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Tony Shankle
Guest
pictures
So let's add some pics...
So let's add some pics...
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tim in tx
Guest
tony
simply awsome pics sir. tim in tx
simply awsome pics sir. tim in tx
Crowns
From my previous post: "do not degrade accuracy unless something is over torqued, out of alignment,or extremely close to the path of the bullet."
I stand corrected. Although I did have some "Unless" qualifications at the end of my earlier statement, I probably should have said that brakes are more likely to degrade accuracy than improve it, but under perfect conditions they are accuracy neutral and may improve the rifle's shootability or even act as a tuner and put the barrel in a better state of tune resulting in better accuracy.
I took a few minutes to review Harold Vaugn's chapter on muzzle blast. He does conclude that muzzle blast pressure affects accuracy and that reducing this pressure improves accuracy. He even goes on to say that the 6PPC optimizes this problem. It does make sense. I can't seem to envision a recessed crown being beneficial since it would only tend to constrain the muzzle blast which in theory would make things worse. Still, unless someone wants to devote the time and money to thoroughly testing those ideas we really don't know.
The best shooters with the most accurate bench guns are capable of agging in the teens in competition and might be able to agg in the zeros in a tunnel or other near perfect condition. If there is a yet to be discovered inprovement that reduces this even further, I would welcome it. At this point, the rest of us seem to be concentrating our efforts on getting our rifles to perform at that high level more often, and it is not easy.
I have heard of benchrest shooters being compared to sheep; that we all do what the winners are doing. Some of the recent winners are using tuners, some are using frozen scopes, gain twist barrels, boat tail bullets, etc. Others manage an occasional win without any of those things.
It takes courage to try something different.
Scott Roeder
From my previous post: "do not degrade accuracy unless something is over torqued, out of alignment,or extremely close to the path of the bullet."
I stand corrected. Although I did have some "Unless" qualifications at the end of my earlier statement, I probably should have said that brakes are more likely to degrade accuracy than improve it, but under perfect conditions they are accuracy neutral and may improve the rifle's shootability or even act as a tuner and put the barrel in a better state of tune resulting in better accuracy.
I took a few minutes to review Harold Vaugn's chapter on muzzle blast. He does conclude that muzzle blast pressure affects accuracy and that reducing this pressure improves accuracy. He even goes on to say that the 6PPC optimizes this problem. It does make sense. I can't seem to envision a recessed crown being beneficial since it would only tend to constrain the muzzle blast which in theory would make things worse. Still, unless someone wants to devote the time and money to thoroughly testing those ideas we really don't know.
The best shooters with the most accurate bench guns are capable of agging in the teens in competition and might be able to agg in the zeros in a tunnel or other near perfect condition. If there is a yet to be discovered inprovement that reduces this even further, I would welcome it. At this point, the rest of us seem to be concentrating our efforts on getting our rifles to perform at that high level more often, and it is not easy.
I have heard of benchrest shooters being compared to sheep; that we all do what the winners are doing. Some of the recent winners are using tuners, some are using frozen scopes, gain twist barrels, boat tail bullets, etc. Others manage an occasional win without any of those things.
It takes courage to try something different.
Scott Roeder
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tim in tx
Guest
here is a pic of the recessed crown i use
it is a 6 dasher with 105vlds,with a 32 degree angle and a 45 degree crown. http://benchrest.com/forums/attachment.php?attachmentid=7146&d=1234051740 tim in tx
it is a 6 dasher with 105vlds,with a 32 degree angle and a 45 degree crown. http://benchrest.com/forums/attachment.php?attachmentid=7146&d=1234051740 tim in tx
PR2Shooter
New member
its an interesting subject. I'm not sure any of us would be capable of truely testing the various crown shapes. There are just so many conditions and parameters that would affect the results. I would assume most smith's are cutting the 90 degree with small counterbore to eliminate indicating the bore one more time. I prefer the 11 degree personally.
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Tony Shankle
Guest
WOW Tim!
So you lost me. I understand the recessed crown as 45 degrees but are the side walls the 32 degrees?
Tell us more please!
So you lost me. I understand the recessed crown as 45 degrees but are the side walls the 32 degrees?
Tell us more please!
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tim in tx
Guest
tony
the side walls are straight around .800 dia and the face down inside is 32 degrees,then i single point cut a slither to cut the final crown at 45 degrees,i can cut it cleaner that way with fewer burrs.i have not experimented with this for the recessed crown but more for an integrated tuner and weak middle barrel by trimming and shooting.but i can say this the recessed crown on this particular rifle has not hurt accuracy one bit,it could have helped but i cannot prove it for sure.the rifle sure shoots good though. tim in tx
the side walls are straight around .800 dia and the face down inside is 32 degrees,then i single point cut a slither to cut the final crown at 45 degrees,i can cut it cleaner that way with fewer burrs.i have not experimented with this for the recessed crown but more for an integrated tuner and weak middle barrel by trimming and shooting.but i can say this the recessed crown on this particular rifle has not hurt accuracy one bit,it could have helped but i cannot prove it for sure.the rifle sure shoots good though. tim in tx
JerrySharrett
Senile Member
Consider this. Many benchrest gunsmiths now use a 90 degree sharp edge crown. Why? It works and it is fast, and, the barrel doesn't have to be indicated perfectly. About 0.001"-0.005" is close enough.
Shoot that barrel for accuracy. Now, take that same barrel and indicate the GROOVES to 0.0001" or less if you can get it there. Machine an approx. 0.005" x 45 bevel on the face/bore intersection. Shoot the barrel again for accuracy. Same? Most likely. At least on 8-10 barrels I tried it on in the last 2-3 years. On the size bevel I use, there is just a faint line visible on the grooves and somewhat more, naturally, on the lands. This is what I consider a 0.005" x 45 bevel.
Now comes the weeding out part. If you have the razor sharp edge at the face/bore intersection it is easy to see that razor sharp edge is very fragile and will show damage soon from cleaning. The 45 degree bevel will be much less fragile and will last much longer without affecting accuracy.
Pulling the last few weeds, if you do your own barrel work, the sharp edge is fine but you will need to refresh it every 250 rounds or so. The micro-beveled barrel can probably go 600 or more rounds without needing to be refreshed.
All this is considering the normal process benchrest shooters use for shooting and cleaning. There are situations where the muzzle bore may be worn to a bell shape by poor cleaning methods or high round count, but, the average benchrest shooter will have tossed that barrel way before the muzzle bore wears any visible or gageable amount.
Shoot that barrel for accuracy. Now, take that same barrel and indicate the GROOVES to 0.0001" or less if you can get it there. Machine an approx. 0.005" x 45 bevel on the face/bore intersection. Shoot the barrel again for accuracy. Same? Most likely. At least on 8-10 barrels I tried it on in the last 2-3 years. On the size bevel I use, there is just a faint line visible on the grooves and somewhat more, naturally, on the lands. This is what I consider a 0.005" x 45 bevel.
Now comes the weeding out part. If you have the razor sharp edge at the face/bore intersection it is easy to see that razor sharp edge is very fragile and will show damage soon from cleaning. The 45 degree bevel will be much less fragile and will last much longer without affecting accuracy.
Pulling the last few weeds, if you do your own barrel work, the sharp edge is fine but you will need to refresh it every 250 rounds or so. The micro-beveled barrel can probably go 600 or more rounds without needing to be refreshed.
All this is considering the normal process benchrest shooters use for shooting and cleaning. There are situations where the muzzle bore may be worn to a bell shape by poor cleaning methods or high round count, but, the average benchrest shooter will have tossed that barrel way before the muzzle bore wears any visible or gageable amount.
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jackie schmidt
New member
Grinding a Crown
Sure, you could grind a crown. My question, as a machinist, would be "Why"??........jackie
Sure, you could grind a crown. My question, as a machinist, would be "Why"??........jackie
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Tony Shankle
Guest
Thanks for your comments Jerry. How many people (what percentage) in the benchrest world refresh their crowns? Is is something seen more in short range benchrest?
JerrySharrett
Senile Member
Tony, lots of considerations in the answer to that question.
Of the 100/200 shooters that do their own barrel work, I'd GUESS 95% would refresh their crowns at least once. Of that same group I'd guess 60-70% refresh chambers.
Of the 600/1000 shooters that do their own barrels there would be considerably less that would recrown or refresh chambers. Many cartridges in the 600/1000 sport, burn so much more powder that rechambering is not as beneficial, UNLESS, some will take their 30" barrel and cut off 3" or so, but that is not a refresh of a chamber. That would be a complete rechamber.
I'll get jumped on this but many 600/1000 shooters are not as accuracy conscious as many 100/200 shooters are. The 600/1000 shooters are just as results conscious but not as accuracy conscious. How many 600/1000 shooters really try to get their barrels to shoot in the teens as do 100/200 shooters? They are just different games. I'd bet 70% of the 600/1000 guns wouldn't even place in the top 50% when shot at a 100/200 shoot. Neither would 70% of the 100/200 guns even place in the top 50% of a 600 shoot, let alone a 1000 yard shoot.
Now, of the 100/200 shooters that go to the Super Shoot, or one of the NBRSA or IBS Nationals shot at Kelblys, many more will get a crown refreshed there. Reason? They have one of the very best benchrest shops just behind the firing line and a couple of years ago their price to recrown was about $25.
Refreshing chambers is a whole 'nuther story.
jackie schmidt
New member
Refreshing
I do set my chambers back after every 300 rounds or so, it is easy for me to do and the cost to me is nothing. The first two times,I set it back about .025-.030, just to freshen up the throat area. The third time, I chop the straight portion of the chamber off, and more or less treat it like a new blank.
The way I chamber barrels makes it quite easy to set them back up in the originol position as when it was first chambered..
Is it worth it. To me it is, but then, I do not have to pay someone to do it.
As for crowns, I will set them back as well, as it only takes a few minutes. But rarely do I find any reason to. I owe that to careful use of the cleaning rod........jackie
I do set my chambers back after every 300 rounds or so, it is easy for me to do and the cost to me is nothing. The first two times,I set it back about .025-.030, just to freshen up the throat area. The third time, I chop the straight portion of the chamber off, and more or less treat it like a new blank.
The way I chamber barrels makes it quite easy to set them back up in the originol position as when it was first chambered..
Is it worth it. To me it is, but then, I do not have to pay someone to do it.
As for crowns, I will set them back as well, as it only takes a few minutes. But rarely do I find any reason to. I owe that to careful use of the cleaning rod........jackie
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Tony Shankle
Guest
OK Jackie and Jerry...
You have now freaked me out a bit.
I have been shooting long range in one discipline or another for over 20 years and I have never had a crown refreshed. I just shot the barrel out and put on a new barrel. Now, for the last couple of days I have been walking around thinking several thoughts....
(1) Of all the great Smiths and Mentors I have had, why didn't any of them tell me to do this?
(2) If the crown is that important, why didn't my performance (grouping) change long before I shot out the barrel? If the impact is that great why didn't I see a change?
(3) Could it be possible that it is more important for certain bullets, cartridges, and ranges?
You both are two guys I would listen to (respect) so please read this as a request for enlightenment and not argument. If I am doing it wrong I certainly want to fix it!
You have now freaked me out a bit.
I have been shooting long range in one discipline or another for over 20 years and I have never had a crown refreshed. I just shot the barrel out and put on a new barrel. Now, for the last couple of days I have been walking around thinking several thoughts....(1) Of all the great Smiths and Mentors I have had, why didn't any of them tell me to do this?
(2) If the crown is that important, why didn't my performance (grouping) change long before I shot out the barrel? If the impact is that great why didn't I see a change?
(3) Could it be possible that it is more important for certain bullets, cartridges, and ranges?
You both are two guys I would listen to (respect) so please read this as a request for enlightenment and not argument. If I am doing it wrong I certainly want to fix it!
JerrySharrett
Senile Member
Tony you may have been shooting Hi Power, Service Rifle or such. Those sports don't require the finite accuracy that benchrest does.OK Jackie and Jerry...
You have now freaked me out a bit.
(1) Of all the great Smiths and Mentors I have had, why didn't any of them tell me to do this?
(2) If the crown is that important, why didn't my performance (grouping) change long before I shot out the barrel? If the impact is that great why didn't I see a change?
(3) Could it be possible that it is more important for certain bullets, cartridges, and ranges?
You both are two guys I would listen to (respect) so please read this as a request for enlightenment and not argument. If I am doing it wrong I certainly want to fix it!
Speaking of accuracy, I've got to finish loading the motorhome. We're leaving tomorrow AM for the IBS 100/200 Nationals.
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Tony Shankle
Guest
Jerry,
You are correct, I spent many years in highpower but when I moved to LR Highpower I decided to also shoot 1000 yard benchrest when I could to increase my accuracy. My memory is foggy but I think my first benchrest shoot was around 13 years ago at Williamsport (rude awaking as I remember with Bruce Baer and those gentlemen from PA spanking this prone shooter hard
). Even though benchrest is not my favorite discipline, I have tried to follow its accuracy standards in my other pursuits. I load to benchrest standards even for tactical matches. Also, most of my Smiths and Mentors were "benchrest" guys. I am just shocked I have gone this long without being told to refresh my crown.Nevermind me, enjoy your shoot and be safe in your travel. I am sure Jackie will jump in and straighten me out while you are gone!