easier expanding at extended ranges. This is all on paper, until I prove them its all a theory.
Again, it seems that RL33 DOES NOT like a lot of bullet jump to the lands so for bullets such as the barnes what need 50-70 thou jump, you may see your ES numbers increase. With bullets that you can seat right up to the lands and even into the lands, ES numbers have been quite impressive so for the Accubonds, SMK and Bergers or any other conventional cup jacketed bullet, I believe you will see very good quality ES numbers.
Hope to get these 300 AX test loads sent down range tomorrow when I test a couple customer rifles. If things hold out, ES numbers should be tight and I am expecting to see the 300 AX be able to drive the 200 gr Accubond to +3400 fps in the 26.5" barrel length. Will report what happens.
Kind of figured it was a typo. I agree, this time of year, lots of things running though the mind!!!
