.280 Ackley improved reamer dimensions

[tbaxl]

My first time really trying to read a reamer print, am I reading this correctly that this reamer has a free bore of 0.179”. I’d like to be able to shoot 175 to 180 grain bullets for hunting and I’m trying to determine if that is doable.

Thanks

 

[LA50SHOOTER]

Yes, - I'm running a 0.165/0.178 (JGS reamer print measurements U & V / T & V) and can keep both 180 Berger VLD's and Hybrids above the neck - shoulder junction.
- Both of these Berger bullets shoot very accurately in a 1-9" twist 30" barrel.

- Ron -

 

[tbaxl]

Yes, - I'm running a 0.165/0.178 (JGS reamer print measurements U & V / T & V) and can keep both 180 Berger VLD's and Hybrids above the neck - shoulder junction.
- Both of these Berger bullets shoot very accurately in a 1-9" twist 30" barrel.

- Ron -

That’s what I wanted to know. I appreciate it.

 

[Walt Krafft]

No. The freebore is not 0.179 long. That is the length of the entire lead angle. They are showing 0 freebore, but are starting the lead angle at 0.2856 in diameter. You would need to trig out the length of the freebore. How that fits with the bullets you are planning to use is another question. I am sure you could use them, but they might be sticking down in the case quite a bit.

 

[DaveTooley]

It actually has zero FB as we think of it. FB meaning a cylinder section followed by the start of the leaded. The .179" is from the .2856" diameter at the neck down to .2770" which is the bore diameter. Because of the larger starting diameter And in relation to the bullet you have approximately .025" FB if you used .2845" as a working FB diameter. You will need to order a custom reamer with a spec'd out throat or use a throating reamer to lengthen the SAAMI throat.

 

[LA50SHOOTER]

@tbaxl

SAAMI drawings are not reamer prints -

Solution is to:
Contact JGS and ask Sarah to send you a print for the 280 Ackley Improved with 0.165/0.178 (JGS reamer print measurements U & V / T & V)

Let them know that you want to shoot 180 gr. bullets.

- Ron -

 

[tbaxl]

@tbaxl

SAAMI drawings are not reamer prints -

Solution is to:
Contact JGS and ask Sarah to send you a print for the 280 Ackley Improved with 0.165/0.178 (JGS reamer print measurements U & V / T & V)

- Ron -

I put up the SAAMI drawings because my smith said his reamer is built to SAAMI specs. And it is a Manson by the way. I was trying to avoid having to purchase a reamer since he has one. I have sent an email to Dave Manson, I just haven’t gotten a response yet.

 

[DaveTooley]

tbaxl

Your smith needs a couple of dummy rounds built on virgin brass and a throating reamer. He should be able to get you very close to the seating depth you want.

 

[Walt Krafft]

Unless you are going to single load, the magazine will very likely set the maximum cartridge length. Need to load some dummy rounds that will fit in the magazine, and then measure what freebore is needed.

 

[LA50SHOOTER]

I put up the SAAMI drawings because my smith said his reamer is built to SAAMI specs. And it is a Manson by the way. I was trying to avoid having to purchase a reamer since he has one. I have sent an email to Dave Manson, I just haven’t gotten a response yet.

Follow what @DaveTooley has stated. - Hopefully your smith has a throating reamer. (Most should)

If it were mine, I'd forgo the magazine and shoot it single feed with the 180's out where they belong.

 

[tbaxl]

Unless you are going to single load, the magazine will very likely set the maximum cartridge length. Need to load some dummy rounds that will fit in the magazine, and then measure what freebore is needed.

That’s the one part I’m not worried about, I’m running it out of a long action and I have 3.715” of usable mag length. So I should have plenty of room to spare. So I’m just trying to find the optimum chamber set up.

 

[LA50SHOOTER]

You'll be good to go with what you've got with the long action & mag. length. - Set them 180's out where they belong and get the performance you deserve.

- Ron -

 

[tbaxl]

You'll be good to go with what you've got with the long action & mag. length. - Set them 180's out where they belong and get the performance you deserve.

- Ron -

That’s the plan, I’m going to call Manson and specify reamer dimensions before I bring it up with my smith though. That way I can have everything figured out and know what I want.

 

[LA50SHOOTER]

here's a photo of a loaded round (180 Berger Hybrid).

 

[DaveTooley]

The nose length on a 180 hybrid is .852" and bearing surface is .430". Case length is 2.525 and chamber length 2.575" That's a delta of .050" between cartridge and reamer.
Now we get into the weeds.
.430" - .225" = .205" FB length minus .015" when using a FB diameter .0005" over nominal bullet diameter. The larger diameter moves the bullet/land engagement point forward slightly so you have to subtract .015".
That gives you a FB of length of .190" minus the delta (.050") for a FB of .2845"X .140" and COAL of 3.532" That's with a leade angle of 1'30"
You can reduce the amount of bearing surface in the neck and lengthen the FB the same amount.

Or at least that's the plan.

I got myself confused and had to go back work it again.

 

[tbaxl]

The nose length on a 180 hybrid is .852" and bearing surface is .430". Case length is 2.525 and chamber length 2.575" That's a delta of .050" between cartridge and reamer.
Now we get into the weeds.
.
.430" - .225" = .205" FB length minus .015" when using a FB diameter .0005" over nominal bullet diameter. The larger diameter moves the bullet/land engagement point forward slightly so you have to subtract .015".
So for an OAL cartridge length of 3.602" you need a FB of .2845' X .190" minus the delta (.050")between the case and reamer. So you end up with .2845" X .140" with .225" of the bullet in the neck.
Or at least that's the plan.

I have a engineering degree and a lot of that went over my head, I’m gonna need a couple minutes to understand what you just did. Granted I’m construction engineering.

 

[DaveTooley]

I have a engineering degree and a lot of that went over my head, I’m gonna need a couple minutes to understand what you just did. Granted I’m construction engineering.

Can I walk under something you designed? My father was a civil engineer and the worst carpenter in the world. My brothers and I spent years propping up things be built. Two story barn and apartment took railroad jacks and huge come alongs to pull it back into the place. Lots of X bracing with steel cables.

 

[tbaxl]

Can I walk under something you designed? My father was a civil engineer and the worst carpenter in the world. My brothers and I spent years propping up things be built. Two story barn and apartment took railroad jacks and huge come alongs to pull it back into the place. Lots of X bracing with steel cables.

I never liked the design work, I took the project management route. So I’ve never actually designed anything.

 

[Ray Gross]

The nose length on a 180 hybrid is .852" and bearing surface is .430". Case length is 2.525 and chamber length 2.575" That's a delta of .050" between cartridge and reamer.
Now we get into the weeds.
.430" - .225" = .205" FB length minus .015" when using a FB diameter .0005" over nominal bullet diameter. The larger diameter moves the bullet/land engagement point forward slightly so you have to subtract .015".
That gives you a FB of length of .190" minus the delta (.050") for a FB of .2845"X .140" and COAL of 3.532" That's with a leade angle of 1'30"
You can reduce the amount of bearing surface in the neck and lengthen the FB the same amount.

Or at least that's the plan.

I got myself confused and had to go back work it again.

Dave,

.225 is the length of bearing surface inside the case neck?

 

[DaveTooley]

Dave,

.225' is the length of bearing surface inside the case neck? The math is pretty easy. Knowing what to subtract for the lengthened bullet/land engagement point from the different diameters comes with experience. It can also be calculated using trig. The larger the FB diameter the further that contact point moves forward. I've out smarted myself a time or two designing a chamber that would handle neglect. In doing so I lengthened the FB to the point it affected accuracy.
Of course all this is based on Berger's number. Bullet dies wear out, dies get adjusted differently, boat tail punches can vary slightly. Much better than the old days but there are +/- tolerances to everything.