Throat to dummy cartridge

DeltaBravo

DeltaBravo

Member
When a barrel maker chambers to "dummy cartridge" what exactly does that mean and how is the dummy constructed? :confused:

I'm having a new pre-fit barrel done up by Shilen - this is my third from them. I want to send in dummy cartridges for throating the chamber, but I'm confused about how to set them up. My current chamber allows me to reach the lands, but there's only about 1/10" of the bullet in the case neck (68 grain BT). For the dummies, do I seat the bullet where I want it in the case neck (2/10" in) and then have the barrel throated so that the bullet touches the lands? Or what?

Thanks.

Dennis
 
Yes, you send them dummies with bullets seated exactly the way you want them and they will throat it accordingly with bullets touching lands (if possible). When you get the dummies back they'll likely have blue dye on the bullets and they'll be marked by the lands where they were fitting them.
 
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Make your dummies a little short , so you can move out as the throat wears.
 
Okay, guys, thanks for the replies. Your answers were what I was thinking, but didn't know for sure. I'm currently 6-thou off the lands (used to be 9 off), so going 2/10 into the case will give me plenty of outward adjustment. My current barrel - same as the replacement except for the taper - has the "standard" throat for the 14-twist and it works very well. So, I'm hoping that the replacement will work even better and provide additional adjustment!

Dennis
 
DeltaBravo said:
Okay, guys, thanks for the replies. Your answers were what I was thinking, but didn't know for sure. I'm currently 6-thou off the lands (used to be 9 off), so going 2/10 into the case will give me plenty of outward adjustment. My current barrel - same as the replacement except for the taper - has the "standard" throat for the 14-twist and it works very well. So, I'm hoping that the replacement will work even better and provide additional adjustment!

Dennis
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Dennis. consider too, what bullets you intend to shoot. For, example, if you intend to shoot 750 jacketed boat tails with a pointy nose, about 0.025" freebore would be ideal. If you intend to shoot 825 jackets with Gary Conaway's 5/9 nose flat base bullets an 0.065" freebore would be about right, IMO/

Its your barrel, Wade and the guys can machine it to whatever. For a time I shot an 0.085" freebore to get case capacity when I had some slow 8208.

.
 
Jerry,

I shoot Bart's 68 BT or 65 BT. Don't know what the pointy-ness is for them, but they definitely shoot! The barrel I'm shooting now is whatever free bore Shilen put in for a 14-twist. I just want to make that a bit less so I have more movement in the neck when needed. Thanks for the reply.

B.Larson, I wouldn't know what to do with a uni-throater. I use one barrel about every 2 years and am happy with Shilen's work. I would likely just screw all that up if I tried to do anything to it myself! Thanks.

Dennis
 
DeltaBravo said:
Jerry,

I shoot Bart's 68 BT or 65 BT. Don't know what the pointy-ness is for them, but they definitely shoot! The barrel I'm shooting now is whatever free bore Shilen put in for a 14-twist. I just want to make that a bit less so I have more movement in the neck when needed. Thanks for the reply.

B.Larson, I wouldn't know what to do with a uni-throater. I use one barrel about every 2 years and am happy with Shilen's work. I would likely just screw all that up if I tried to do anything to it myself! Thanks.

Dennis
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Dennis, if the barrel you have was done by Shilen they probably have a file on it and an duplicate it.

There was something awhile back about something Shilen had done years ago and Wade had to go into the attic but he found the info.


.

.
 
Jerry, I don't really want to duplicate what I have now even tho it shoots really well. I want to have a bit more OAL adjustability, just cuz! I'm not much of an experimenter, I find what works and stick with it, but now that I'm a few years into this, I want to have a little more challenge, stupid or not!

Dennis
 
Make sure that if you send dummy rounds to use new brass that hasn't been fired in a chamber. I've had dummies sent to me that were fired in an oversize chamber. When using those dummies, the cases don't bottom out on the shoulder in the chamber. To get a correct throat length, the case has to bottom out on the shoulder and not on the body.
 
Mike Bryant said:
Make sure that if you send dummy rounds to use new brass that hasn't been fired in a chamber. I've had dummies sent to me that were fired in an oversize chamber. When using those dummies, the cases don't bottom out on the shoulder in the chamber. To get a correct throat length, the case has to bottom out on the shoulder and not on the body.
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M&M,

Once again, I'm confused on a much higher plane than before. :confused:

The chamber should be nearly identical - within reason - to the chamber I have now. Same .266 neck 6BR reamer would be used, I hope. It seems to me that given the similarities, I "should" send in fired brass for this instead of new as I don't see how my brass can be oversized; but then I really don't know, that's why I posed the question. My brass has all been fired 15+ times, annealed every 2 or 3 times, and fits the chamber quite well with minimal sizing.

I have new brass, but would have to turn the necks to fit the .266 chamber, so new brass is doable.

Please explain further.

Thanks.

Dennis
 
DeltaBravo said:
M&M,

Once again, I'm confused on a much higher plane than before. :confused:

The chamber should be nearly identical - within reason - to the chamber I have now. Same .266 neck 6BR reamer would be used, I hope. It seems to me that given the similarities, I "should" send in fired brass for this instead of new as I don't see how my brass can be oversized; but then I really don't know, that's why I posed the question. My brass has all been fired 15+ times, annealed every 2 or 3 times, and fits the chamber quite well with minimal sizing.

I have new brass, but would have to turn the necks to fit the .266 chamber, so new brass is doable.

Please explain further.

Thanks.

Dennis
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Call Wade and see what he needs. Probably fired and f/l sized brass...don't bump the shoulder.

These large custom gunbuilders, over time, have their reamers reground several times and it is impossible, even with CNC to get all the dimensions exactly duplicated to the point to where your fired case will fit a new chamber.



.
 
Thanks, Jerry. Looks like a phone call is in order. I just hate to bother them for a one-off barrel that only gets replaced every couple years!

Dennis
 
Well, thanks to everyone for their input and feedback on this - I learned a lot! It's become a moot point, tho, because my barrel will be delivered tomorrow!!! That's only 5 weeks since ordering it, as opposed to the "usual" 12 to 16 weeks! I guess the best time to order a new barrel is the middle of summer when everyone is out competing! :cool:

Thanks.

Dennis
 
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