Which 6mm with small primer

T

Tom Howell

Guest
I am looking to rebarrel a Hall Model M with a .473 boltface into a 6mm of some kind to shoot 85 grain Barnes Triple Shocks for hunting antelope, small deer etc and to also shoot 68 grain match bullets at paper and ground squirrels. Because I want to shoot game, I am looking for as much horsepower as I can get so am leaning toward a 6x6.5x47 but maybe I can get by with an improved BR? What would anybody suggest and what twist would you use? Thanks for any help. Tom
 
Hey Tom,

Randy Tidwell from San Grabrial,

Sure hope they get our BR range done soon!

First, I shoot a 6 Dasher for my long range varmint shilo matches, it launches a 105 easily at 3100 fps. And the accuracy is fantastic.:D:D

Regarding the small primer, not sure why you want to go there, but cases with much capacity over 35 grains work more consistant with the large primer.

Years ago when I shot High Power Shilo, I got a bunch of the small primer 308 cases. Thinking the small primer was better, I tried them. Seen my scores drop, not much, but they did drop.

At the time I hand a home built rail gun with a couple of 308 barrels, so we did some experimenting, the large primer n the 308 worked better.

If you want to chat about the Dasher, let me know or get ahold of Mike Sosenko. Impressive littel round!

Randy
 
Hi Randy. My benchrest guns continue to rust away! Sounds like progress at the new range is coming along. In the meantime, I have been working on building a hunting rifle for coyotes, squirrels, deer and antelope and was going to go with some kind of a 6mm. I was thinking the small primers might handle pressures better but am probably all wet in that thinking. If you are getting 3100 out of a 105 grain bullet, I should get better than 3200 easy with the 85 grain bullets that I would hunt with. What twist would you use? I even tried some 80 grain Speer Hot Cores in the drop port the other day in the 6ppc and got pretty good groups with some vertical that I could tweak out I am sure. I was using H322. Hope to see you and all the guys around the first of the year. Tom
 
Tom Howell,

I can tell you flat out WHY you want the small primer.........VELOCITY!!!

Large primers SUCK.

I've spent extensive time with the .243AI, .243, 22-250, 6X250, 6mm, 6mmIMP and a host of other .308-case variants and there's NOTHING to compare with the small primer.


Ive spent the last few weeks working with the new 6.5X47 brass necked down to 6mm and I gotta' tell ya' it's HOT! One of my FIREFORM loads for my 6X47 uses VARget with a 70gr Match bullet at almost 4000fps! The caseful of VARget averages 3970fps while fireforming with one round going up to 4002 and another at 3987......... You can't get a .243AI to last above 3650 but this new case will RUN at 3900 forever........


105's coast at 3150 and a properly seasoned case seems to give unlimited caselife at 3200 (w/weighed charges.....it's right on the edge) I don't KNOW yet but I've got a set of cases with 7 reloads at 3200 flat using Euber 108's and the primers are still tight. My gut is that 3200 with the new case is about the same pressure as the 6BR at 2900fps.


I'm still new with this round, only about 350rds fired so far, all in workup and fireform but the numbers are astounding so far. I fully expect 85-88gr bullets to make 3600-3650 with ease.



But I still can't believe 4000fps with 68-70gr bullets. This is like a varminters wet dream.


al
 
Al, would you go with a tight neck and what twist if you were to shoot 85 grain Barnes and 68 grain match bullets? Tom
 
Tom, I believe in ONE twist rate only for my non-PPC 6mm's...........8"twist.

I spent all day Saturday fireforming 150rds (over a full set of flags) for my new 6X47 and part of the time was pushing 70gr Sierra HPBT Match bullets at 3900+ with the 8" twist. It was blowing the target paper off! Freakin' ex'PLOSIVE!


300,000rpm's showin' on the tach but I never blew up a bullet.


I predict that this new 6X47 round will absolutely push A-Max's until they pop. Also the older Bergers from 88gr up need to be run at light throttle or they'll vaporize enroute but I haven't blown up a Sierra, a Nosler or a Euber yet.


For varminting, casual 100-200yd and serious 300-600-1000yd target work there is absolutely no downside to the 8" twist. I own or have owned 6BR's, .243AI's, 22BR's and 6PPC's in all of the twist rates from 8 to 14" twist. I now ONLY order 14's and 8's.


That said, I MAY have to order a 12"er for use with ONE particular bullet for a 600yd gun. I might set up a rifle JUST to shoot the 88gr Berger LD's because I expect that the 8" twist will probably blow them up from over-rotation.


Regarding the neck turning thing:

6BR I'd go no-turn. I've got .262, .265, .268, .270 and .271 chambers and of them I prefer the .270 BUT you get'cherself a neck/shoulder gizzie and you check every round if you're into fireforming hot with a jam!

6X47 I'll strongly recommend a .266nk, I have a .268 and am going to buy a .266 next time. (BTW, I currently own two 6BR reamers which work "almost" perfectly for making chambers and dies for both the 6BR and the 6X47L. By "almost" i mean that the sizes are perfect but my next reamer will be cut with a shorter neck and to .266 diameter. I'm also gonna' make the base even FATTER than the .004 0ver SAAMI min that I'm running now.....)

Regarding the small primers:

The Rem URBR Brass is dreadful stuff. It does have the small primer but it's also got a gynormous flashhole which cuts down on the primer blast AND meters so much gas that the primer pockets expand nearly as bad as big-pocket brass. The Rem brass is also wicked soft. The Lapua small primer brass will gain several hundred fps over the URBR stuff.



You really wanna' play????

Just get the 6X47 and THEN if you want you can improve it! It's nothing more than a stretched 6BR right now............in fact EXACTLY a stretched 6BR, I use the same reamers.


There are some tricks to using the same reamers PROPERLY....... just remember that when you neck the 6.5 brass down to 6mm the neck shortens by 25thou or so...........ya' gots to accommodate fo it.


Here's my thing. After messing with 5 6BR reamers (and about 15 others of various calibers in the learning curve) I've now got two reamers that between them will make BOTH the perfect 6BR and the perfect 6X47 chambers AND THE DIES!!!


AWEsome........


al
 
Not to be augmentative,

First, the following is just my opinion and I believe Aliwa has more experience than I do, but I have my beliefs and experiences.

Comparing the performance of a small primer to a large is very difficult at best! With few acceptions, cases are not available with both size primers. I have cases with large primer pockets made from 7.62 x 39 for a PPC on a 40X I use for squirrels. I have shot groups (rarely) in the mid .1's. I will never claim it to be a sub .200 gun, but it doesn't shoot any better with Lapua brass either.

When we were playing with the 308 small primers, the SD's were all over the place, I believe this was due to inconsistent ignition with the longer column of powder (jmho). I think the 6 x 47 is right at the max powder capacity to use the small primer and would perform exactly the same way with a large primer.

Regarding the 6x47, you are absolutely right, fantastic case. Seems to be very balanced. But I also feel the same about the Dasher and 6BR. So, it is a Ford and Chevy debate. I have an XP-100 pistol with a 14" 6BR barrel that I have sent more than one guy home with his tail between his legs wanting to throw his varmint rig in the dirt.

Regarding twist, the 8 twist barrels are fantastic for their intended use, that is all we use for the varmint Shilo matches. And yes they will work with the lighter shorter bullets. However, if a 14 twist barrel gives the best performance with a 68 grain bullet and the 8 twist gives best with the long VLD style 105's, it only stands to reason the best twist for an 80-90 grainer lies between, 10-12 twist.

If you do the math on a bullet moving at 3600 fps out an 8 twist barrel, the rpm is incredible!

When most of us build rigs today, we try to get every ounce of performance we can, we're all spoiled with our BR rigs. I believe (humble opinion again) that you are giving up some performance with an 8 twist and 80-90 grain bullets.

I have seen 105's pushed over 3150 come apart. That is one of the reasons I stopped shooting one of the big name brands of VLD bullets and went to the Lapua Scenars (and I love them), have not seen one come apart yet.

Tom, you can't go wrong with any of these newer performance cartridges, they flat work. I absolutely love my Dashers. Easy to load for, less powder consumption (at the prices today, that is a concern), no neck turning, load standard 6BR case, shoot it....pretty dern simple to me.

I am just about done with all that neck turning hoop-la, I am looking real hard at the 6mm Beggs with a no turn neck. My Dashers are no turn and they will stay that way.

All this neck turning stuff started when the BR guys did not have good cases, I question whether it is worth it today.

JMHO

Randy
 
I have to agree with Ram here.

My 1:8" blows up 75 and 87 gr V-Maxes if they are pushed hard, and I've got to slow 'em down quite a bit to get 'em to shoot well out of a 6mm Rem AI. I'm happy with it shooting .4" slowed down. The 105 gr. Lapua is a fantastic bullet, one which Ram was kind enough to send me a sample to try in my rifle. They shoot MUCH MUCH MUCH better than the 87s ever will in my 1:8". The only bad thing about the Lapua is it tends to go right through prairie dogs. So for long range shooting, I'm running the Lapuas, and for a blood 'n' guts critter load, I run 87 gr. V-Maxes. If my little experience in 6mm is worth anything, twist rate is going to be a compromise no matter what you do.
 
Bullet RPM Calculator

I know this is off track for the original question, but I thought some might enjoy having this spread sheet for reference.

Attached is a spreadsheet I built awhile back. I cleaned it up a little today to make it a little bit more presentable.

It has columns for different twist rates that can be changed to match your particular barrel, I put in the most popular ones. After setting up the desired twist rates you want to compare, you can change the bullet velocity to see the results.

I have no idea where the thresholds are for bullet RPM, but it does open your eyes to just how fast we are spinning these bullets out these fast twist barrels! After seeing 105's come appart, the only conclusion we could come up with is they spun apart? Aparently the threshold for one brand of 105's is about 300,000 Rpm.

Regarding the original question, I personally would not make a choice based on the primer size, I think there are far more important factors to look at! You will go a long long way to prove a small primer is any more or less accurite than the large primer, especially in a varmint rig.

Remember, if something works, someone will jump on the band wagon to make it available. If Lapua/Norma/Rem/etc. thought they could make brass for us that is more accurite with a small primer, we would have it.

A good friend of mine has a saying for his varmint rigs "It shoots Minute of Squirrel, that's all I need" :D :D :D

Randy
 

Attachments

  • Bullet RPM.xls
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Talking about something for groundsquirrels and antelope, that's a huge jump. Using 6mm bullets on an 8oz gopher is a waste and pretty unnecessary. But whatever your conditions, just choose the cartridge and don't worry about primer size.

A friend shot benchrest for several years. He made PPC cases from PMC 7.62x39 brass which uses a large primer. It shot well enough to win matches. That went against conventional wisdom and some of the other shooters just couldn't believe such a thing was possible. He also found that a large primer in that small PPC sized case gave the same velocity with 1gr less powder. Or taken the other way, 150fps more velocity with the same load. I knew another guy who modified the BR case for a large primer and also got similar increase in velocity. Years ago the 22Cheetah with it's .243-sized powder capacity and small primer was supposedly the next most wonderful thing, but it gave unreliable ignition under some conditions. Each case is what it is and there're no options. I wouldn't be choosing a cartridge according to primer size, but if given the choice I'd rather a large primer in the .473 casehead.
 
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A word about small primers.

Small primers MUST be coupled with a small flashhole for them to work. I've got boxes of small primer URBR brass and it's junk. It's simple hydraulics, the large flash hole meters too much gas into the pocket.

As per "whether or not" the small flashhole makes a difference, this isn't really subject to argument. Anyone who owns both can test it rather simply by shooting both.

I've got 6BR, 6PPC and a shortened .308HBR round which can share brass easily and the small primer alone is worth 300-400fps velocity straight across the boards. SAME chamber. I've run the tests with all three chambering using Lapua brass. A case in point is that I've had a dozen .243AI's all shooting Lapua brass and this new 6X47L case simply blows it away with substantially less capacity. The same can be said for the 6-250 "Tubb" style case, with essentially identical capacities the 6X47 beats the 6-250 by 300fps.

al
 
Ohh, and BTW Randy........


"Remember, if something works, someone will jump on the band wagon to make it available. If Lapua/Norma/Rem/etc. thought they could make brass for us that is more accurite with a small primer, we would have it."


That's exactly what Lapua did! I tried for two years to get Kaltron Pettibone to intercede with Lapua on our behalf..........You could probably still find posts on this board predating the 6.5X47 case by at least two years. We BEGGED for this case for YEARS until Lapua produced it. I ordered 500 cases sight unseen several months before they hit the market.

I tried for 7yrs to get Lapua to interrupt a production run. I promised I'd order 10,000 cases with NO flash hole and they wouldn't do it.

But they did give us this new case, and it ROCKS!!

:)


al
 
alinwa said:
Ohh, and BTW Randy........


"Remember, if something works, someone will jump on the band wagon to make it available. If Lapua/Norma/Rem/etc. thought they could make brass for us that is more accurite with a small primer, we would have it."


That's exactly what Lapua did! I tried for two years to get Kaltron Pettibone to intercede with Lapua on our behalf..........You could probably still find posts on this board predating the 6.5X47 case by at least two years. We BEGGED for this case for YEARS until Lapua produced it. I ordered 500 cases sight unseen several months before they hit the market.

I tried for 7yrs to get Lapua to interrupt a production run. I promised I'd order 10,000 cases with NO flash hole and they wouldn't do it.

But they did give us this new case, and it ROCKS!!

:)


al
Click to expand...

My point exactly. When it works someone will do it.

Per the subject of this thread, if a small primer would increase the performance of a given case, somebody would be making them. So making a choice based on the size of the primer is not an advantage, in my opinion.

The success of the 6x47 is because it is a well designed and balanced case, not because it uses a small primer. I believe it would shoot just as well with a large primer set up properly. No proof, just my feeling.

When I did my Dashers, I was looking very hard at the 6x47. But the brass was about 3 months away.

I don't think the Dasher gives up anything, but I don't like the fact that you have to hot rod the case some to get the performance.

Next time around, I may change to the 6x47, depending on the barrel life I get out of the Dashers. So far barrel life has been good.

Randy
 
Randy, no wonder bullets fly apart on occasion! That is some eye opening rpm info. I am still trying to decide on a caliber. The Dasher has me interested in that I can probably make it work in the drop port which I think would be really advantagous in the field as the brass is just going to fall out, but my drop ports both have 6ppc bolts and I would have to buy another bolt as well as a barrel. I was going to shoot the 6ppc with 80 grain bullets again before I make up my mind on what to do. Even with a 1:14 twist it is showing some pretty good promise with mostly vertical that I want to try to tune out with increased powder charges. The 6x47 shows good velocity with so much less powder than a 243 that it would be my first choice for the Hall if I go with that action. Thanks for all the help guys. Tom
 
Tom,

You can't make a mistake with either case, I have not had a 6x47 yet, but hear nothing but good.

But I am also very sold on the Dasher. But I have always been a fan of the BR, so the Dasher is just a natural.

Hope to see you at a Br match when we get our range open again...

Randy
 
I can get 6mmPPC take off barrels for $75, ream them out to 6mmBR and get small groups.

But the bullets are light, and the velocities are low.
1) With a 1 in 14" twist rate, 65 gr stabilize, 75 grain iffy
2) Short barrel is slow
3) Fat barrel is heavy
4) CCI450 small rifle magnum primers will pierce with an ordinary firing pin hole at extreme pressures.
I have never done biz with him, but he looks like the guy:
http://www.gretanrifles.com/index.asp
Bush firing pin hole and turn pin $50.00

What does it all mean?
To hunt big game with a 6mmBR you may want a long, fast twist, sporter taper barrel and a bushed firing pin hole.
Click to expand...
 
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