Bob Kingsbury
New member
Anyone have any thoughts on throat length for 6 Dasher using 107
Sierra.
Sierra.
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Throat in Dasher
- Thread starter Bob Kingsbury
- Start date
R
rcw3
Guest
With a max chamber length for the reamer between 1.555" and 1.560", around .120" - .125" free bore with a one and a half degree throat angle is excellent - keeps the full bearing surface of the bullet up in the neck, but still with plenty of neck purchase - and if you can keep the free bore diameter on the reamer in the range of .2433" - .2435", you will be doing well.
Robert Whitley
Robert Whitley
B
Baron Graham
Guest
Bob,
Dave Kiff at PT&G and I worked together to set up my 6 Dasher Reamer (supposed to be the same FB as the World Record Dasher). It was spec’d for the Berger 105 VLD, but none of the four Dashers chambered with my reamer shoot best with the 105 VLD! One shoots bug holes with the Berger 108 BT, two shoots bug holes with BIB 108 BT (My pair) and one shoots bug holes with the 107 SMK. Although my pair will shoot bug holes with 107 SMK’s, I elected to shoot the BIB. My reamer has a “.104 Freebore”! A .104” FB gives you .016” extra throat chasing over the .120”. Although M. Eddy’s 6 Dasher reamer has a .120” FB and Thomas Ellington out of NC shoots extremely well with it.
Baron Graham
Dave Kiff at PT&G and I worked together to set up my 6 Dasher Reamer (supposed to be the same FB as the World Record Dasher). It was spec’d for the Berger 105 VLD, but none of the four Dashers chambered with my reamer shoot best with the 105 VLD! One shoots bug holes with the Berger 108 BT, two shoots bug holes with BIB 108 BT (My pair) and one shoots bug holes with the 107 SMK. Although my pair will shoot bug holes with 107 SMK’s, I elected to shoot the BIB. My reamer has a “.104 Freebore”! A .104” FB gives you .016” extra throat chasing over the .120”. Although M. Eddy’s 6 Dasher reamer has a .120” FB and Thomas Ellington out of NC shoots extremely well with it.
Baron Graham
R
rcw3
Guest
Bob,
Dave Kiff at PT&G and I worked together to set up my 6 Dasher Reamer (supposed to be the same FB as the World Record Dasher). It was spec’d for the Berger 105 VLD, but none of the four Dashers chambered with my reamer shoot best with the 105 VLD! One shoots bug holes with the Berger 108 BT, two shoots bug holes with BIB 108 BT (My pair) and one shoots bug holes with the 107 SMK. Although my pair will shoot bug holes with 107 SMK’s, I elected to shoot the BIB. My reamer has a “.104 Freebore”! A .104” FB gives you .016” extra throat chasing over the .120”. Although M. Eddy’s 6 Dasher reamer has a .120” FB and Thomas Ellington out of NC shoots extremely well with it.
Baron Graham
The reamer you have has a max case length of 1.570" vs mine that has a 1.555" max case, so your analysis of having an extra .016" to chase the throat is just not correct (i.e. it's only a .001" difference) - you just have a bigger gap between the end of the mouth of your brass and the end of the chamber.
Robert Whitley
Last edited by a moderator:
R
rcw3
Guest
I`d call .160" just about perfection with that bullet. This with a 1.570" chamber length, 1 1/2* leade.
You must like the bullet pretty far up in the neck. With a 107 Sierra bullet that leaves only about .150" of the neck holding onto the bullet.
Robert
Bob Kingsbury
New member
What would the standard dasher throat be as ground by Pacific--
You must like the bullet pretty far up in the neck. With a 107 Sierra bullet that leaves only about .150" of the neck holding onto the bullet.
Robert
Robert,
No mater what the case length and free-bore of the 6Dasher reamer's, the point at a bore diameter of 0.234" (your last reamer print length measurement) will tell you the differences in bullet placement to the neck.
Your .115-FB reamer print (#30110) compared to Tim's .160-FB is .060" difference from the .234" datum. So to be at a equal seating depth to the lands, Tim's bullet will be .060" further up the neck. And stands to good reason why he opp'ed to have a 1.570" case length. Verses say your 1.555", which gives him .015" more usable neck, which in return knocks it down to .045" more is all, from the case end to bullet datum.
For your math with a 107-SMK, a datum point of .234" will be around .555" behind the tip of the bullet (no matter what the bullet OAL of a given bullet Lot, The tip diameter will remain closest from Lot to Lot, is why I base the .555" datum point from the tip, and based on a equal ogive bullet design).
Happy Shooting
Donovan Moran
Last edited:
Chambering the 6BR and 6 Dasher
The Right Reamer Makes All the Difference -- Dave Kiff
Profile: Dave Kiff directs the operation of Pacific Tool & Gauge, the premier custom reamer maker on the West Coast. His reamers have been used on many match-winning rifles, both in standard 6BR and 6 BR Improved chamberings. The man knows his stuff. When you give him a call, he will listen carefully to your design goals, and provide you with a custom reamer ideally suited to your needs, delivered quickly, at a fair price.
6mmBR.com asked Dave about PT&G and what is involved in designing and machining a custom reamer for a 6BR rifle.
Q: Dave, tell us about Pacific Tool & Gauge...
We manufacture precision chamber reamers, gauges and a wide variety of other specialty tools for the firearms industry including Remington replacement bolts for benchrest rifles. We've grown from a two-person operation to a 34-employee shop, doing work for all the major gun manufacturers. At the same time we take pride in our custom work, providing one-on-one service for each individual customer. I've been doing precision machining for over 20 years, and I learned about making reamers from some of the best tool-makers in the business, Keith Francis and Red Elliot.
Q: What sets PT&G apart from other firms that produce reamers?
We are one of the only companies that still handcrafts reamers on Crystal-Lake belt driven grinders. I also personally hand-stone each and every PT&G reamer that leaves our doors. Unlike other companies, we do not charge extra for wildcats like the 6 Dasher, nor do we charge extra to custom-spec your reamer from your dummy case. And our track record in competition in unsurpassed. In fact, a new world record was recently set with a 6 Dasher chambered with a PT&G reamer.
Q: What are the advantages of a custom PT&G reamer--What do I get for my $138 investment?
You get better accuracy, reduced ES, longer brass life, and most importantly you get exactly the chamber that you want. The throat will be set precisely to match the bullets you shoot and the seating depth you want. And you can pick a neck-size to suit your needs. Whether you want a .272" no-turn neck or a minimum-turn .269" neck (which is very popular now), we can make that, or any other neck diameter you want all the way down to .261". Because you can set the exact neck-wall thickness you want, you get better control over neck tension which reduces velocity spreads. And the body dimensions are ideally matched to Lapua brass so you get less case expansion, without sacrificing feed reliabilty. Brass that isn't worked as much during sizing lasts longer.
Let me give you an example of how important a good chamber is. We've seen super-expensive barrels on thousand-dollar actions that did not shoot well at all, because the throating was bad. The throat will make or break a benchrest gun. When they were rechambered with our reamers, group size was reduced by 50% or more. We've had other customers that start out with non-premium, inexpensive barrels, but still end up with very competitive guns because they have perfect chambers and throats. A concentric, close-fitting chamber and a good throat are the keys to accuracy.
Q: Without revealing any trade secrets, what throat lengths do you recommend for a 6mm BR case?
We normally go with a 1.5 degree lead angle, unless the customer wants something different. For 60-68gr bullets we recommend a .060" freebore. For the 80gr bullets, .080" is a good setting. For the 100-107gr VLDs, a .115" -.120" freebore will allow you to get the base of the bullet up out of the doughnut area. This will save you lots of aggravation over the life of the barrel.
Q: There are a variety of 6BR Improved case profiles out there. Which wildcat version works best, based on reports from your customers?
We have prints for all the popular 6 Improved cases including the Dasher, the 6 BRBS (Shehane), and Bob Crone's 6 BRX. Based on customer reports, it is our strong opinion that the 6 Dasher is by far the best for 1000-yard accuracy. You get a bit longer neck, and the Dasher has a 40° Improved body. This 40° shoulder provides the most ideal turbulence pattern for consistent powder ignition. Bottom line, the 6 Dasher is the winningest 1000yd cartridge based on the 6mm BR parent case. If I built a 6BR wildcat rifle for myself, it would definitely be a Dasher.
Q: What kind of chambering reamers are preferred by your customers?
By far, the majority of our custom reamer orders are for removable-pilot reamers (live pilot) for the full chamber (neck and body). Definitely go with a live pilot for any custom reamer you have ground. Solid piloted reamers can scratch the lands.
Live-Pilot Reamer from ECT (Elliot Tool), a PT&G company.
Q: What about neck-only reamers--do you recommend doing the neck with a separate neck reamer?
No. We always recommend using a full neck+body reamer for a high-grade custom rifle, particularly if you plan to have more than one barrel. Yes, a very talented smith can finish a chamber with a separate neck reamer (which we sell), but to get absolute 100% consistency from barrel to barrel it is best to cut the chamber with our live pilot reamer that does the neck and body at the same time. When the barrel is shot out, you can take that reamer, give it to any good smith, and get an identical chamber.
Q: If my smith has a 6BR reamer in stock, why should I buy my own reamer from PT&G?
First and foremost, we can give you a reamer with the throat set ideally from your dummy round, with freebore measured from the bullet ogive. And the body diameter will be a perfect fit for Lapua brass. Having the throat and lead set for your case and bullet choice will provide the best accuracy for the gun. You can spend thousands on your action, barrel, stock and scope, but if the throat is not right, your gun may not shoot to your expectations.
Also, consider that your smith's reamer may be an older model designed for 6 BR Remington brass. This will cut a chamber dimensionally incorrect for Lapua brass. The neck will be short and it will be tight at the casehead. Second, if it is a full SAMMI-spec reamer you may end up with a neck diameter much larger than you want, .276" or even larger, when .272" is all you need for a no-turn neck. Order from us and we can give you precisely the dimensions you want for both neck and body. Lastly, your smith's reamer may have a lot of miles on it. Worn-out reamers cut poor chambers.
We always recommend that you use a sharp reamer that cuts on all flutes. A worn reamer or a reamer that does not cut on all flutes can give you a small or short throat also a larger body than needed. Always check your reamer before you use it.
Q: How long does it take to get a 6mm BR or 6BR improved reamer? Does the customer need to send you a spec sheet or can you work off a sample round?
When a customer calls, I ask what brass he will be using and what bullet he plans to shoot. I can usually spec the right throat length and headspace based on this information alone, but it is best if he sends a dummy round with a bullet seated exactly where he wants it--for example with the top of the boat-tail .050" above the neck-shoulder junction. I measure the dummy round off the ogive with a 100-power Deltronic comparator, inspect for concentricity and gauge the headspace. Then I prepare a print for the job right away. The completed reamer is usually ready in two to six weeks.
Q: Do you sell non-custom 6BR reamers as well?
Yes, through MidwayUSA we sell both a $89 SAAMI standard 6mm BR Norma reamer (solid pilot) and a $105 Match Grade reamer (live pilot). These are produced by our subsidiary ECT (Elliot Tool Company), but I still personally hand-finish the Match Grade reamers. The Match Grade 6BR reamer, Midway item # 555174, features a .272" no-turn neck and a .113" freebore. This is ideal for shooting 107gr Sierra MKs with a no-turn neck, or shooting Lapua factory-loaded 105gr ammo. This is a great value for anyone wanting to shoot the 100gr bullets with a no-turn neck. And you can buy it off the shelf. And let your readers know we also stock off-the-shelf reamers for Tubb's 6XC cartridge and the 6x47 Swiss Match.
Q: Last Question. Do you have any new products in the pipeline we should be looking for?
Yes, we have a number of projects in the works, but I think your readers will be most interested in our new precision-made Remington replacement bolt. It is available with either a Rem standard extractor or a Sako-style extractor for $125. The tolerances rival that of the bolts found in custom actions.
Pacific Tool & Gauge
P.O. Box 2549 - 598 Ave C
White City, OR 97503
Phone: (541) 826-5808; FAX: (541) 826-5304
The Right Reamer Makes All the Difference -- Dave Kiff
Profile: Dave Kiff directs the operation of Pacific Tool & Gauge, the premier custom reamer maker on the West Coast. His reamers have been used on many match-winning rifles, both in standard 6BR and 6 BR Improved chamberings. The man knows his stuff. When you give him a call, he will listen carefully to your design goals, and provide you with a custom reamer ideally suited to your needs, delivered quickly, at a fair price.
6mmBR.com asked Dave about PT&G and what is involved in designing and machining a custom reamer for a 6BR rifle.
Q: Dave, tell us about Pacific Tool & Gauge...
We manufacture precision chamber reamers, gauges and a wide variety of other specialty tools for the firearms industry including Remington replacement bolts for benchrest rifles. We've grown from a two-person operation to a 34-employee shop, doing work for all the major gun manufacturers. At the same time we take pride in our custom work, providing one-on-one service for each individual customer. I've been doing precision machining for over 20 years, and I learned about making reamers from some of the best tool-makers in the business, Keith Francis and Red Elliot.
Q: What sets PT&G apart from other firms that produce reamers?
We are one of the only companies that still handcrafts reamers on Crystal-Lake belt driven grinders. I also personally hand-stone each and every PT&G reamer that leaves our doors. Unlike other companies, we do not charge extra for wildcats like the 6 Dasher, nor do we charge extra to custom-spec your reamer from your dummy case. And our track record in competition in unsurpassed. In fact, a new world record was recently set with a 6 Dasher chambered with a PT&G reamer.
Q: What are the advantages of a custom PT&G reamer--What do I get for my $138 investment?
You get better accuracy, reduced ES, longer brass life, and most importantly you get exactly the chamber that you want. The throat will be set precisely to match the bullets you shoot and the seating depth you want. And you can pick a neck-size to suit your needs. Whether you want a .272" no-turn neck or a minimum-turn .269" neck (which is very popular now), we can make that, or any other neck diameter you want all the way down to .261". Because you can set the exact neck-wall thickness you want, you get better control over neck tension which reduces velocity spreads. And the body dimensions are ideally matched to Lapua brass so you get less case expansion, without sacrificing feed reliabilty. Brass that isn't worked as much during sizing lasts longer.
Let me give you an example of how important a good chamber is. We've seen super-expensive barrels on thousand-dollar actions that did not shoot well at all, because the throating was bad. The throat will make or break a benchrest gun. When they were rechambered with our reamers, group size was reduced by 50% or more. We've had other customers that start out with non-premium, inexpensive barrels, but still end up with very competitive guns because they have perfect chambers and throats. A concentric, close-fitting chamber and a good throat are the keys to accuracy.
Q: Without revealing any trade secrets, what throat lengths do you recommend for a 6mm BR case?
We normally go with a 1.5 degree lead angle, unless the customer wants something different. For 60-68gr bullets we recommend a .060" freebore. For the 80gr bullets, .080" is a good setting. For the 100-107gr VLDs, a .115" -.120" freebore will allow you to get the base of the bullet up out of the doughnut area. This will save you lots of aggravation over the life of the barrel.
Q: There are a variety of 6BR Improved case profiles out there. Which wildcat version works best, based on reports from your customers?
We have prints for all the popular 6 Improved cases including the Dasher, the 6 BRBS (Shehane), and Bob Crone's 6 BRX. Based on customer reports, it is our strong opinion that the 6 Dasher is by far the best for 1000-yard accuracy. You get a bit longer neck, and the Dasher has a 40° Improved body. This 40° shoulder provides the most ideal turbulence pattern for consistent powder ignition. Bottom line, the 6 Dasher is the winningest 1000yd cartridge based on the 6mm BR parent case. If I built a 6BR wildcat rifle for myself, it would definitely be a Dasher.
Q: What kind of chambering reamers are preferred by your customers?
By far, the majority of our custom reamer orders are for removable-pilot reamers (live pilot) for the full chamber (neck and body). Definitely go with a live pilot for any custom reamer you have ground. Solid piloted reamers can scratch the lands.
Live-Pilot Reamer from ECT (Elliot Tool), a PT&G company.
Q: What about neck-only reamers--do you recommend doing the neck with a separate neck reamer?
No. We always recommend using a full neck+body reamer for a high-grade custom rifle, particularly if you plan to have more than one barrel. Yes, a very talented smith can finish a chamber with a separate neck reamer (which we sell), but to get absolute 100% consistency from barrel to barrel it is best to cut the chamber with our live pilot reamer that does the neck and body at the same time. When the barrel is shot out, you can take that reamer, give it to any good smith, and get an identical chamber.
Q: If my smith has a 6BR reamer in stock, why should I buy my own reamer from PT&G?
First and foremost, we can give you a reamer with the throat set ideally from your dummy round, with freebore measured from the bullet ogive. And the body diameter will be a perfect fit for Lapua brass. Having the throat and lead set for your case and bullet choice will provide the best accuracy for the gun. You can spend thousands on your action, barrel, stock and scope, but if the throat is not right, your gun may not shoot to your expectations.
Also, consider that your smith's reamer may be an older model designed for 6 BR Remington brass. This will cut a chamber dimensionally incorrect for Lapua brass. The neck will be short and it will be tight at the casehead. Second, if it is a full SAMMI-spec reamer you may end up with a neck diameter much larger than you want, .276" or even larger, when .272" is all you need for a no-turn neck. Order from us and we can give you precisely the dimensions you want for both neck and body. Lastly, your smith's reamer may have a lot of miles on it. Worn-out reamers cut poor chambers.
We always recommend that you use a sharp reamer that cuts on all flutes. A worn reamer or a reamer that does not cut on all flutes can give you a small or short throat also a larger body than needed. Always check your reamer before you use it.
Q: How long does it take to get a 6mm BR or 6BR improved reamer? Does the customer need to send you a spec sheet or can you work off a sample round?
When a customer calls, I ask what brass he will be using and what bullet he plans to shoot. I can usually spec the right throat length and headspace based on this information alone, but it is best if he sends a dummy round with a bullet seated exactly where he wants it--for example with the top of the boat-tail .050" above the neck-shoulder junction. I measure the dummy round off the ogive with a 100-power Deltronic comparator, inspect for concentricity and gauge the headspace. Then I prepare a print for the job right away. The completed reamer is usually ready in two to six weeks.
Q: Do you sell non-custom 6BR reamers as well?
Yes, through MidwayUSA we sell both a $89 SAAMI standard 6mm BR Norma reamer (solid pilot) and a $105 Match Grade reamer (live pilot). These are produced by our subsidiary ECT (Elliot Tool Company), but I still personally hand-finish the Match Grade reamers. The Match Grade 6BR reamer, Midway item # 555174, features a .272" no-turn neck and a .113" freebore. This is ideal for shooting 107gr Sierra MKs with a no-turn neck, or shooting Lapua factory-loaded 105gr ammo. This is a great value for anyone wanting to shoot the 100gr bullets with a no-turn neck. And you can buy it off the shelf. And let your readers know we also stock off-the-shelf reamers for Tubb's 6XC cartridge and the 6x47 Swiss Match.
Q: Last Question. Do you have any new products in the pipeline we should be looking for?
Yes, we have a number of projects in the works, but I think your readers will be most interested in our new precision-made Remington replacement bolt. It is available with either a Rem standard extractor or a Sako-style extractor for $125. The tolerances rival that of the bolts found in custom actions.
Pacific Tool & Gauge
P.O. Box 2549 - 598 Ave C
White City, OR 97503
Phone: (541) 826-5808; FAX: (541) 826-5304
R
rcw3
Guest
Robert,
No mater what the case length and free-bore of the 6Dasher reamer's, the point at a bore diameter of 0.234" (your last reamer print length measurement) will tell you the differences in bullet placement to the neck.
Your .115-FB reamer print (#30110) compared to Tim's .160-FB is .060" difference from the .234" datum. So to be at a equal seating depth to the lands, Tim's bullet will be .060" further up the neck. And stands to good reason why he opp'ed to have a 1.570" case length. Verses say your 1.555", which gives him .015" more usable neck, which in return knocks it down to .045" from the case end to bullet datum.
For your math with a 107-SMK, a datum point of .234" will be around .555" behind the tip of the bullet (no matter what the bullet OAL of a given bullet Lot, The tip diameter will remain closest from Lot to Lot, is why I base the .555" datum point from the tip, and based on a equal ogive bullet design).
Happy Shooting
Donovan Moran
I understand what you are saying but what is your point?
Robert
Robert,
You quoted "that leaves only about .150" of the neck holding onto the bullet" which I believe your math is wrong to, was my point.
My math computes it to be another .035 to .045" more (depending on his trim length) of hold on the bearing surface, then what you quoted.
Happy Shooting
Donovan Moran
You quoted "that leaves only about .150" of the neck holding onto the bullet" which I believe your math is wrong to, was my point.
My math computes it to be another .035 to .045" more (depending on his trim length) of hold on the bearing surface, then what you quoted.
Happy Shooting
Donovan Moran
R
rcw3
Guest
Robert,
You quoted "that leaves only about .150" of the neck holding onto the bullet" which I believe your math is wrong to, was my point.
My math computes it to be another .035 to .045" more (depending on his trim length) of hold on the bearing surface, then what you quoted.
Happy Shooting
Donovan Moran
Therein lies the issue doing things with math and drawings alone. The .150" number (actually it was .148" but I rounded it up to .150") is an actual measurement I did based off actual chambers cut with certified Dasher reamers (cross checked with different reamers I have) and actual Sierra 107's and actual Dasher brass (i.e. .150" worth of neck brass holding the bearing surface of the bullet when it hits the lands in a chamber with a 1.570" max chamber length with a .160" free bore and a one and a half degree throat angle with a .2435" free bore diameter). In my experience, doing it on paper is one thing, but that is not always quite the same as working with the real thing. All the numbers on the prints are also subject to the "Tolerances" box on the print and the spread of those tolerances can also make a big difference what you get in actuality (that's also why I use certified reamers that have the measurements confirmed in a comparator).
Bear in mind I said "about" .150" holding onto the bullet, because I realize that what one uses for a trim length matters too, as the Dasher is a wildcat and there is no exact specs for things, etc..
Robert
Last edited by a moderator:
Robert,
I have 6Dasher's with .160-FB / 1.570-CL..... Just put a 107-SMK in one to the Lands. Here is the "actual" math to it:
Case OAL =1.560" -- Bullet OAL=1.230 -- BT-Len.=.175 -- Neck-Len.= .261
With that there is .102" of the bullet behind the junction, which leaves .073" of the Boat-tail in the neck, which leaves .187" of hold on the bearing.
Pretty much spot on math........
Happy Shooting
Donovan Moran
I have 6Dasher's with .160-FB / 1.570-CL..... Just put a 107-SMK in one to the Lands. Here is the "actual" math to it:
Case OAL =1.560" -- Bullet OAL=1.230 -- BT-Len.=.175 -- Neck-Len.= .261
With that there is .102" of the bullet behind the junction, which leaves .073" of the Boat-tail in the neck, which leaves .187" of hold on the bearing.
Pretty much spot on math........
Happy Shooting
Donovan Moran
R
rcw3
Guest
Robert,
I have 6Dasher's with .160-FB / 1.570-CL..... Just put a 107-SMK in one to the Lands. Here is the "actual" math to it:
Case OAL =1.560" -- Bullet OAL=1.230 -- BT-Len.=.175 -- Neck-Len.= .261
With that there is .102" of the bullet behind the junction, which leaves .073" of the Boat-tail in the neck, which leaves .187" of hold on the bearing.
Pretty much spot on math........
Happy Shooting
Donovan Moran
Please feel free to pat yourself on the back and give yourself a gold star for your smartness.
Robert
Bob Kingsbury
New member
Please fill me in here, what is a certified reamer. Now I have used optical comparitors
before, and though they are great for checking angles and radius, not a defining way
to measure things
before, and though they are great for checking angles and radius, not a defining way
to measure things
To get back to the original question, with regard to what? Are you trying to *precisely* keep a certain portion of the bullet in the neck?Anyone have any thoughts on throat length for 6 Dasher using 107
Sierra.
Reason I ask is what I would do is to figure the (eventual) case length, trim a standard 6mm BR case to that length, seat a 107 Sierra to taste, and using the comparator, figure out where the forcing cone should begin.
Actually, I'd get several 6mm long-range bullets and pick a freebore length so I could use more than one bullet. Had a bad experience specifying a 6.5 reamer that put 142 SMKs exactly where I wanted them. Unfortunately, that was a bit long to use any other bullet except the generally unavailable Clinch River 140 flatbase. Now I specify freebore length for the shortest bullet, and throat the chamber out if I decide on a bullet needing a longer freebore.