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87 V-Max/Dasher Issues

RAG

I took delivery of a used Borden BRM with new/unfired Krieger chambered in 1-8 Dasher a few days back. Primary purpose will be long range pdogs, and of course punching paper for fun. My hope was that it would like the 87 Vmax, though it seems about 75% of folks with 1-8 twists struggle to get good accuracy. Well, first real 5-shot group with 87 Vmax after break-in and velocity testing a couple powder/bullet combinations, came in right at 1.6" at 500 yards. I take it! But then the problems started...the rounds I had pre-loaded started getting very difficult to chamber, so I thought I had a seating issue. After getting home and pulling my hair out for a while, AckleymanII helped me diagnose the likely problem...we took out our calibrated micrometers and both came up with bullet diameter (on the body/BS) of .2434 - .2435 whereas all the other 6mm bullets in my arsenal measure out .2430. So the Vmax is over sized by 1/2 thousandths...and we surmise my new chamber most likely has a "tight throat" somewhere in the vicinity of .2435, creating a problem as soon as the carbon starts building up. Guess I'm going to have to find another bullet; I'll be trying the Berger 88s next.

Not sure if anybody else has encountered this issue, but I wonder if this oversizing of the 87 Vmax is part of the reason so many people struggle to get this bullet to shoot to a high standard, as many of these 1-8" "match" chambers likely have a tighter throats.
 
That 88 gr. F B Berger will make you happy if you load it at or close max. My 6BRX likes VV-N135 30.5 GR. PRIMER CCI 450M at about .006 off the lands. Have shot in the ones with it so far.
 
urbanrifleman said:
How do they blow up? I have a bunch of them.
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Surely not great. I shot quite a few105 VLDs at prarie dogs (mostly small ones the size of large squirrel) and I got them to be pretty explosive by chucking the bullet, and then opening the meplat with a .050 drill bit ( tried a few different micro-bit sizes actually), and thinning the outside of the jacket leading edge with metal file. I didn't notice any adverse affect on accuracy in range tests...but obviously adds a lot of work to the process, so I was sure hoping to shoot the 87 Vmax.
 
RAG said:
Surely not great. I shot quite a few105 VLDs at prarie dogs (mostly small ones the size of large squirrel) and I got them to be pretty explosive by chucking the bullet, and then opening the meplat with a .050 drill bit ( tried a few different micro-bit sizes actually), and thinning the outside of the jacket leading edge with metal file. I didn't notice any adverse affect on accuracy in range tests...but obviously adds a lot of work to the process, so I was sure hoping to shoot the 87 Vmax.
Click to expand...

The Bergers 80s blew up great at 3550 fps. Like hand grenades.
 
My apologies, misread the original post.

If the neck of your chamber is so tight that .0005" makes a significant difference, I would say that you need to be turning your necks for that brass and chamber combo. For varmint shooting I would want .003" total clearance, for match use maybe .002". You know most custom match bullets have a pressure ring that is +/- .0005 so the 87 V-Max being a little fat may be a good thing if you get the other parameters worked out. I'm working on the same thing, 6 Dasher - 87 V-Max in 8 twist, so will be interested to follow this thread.
 
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X-Caveman said:
I think OP is concerned with his freebore diameter, not so much his neck diameter. Maybe I’m wrong.
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YEs, this is correct. It's a .272 neck, so ample clearance there...

I just got my hands on 4 Dasher reamer prints. The freebore/throat "Diameter" ranged from .2433 to .2435. The problem here is that the 87 VMAX, over the entire body (bearing surface) is .2434-.2435 (I have calibrated micrometer, as does AckleymanII, and over the phone we measured 87 vmax and came up with the same). So after shooting, the freebore, with microscopic fouling/carbon buildup, the Freebore effectively becomes less than zero. I really bet this is why so many people with match grade guns (thus match chambers) have issue getting these bullets to shoot. Again, I'm still breaking this barrel in, but I fired a .3MOA group at 500 yards with these on first group, then the groups went to hell, and then I couldn't even chamber a round.

FWIW, I also have Hornady 105 Amax, and 108 ELD-M bullets to measure, and these came right at .2430...so I don't think this oversized bullet issue is a Hornady thing, just an 87-Vmax issue.
 
w hat kind of action are you using? have you checked your push back on the shoulder? Take the firing pin out of the bolt and insert the bolt the handle should fall shut. Insert a fired sized case and see if the bolt still falls shut . If not readjust the die till the bolt just falls shut. If your push back is not far enough the case will cause hard chambering. hope you have checked this
 
lakehawk said:
w hat kind of action are you using? have you checked your push back on the shoulder? Take the firing pin out of the bolt and insert the bolt the handle should fall shut. Insert a fired sized case and see if the bolt still falls shut . If not readjust the die till the bolt just falls shut. If your push back is not far enough the case will cause hard chambering. hope you have checked this
Click to expand...
IT's a Borden BRM, and yes, that was one of the first things I checked, thank you. Undoubtedly, the problem is...the bullet (starting at the ogive) is the same diameter, or .0001 off, from the diameter of the freebore/throat/lead.

I just had PTG send me 4 reamer prints, and 2 of them had a SMALLER diameter in the freebore/lead section than the diameter of the 87 Vmax. How crazy is that!
 
RAG said:
I took delivery of a used Borden BRM with new/unfired Krieger chambered in 1-8 Dasher a few days back. Primary purpose will be long range pdogs, and of course punching paper for fun. My hope was that it would like the 87 Vmax, though it seems about 75% of folks with 1-8 twists struggle to get good accuracy. Well, first real 5-shot group with 87 Vmax after break-in and velocity testing a couple powder/bullet combinations, came in right at 1.6" at 500 yards. I take it! But then the problems started...the rounds I had pre-loaded started getting very difficult to chamber, so I thought I had a seating issue. After getting home and pulling my hair out for a while, AckleymanII helped me diagnose the likely problem...we took out our calibrated micrometers and both came up with bullet diameter (on the body/BS) of .2434 - .2435 whereas all the other 6mm bullets in my arsenal measure out .2430. So the Vmax is over sized by 1/2 thousandths...and we surmise my new chamber most likely has a "tight throat" somewhere in the vicinity of .2435, creating a problem as soon as the carbon starts building up. Guess I'm going to have to find another bullet; I'll be trying the Berger 88s next.

Not sure if anybody else has encountered this issue, but I wonder if this oversizing of the 87 Vmax is part of the reason so many people struggle to get this bullet to shoot to a high standard, as many of these 1-8" "match" chambers likely have a tighter throats.
Click to expand...
I just measured some 87 V Max's that I had, they are a few years old.

They measured .2432-.2434 . Lot # 2150463
 
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