GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Big Bore AirGun Gate => Topic started by: Rizen 1 on September 03, 2015, 10:51:51 PM
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Well, here is the start of the "WHITEOUT" build... We (Brent Hoag, Chris Alls and I) started this build to test the 200 gn "WHITEOUT" bullet that Bob designed. With the help of Bob and many others, here is our progress so far....
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More pics....
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Everything looks great, guys.... the bullet looks awesome, can't wait to see how it shoots....
Bob
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Bob, what do you think of the adjustable bolt probe?
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Looks great.... I had a replaceable one in my Hayabusa .357, two different lengths, with a short one for bullets and a long one for pellets.... The face of the bolt was flush with the back of the barrel port and the probe just threaded into the nose.... Same basic idea, without the adjustment and lock nut.... On the Disco Double I used a retractable bolt with the handle running in a "J" slot.... Push the bolt forward to seat the pellet or bullet (using the base).... then swing the handle down to the lock position and then withdraw it so that the nose is flush with the back of the barrel port.... The only problem is that the O-ring needs to be in the barrel instead of on the bolt, as the bolt has to withdraw about 1/2".... It completely clears the barrel and port, so no restriction at all.... and you can tune the gun by limiting how far back the bolt pulls and have the nose cover part of the barrel port like a slide throttle in a motorcycle carb.... It's nice for dialing the power way down for pellets....
Bob
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Bob, the Gen1 marauder breeches are so easy to implement this on...very good performance indeed.
I am at a bit of a loss as to why the extreme high power folks don't use it exclusively.
cheers,
Douglas
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This is interesting. I'm in the market for a big bore and maybe this is the one. Your details are a little sketchy. How many shots are you trying to achieve. The current .308 Brent builds gets 3 shots. Do you expect more or less? What type of distances are you expecting to shoot this to accurately?
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This is being built as a 200 yd. rifle, shooting a 200 gr. bullet boattail (shown) at over 1000 fps....
Bob
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This is being built as a 200 yd. rifle, shooting a 200 gr. bullet boattail (shown) at over 1000 fps....
Bob
Thank you for the information. Will be watching this for sure.
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Anything new going on with this build?
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I understand the rifle is complete and ready for testing....
Bob
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Chris and I went to Brent's for a few days to finish the Whiteout build and do some testing. Here are a few pics.... The gun is incredible!!!!
The groups were shot at 100yds after about 9 hours of testing and tuning.. :o
Chris is a genius with tuning Brent"s guns ;D as you can see with our final groups WITH THE 200 GN BBT 8)
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NICE... 8)
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Very nice! Thank you for sharing.
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Looks great, Mike.... How big is the 10-ring and the red dot (or what did the group measure)?.... and how many shots in the groups?.... Certainly looks like both bullet and gun are doing the job.... What velocity did you end up using?....
Bob
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Looks great, Mike.... How big is the 10-ring and the red dot (or what did the group measure)?.... and how many shots in the groups?.... Certainly looks like both bullet and gun are doing the job.... What velocity did you end up using?....
Bob
The red center dot measures .6" and there are 5 shots in each group. The bullet/gun combo looks to prefer a muzzle velocity of 970fps. The gun likes to be held and shouldered firmly as we found out after Mike shot those two groups.
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ohhh my gooddddddd :o :o :o :o :o :o :o :o :o :o :o :o
YO QUIERO UNO ( I want one )
it would be possible to know what kind of valve has been used in this incredible PCP? design measures etc ....
I'm looking for good design to make my PCP valve ....
A greeting
Pau
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ohhh my gooddddddd :o :o :o :o :o :o :o :o :o :o :o :o
YO QUIERO UNO ( I want one )
it would be possible to know what kind of valve has been used in this incredible PCP? design measures etc ....
I'm looking for good design to make my PCP valve ....
A greeting
Pau
Unfortunately I believe Extreme Bigbore is pretty secretive of their valve specifics.
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That is a awesome rifle, the boolit looks like a missile and the accuracy with it was great, how many shots do you get with it untethered.
Thanks Terry
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That is a awesome rifle, the boolit looks like a missile and the accuracy with it was great, how many shots do you get with it untethered.
Thanks Terry
Well the air tube is a shortened 20" version of Extreme's standard 24" 300cc air tube. With the shorter tube, using Helium, a 4500 psi fill and a 12 lbs/in spring running around 1/2" preload I can shoot 3 shots inside a % 3 extreme spread. The gun uses almost exactly 450 psi per shot and that's pushing the 200 grain BBT bullet at 970fps for roughly 420ft/lbs. As I've said many times the Extreme Bigbore guns respond well to different tunes.
After meeting Brent I now understand why he builds his guns and tunes them how he does. He specifically makes his guns with the big game hunter in mind. The good news is with nothing more than the proper spring and the owner being okay with a slight decrease in power the guns can easily be tuned for 3 tight shots.
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Very KEWL, guys!.... The three of you are to be congratulated, you have done a fine job in a very short period of time.... Getting less than MOA accuracy out of a new bullet in a new gun the first time out is pretty astounding.... I couldn't be happier for you....
Bob
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Bob, we will have some bc numbers for you as well as some 200yd groups this weekend.. ;D And THANK YOU FOR ALL YOUR HELP!!! ::)
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Bob, we will have some bc numbers for you as well as some 200yd groups this weekend.. ;D
We shooting over your chrony or mine at 200 yards? Lol.....
Bob this bullets rocks! AM I mistaken or did you design a bullet exactly like the Whiteout but lighter? If so I think I'll get a mold coming so I can shoot this thing on air when I don't want to shoot off helium.
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WE ARE SHOOTING OVER YOURS AT 200 YDS!!!! OF COURSE..... :o LOL!
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C.ALLS.... Since designing the Whiteout bullet, I have done more research on the relationship between Meplat and Sectional Density, and have a series of bullets drawn in .257 cal from 65 gr. to 111 gr.... The heaviest is virtually a scaled down version of the Whiteout, but exactly 4 calibers long so a fraction lighter.... The series of bullets, all of which use the new 8* boattail like the Whiteout, can be seen in this thread.... http://www.gatewaytoairguns.org/GTA/index.php?topic=94920.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=94920.0)
If those bullets are scaled up to .308 cal, they would have the following weights.... 112 gr., 133 gr., 153 gr., 172 gr., and 191 gr.... They have the full bore-riding nose, but can easily be changed to the larger nose which engages the rifling like in the Whiteout bullet, with a slight increase in weight.... Other weights are also possible in between, but would mean a complete redesign of course.... Some of the lighter bullets could be made with existing patterns for the ogives that Veral has.... others, such as the 172 gr., would need a new ogive pattern, at additional cost of course.... If you let me know, here or in PM, what weight you want, I will have a look and advise my recommendation....
Bob
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What's the volume of the air reservoir?.... I'd like to calculate the efficiency....
Bob
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What's the volume of the air reservoir?.... I'd like to calculate the efficiency....
Bob
I'm not sure. I know you've calculated the volume of their standard 24" tube as 300cc but this air tube is a cut down version at only 20".
I'll think about the bullet I'd be interested in and let you know. I'm pretty sure it'd be under 150 grains. That 133 and 112 would most likely be perfect using regular air/nitrogen.
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Chris must still be asleep... ;D the charge tube is 20 inches long.
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Chris must still be asleep... ;D the charge tube is 20 inches long.
Thanks for the correction lol....
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That was what I remember, so the volume is 246 cc (15 CI).... At 450 psi (31 bar) per shot that is 466 CI of air to produce 420 FPE, or 0.90 FPE/CI.... For that amount of power in a .30 cal, I think that's pretty good efficiency....
Veral has a pattern for a 1.0" Ogive, which would be great for the 133 gr. bullet, and he also has a smaller pattern for the 112 gr.... To make the 153 gr. or 172 gr. bullets a longer ogive radius pattern would be reguired.... I would suggest you consider the 133 gr.... That would be 266 FPE at 950 fps, and 295 FPE at 1000 fps.... Let me know which nose style you would like and I'll draw it up for you to send to Veral....
Bob
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That was what I remember, so the volume is 246 cc (15 CI).... At 450 psi (31 bar) per shot that is 466 CI of air to produce 420 FPE, or 0.90 FPE/CI.... For that amount of power in a .30 cal, I think that's pretty good efficiency....
Veral has a pattern for a 1.0" Ogive, which would be great for the 133 gr. bullet, and he also has a smaller pattern for the 112 gr.... To make the 153 gr. or 172 gr. bullets a longer ogive radius pattern would be reguired.... I would suggest you consider the 133 gr.... That would be 266 FPE at 950 fps, and 295 FPE at 1000 fps.... Let me know which nose style you would like and I'll draw it up for you to send to Veral....
Bob
I was talking to Mike about the current Whiteout bullet and while we we're really excited about the bore riding we're also glad the bullet morphed into the finish product it is. We like the fact it can be sized so I think I want the 133 grain the same way. I figure after all the talk about not allowing Helium at future events we will need something we can shoot on air in the 1000fps range. Thanks for everything you've done for us Bob and I hope you know it's appreciated.
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Bob the charge tube is 20 inches long but the fill end and valve each take up 1 inch and the bore on the white out is 1.018 inner diameter but the way the valve is designed you will want to use an inner diameter of 1.018 and a charge tube of 18.5 inches long for more exact calculations.
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HI Brent.... That gives me 15.05 CI of volume, which is 247 cc.... Close enough....
Chris, it figures they might change the rules to no Helium.... *LOL*.... Here is the design for the optimized 2.5 cal long bullet with the .308 cal nose.... It worked out to 132 gr.... 295 FPE at 1000 fps MV, and 250 FPE remaining at 200 yards.... The wind deflection should only be about 1/4" more at 200 yards than the Whiteout in a 10 mph wind.... A 14" twist would give a stability factor of 1.3 at 1000 fps, and higher below that.... but I think it should work fine in your faster twist barrel....
(http://i378.photobucket.com/albums/oo221/rsterne/Bullet%20Casting/308%20cal%20BBT%20132%20gr_zpsz61vidtl.jpg) (http://s378.photobucket.com/user/rsterne/media/Bullet%20Casting/308%20cal%20BBT%20132%20gr_zpsz61vidtl.jpg.html)
I know that Veral has a 1.00" radius Ogive pattern, and this uses the 8* Boattail pattern from the Whiteout, just shortened as appropriate.... so there should be no additional pattern charge.... The dotted line is where the ogive will start to engage the rifling, so the supported section is over 1 caliber long, which should certainly keep the bullet straight in the bore.... and it can, of course be sized.... The Meplat is a lot larger than on the Whiteout, but I spent a lot of time with the McDrag program optimizing the relationship between Meplat and Ogive, and that is what has the least drag and the flattest drag curve in the Transonic range for this length bullet.... Anyway, there you are.... If you need any changes, let me know, otherwise it's ready to send to Veral on your OK....
Bob
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The bullet looks great Bob! I'll talk with Veral after the shoot and we'll get the ball rolling on the new bullet. As far as the helium issue I don't understand what the problem is. They claim Helium is hard to source on the west coast but I know the last time I was in Colorado the local grocery stores had Helium balloons all over. That's the route I had to take after being told a 6500psi tank wasn't going to happen.
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I plan exactly the same route, I am building a pneumatic powered booster (130 psi shop air) to boost the 500-2000 psi Helium to 3.6K for my Hayabusa.... The 2K Helium tanks are readily available here, in several sizes, with or without the regulator for filling party balloons.... and we live in a town of only 3500 people (actually only 85, but that is the nearest shopping area).... The supplier has been told, however, they are rationed to only 90% of the previous year's supply each year, because of shortages....
Let me know if you want me to send Veral the drawing, and when.....
Bob
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I plan exactly the same route, I am building a pneumatic powered booster (130 psi shop air) to boost the 500-2000 psi Helium to 3.6K for my Hayabusa.... The 2K Helium tanks are readily available here, in several sizes, with or without the regulator for filling party balloons.... and we live in a town of only 3500 people (actually only 85, but that is the nearest shopping area).... The supplier has been told, however, they are rationed to only 90% of the previous year's supply each year, because of shortages....
Let me know if you want me to send Veral the drawing, and when.....
Bob
I use my Shoebox compressor to boost the helium. That allows me to pretty much deplete the tank and fill all my other tanks to 4500psi. I've also used my booster and that worked well and those booster pumps are super reliable.
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That's one wicked rifle! Very nice work, and great results. Have you considered trying Nitrogen instead of the Helium? Nice and dry, and available at any gas supply or welding supply.
Casey
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Nitrogen is nearly as heavy as air, and would show almost no gains.... Helium works because it is less massive, wasting less energy accelerating itself.... plus the velocity of the atoms/molecules and the speed of sound is much higher in Helium....
Bob
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That's one wicked rifle! Very nice work, and great results. Have you considered trying Nitrogen instead of the Helium? Nice and dry, and available at any gas supply or welding supply.
Casey
The gun will be using air and or nitrogen after the shoot. I'll most likely only use Helium for long range shooting.
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Has the rifle been tested for accuracy using air?
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No, not yet Jim..I am sure it will perform well with air also.
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Has the rifle been tested for accuracy using air?
I'll give you a full report using air in a few weeks. I have no doubt it'll be an MOA rifle on air.
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Thanks for the clarification Bob, I had only heard of many people using Nitrogen, and didn't know about the added benefits of helium.
Again great rifle and shooting guys,
Casey
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I am pulling for you guys... I just bet my neighbor a lawn mow each way that at 200 yards sub moa...
I am optimistic about conditions and ability so will venture you achieve about a 1.75" group...
Man it has to be satisfying after all the work, and going this direction with the round despite the nay saying...
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I am pulling for you guys... I just bet my neighbor a lawn mow each way that at 200 yards sub moa...
I am optimistic about conditions and ability so will venture you achieve about a 1.75" group...
Man it has to be satisfying after all the work, and going this direction with the round despite the nay saying...
Thanks for the kind words of encouragement. We're actually hoping the conditions (wind) is at its worst so the 200 grain BBT can do what it does best BUCK WIND.
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am pulling for you guys... I just bet my neighbor a lawn mow each way that at 200 yards sub moa...
I am optimistic about conditions and ability so will venture you achieve about a 1.75" group...
Man it has to be satisfying after all the work, and going this direction with the round despite the nay saying...
Better tell your neighbor to get his lawn mower ready! LOL! :o
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Looking good gentlemen, I am looking forward to your 200 yard results!
Side note:
Are those stocks hydrodripped?
If so who do you have do it?
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Yes they are dipped. Virginia hydro designs in Winchester VA. Is who did these. Dustin Fauver is the owner and a personal friend of mine. He does beautiful work.
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Extreme 308's won both first and second in the extreme benchrest big bore shoot in Mesa AZ this weekend using the 200 gn BBT in less than favorable conditions. Winds varying from 12-20 mph with little to no wind correction. Thanks for the winning bullet Bob Sterne!
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I'm extremely pleased that the .308 Whiteout bullet performed as intended.... I let Veral know that it was a success.... Thanks, Mike, for requesting that I design a bullet for this task.... It was a pleasure working with you, Chris, Brent, and Veral on this project....
Bob
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Let's get started for next year! ;)
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Helium or Air?.... If air, do you think the 132 gr. is the way to go, or should I do up a drawing for the 153 gr?.... The 132 gr. Veral already has a nose pattern for, heavier ones would require a new ogive pattern.... All will use the 8* boattail pattern from the Whiteout.... with the base shortened as appropriate....
Bob
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Extreme 308's won both first and second in the extreme benchrest big bore shoot in Mesa AZ this weekend using the 200 gn BBT in less than favorable conditions. Winds varying from 12-20 mph with little to no wind correction. Thanks for the winning bullet Bob Sterne!
How do you win 1st AND 2nd place? We're they judging bullet looks too? Oh wait, multiple shooters?
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My son and I were able to have dinner and sit next to them at their table while the rewards were handed out. On top of having a top notch gun and bullet combo they are some of the nicest and most humble guys you can meet. It was a real pleasure to meet them and watch them receive their well deserved victory. Great job guys.
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We had two guns shooting the BBT'S.. the Alpha 30 and the Whiteout . Both guns built by Brent Hoag at Extreme Big Bore. We placed 1st and 2nd with these guns. Thank you for the kind words Nick. It was a pleasure meeting you and your son. Good luck with your swaged bullets. They looked amazing! I'm sure we will be ordering some in 22 cal when you are ready.
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Mike, Chris you guys ROCK!!!!!!!! I just want to thank you guy's and I am so glad that I made that late night phone call to Chris and said lets build a rifle and go win this thing and he called you and asked if this guy meaning me is for real. So then the white out was born then you have to come up to the north land and some how sweet talk the alpha 30 out of me in a couple days LOL it just goes to show you when people go the extra mile it all works out and there was not one person on this team that did not do everything in there power to make this happen. Give both of yourself credit it was ultimately you two that made it happen again GREAT job.
Brent Hoag
Extreme
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I was looking back through my files, photos, and old posts tonight, trying to figure out when I first started talking about the possibility of using boattails for subsonic use in airguns.... The earliest thing I could find was Oct. 26, 2013, when I first suggested they were worth investigating.... By early December of 2013, I had cast my first Bob's Boattail, a .300 cal in 70 gr.... We've come a long way in less than 2 years.... 8)
Bob
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A Big Congrats Guy's!!! 8)
Knife
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Congrats guys, very fine work indeed!
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When will some test results be posted using air only?
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When will some test results be posted using air only?
I'll get some results up ASAP. What are you wanting in a rifle?
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1st place is a big accomplishment in a field 14. 1st and 2nd is outstanding. Congratulations to everyone involved.
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When will some test results be posted using air only?
I'll get some results up ASAP. What are you wanting in a rifle?
.257 or .308
200-250 yards
I like accuracy. I don't hunt any more.
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I decided to login and tell my side.
It was a pleasure to hang out with Mike and Chris. Really nice guys and there guns looked and shot real nice. But after seeing how they group I don't think it was the right setup. I'm not knocking there guns its just the way they shoot 2-3 good shots and then the next is 4-6" off. They are great hunting gun. I'm sure the thin barrel is a factor and not sure if the barrel band has a part in it also. I think the bullet was just to big. I shot a 112 gr accurate mold bullet at 3200 psi with no wind correction at 1000 fps
I planned on shooting .257 in the 200 yd event. After 2 days of shooting in there wind I decided to pull the scope off of my .25. It is a 10-50x60 sightron. The problem was I couldn't see where I was hitting the paper most of the time with the 6-24×56 hawke. So after messing with it Saturday before and after I shot in the extreme 75 yd event I was frustrated and pulled my regular setup. I then started shooting off my old tank to see what was going to work. Then they kicked us out because the range closed.
So now I'm at a loss as to what to do. So I decide to shoot the .308. I take it in the room and clean the barrel. I sized half the bullets I had for me and Tom sized the half he was going to use if he shot his .308.
So we plan to go to the range before they open and sight in at the rifle range. Tom with his .357 and me with my .308.
I take a shot at the 200 yd berm to see where it was at and it was a little high. Made a adjustment and shot again. It was right where I aimed. So I shoot 4 shots on the target that Tom had set out and it grouped good enough not to shoot anymore.
So I have taken 6 shots with my .308 before the event. So I was in the first relay. I decided to fill after every shot because I don't have it setup to shoot a curve.
Match starts and I take 2 shots a the sighter target and there both in the black. I move up and start shooting the lower right target. I take 5 shots I think. I look and can't find all 5 shots. I decide to move on to the next target. So I shoot out the next target. Well somewhere in the shooting I had a partial shot. Anyone that has a airforce and has not closed the breech all the way knows what I'm talking about. It is like a half shot and falls way short.
So I go on and finish my shooting. I then take a look back at 1st target and can see 5 shots now. So I'm done. I shot my .308 a total of 31 shots 6 before and 25 in the event. If I would have spent the time I did with the .257 who know what would have happened.
After thinking about it for awhile the only thing I can figure is the partial shot dropped into the lower target giving me a 6th shot on it.
So not closing the breech cost me 20 points and I lost by 5.
I learned a lot. Defiantly not to shoot the bottom targets first. I also made the finals in the 75 yd extreme which was 100 yd final. Winds were so bad that you would hit the target next to the one you were aiming at. I ended up finishing 15th in the final. I was happy to make the final.
I'm hoping I made 2 new friends and would like to keep in contact. I won't give it away next year I tell you that right now. I will be way more prepared with a spotting scope also.
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Doug, it was awesome meeting you! We are still on the road.... 6 more hours :o. You have definitely made 2 new friends. Competition is one thing... Friendships are another. I would never let the frustrations of competition ruin a friendship. You definitely would have won if it were not for the deduction... I apologize if we offended you in any way. We worked so hard and there were Alot of people involved in our build, we got so excited that we placed that I let it overshadow everything else. We had issues also.... Only having 24 power scopes and not being able to see the holes was only one of the issues....We have shot 2 inch groups with our guns and we have shot 10 inch groups. After initial testing, Bob thought the bullet was a little to long... Kip confirmed that by showing us on our targets that the bullet was yawing. We fought bad leading of the barrel and ran out of time for testing, but decided to come give it a shot anyway. Right before the 200 yd shoot Chris shot the best 5 shot group ever at 2.1 inches, then we shoot in the competition and they are 2-3 touching and the other 2-3 out of the Black.... I think we are close to the right set up, but definitely need to make some adjustments. It was an honor getting to shoot with you and we look forward to next year.
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It sounds like the event was pretty typical for an important contest.... last minute changes that you always wonder about, or just plain running out of time to prepare.... and the inevitable lady luck smiling or frowning as the case may be.... The friendships made, however, are far more important, and last long after the event is forgotten.... My congratulations to all three of you....
I received some samples of the Whiteout bullet tonight, along with some great T-shirts, complements of Mike.... thanks so much for those.... I measured the bullets, and they are 1/16" longer than the design I gave Veral.... The Meplat is slightly smaller as well, but that doesn't concern me as much as the overall length.... That is the most critical dimension for bullet stability, and with the Whiteout printing 5 shots touching, consistently, at 100 yards.... but being inconsistent at 200 yards.... and showing evidence of the bullets yawing in the target.... we certainly know where to look to improve the consistency.... Pushing the Meplat back to the original length by installing a 1/8" diameter HP pin to increase the diameter should make the bullet shoot at 200 yards and beyond as good as it does at 100....
So much for the coulda-woulda-shoulda.... ;D .... I have feeling that Chris, Mike, Doug, and Tom (and probably others) will all be there again next year.... with properly sorted equipment and wayyyyyyyyyyyy more experience.... Our little group from the GTA (and I take pride in being involved, even if I didn't get to shoot) has made its mark.... and I see great things in the future....
Bob
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I have been a professional snowmobile racer for the last 18 years and have come up with a formula for success for any competition. preparation + proper performance + %10 luck = success take out any of the three and it usually will notwork out for you great shooting by all but at the end of the day it is what it is.
Brent Hoag
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I too have a custom built .308 Extreme. Mine has a 32" Shilen match grade 1 in 10" twist stainless steel barrel with an outside diameter of .800" inches. Most of my shooting is at my home range, Tri-County Sportsman Club. It's a 300 yard range. I don't believe in 3 shot groups. Anyone can get lucky from time to time and shoot a screamer. I do all of my testing with 10 shot groups. My best 300 yd. 10 shot group is a 5.1" group. Velocities are 830 fps with a 183 gr. bullet and 910 fps with a 153 gr. bullet on "air" regulated to 3800 fps. So those of you wondering what the Extreme velocities would be on air, here is a base line to compare to. Neither bullet has shown any tendency to yaw on target even out to 700 yards. The bullets are the RCBS 180 gr. and 165 gr. Silhouette bullet. If I would have the rifle rebuilt a 3rd time, I probably would have the chamber specified to be no larger than .3095" As it is, the chamber is .3104" and I have to shoot .3103" bullets for maximum accuracy. The bullets are probably being swaged down on entry to the barrel, but if the bullet enters the barrel crooked from a loose chamber your accuracy is all ready down the drain. .309" bullets routinely get beat by the .3103" bullets. And .308" bullets shoot down right bad. What was the barrel twist in the rifle shooting the Whiteout bullets. Just from the look of them I would guess a 1in 8" twist would the minimum required.
What I'd really like to know is what B.C. you're getting out of that Whiteout bullet. I took my bullets and shot them over the chronograph at 1" foot from the muzzle. Then I set my chronograph and CAREFULLY shot over the chronograph at 100 yards. Then I took the velocity loss calculation and entered it into the JBM Ballistics Program for a ballistic coefficient. My best bullet only performed at a B.C. of .250. That means that with a 10 mph crosswind at 200 yards my bullet will be pushed a match losing 7.5". So in my humble opinion, a bullet--which is accurate and creates an improvement in B.C. is an improvement in the right direction.
Helium is a good way to game a match-- but for normal shooting, I don't want to deal with the hassle and cost of using an exotic gas. If the match directors want to create an "Unlimited Division" then go for it. But the regular shooter should not be pushed into such exotic and expensive measures to be competitive. I'm all for eliminating Helium for the regular match competitor, but for the continuing scientific push to take air rifles to the limit of their capabilities, create an unlimited/experimental division.
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well in the design thread it was estimated and I will look to find it... I do remember it was basically very close to that of the Lapua 200g subsonic...
http://www.midwayusa.com/product/381996/lapua-subsonic-bullets-30-caliber-308-diameter-200-grain-full-metal-jacket-boat-tail-box-of-100 (http://www.midwayusa.com/product/381996/lapua-subsonic-bullets-30-caliber-308-diameter-200-grain-full-metal-jacket-boat-tail-box-of-100)
now if you want what it really does then Lapua uses Doppler to get their figures...
http://www.lapua.com/en/products/reloading/bullets/centerfire-rifle-bullets/15 (http://www.lapua.com/en/products/reloading/bullets/centerfire-rifle-bullets/15)
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Chris used the drop from a 75 yard sight in to a 200 yard target (46") to estimate the BC at ~0.475.... He plans downrange Chrony tests soon....
Bob
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found the initial estimate...
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The JBM Ballistics Calculator says that over that velocity range the G1 BC is a staggering 0.80-0.855.... I think a fairer measure would be to use the G7 (boattail) standard, where the BC over that velocity range is 0.351-0.367....
"
http://www.gatewaytoairguns.org/GTA/index.php?topic=93646.0 (http://www.gatewaytoairguns.org/GTA/index.php?topic=93646.0)
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Chris found a source for 2500 psi helium tanks for around $125.00 per tank. They are standard tanks used for filling balloons... Running it through his shoebox compressor to fill our omega tanks, we get 3 full 4500 psi omega tanks from that one 2500 psi tank. With our booster setup, we then get 350-400 shots from 1 of those omega tanks. So we get about 1200 shots on that one $125.00 tank..... which is about $.10 cents a shot....... :o Depending on where and how you get your air, if You have the right setup, Helium can be as cost effective as air if not more so....PRODUCING ALMOST TWICE THE POWER, enabling us to experiment with taking airgunning to the next level. ;D
Here are a few more pics...
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Hmmmmmmmmmm.... about 10 cents a shot, at 400 FPE each?.... It costs about 2 cents a shot for CO2 in a gun that only puts out 7 FPE (2240).... Yeah, but air is free, right?.... Not if you fill your tanks commercially it's not (and you aren't going to hand pump to 4500 psi)....
Bob
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I know that after the last 3 months of experimenting with Helium I will never be without a tank in my garage. I suggest anyone wanting more power from their bigbore give it a try.
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It's a 300 yard range. I don't believe in 3 shot groups. Anyone can get lucky from time to time and shoot a screamer. I do all of my testing with 10 shot groups. My best 300 yd. 10 shot group is a 5.1" group. Velocities are 830 fps with a 183 gr. bullet and 910 fps with a 153 gr. bullet on "air" regulated to 3800 fps. So those of you wondering what the Extreme velocities would be on air, here is a base line to compare to.
Have you tuned the gun for a 3800 psi fill?
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The only thing that I have done to the .30 cal Extreme in the way of tuning it to cut about 1 1/4 coils off of the stock hammer spring. I regulate at 3800 psi. and Brent sets the guns up for 4500 psi. I get about 40 shots per 90 cu. ft. bottle when regulating at 3800 psi. with the cut hammer spring. Cutting the hammer spring also reduced my extreme spreads. From time to time I'll shoot an entire session over the chronograph. Before I cut the spring it would not be uncommon to have a 15 fps. extreme spread in a 10 shot string of fire. By cutting the spring, air consumption improved and my extreme spreads for a 10 shot string tend to average about 7 fps.
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In the mid 900s with a 153 gr. bullet is just about where I would like to see a .308 using air for the next EBR.... or drop the caliber to .257 and the bullet weight to just over 100 gr. at the same speed...
Bob
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The only thing that I have done to the .30 cal Extreme in the way of tuning it to cut about 1 1/4 coils off of the stock hammer spring. I regulate at 3800 psi. and Brent sets the guns up for 4500 psi. I get about 40 shots per 90 cu. ft. bottle when regulating at 3800 psi. with the cut hammer spring. Cutting the hammer spring also reduced my extreme spreads. From time to time I'll shoot an entire session over the chronograph. Before I cut the spring it would not be uncommon to have a 15 fps. extreme spread in a 10 shot string of fire. By cutting the spring, air consumption improved and my extreme spreads for a 10 shot string tend to average about 7 fps.
Brent does set his guns up for a 4500psi fill but his springs don't get into a bell curve till around 4800-5000psi. You really should spend the time to find an appropriate spring for your fill range. I tuned our guns and set them up to be filled to the sweet spot between shots. We can be 100-150psi off in either direction and the guns will still be well under %1ES from shot to shot. I bet you would get way more shots from your tank once the gun is not wasting so much air.
Another thing we've been experimenting with is lock time. The Extreme guns have a little over a 2 " hammer travel after the trigger is pulled to when the valve is hit and opened. That's a good bit of time for things to change before the bullet gets out of the barrel. The Whiteout hammer travels 1.6" and just the small change made the gun shoot better IMO. I'll be trying a 1.25" hammer travel soon and I believe that will be even better.
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To be honest I really have not been concerned about even having a bell curve. I always shoot tethered and regulated. I had the rifle built as an experimental test bed for long range air rifle shooting. It was never going to be used for hunting. So long as I get a reasonable number of shots out of a tank (40 shots- and I have more than 1 tank) and really low extreme spreads I'm happy. Your extreme spreads of 1% on 1,000 fps would be 10 fps. My extreme spread average in a 10 shot string is only 7 fps. So I'm doing all right in that category. Because I'm using air, if I'm a little inefficient it doesn't cost me anything.
If I were to get into Helium I'd be more concerned with efficiency. And you have picked my interest in the use of Helium. But getting into Helium runs contrary to the very reason that I got into air rifles in the first place and that is they're cheap to shoot. If I drive up my air rifle shooting cost to where shooting firearms becomes cheaper--to me--I've lost sight of my goals. I am much more interested in taking your research and modifying it to maximize what an "air" powered rifle can do. I'm thinking using the Whiteout concept of a bullet shape at about 160-170 grains. Something that would work with my 1 in 10" inch twist air powered rifle. I'm thinking that a good profile for the bullet would be to take a Berger Hybrid bullet of about 160-170 grains, then cut that chunk out of the middle bore riding area so that you end up with the front and rear driving bands similar to the Whiteout.
The lock time issue is huge on our air rifles. They are more like shooting flintlocks--pssst wait bang! I had a heavy flat bottomed "F" class stock fitted to my Extreme to help stabilize it off of the benchrest. I even shoot the rifle different than any of my firearms in that my left arm solidly holds the flat bottom of the stock down against the front benchrest. Of course the rear of the rifle is on the sandbag. The Bald Eagle benchrest has the adjustments for up and down & right and left built into it so that frees both arms for stability and follow through. So yes, I am interested in reducing the lock time on the Extreme. If your test workout on the 1 1/4" hammer I'd be interested in obtaining one. How would I go about that?
What twist rate are you using on your Extreme? You mentioned you were experiencing some bullet instability, are you going to shorten the bullet or increase the twist rate? Stew
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I understand that you're happy with your ES but what I think you're missing is that a better suited spring for a 3800psi fill will give you your same results with a less violent hammer to valve hit. When a hammer spring and valve are inside their sweet spot the relationship is much easier on the pair and less violent which results in a smoother shot cycle and a gun that's easier to shoot accurately IMO. You could continue to modify your stock spring but every time you shorten that spring by removing coils you're actually making it a stiffer spring rate and what I think you'll find is that in order to get that spring to operate in a 3800psi sweet spot you'll end up with a negative preload situation which doesn't work well with these rifles.
The shorter lock time hammers are available through Brent but they're in the testing stages and I suggest you wait till I figure out the best combination before ordering one. Also we're using a 1:8" twist barrel and the Whiteout bullet as designed would've stabilized perfectly but the mold maker decided to build the bullet mold about 1/16" longer than specified so......
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I have found that proper tuning is just as important with a regulated PCP as an unregulated one.... While reducing the hammer strike may not drop the velocity at all, it will save air.... and you can save half the air over the "wrong" tune or even more, getting double the number of shots or more at the same velocity.... If you want the ability to shoot a few shots untethered, you can even come up with a tune that will allow say 3 shots off tether with an extremely tight ES (1% or less) and when you are tethered, you are shooting the first shot of that 3-shot string, and hence on the "efficient" side of the curve.... If you need to get away from the tether (eg. for the EBR), you can fill from the regulator and get 3 shots before refilling.... Not only that, when properly done, you can be within a few percent of the maximum the gun can shoot if power is what you need....
Stew, if you want a bullet design similar to the Whiteout but lighter, I already have three done, 133 gr., 154 gr. and about 172 gr.... The 154gr. needs, in theory, an 11" twist, the 200 gr. Whiteout uses an 8", so I would think the 172 gr. would need about a 9", but might work in a 10".... Boattails require a faster twist than the same length flat-based bullet.... Send me a PM or email if you want a drawing....
Bob
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Until someone is actually shooting extreme spreads averaging lower than 7 fps for a 10 shot string I'm not going to fiddle with the hammer spring. I've had 10 shot strings as low as 4 fps extreme spread. There's not a lot improvement left in this arena. And I'm not going to worry about shot count. I already get 80 shots per outing (2 bottles) and it's always been more shots than I needed. I am interested in improving the B.C. of my bullet. And lock time. That's where I will focus my improvement efforts.
I think the EBR rules need to be re-evaluated. I mean, if an individual is charging an air rifle for "every" shot-- what's the difference in allowing it to be regulated and tethered to obtain the same effect. Is the EBR implying that tethered/regulated rifles have no relevance in the hunting world while charging a rifle for every shot does? Get real. Neither is relevant to a hunter. The tethered/regulated rifle is going to work just fine in a hunting situation un-tethered for 1 shot. If we are going to recharge every shot in the field we are going to have to be carrying buddy bottles everywhere we go. Just acknowledge that both systems are unrealistic for the hunting world and allow regulation and tethering for the big bores. They need to re-evaluate their rules. Our sport is still in its infancy. We'll learn.
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Our extreme spreads our WELL UNDER %1 and we're refilling every shot so there's human error with the reading of the gauge ect. If we shot tethered WITH a good regulator I'd be surprised if our ES was anything over 4-5fps. That wouldn't be a big deal over your already low 7 fps spread but I guess I just don't understand putting all the time and effort into a long range rig and not spend a little extra time to set it up for the best efficiency. To each his own I guess.
Now on the lock time we're experimenting with the best setup and by shortening the lock time and decreasing the hammer travel the gun is becoming even more efficient and I have to believe the less extra air trying to blast its way around the bullet when it's exiting the barrel the better.
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I agree, not allowing a tether at the EBR, but allowing you to fill after every shot, makes NO sense, as functionally they give the same results, and neither is great for a lot of hunting situations.... However, shooting from a tether IS practical for shooting/varminting at 200 yards, and a lot of the big bore guys here do just that.... IMO they should either allow a tether, or restrict you to shooting each 5-shot target with a single fill.... The latter you can get around by hanging a large tank on your gun, so just allow a tether and be done with it, IMO....
Anyone who hasn't played with a preload adjuster on a big bore (or any PCP) really needs to get with the program.... Here is what happens with my .284 cal Hayabusa, tethered at 2900 psi....
(http://i378.photobucket.com/albums/oo221/rsterne/Hayabusa%20PCP/Hayabusa%207mm%20Preload_zpsjnfgxgmr.jpg) (http://s378.photobucket.com/user/rsterne/media/Hayabusa%20PCP/Hayabusa%207mm%20Preload_zpsjnfgxgmr.jpg.html)
The gun uses about half the air per shot at 4 turns out than it does with the preload maxed out, and the velocity is the same.... The ES is much tighter at 4-5 turns out as well.... Also, the gun is so much quieter at 4 turns out you would think it was a different gun.... Efficiency matters, even when on a regulator.... Why big bore manufacturers don't install a preload adjuster on their guns I will never understand.... Regulated or not, it's a necessity, IMO....
Bob
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Maybe someone out there in the aftermarket air gun world could make a threaded end cap with an allen screw that could move a spring guide/plug fore and aft for our Extremes so that it would be easy to try different pre-loads. As it is, you either cut coils or keep swapping out springs. Brent are you listening?
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Chris and Mike made them.... but I'm not sure if they will work with the stock stock.... (do I hear an echo?)....
Bob
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Maybe someone out there in the aftermarket air gun world could make a threaded end cap with an allen screw that could move a spring guide/plug fore and aft for our Extremes so that it would be easy to try different pre-loads. As it is, you either cut coils or keep swapping out springs. Brent are you listening?
They're available but as Bob said the factory stock needs modified slightly.
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Chris and Mike made them.... but I'm not sure if they will work with the stock stock.... (do I hear an echo?)....
Bob
Wish I could take credit for that creation but that was all Mike.
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1-8" twist? I find it pretty tight comparing those generally told before. You guys found any keyholing due to fast spinning?
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A keyhole is yaw from not spinning fast enough.
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While there is a possibility of over stabilizing a shorter/lighter bullet the effects wouldn't be seen till the bullet was way outside the range we would be shooting them. The 1:8" twist managed to stabilize the 200 grain BBT (most of the time) that was built to the wrong specs and ended up 1/16" longer than designed. So once the mold is corrected and the bullet is the correct length I feel we'll be able to easily hold 2.5" or better groups at 200 yards.
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Double post.
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At only 970 fps and 8" twist, the bullets definitely are NOT over stabilized. Push em faster "FORWARD" and that stability/yaw might be corrected. Wow, 8" twist is superfast and seems to restrict forward speed even using helium IMO. I've heard of you guys testing in the near future using plain ole HPA but i wonder..............
My question is though, is a 1/16" shorter bullet gonna correct the yaw issue. Thats really minute in OAL........
I say a little lighter of a bullet will help cause you will have more forward speed which helps SPIN the bullet FASTER along with that twist. I'm just assuming here though and really don't know the answer............
Bullet RPM = MV X 720/Twist Rate (in inches)
87,300 RPM for the 200 gr WHITEOUT (roughly)
I'm really interested in this and how its going to turn out. The more CONCRETE info, the better. I can't wait to read the future progress once the corrections are all made up and tested........
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I'll admit I'm no bullet expert but the original 200 grain boattail design required a 1:8" twist and I have to imagine adding 1/16" to the length can't help. The thing you said about pushing them faster makes sense. My gun pushes the bullets about 60 fps faster than Mike's and his gun suffers from flyers more so than mine. I have a little more power available. Maybe I should send them out the barrel closer to 1100fps?
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The stability decreases with velocity until you hit Mach 1, where it is the worst.... beyond that things are completely different, but we can't launch bullets fast enough to stay above Mach 1 out to 200 yards, and if we did, they would have MUCH more wind drift, so what's the point....
The Whiteout shoots 5 holes touching at 100 yards, but some of the holes are showing yaw at 200.... To me that means it is VERY close, so that extra 1/16" in length could make the difference.... it destabilizes the bullet by about 8%.... Only testing that idea will tell for sure....
Bob
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Nice work! I like the camo.
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Simple enough to check the theory. simply make a jig to hold the bullet in a mill, and mill the desired amount off the nose.
I did this before modding any of the NOE Molds here in my shop. this allowed for through testing before any mod's to the mold's were done. That is how I settled on a 80 gr. Spitzer for the .250 with it's 1-14 twist barrel. I sent a bunch to Doug to use at the EBR as they are very accurate bullets, however, Doug had problems with the Reg. on the .257 and switched to the 30 cal for the event. A shame, as the .257 is more accurate than the .30 Doug is shooting.
As far as Tethering goes, We Americans are far to proud,and down right stubborn to pay attention to how is being done in other parts of the world.
As I explained to Doug, Bench Rest is all about the very best accuracy obtainable from both the shooter, equipment, and gun. Not whether it translates to any perceived Hunting arena.
Not allowing tethering, which
is just about necessary in a big bore match, is foolish in my opinion. and in the opinion of match rules all over Europe. For some reason, the EBR seems *(&^ bent on making it difficult for Big Bore Shooters. Not that it surprises me in the least!
In fact, it is exactly what I would expect them to do, either out of disdain for Big Bores, or willful ignorance. Either- or, if not both. .
Knife
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One thing I think we need to remember is that this was the very first year the EBR had a bigbore category..... There is a learning curve when stepping out into something like that... AOA did a great job with the event, and I am sure there will be changes next year, as the bigbore market continues to expand. ;)
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I think that everybody did a great job the group from the EBR shoot set the rules that everyone new before hand and one rule was no tethering which I think is a great idea it puts more on the shooter if the shooter can not fill his rifle exactly the same they will not have the same point of impact for each shot. Especially for big bore rifles they are for most of the people that own them they bought them with hunting in mind and I would have to say in most cases for hunting tethering is not practical I am not saying that some people do not tether while hunting but would have to bet most do not. Like I have stated before I have raced snowmobiles professionally for 18 years and believe me I hate some of the rules we have to follow but any competition without clearly defined rules and enforced will eventually fail I have witnessed this time after time over the years with different racing organizations the organizations that did not set and enforce the rules did not last very long.
Brent Hoag
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Tethering for a prairie dog shoot would probably work out. Especially if there's an air stripper and you are not spooking them too much.
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Simple enough to check the theory. simply make a jig to hold the bullet in a mill, and mill the desired amount off the nose.
I did this before modding any of the NOE Molds here in my shop. this allowed for through testing before any mod's to the mold's were done. That is how I settled on a 80 gr. Spitzer for the .250 with it's 1-14 twist barrel. I sent a bunch to Doug to use at the EBR as they are very accurate bullets, however, Doug had problems with the Reg. on the .257 and switched to the 30 cal for the event. A shame, as the .257 is more accurate than the .30 Doug is shooting.
As far as Tethering goes, We Americans are far to proud,and down right stubborn to pay attention to how is being done in other parts of the world.
As I explained to Doug, Bench Rest is all about the very best accuracy obtainable from both the shooter, equipment, and gun. Not whether it translates to any perceived Hunting arena.
Not allowing tethering, which
is just about necessary in a big bore match, is foolish in my opinion. and in the opinion of match rules all over Europe. For some reason, the EBR seems *(&^ bent on making it difficult for Big Bore Shooters. Not that it surprises me in the least!
In fact, it is exactly what I would expect them to do, either out of disdain for Big Bores, or willful ignorance. Either- or, if not both. .
Knife
Good call Knife. Some aluminum soft jaws with a bisected hole gaped about 1/32" . For as much material that is being removed the weight of the vice handle would just about be enough to hold the slug. Imagine that would keep the deformation to min.
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Tethering for a prairie dog shoot would probably work out. Especially if there's an air stripper and you are not spooking them too much.
It does work and works well. I did just that last year on a PD shoot. The BLAST of a mid/big bore isn't really that bad when you are in the wide open desert. They get spooked MORE from a close MISS than muzzle blast ;D ;) Mostly mine were 100 yards or more out.