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Powder Testing to Identify Barrel Sweet Spot (Read 15628 times)

Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #15 - Mar 2^nd, 2013 at 1:18pm	Print Post
	I have been getting 2 to 5 fps SD velocities with my Lyman 55 used to bulk load my competition rounds. The technique I use: -I use no reservoir baffle -I only load with a full reservoir and refill it after only using about 600 to 750 grains (only use top 10% of the reservoir before refilling). - use slow motion lifting or dropping the handle and hesitate for a second before moving handle or removing the case When I first started the old school boys told me to use the knocker. OOPs. That added 100 to 150 fps to my SD of velocities. I then learned you have to be careful not to jar the measure by using the knocker or from banging the handle too hard when you lift it when measuring ball powders. All the knocker is good for is to jar loose those big stick powders that jamb in the drop tube. Powders stick from static electricity to my plastic loading funnels. I was looking for a metal funnel. Instead I will try the graphite trick on the plastic funnel. To throw a rough charge which I then increase by trickle charging in the RCBS 10-10 weighing pan; I use a Lee powder measure to start loading of test loads.
	« Last Edit: Mar 2^nd, 2013 at 1:39pm by Schuetzendave »

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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Powder Testing to Identify Barrel Sweet Spot Reply #16 - Mar 3^rd, 2013 at 5:56am	Print Post
	Dave; o I understand this correctly? You shoot 5 shot groups at .1 grain intervals to identify suspected sweet spots. Then you shoot 30 shot groups at the suspected SS, +.1 grain, and -.1 grain. That's 90 shots around a suspected SS. Then you do it again, twice more? For 270 shots around the suspected SS? Have I got it right? Would you write about a test for sweet spots for a certain gun/barrel? With the number of shots fired, and group sizes, etc? Thanks; joe b. Schuetzendave wrote on Mar 1^st, 2013 at 1:04pm: Joe I start with single 5 shot groups to develop a map that indicates where sweet spots are and whether the sweet spots increase or decrease in group size with the amount of powder. This is not a statistical approach; it is a mapping initiative to initially identify where and what I need to statistically verify. Then I select what appears to be specific sweet spots and ussually test 3 thirty shot groups shot under heavy wind conditions where one powder load is 0.1 grain more, plus the powder load selected plus a 30 shot powder load of 0.1 grain less. This test is done three times to verify differences in the average 30 shot group size between different powder loads tested on a head to head basis (+/- 0.1 grain). 5 shot groups are shot initially to provide a map for testing and are not the statistical verification of the sweet spot selected. More intensive sampling and verification is required to verify a selected sweet spot. When a sweet spot is found there is a very prounounced difference in group size and generally I do not need to do extensive sampling to demonstrate a difference between sweet spot accuracy versus non-sweet spot accuracy. But I do use 30 shot group samples for the final statistical verification and replicate it three times.


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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Powder Testing to Identify Barrel Sweet Spot Reply #17 - Mar 3^rd, 2013 at 6:12am	Print Post
	Dave; 2 to 5 fps SD velocities is just amazing, I've never got or even read about such consistent velocities. During The Astounding Powder Measure Test I could find no evidence of "head" pressure in the 8 measures tested-powder height didn't vary charge weight. The Test showed the Lyman 55 with charge weight SD of .037 grains, nudging the accuracy of the RCBS 10-10 scale used. This while knocking that knocker every single time, as I've done since 1960 when I bought it. I'm amazed that knocking makes your charges/loads vary so much; and how our experience differs so much. joe b. Schuetzendave wrote on Mar 2^nd, 2013 at 1:18pm: I have been getting 2 to 5 fps SD velocities with my Lyman 55 used to bulk load my competition rounds. The technique I use: -I use no reservoir baffle -I only load with a full reservoir and refill it after only using about 600 to 750 grains (only use top 10% of the reservoir before refilling). - use slow motion lifting or dropping the handle and hesitate for a second before moving handle or removing the case When I first started the old school boys told me to use the knocker. OOPs. That added 100 to 150 fps to my SD of velocities. I then learned you have to be careful not to jar the measure by using the knocker or from banging the handle too hard when you lift it when measuring ball powders. All the knocker is good for is to jar loose those big stick powders that jamb in the drop tube. Powders stick from static electricity to my plastic loading funnels. I was looking for a metal funnel. Instead I will try the graphite trick on the plastic funnel. To throw a rough charge which I then increase by trickle charging in the RCBS 10-10 weighing pan; I use a Lee powder measure to start loading of test loads.


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digitall423 Oldtimer Offline Posts: 747 Location: Mexico Beach, FL Joined: Aug 5^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #18 - Mar 3^rd, 2013 at 8:13am	Print Post
	40 Rod, My son and I both have the Harrell Schuetzen measure. A while back I loaded them both with AA9 and adjusted them both to throw 13 grains. The dial was exactly the same on both measures. I don't know if they will all do this but ours did. I think that speaks of real production precision. Bill


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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #19 - Mar 3^rd, 2013 at 8:49am	Print Post
	Joe: I only get that precision with the Lyman 55 using very fine ball powders (AA#9, AA 4100, H108, WC820). What powders did you use in your trials? When I did the knocker trials I gave it an extremely hard whack. Not just a slight tap. Extremely gentle and consistent actions using the Lyman 55 do make a difference. The slightest tap can change the density of the powder. This changes a powder loads variation. This can also happen from significant changes in head volume. I believe my technique eliminates that and that is how I have better accuracy when I use the Lyman 55. Also remember I am using a fine tuned rifle for my testing. Possibly using a rifle that is not fully tuned may impact your testing precision. Dave
	« Last Edit: Mar 3^rd, 2013 at 9:15am by Schuetzendave »

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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #20 - Mar 4^th, 2013 at 3:13pm	Print Post
	I am being asked if the rifle action contributes to the accuracy obtained. I have been able to fine tune and to get a number of single shots to shoot this accurately. I have shot 1/2 MOA with plain based cast bullets using a .32 RKS case with a S.D. Meachem Hoch, 1885 Winchester High Wall, Yost Single Shot, as well as my Miller-DeHaas. When a gunsmith aligns the block squarely to the barrel any fine tuned single shot will shoot as accurately with proper bench technique; even if it has a bad trigger. However in competition time becomes more important and you then have to shoot quicker due to sudden wind variations or as you drift across the bulls eye while holding offhand. Then the quality of the trigger in the receiver becomes ultimately important. To prevent firing at the wrong time you need a trigger that has no creep, is consistent and light enough for quick release. So the Hoch could shoot 1/2 MOA but I frequently missed an offhand shot or could not fire under my preferred wind condition because the trigger was creepy and hard to pull. You do need a good quality trigger capable of shooting consistently and quickly to shoot accurately.
	« Last Edit: Mar 6^th, 2013 at 2:48pm by Schuetzendave »

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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #21 - Mar 5^th, 2013 at 10:27pm	Print Post
	Joe B.: I found some of my test data from when I evaluated my careful use of the Lyman 55 powder measure throwing AA #9 loads for my .32 RKS. For this 70 shot test the Standard Deviation for each 10 shot group was: 1.) 2.64 fps SD 2.) 5.00 fps SD 3.) 3.31 fps SD 4.) 2.82 fps SD 5.) 7.14 fps SD 6.) 2.82 fps SD 7.) 2.64 fps SD Average SD of 3.77 fps (with careful, gentle and slow loading techniques with Lyman 55 and at least 90% full hopper) I believe precision in your powder load weights is absolutely essential to obtain shooting accuracy. This should be Rule #1. I could not find my data from my knocker trials. The SD were so bad from this practice I never kept the data.
	« Last Edit: Mar 6^th, 2013 at 2:34pm by Schuetzendave »

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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #22 - Mar 6^th, 2013 at 11:22am	Print Post
	Would you write about a test for sweet spots for a certain gun/barrel? I have already assessed all of my barrels and once I fine tuned them I have not kept all of the data to do a good report. Lost most of my data in a computer crash. To do this I would need to start with another rifle. I would need to have someone donate me their equipment and I could do a complete assessment and record each step throughly to write a proper detailed report of the procedure plus the results. Yes I do start out recording a string of 5 shot groups (jacketed bullets) and 10 shot groups (cast bullets) to identify possible sweet spots. This mapping excercise identifies which sweet spot(s) that occurs around 0.3 grains of powder that would be best to assess with detailed and more statistically accurate testing with replication. I find this may not seem appropriate to a statistician; however extensive loading and firing is too expensive in time and money and wears out my equipment. Thus I do use low sampling to map out or provide indicators of how to minimize the amount of loads I need to test.
	« Last Edit: Mar 6^th, 2013 at 6:09pm by Schuetzendave »

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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #23 - Mar 6^th, 2013 at 1:44pm	Print Post
	Here is a string of 5 shot groups by powder load shot to identify potential sweet spots with a Mauser 98 barreled to 308 Win. This was the pre-mapping exercise to determine what powder loads needed to be assessed. Bullet: Grains: Powder: Grains: Group Size: Group Shape: Velocity: Sierra MatchKing 175 Varget 44.1 0.509 Small Cluster 2638 Sierra MatchKing 175 Varget 44.2 0.687 Shotgun 2644 Sierra MatchKing 175 Varget 44.3 1.189 Shotgun 2649 Sierra MatchKing 175 Varget 44.4 0.628 Cluster + Flyer 2655 Sierra MatchKing 175 Varget 44.5 0.923 Up Down 2661 Sierra MatchKing 175 Varget 44.6 0.501 Small Cluster 2667 Sierra MatchKing 175 Varget 44.7 0.924 Shotgun 2673 Sierra MatchKing 175 Varget 44.8 0.913 Shotgun 2678 Sierra MatchKing 175 Varget 44.9 0.855 Shotgun 2684 Sierra MatchKing 175 Varget 45.0 0.607 Small Cluster 2690 I then tested 44.1 and 44.6 grains of Varget to statistically verify if I had identified a good sweet spot. Unfortunately due to computer crashes I have lost the 30 shot tests to verify the accuracy. Although a single five shot group is not statistically valid this process will show where tighter groups occur due to lesser barrel vibrations relative to powder load. It will also show the cycle of where and how frequently you find a minimal barrel node for vibration. Yes it is not accurate but it is a good indicator to direct/initiate your testing. Yes I did put a RKS barrel on the Mauser 98. A brand new Luftwaffe receiver manufactured in 1943 that had never been barreled.
	« Last Edit: Mar 6^th, 2013 at 7:40pm by Schuetzendave »

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Cat_Whisperer Frequent Elocutionist Offline No 1, 9.3x74R Posts: 3889 Location: Mountains of Virginia Joined: Apr 17^th, 2004	Re: Powder Testing to Identify Barrel Sweet Spot Reply #24 - Mar 6^th, 2013 at 4:11pm	Print Post
	Schuetzendave wrote on Mar 6^th, 2013 at 1:44pm: ... Although a single five shot group is not statistically valid this process will show where tighter groups occur due to lesser barrel vibrations relative to powder load. It will also show the cycle of where and how frequently you find a minimal barrel node for vibration. Yes it is not accurate but it is a good indicator to direct/initiate your testing. ... EXCELLENT summary of the use of 5 shot groups and statistics. Too often we jump to making conclusions because someone somewhere mentioned mean and standard deviation (for a rediculously small sample).

	Cat Whisperer (trk) Chief of Smoke Pulaski Coehorn Works and Skunk Works Drafted May 1970, Retired Maj. U.S.Army assra #9885
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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #25 - Mar 6^th, 2013 at 5:59pm	Print Post
	I should mention when I do the pre-mapping testing I shoot 5 shot groups for the higher velocity jacketed bullets which are more consistent in accuracy. However when I pre-test breech seated cast bullets or BPCR fixed cases I shoot 10 shot groups since they are more sensitive to the wind. I believe we will have fairer shooting competitions in the future when everyone shows up with a fine tuned rifle. Then we will be competing with the shooters instead of out shooting their equipment. Once we have fine tuned rifles then we can fine tune the shooters. Scotch works good for this as well. Or is that just re-tuning?
	« Last Edit: Mar 7^th, 2013 at 1:24am by Schuetzendave »

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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #26 - Mar 11^th, 2013 at 4:19pm	Print Post
	I had a PM about: What rifles have you fine tuned and have you had problems finding a sweet spot? I have fine tuned one or more Miller-DeHaas, Yost, Winchester 1885 High Wall, S.D. Meachem Hoch, BSA Martini Cadet Model 4, CPA Stevens 44 1/2, Tikka M685, Tikka T3, Sako L651, Sako 85, Bruno 527, Cooper, Winchester Model 70, Remington 700, Savage 210, Ruger M77, Mauser K98, Parker Hale, Steyr, Husqvarna Crown 300, Remington No. 1 Rolling Block with factory barrels or custom RKS gain twist barrels or Douglas air gauge barrels or Womack barrel. There were only a few times when I had trouble seeing the 0.3 grain pattern showing different sweet spots. When I had poor information as to where the nodes might be; I went up or down on my powder loads or changed bullets and eventually found the node distribution from my pre-testing with firing of small groups.
	« Last Edit: Mar 12^th, 2013 at 1:45pm by Schuetzendave »

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joeb33050 Frequent Elocutionist Offline Posts: 2613 Location: Marathon, FL Joined: Apr 20^th, 2004	Re: Powder Testing to Identify Barrel Sweet Spot Reply #27 - Mar 14^th, 2013 at 5:00am	Print Post
	Dave; Do you shoot bullets in the order cast? Do you orient/index bullets? Cases? Both? Thanks; joe b.


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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #28 - Mar 15^th, 2013 at 1:25am	Print Post
	Joe: I keep the bullets together in lots that were cast on the same day to minimize major differences in weights. I completely ignore the minor weight changes that can result from time of casting within a day. I have found slight bullet weight variations have no impact on accuracy. However powder weights need to be absolutely precise to obtain good accuracy. I have never worried about case weights, indexing cases or bullets. Custom bullet molds usually throw very perfectly concentric bullets. If you need to align each bullet you would be better to buy a good quality bullet mold that throws perfectly round bullets (I use Paul Jones). If your bullets are not perfectly round the locking pins may have worn and may need to be tapped out further to better align the mold halves. I do use a sizer to ensure my bullets are perfectly round; a sizer one thousand wider (0.323) than my bullet (0.322 to 0.323) to just shave off any flashing or feathers, for my 0.321 diameter barrel (chamber) which chokes down to 0.3206 (at the muzzle). If your gunsmith has absolutely centered and squared the chamber then there is no need to index a case. However if you do have an out of alignment chamber then you may have problems that may be alleviated by lining up the case to the position it was last fired in the chamber. So far I have had an excellent barrel maker and gunsmith (Ron Smith) and have no need to align my cases. Dave
	« Last Edit: Mar 15^th, 2013 at 10:41am by Schuetzendave »

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Schuetzendave Frequent Elocutionist Offline Retired Ex-Shooter Posts: 4076 Location: St. Albert, Alberta Joined: Jan 28^th, 2005	Re: Powder Testing to Identify Barrel Sweet Spot Reply #29 - Mar 23^rd, 2013 at 11:29am	Print Post
	When I do the three 30 shot group tests I get different group sizes and patterns between the three. I usually get a large shotgun group, a flat linear group and a smaller cluster group. Many shooters select the flat group with minimal elevation change as being the most accurate. However with time I found these groups were demonstrating more sensitivity to the wind and seemed to move twice as far on a wind condition. I now select the smaller group pattern which shows slightly more change in elevation, but significantly less impact from windage. This group patterning shows frequently when testing powder loads +/- 0.1 grains apart from my test load. Also when I fine tune the air space when adjusting my bullet seater; I look to find a tighter group cluster as opposed to a flat right-left group.
	« Last Edit: Mar 23^rd, 2013 at 11:36am by Schuetzendave »

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