6mm arc reloading (bolt action)

[Asumner]

I am new to reloading and the first caliber I have tried is my 6mm arc. I am using Hornady brass ( I know) with varget and 105 hybrids the primers if needed are federal small rifle match.

My question is, when I tested for jam I found that I was at 1.710 base to ojive so I started my testing at 1.690. I ended with a load that was 27.6gr. At 1.684. Here begins the issue. I started annealing now and used a mandrel for better neck tension and now my bullets will pull out and become stuck in the barrel until 1.660 now. Is this because I had a false positive on jam or is it that my neck tension is too little? I only realized this when I made a random dummy round and the bullet was removed so I tried it with one of my loads and it seated an extra 8 thou deeper. Any help or advice would be great.

 

[gunsandgunsmithing]

I am new to reloading and the first caliber I have tried is my 6mm arc. I am using Hornady brass ( I know) with varget and 105 hybrids the primers if needed are federal small rifle match.

My question is, when I tested for jam I found that I was at 1.710 base to ojive so I started my testing at 1.690. I ended with a load that was 27.6gr. At 1.684. Here begins the issue. I started annealing now and used a mandrel for better neck tension and now my bullets will pull out and become stuck in the barrel until 1.660 now. Is this because I had a false positive on jam or is it that my neck tension is too little? I only realized this when I made a random dummy round and the bullet was removed so I tried it with one of my loads and it seated an extra 8 thou deeper. Any help or advice would be great.

I think you can answer this yourself better than anyone, by simply eliminating the mandrel step, seating a bullet and inspecting for any marks on the bullet. Ya might also give it a very thorough cleaning and make sure a carbon ring hasn't developed, causing the issue. Clearly, there is interference from something.

 

[Asumner]

Imm

I think you can answer this yourself better than anyone, by simply eliminating the mandrel step, seating a bullet and inspecting for any marks on the bullet. Ya might also give it a very thorough cleaning and make sure a carbon ring hasn't developed, causing the issue. Clearly, there is interference from something.

i did not think of the carbon ring.

 

[SD guy]

I expect you are doing a fairly good job of answering your own questions. Your original measurement on base to lands (base to ojive does sound long. Not to discourage your current path, though the following data may go a little ways towards another reference for a starting point for your initial load data. Vihtivori load data offers a OAL to match up with typical mag length.

Sammi offers intended Sammi chamber head space & throat specifications. I find the data to be rather interesting at the very least. Yet your chamber may & throat may vary.

https://saami.org/wp-content/uploads/2025/02/SAAMI-Z299.4-CFR-2025-Centerfire-Rifle-Approved-2-10-2025.pdf

Rifle reloading data | Handloading | Rifle calibers | Centerfire Rifle bullets | Reload your own ammo - Vihtavuori

Vihtavuori offers rifle reloading data for numerous calibers and bullets for match and hunting purposes. Never exceed maximum loads.

www.vihtavuori.com

 

[JMayo]

Jam & touch difference.
Anything longer than touch is a jam.

 

[Asumner]

Jam & touch difference.
Anything longer than touch is a jam.

Yes I am going to jam not touch. I just tried some brass without using my mandrel and I got the exact dimension as my original test a few months ago. I then tested with my mandrel and it shoved my bullet much deeper. The difference is one I used the stock expander ball and the other I used a separate mandrel instead. I do know I am now getting pressure signs on my brass at max load where the longer length I wasn’t lol.

 

[DHD]

I have a Forster FL 6mm ARC die that does not size the brass enough for my liking. I also have a Wilson bushing FL die that let's me do what I want (as long as I buy bushings that is). I don't use the Forster unless I am converting Lapua Brass now. I had some issues with bullets being seated deeper after a trip from the magazine to the chamber (one magazine didn't like one particular lower). The brass sized using a smaller ID didn't do that.

Not saying you don't do this already, but I get my measurements from a clean barrel so my data is more than likely to be accurate.

 

[KMW 1954]

Yes I am going to jam not touch. .

I do know I am now getting pressure signs on my brass at max load where the longer length I wasn’t lol.

I too am loading a 105gr Berger Hy-brid in a 6ARC using a light jam and am get a BTO length measured with a Hornady tool much longer than yours. This could be because of one of many differences, such as the measuring tool or the barrel chamber or even the head space length.

I now have my length set to where I can extract a loaded case and the bullet does not pull out. I am Full Length Resizing with an off the shelf Lee die. I also now have enough rounds thru this barrel that the soft jam I started with is now probably a short jump.


Here is a league target that was just shot 2 weeks ago for our final week. The red target was with an adjustment made from 300yds to 200 yds. The black target is 5 shots that most likely I will never duplicate again. The scope used has 1/8" adjustments.

 

[Asumner]

I too am loading a 105gr Berger Hy-brid in a 6ARC using a light jam and am get a BTO length measured with a Hornady tool much longer than yours. This could be because of one of many differences, such as the measuring tool or the barrel chamber or even the head space length.

I now have my length set to where I can extract a loaded case and the bullet does not pull out. I am Full Length Resizing with an off the shelf Lee die. I also now have enough rounds thru this barrel that the soft jam I started with is now probably a short jump.

View attachment 1644983
Here is a league target that was just shot 2 weeks ago for our final week. The red target was with an adjustment made from 300yds to 200 yds. The black target is 5 shots that most likely I will never duplicate again. The scope used has 1/8" adjustments.

I use the SAC tool, my full length sizer is a Hornady and my mandrel and seater are l.e. Wilson. I am now loading some new rounds and a much shorter length for testing. My old length I was getting really solid results at 150… long story I can’t do 100 lol for stupid reasons. My barrel was done by preferred barrels and my action is a TL3. Eventually I will make it a dasher or a gt or something but because at the time I didn’t reload I thought the arc was a cheap and easy 6 to play with. I didn’t want a creed for no reason other than I didn’t lol. Could you tell me your length as I am curious. I am learning so anything is helpful.

 

[Asumner]

I have a Forster FL 6mm ARC die that does not size the brass enough for my liking. I also have a Wilson bushing FL die that let's me do what I want (as long as I buy bushings that is). I don't use the Forster unless I am converting Lapua Brass now. I had some issues with bullets being seated deeper after a trip from the magazine to the chamber (one magazine didn't like one particular lower). The brass sized using a smaller ID didn't do that.

Not saying you don't do this already, but I get my measurements from a clean barrel so my data is more than likely to be accurate.

I assume you are converting Grendel brass. I was thinking of buying a better die and doing the same thing with my Hornady die. That said I seem to be getting consistent forming with my Hornady die as long as I don’t use the expander ball. I have never converted brass as I have only been loading for a few months and most of that time I have been traveling so more researching than loading sadly but I have done around 300ish rounds I guess screwing around. I do want to use better brass once I get better because even I can see issues with my brass especially when trying to seat a primer in the co-ax. Sometimes they don’t like to fit due to variance.

 

[KMW 1954]

. Could you tell me your length as I am curious. I am learning so anything is helpful.

Reluctantly, because this is sized for my chamber and measured with my tools which of course yours could be different. Using a Hornady comparator tool I am loading BTO 1.750" with the Berger 105. When using a Barnes 105 Match Burner it is 1.746"

As to reforming Grendel into ARC I have been doing it with my Lee FL die and before annealing and so far have not distorted a case.

 

[DHD]

I assume you are converting Grendel brass. I was thinking of buying a better die and doing the same thing with my Hornady die. That said I seem to be getting consistent forming with my Hornady die as long as I don’t use the expander ball. I have never converted brass as I have only been loading for a few months and most of that time I have been traveling so more researching than loading sadly but I have done around 300ish rounds I guess screwing around. I do want to use better brass once I get better because even I can see issues with my brass especially when trying to seat a primer in the co-ax. Sometimes they don’t like to fit due to variance.

I have found Starline 6mm ARC brass to be more consistent in weight than Hornady and bought 250 not long after they started making it and it was readily available. The Hornady brass I have came from factory ammo and while I have prepped it, I don't use it.

The only reason I converted Lapua 6.5 brass was to see what the fuss was about and because I have so much of it. 50 pieces of new and 50 pieces of once or twice fired was all I did. It wasn't too much trouble and I don't remember loosing any to the experiment. My weight variance is better with the Lapua Brass, the case head itself is strong (primer pockets stay tight longer), and I get that small flash hole certain Lapua cases have. These cases are used for specific loads I might want to test as I am typically a tinkerer....

I always felt someone needed to make a base sizer for the Grendel brass (think Lee Bulge Buster for pistol calibers) as I had found Proof Research Grendel barrels to be tighter at the base (last .200"ish and rim) than my AA or Satern barrels. The Lapua/AA brass I had used in my Satern cut-rifled barrel would not fit in my new Proof barrels and it bothered me to have 500 + cases I could not use. About a year ago I found one made by Sergeant of Arms and my large stash of Lapua/AA 6.5 Grendel brass was all sized back to factory dimensions at the case head and it was all usable again. This may be of no importance to you as you may only load for one barrel or .441" case head caliber.

 

[Asumner]

Reluctantly, because this is sized for my chamber and measured with my tools which of course yours could be different. Using a Hornady comparator tool I am loading BTO 1.750" with the Berger 105. When using a Barnes 105 Match Burner it is 1.746"

As to reforming Grendel into ARC I have been doing it with my Lee FL die and before annealing and so far have not distorted a case.

Wow, ya I can definitely not load to that. When I first tested 1.710 was hard jam lol.

 

[Asumner]

I have found Starline 6mm ARC brass to be more consistent in weight than Hornady and bought 250 not long after they started making it and it was readily available. The Hornady brass I have came from factory ammo and while I have prepped it, I don't use it.

The only reason I converted Lapua 6.5 brass was to see what the fuss was about and because I have so much of it. 50 pieces of new and 50 pieces of once or twice fired was all I did. It wasn't too much trouble and I don't remember loosing any to the experiment. My weight variance is better with the Lapua Brass, the case head itself is strong (primer pockets stay tight longer), and I get that small flash hole certain Lapua cases have. These cases are used for specific loads I might want to test as I am typically a tinkerer....

I always felt someone needed to make a base sizer for the Grendel brass (think Lee Bulge Buster for pistol calibers) as I had found Proof Research Grendel barrels to be tighter at the base (last .200"ish and rim) than my AA or Satern barrels. The Lapua/AA brass I had used in my Satern cut-rifled barrel would not fit in my new Proof barrels and it bothered me to have 500 + cases I could not use. About a year ago I found one made by Sergeant of Arms and my large stash of Lapua/AA 6.5 Grendel brass was all sized back to factory dimensions at the case head and it was all usable again. This may be of no importance to you as you may only load for one barrel or .441" case head caliber.

Ya I only load for the arc and when this barrel is shot out I will stay with the same company. That said I am always learning as I have multiple other rifles that use the same caliber and could someday run into this issue. Currently all of my reloads for the arc are from factory brass. I am on the 4th firing of the first 50. Every once in a while I will get a pretty good spike in velocity on my load that I had and I have always wondered if the brass was the issue. Sadly I never marked that brass to find out but these are things I plan to do now. Once I feel like I understand what I am doing and won’t ruin a much better piece of brass I will go out buy some and finalize my loads.