Gunsmithing Throat to a dummy cartridge

[Deleted member 10043]

So, I'm ordering a new barrel and I need some dummy cartridges so the manufacturer can do that. I've never been asked this before and the guy explained it to me over the phone and I need to call him back but basically I still don't know how to do this with just a specific bullet, brass, and die. Can somebody shed some light on this?

Cartridge: 6mm Remington
Bullet: 110 gr. SMK or 107 gr. SMK.

 

[Subwrx300]

Super easy: take 3-4 pieces of new brass of the type you want to shoot and seat them to the length you want to load them. Usually this means either to -.020-.030 shorter than mag length (if possible without seating past ogive) to give yourself room to seat longer as lands move forward.

Measure the longest bullet seating depth that will fit in your mag and work backwards. Make 4-5 and measure that ogive is in same place for each round and ship him the dummy's.

I'm sure a couple of guys here can chime in if they have good starting length.

 

[Deleted member 10043]

This is a single shot sled rifle. The 110 SMK is so new it is still not in Sierra's or any other reloading manual. But for the 107 gr. Sierra is saying max length is 3.105" and the Hodgen reloading manual is stating the OAL was 2.95". But the guy at Northland is saying don't use reloading manuals for this. I can call him back but I'm still confused on the starting point.

 

[Shifty6BR]

I'm sure others will chime in but if you want visual info Gre-Tan has an excellent video explaining things on youtube.

 

[Shifty6BR]

 

[Supersubes]

Since you aren’t mag feeding, simply seat a bullet to your liking into a virgin case. Most would prefer that the bottom of the bearing surface to be above the neck shoulder junction. .030-.050 above should be fine, regardless of cartridge.

 

[spaniel]

Since you aren’t mag feeding, simply seat a bullet to your liking into a virgin case. Most would prefer that the bottom of the bearing surface to be above the neck shoulder junction. .030-.050 above should be fine, regardless of cartridge.

This. For a single feed, just seat the base of the bullet above the neck/shoulder junction so you never have to worry about donut issues interfering with the bullet seating.

 

[Deleted member 10043]

Okay, I get it know. I resize my virgin brass like I normally do .002" bumped shoulder and then set the HPBT base just above the neck juncture. My concern being I need to ship these to the manufacturer and don't want to lose my COAL. I take a piece of masking tape and write the COAL on each case as a precaution. Also, I see if I use the 107 gr. SMK that I will get a little deeper seating depth with the 110 SMK. That should be okay if I decide to go with 110 SMK in the future with this barrel. Correct?

 

[Subwrx300]

Okay, I get it know. I resize my virgin brass like I normally do .002" bumped shoulder and then set the HPBT base just above the neck juncture. My concern being I need to ship these to the manufacturer and don't want to lose my COAL. I take a piece of masking tape and write the COAL on each case as a precaution. Also, I see if I use the 107 gr. SMK that I will get a little deeper seating depth with the 110 SMK. That should be okay if I decide to go with 110 SMK in the future with this barrel. Correct?

Hard to say without knowing the bullet base to bearing surface and base to forward ogive dimensions.

If you already have both bullets in hand, you should be able to find the relative change with a 6mm comparator. You'd want to set the throat for the longer bullet if you think you will use it. If 110gr is seated .030 forward of neck/shoulder junction, the 107 should be forward of that.

You might see if Sierra can send you prints of each bullet so you can do some math to make sure your tests match up somewhere close to the Sierra print dimensions.

Regarding shipping, I think your plan is spot on. Write measured coal on case in sharpie (avoiding tape residue) and pack them in foam: cut slots into foam and slip them in. Package with some peanuts or lots of paper and good to go!

 

[Supersubes]

Okay, I get it know. I resize my virgin brass like I normally do .002" bumped shoulder and then set the HPBT base just above the neck juncture. My concern being I need to ship these to the manufacturer and don't want to lose my COAL. I take a piece of masking tape and write the COAL on each case as a precaution. Also, I see if I use the 107 gr. SMK that I will get a little deeper seating depth with the 110 SMK. That should be okay if I decide to go with 110 SMK in the future with this barrel. Correct?

No need to bump the shoulders on virgin brass unless you’ve discussed something specific with the smith, and he wants that way. It’s a zero factor for his throating, and would just be bad practice going forward if he headspaces your barrel a smidge longer than go, as is standard. Essentially you’d be shortening an already short case.

 

[Deleted member 10043]

I'm starting to get the picture. I'm visual by nature and I need to think backwards here. Like seat the bullet a little forward of the neck junction to allow seating live ammo off the lands and don't bump the shoulder with a FL die to achieve the basically the same type of room for that process as well.

I've been in contact with Sierra and will ask for the dimensions or even some 110s. I'll start another topic in a different forum here on the performance between the 107 and 110.

 

[Geno C.]

I think you're over thinking it for a single shot rifle. Seat the bullet in the cases where you want them to be. You've shot enough to know to consider donuts and throat erosion. If you think you want to run the 107 and 110, send in both and let them know that you'd like that. The 110 could end up a little deeper than your dummy and your 107 a little long.

One thing a lot of guys don't consider is you might run into a bullet that likes a lot of jump. Hat will mess with everything. Say you set the land to touch when the heel of the bullet is .020" above the neck/shoulder junction. You find out later that the 110 likes a .035" jump. Now the heel is below that junction.

Just set the bullets where you think would be idea for a new barrel. Tape on the bullet to hold it won't hurt; writing the coal of each round won't hurt either.

 

[sandwarrior]

Okay, I get it know. I resize my virgin brass like I normally do .002" bumped shoulder and then set the HPBT base just above the neck juncture. My concern being I need to ship these to the manufacturer and don't want to lose my COAL. I take a piece of masking tape and write the COAL on each case as a precaution. Also, I see if I use the 107 gr. SMK that I will get a little deeper seating depth with the 110 SMK. That should be okay if I decide to go with 110 SMK in the future with this barrel. Correct?

Don't resize back .002". that will make the gunsmith think he wants to go .002" short. You want the chamber to be the finished size, so your brass can expand .002" then size it back down.

Just size your dummy round so that it's round for the bullet to go in and straight. Meaning within your load limits on runout should be how you normally load.

 

[Deleted member 10043]

Got it, thanks.

 

[sandwarrior]

Got it, thanks.

I added a line.

 

[sandwarrior]

I'm starting to get the picture. I'm visual by nature and I need to think backwards here. Like seat the bullet a little forward of the neck junction to allow seating live ammo off the lands and don't bump the shoulder with a FL die to achieve the basically the same type of room for that process as well.

I've been in contact with Sierra and will ask for the dimensions or even some 110s. I'll start another topic in a different forum here on the performance between the 107 and 110.

Something to think about asking your gunsmith is putting a "Wylde' type throat/freebore. It's a tight diameter with minimal taper out farther than a normal throat. As Geno C. said some bullets like a lot of jump. And, Ive found that a Wylde throat in a .223 gives great accuracy and it's longer in total than a 5.56 free-bore. I know you are talking about 6mm Rem, but the principle is the same. Run the free bore out 1/4" past where the longest bullet would be seated. But the bore in that throat is only .0005" over bullet diameter. five ten-thousandths.