Normally one can associate elevation spread with ignition. If its just high, then its likely not firing pin spring weakness. I'd lean toward case volume variation that would increase the pressure slightly and thus send the bullet high. Might try comparing the capacity of the cases where you have a high shot to those that seem fine. If its less, then you may have found the culprit.
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The new 33XC & 37XC cartridges designed by David Tubb
- Thread starter Butler12
- Start date
I run 7 saum and 338LM with the same can and I don’t experience it with those. Just the 33xc.
i wonder if it has anything to do with the gain twist shooting monos.
Mark from mark and Sam after work had the same issues with their gain twist 375 ct imp. And monos. He switched to straight 8 twist I believe and is getting better results so far.
Hi,
@Bravo6niner
Do you have the same random impact here and there when you single feed ammunition or have you checked that?
Reason I ask is that maybe under recoil and such the powder "placement" can vary; in which can cause enough MV changes to be your random impact problem.
I have not tested that concept in an 33 or 37XC but in standard 375CT we can get up to 20fps MV variation during T&E of purposely keeping powder to rear and/or front of case while single feeding.
Sincerely,
Theis
@Bravo6niner
Do you have the same random impact here and there when you single feed ammunition or have you checked that?
Reason I ask is that maybe under recoil and such the powder "placement" can vary; in which can cause enough MV changes to be your random impact problem.
I have not tested that concept in an 33 or 37XC but in standard 375CT we can get up to 20fps MV variation during T&E of purposely keeping powder to rear and/or front of case while single feeding.
Sincerely,
Theis
I can see where that would mess with ignition.
I’m single feeding all the rounds and while I don’t have an exact % I’m pretty sure case fill is 90%+
Received my Schneider blank on friday and just about have the barrel finished for my Desert Tactical SRS. I got some brass from Tubb along with the dies about a month ago. Right now I'm working with the Cutting edge Lazers as a friend has been dealing with them for his 375 Cheytac HTI and doing quite well out to 2700yds. I need to start looking at powders. Getting close.
Reading through I see a number of questions as to why someone would go with the 33 or 37 XC over one of the larger guys. I think the main reason is using an existing rifle. I can build a barrel for my standard SRS Desert Tactical rifle and not shell out another $5K or more for a custom 375CT or bigger rifle. I've got a few friends and customers in the same boat....waiting to see how this works out. With the switch barrel rifles its a no brainer to build a barrel to test the waters before jumping in. ELR takes some dedication along with the cash too. Looks like more math classes and calculations.....
Frank
Reading through I see a number of questions as to why someone would go with the 33 or 37 XC over one of the larger guys. I think the main reason is using an existing rifle. I can build a barrel for my standard SRS Desert Tactical rifle and not shell out another $5K or more for a custom 375CT or bigger rifle. I've got a few friends and customers in the same boat....waiting to see how this works out. With the switch barrel rifles its a no brainer to build a barrel to test the waters before jumping in. ELR takes some dedication along with the cash too. Looks like more math classes and calculations.....
Frank
Keep us Posted Frank!!!! Im really interested is seeing if there is any possible way in gettiing the 33XC to mag feed SMK’s in my DT SRS as well??? Is also very appealing in using existing Press setups... without having to jump into BMG sizes...
I know the 338 lapua AI can have issues because the shoulder is where the mag narrows down. The xc won't fit in the magazine.
I'll have a look in a bit but I don't think the brass case will fit in the mag much less one with any bullet seated. Its pretty much a single feed setup and I bought it with that in mind. I tend to single feed anyway. I don't like the shoulder stop on the mag as it prevents a lot of other rounds from fitting like the 510 whisper. Overall length on the XC is a problem for the mag with or without the shoulder though so no mag feed I can see.
Frank
Frank
I did check the mag. The 33XC case will not fit in the mag due to the shoulder being ahead of the mag shoulder. Its too wide. The loaded round only hangs over a bit.....
I got the barrel done enough to test fire and check the chamber. It works fine and is good to go. I just need to engrave the cal and twist on it now. I hope to get started on load development this week. The barrel ended up 31" long and is heavy but I'm not going to carry it far. It doesn't tip the rifle on the bipod as some might think despite the length and weight...and the covert handguard.
So far so good.
Frank
I got the barrel done enough to test fire and check the chamber. It works fine and is good to go. I just need to engrave the cal and twist on it now. I hope to get started on load development this week. The barrel ended up 31" long and is heavy but I'm not going to carry it far. It doesn't tip the rifle on the bipod as some might think despite the length and weight...and the covert handguard.
So far so good.
Frank
Attachments
I am running a Schneider 31in 1-8 twist barrel shooting the 300 grain Berger and can only get 117.6 grains of BMG-50 before its starts to show pressure on the primmer. this gives me 3040 FPS. So far accuracy has been very good.
Mine is also a Schneider 1-8 P5 at 31" but I'm looking at the 265 Cutting Edge Lazer. Hope to get some velocity and load info this weekend. Just watching the weather.....
Frank
Frank
The 9in twist rate should be fine with the 300gr bullets. Velocity will be higher and so will spin rates.
Got to shoot the new barrel today and learned a lot. I was running 250 Cutting Edge Lazers to start while waiting for the 265's to get here. I started at 120gr of Reloader 33 and worked up to 123gr. ES started at 70fps at the low charge and got down to 4fps with the 123 gr charge. Groups were tightening up too. I think I'm going to go a bit higher on powder and see how that goes. No pressure signs so far. Velocity at 123gr average was 3388 out of the 31" barrel so not too far off Tubbs results. The Desert tactical rifle shoots great with this barrel and with the 70MOA scope mount I've got 120MOA of adjustment up while shooting dead on 3.4 MOA off the bottom stop at 100yds.
I also tried a couple strings of WC868 and WC872. The 868 looks promising with 3350fps avg of 5 at 120gr and no pressure signs. The 872 looks a bit off running 3150fps avg of 5 with no pressure signs. Maybe its too slow? Groups with these two were not bad but I knocked the ammo box off the bench and broke the plastic tips on a couple bullets when it hit the ground. Not a very good test.....
Frank
Got to shoot the new barrel today and learned a lot. I was running 250 Cutting Edge Lazers to start while waiting for the 265's to get here. I started at 120gr of Reloader 33 and worked up to 123gr. ES started at 70fps at the low charge and got down to 4fps with the 123 gr charge. Groups were tightening up too. I think I'm going to go a bit higher on powder and see how that goes. No pressure signs so far. Velocity at 123gr average was 3388 out of the 31" barrel so not too far off Tubbs results. The Desert tactical rifle shoots great with this barrel and with the 70MOA scope mount I've got 120MOA of adjustment up while shooting dead on 3.4 MOA off the bottom stop at 100yds.
I also tried a couple strings of WC868 and WC872. The 868 looks promising with 3350fps avg of 5 at 120gr and no pressure signs. The 872 looks a bit off running 3150fps avg of 5 with no pressure signs. Maybe its too slow? Groups with these two were not bad but I knocked the ammo box off the bench and broke the plastic tips on a couple bullets when it hit the ground. Not a very good test.....
Frank
Tubb recommends a 9 twist if you are running jacketed bullets like the 300 grain berger. Biff, I've read several people have had similar results with RL33 and the ES tightening up as the case fill % goes up with other calibers. Those are some impressive numbers, I may have to get a barrel for my Desert Tech so I can get my toes wet in ELR.
No idea on the snipetac. Can't have em all so picking one and getting started is about the only way to get things done. I picked the 33XC.
Got to shoot again last weekend and had some odd results. I switched from the 250 gr Cutting edge Lazers to the 265 gr. Started at 123gr of RL 33 and went to 124. Average vel on the 123 gr load was 3462 but the ES was up there over 80. Group was about an inch at 100. I had problems with the 124gr load piercing primers which is something I'd not seen since I bought a mauser with a broken firing pin in about 1976. Primers weren't flat, no sign of ejector pin flow or any other high pressure signs. I'm wondering if its a Desert Tactical problem with the tiny firing pin in the too big hole in the bolt face or is high pressure something that would do this? The little slugs from the primer jammed up the firing pin so I had to take the bolt apart after every shot. Not an easy thing with a gen 1 bolt and after 3 rds I stopped. The firing pin was a little rough so maybe it was damaging the primer?
Anyway, I also tried the WC868 loads at 122 and 123 gr. They were quite a bit slower than the RL33 at 3360 for the 122 and 3370 for 123 with an ES of 15 for the 122gr load. I'll fiddle with this one a little. It might be better to be consistent than fast. No pressure signs with these but oddly the last round fired had a pierced primer.
Frank
Got to shoot again last weekend and had some odd results. I switched from the 250 gr Cutting edge Lazers to the 265 gr. Started at 123gr of RL 33 and went to 124. Average vel on the 123 gr load was 3462 but the ES was up there over 80. Group was about an inch at 100. I had problems with the 124gr load piercing primers which is something I'd not seen since I bought a mauser with a broken firing pin in about 1976. Primers weren't flat, no sign of ejector pin flow or any other high pressure signs. I'm wondering if its a Desert Tactical problem with the tiny firing pin in the too big hole in the bolt face or is high pressure something that would do this? The little slugs from the primer jammed up the firing pin so I had to take the bolt apart after every shot. Not an easy thing with a gen 1 bolt and after 3 rds I stopped. The firing pin was a little rough so maybe it was damaging the primer?
Anyway, I also tried the WC868 loads at 122 and 123 gr. They were quite a bit slower than the RL33 at 3360 for the 122 and 3370 for 123 with an ES of 15 for the 122gr load. I'll fiddle with this one a little. It might be better to be consistent than fast. No pressure signs with these but oddly the last round fired had a pierced primer.
Frank
I can not compare the two as I have not fired a snipetac.
David’s platform in the 33XC was well beyond accurate and had SD around 6 ish. Shoulder pressure variation can achieve highly variable velocities and there are so many variables that affect the ultimate muzzle velocity.
It is incredibly accurate.
David’s platform in the 33XC was well beyond accurate and had SD around 6 ish. Shoulder pressure variation can achieve highly variable velocities and there are so many variables that affect the ultimate muzzle velocity.
It is incredibly accurate.
I did the barrel for my DT as I have done for all of them other than the factory 338 Lapua which is pretty rough inside. I've also done a lot of barrels for others in oddball cals like the 12.7 X 48 (510 Whisper equivalent), 338BR, 6.5X47 before it became more mainline, 7.5 Swiss, 26 Nosler, 300 Norma Mag, a few variations on the 300 win mag....and I'm sure there were others but can't remember them all. The 33XC barrel is heavy at 10lb but I'm not going to carry it anywhere and I wanted it solid and useable with a suppressor. I've seen some of the longer barrels having issues with cans hanging out on the end and didn't want that to happen.
Frank
Frank
Thanks for your info, very detailed. So, the SRS platform looks like a very suitable one to use with the XC cartridges, Just a .338 bolt and new barrel? Am I getting it right?
You pretty much have it. They'll be single load cartridges due to length of course but a lot of the long range types hand feed singles anyway.
One other little detail, I'm running a covert handguard with the bipod mounted a little behind the end. Even with a 10 lb 31in barrel the rifle is not tippy.....it sits back on the monopod just fine. Others will tell you that you need to get the bipod as far forward as possible but its not really necessary.
Frank
One other little detail, I'm running a covert handguard with the bipod mounted a little behind the end. Even with a 10 lb 31in barrel the rifle is not tippy.....it sits back on the monopod just fine. Others will tell you that you need to get the bipod as far forward as possible but its not really necessary.
Frank
because its 31" long and is a large diameter to keep it from being whippy at that length. That makes it heavy.
Frank
Frank
Anyone get to try N570 in their 33xc yet? I’m looking at that in mine when its done. This is for hunting exclusively, and temp stability is paramount
I have some on back order but none yet. Looking to use in 338lm, 33xc and 375CT when ever it comes in. A friend is using it in his 300 nm and is about 40 FPS faster them Retumbo and the sd's are single digit.
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Got to run some more tests with the RL33 on saturday. Its a new lot so I loaded up a few rounds to make sure it wasn't way off. This lot is hotter and slower. I'm seeing pressure signs with 2 grains lower charge weight and the velocity is down by about 80fps. Glad I started low. The 265 Lazers are still running at 3360 with no pressure signs so that should be good. Accuracy has improved as I've run more down the tube. The last batch were grouping .65-.75 in at 100. Looking forward to the long shoot in a couple weeks than I've got more time to find a better powder? and load. Maybe the VV N570 will return or some H50 BMG?
Frank
Frank
MidSouth is accepting backorders for VV-N570 and the new VV-N565 powders. I just (back-)ordered 4 pounds of each for our 338 LM testing of 245.3-gr copper ULD bullets. Dan Warner made these Mark IIb 338-caliber ULD bullets with 0.3386-inch rear driving band OD, convex radiused bases, and 0.125-inch base drilling for our testing here and for testing by David Tubb. The ogive is secant with RT/R of 0.500 and a full length of 3.2 calibers. The ogive is truncated with a 0.100-caliber meplat for lower total air drag.
The test firings are going well with Alliant RL-26 powder which is slightly too fast. We are sorting bullet seating and neck tension issues currently. We hope to get sub-0.25 MOA ES 5-shot groups with sub-10 fps MV spreads soon in my 105-yard indoor BR range. Currently seeing negligible vertical spread at the "too slow" node at 2875 fps (88.3-gr RL-26). But the horizontal spread (0.375 MOA) is correlated with +/- 25 fps velocity spreads. I believe finding correct COAL and neck bushing size will improve this considerably. Currently testing in 7.0-inch twist 28-inch Schneider P5 barrel. Will also test in 28-inch Bartlein barrel with 6.6-inch twist 5R rifling and a conventional 338 LM chamber.
The test firings are going well with Alliant RL-26 powder which is slightly too fast. We are sorting bullet seating and neck tension issues currently. We hope to get sub-0.25 MOA ES 5-shot groups with sub-10 fps MV spreads soon in my 105-yard indoor BR range. Currently seeing negligible vertical spread at the "too slow" node at 2875 fps (88.3-gr RL-26). But the horizontal spread (0.375 MOA) is correlated with +/- 25 fps velocity spreads. I believe finding correct COAL and neck bushing size will improve this considerably. Currently testing in 7.0-inch twist 28-inch Schneider P5 barrel. Will also test in 28-inch Bartlein barrel with 6.6-inch twist 5R rifling and a conventional 338 LM chamber.
They exist. I have 230 of the 375 CT with the Lapua boltface that I’m not going to end up using. Peterson did these for Tubb and I got them from SSS (Tubb) a while back. I’ll probably throw them up in the Reloading For Sale section soon as I’ll end up going with the XC down the road.
a wise man would move the shoulder back and neck to 338 or 358 and to end up with about 142 grains h20 better sds and performance
Isn’t that a SnipeTac? Good thought and badass round but I am trying to shoot it out of my Desert Tech SRS, which doesn’t work so well with the Cheytac case. I don’t shoot it enough to make an HTI or a Cheytac action worthwhile.
I finally got a few rounds downrange today starting at 500 to check my zero and working out to 2500. I was all around the 2700 yd target but with wind issues I just couldn't quite nail it down. Tomorrow is another day and we have targets out to 2 miles. Not sure how much I can really go beyond 3000yds as my scope will be topped out and I'm not great with holdovers using the reticle. We'll see. The round seems to be really solid and the dope worked out pretty well though it was about 2 moa low the whole way out. Using my results from the various ranges I've tweaked the program and hope to see it a little better tomorrow. The 265gr Cutting Edge Lazers are really consistent and I've been very pleased. More info as I get it tomorrow.
As an aside, my buddy's HTI in 375 Cheytac has made it to 3166yds today and was all around the 3460yd target with the same wind Issues I had at 2700. Hopefully tomorrow we'll both get a bit more down the road.
Frank
As an aside, my buddy's HTI in 375 Cheytac has made it to 3166yds today and was all around the 3460yd target with the same wind Issues I had at 2700. Hopefully tomorrow we'll both get a bit more down the road.
Frank
Today was pretty good as the winds died down a bit for a while this afternoon. My buddy was able to hit at 2 miles with his Desert Tech HTI in 375 Cheytac. I tried once again to hit the 2600 and 2700 yd targets but by the time I got to shoot the wind had picked back up. Oh well....thats how it goes. My buddy did get a 2600yd hit with my 33XC though so maybe I wasn't holding my mouth right or something. The rifle and round are capable and I'd recommend it to anyone thinking that direction. I'm happy with getting out to 2500 with the 33XC.
I also took the 7.5X55 Swiss barrel I built for my SRS out to 2000yds today. Checked dope from 500 to 1000 and went to 1400, 1620 and then 2000yds. Wind was picking up when I got there but made it with this one. Probably should have started with the 33XC but I was really curios how the Swiss round would do.
Frank
I also took the 7.5X55 Swiss barrel I built for my SRS out to 2000yds today. Checked dope from 500 to 1000 and went to 1400, 1620 and then 2000yds. Wind was picking up when I got there but made it with this one. Probably should have started with the 33XC but I was really curios how the Swiss round would do.
Frank
Not a lot of new stuff to report today. I let a newer shooter have a go with the 33XC at 2000 in the windy conditions prevailing today. She hit the target after 6 shots. She then managed to hit at 2500 yds with my buddy's 375 Cheytac HTI. I tried 10rds at 2700 with the HTI but the wind kept pushing one way and the other and I had hits all around the target but nothing on. Winds increasing as we shot but me being a long range newbie is probably the most likely explanation. I think the 33XC is a great learning tool for getting into the long range niche without spending a fortune. It will help you learn what thin reticles are all about and what the importance of winds and other details mean when you get past 1000yds. Love to have an HTI but really glad to have my SRS still in the program. I can see where any of the switch barrel 338LM rifles could benefit as well.
Done with the shooting today... back to the grind on monday. Very nice to have had the opportunity to wring a bit out of the round and shooter.. Thanks to Tubb and his bunch as well as the guys here who helped me with the program.
Frank
Done with the shooting today... back to the grind on monday. Very nice to have had the opportunity to wring a bit out of the round and shooter.. Thanks to Tubb and his bunch as well as the guys here who helped me with the program.
Frank
David Tubb test-fired my latest Mark IIb copper ULD bullets in 338-caliber two days ago. These new bullets weigh 245.3-gr and have a larger (0.3386-inch OD) rear driving band and 0.125-inch base-drilling for better gas sealing. The base of the ogive is machined convex at 0.936-caliber radius for reduced de-stabilization in the muzzle-blast zone. The rear driving band was widened by 0.1-caliber, and the ogive was lengthened to 3.2-calibers complete length. A very small 0.100-caliber meplat truncates the ogive for lowest total air drag.
David fired six shots with a "last 5-shot" mean MV of 3394 fps measured with his Oehler System 88 set up over 995.7 yards. The mean BC(G1) measured was 0.901 (relative to a standard ASM atmosphere). Actual conditions were 78 degrees F, 27.74 inHg air pressure, 44-percent RH, and 10 mph wind from 9 o'clock. Mean time-of-flight was measured at 1.04086 seconds. The average airspeed over David's 2987-foot firing range was 2870 fps (or Mach 2.524 at 78-degrees F). Mean impact velocity was calculated at 2434 fps by Oehler. David used his 35-inch long, 7.5-inch (22.7-caliber) twist-rate Schneider P5 barrel chambered in his new 33XC cartridge.
I estimate his initial gyroscopic stability (Sg) at 2.20 with these new 1.902-inch long copper bullets using McGYRO. Use of a 20-calibers per turn (6.6-inch) twist-rate instead would allow early hyper-stable flight to be achieved in less benign firing conditions. I am particularly pleased that David achieved this high BC measurement firing with less than my recommended initial Sg of 3.0.
This BC(G1) of 0.901 at 2870 fps (Mach 2.524) average airspeed corresponds to a BC(G7) of 0.448 after adjusting to the standard sea-level ICAO atmosphere used by ballisticians. I had estimated a BC(G7) of 0.433 for these new-design copper bullets. Very few copper ULD bullet designs can match this BC in 338-caliber, especially at this very "light for caliber" bullet weight. The G7 Form Factor (i7) calculates to 0.717, which is incredibly low. If these bullets are simply lengthened to increase throw weights, their air-drag will increase slightly.
While not fired for accuracy, the Oehler System 88 measured a 14-inch group at the target distance.
All is not unicorns and roses, however. The 5-shot MV spread was not acceptable at 32 fps ES (13 fps SD). That agrees with our early test-firings of my 338 LM here in my 105-yard indoor range. We still have some work remaining in learning to fire these bullets, but the basic air-drag problem is pretty well licked. I wonder if a friction-modifier coating on these copper bullets might reduce these MV spreads.
David fired six shots with a "last 5-shot" mean MV of 3394 fps measured with his Oehler System 88 set up over 995.7 yards. The mean BC(G1) measured was 0.901 (relative to a standard ASM atmosphere). Actual conditions were 78 degrees F, 27.74 inHg air pressure, 44-percent RH, and 10 mph wind from 9 o'clock. Mean time-of-flight was measured at 1.04086 seconds. The average airspeed over David's 2987-foot firing range was 2870 fps (or Mach 2.524 at 78-degrees F). Mean impact velocity was calculated at 2434 fps by Oehler. David used his 35-inch long, 7.5-inch (22.7-caliber) twist-rate Schneider P5 barrel chambered in his new 33XC cartridge.
I estimate his initial gyroscopic stability (Sg) at 2.20 with these new 1.902-inch long copper bullets using McGYRO. Use of a 20-calibers per turn (6.6-inch) twist-rate instead would allow early hyper-stable flight to be achieved in less benign firing conditions. I am particularly pleased that David achieved this high BC measurement firing with less than my recommended initial Sg of 3.0.
This BC(G1) of 0.901 at 2870 fps (Mach 2.524) average airspeed corresponds to a BC(G7) of 0.448 after adjusting to the standard sea-level ICAO atmosphere used by ballisticians. I had estimated a BC(G7) of 0.433 for these new-design copper bullets. Very few copper ULD bullet designs can match this BC in 338-caliber, especially at this very "light for caliber" bullet weight. The G7 Form Factor (i7) calculates to 0.717, which is incredibly low. If these bullets are simply lengthened to increase throw weights, their air-drag will increase slightly.
While not fired for accuracy, the Oehler System 88 measured a 14-inch group at the target distance.
All is not unicorns and roses, however. The 5-shot MV spread was not acceptable at 32 fps ES (13 fps SD). That agrees with our early test-firings of my 338 LM here in my 105-yard indoor range. We still have some work remaining in learning to fire these bullets, but the basic air-drag problem is pretty well licked. I wonder if a friction-modifier coating on these copper bullets might reduce these MV spreads.
What's the Sg using Miller's? McGyro's data is not easily available to get, Very cool work!
Don Miller's VLD algorithm calculates an initial Sg of 2.2362 for David's MV versus 2.1954 from Bob McCoy's McGYRO program. The VLD algorithm slightly overestimates Sg for ULD bullets. I just use it for a "sanity check." My new Sg algorithm estimates an initial Sg of 2.1774 for this 245.3-gr ULD bullet from a 7.5-inch twist barrel. It uses Dr. Kneubuehl's cone-on-cylinder bullet modeling.
These are all Sg values for a sea-level ICAO standard atmosphere. At David's range altitude of about 3000 feet and at 78-degrees F, all of these Sg values would be significantly larger (by 11.81 percent).
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Thanks for replying. Just one more question, in this case the use of a higher Sg to achieve hyper stab is not needed or is it still desirable to do so just to fight transonic ill effects?
My recommended initial Sg of 3.0 is based on damping out any significant initial bullet yaw as quickly as possible during the bullet's highest-drag early flight. In David's case, I believe that he was able to fire these new bullets without them having "significant initial bullet yaw" when they began aeroballistic flight, so the initial Sg did not matter very much. The crosswind recorded at the firing point was only 10 mph, for example, so his initial crosswind yaw was only 4.2 milliradians (0.24-degrees) at his very high average MV of 3394 fps. Minimum long-term yaw in hyper-stable flight is something less than 0.10-degrees due to gravity. His muzzle brake did not induce significant yaw or yaw-rate due, no doubt, to its good design. The convex base of these new bullets probably helped also by minimizing yaw disturbance in the muzzle-blast zone (as I intended). We simply cannot always fire our copper bullets this well. Spinning these copper bullets faster than sometimes needed cannot hurt anything.
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Thanks again for a thorough answer! Any plans for a 0.375 bullet anytime soon?
Yes, we want Dan Warner to make the Mark IIB ULD bullet in 375-caliber next. They should weigh 335-gr and have a BC(G7) of 0.480.
