Uh-oh! 20 Practical in AR format, what Neck Bushing do You use?

[TheCZKid]

It's been a few years since I played with my 20 Practical, and I wanted to test some more loads to get some accurate 32 and 40 final options. I have a 24" WOA barrel 1:10 twist in an AR upper.
So I brought out my already sized brass (I use Lake City brass, 1x shot, necks not turned), which I had prepped a while ago... But I realized I have a 226 and 225 neck bushing, and I had sized all that brass using the 226 bushing. And the thought occurred to me, If using my AR, would the bolt flying forward cause the bullets to slide forward, when they were chambered in my AR?

So I made up two test loads - one with the 226 neck, and then sized one to 225, and put them both in my magazine. I had the bolt locked back, and the 226 round was on top, and I let the bolt fly forward, and WHAM dropped the bolt. Then I tried to eject the round to see if the bullet moved forward. The bolt didn't want to go back. So I really pulled back on the charging handle, and the case came out (spilling powder all over), but the bullet didn't! It was stuck in the lands. So, with my .17 caliber cleaning rod and no tip, I was able to put it down the barrel and get it unjammed, but it was really stuck in there!

So I put the magazine back in with the 225 necked round in, and just pulled the charging handle back and let it go forward into battery (Not locked back). Then ejected that round, and the bullet was still in it, and it had gone from 1.8675" to 1.8685" BTOL or about .001 forward.

So, I was curious if you guys who use AR's use the 225 bushing? And if you neck turn (which I haven't so far with this round) do you adjust neck tension by maybe using a 224 bushing? I'll probably be necking ALL my prepped cases to 225, but wanted to know what others do.
And do you find turning necks on your AR used 20 Practical loads give you any better accuracy?
Your input appreciated!

 

[KMart]

And do you find turning necks on your AR used 20 Practical loads give you any better accuracy?

Probably not.

 

[jelenko]

Hmm. Sounds more like the rounds are too long to begin with and the bullet was driven into the lands.

 

[L.Sherm]

This ^^^^

 

[Coyotefurharvester]

I run a 225 bushing, have even tried a .201 mandrel after. Seat off the lands and never had bullets "move". I use LC brass, a friend made me some from new Win brass that I going to try. Standard BCG and generic spring/buffer with skeleton stock.

 

[hogpatrol]

What is your loaded round diameter?

 

[GLShooter]

224/225 for me in my AR and make dang sure you aren't in the landsa as mentioned above. I've put some in the lands way to far single loading before and OMG the pressures went through the roof. I have a new bolt gun REMAG that I am using a 226 on with Winchester brass that gives me a 228 loaded neck.

Greg

 

[TheCZKid]

What is your loaded round diameter?

I'm assuming you mean diameter of the neck. With 32 V-max bullets loaded it varies between .2275 and .2285 OD.

Hmm. Sounds more like the rounds are too long to begin with and the bullet was driven into the lands.

The 32 V-max bullet hits the lands at 1.873" and I seat them to 1.865" as that is most accurate.

 

[L.Sherm]

I would be looking at your lands measurements. I have same loaded round nk dia as you with LC brass but my 20 prac is a bolt gun

 

[hogpatrol]

My 20 P AR at the lands is 1.795 with 32 Zmax (same as Vmax). Seems like a lot of freebore for that rifle. My bolt guns have zero freebore and the base to lands is within a few thousandths of the AR. May be a good idea to recheck your land measurements.

 

[TheCZKid]

My 20 P AR at the lands is 1.795 with 32 Zmax (same as Vmax). Seems like a lot of freebore for that rifle. My bolt guns have zero freebore and the base to lands is within a few thousandths of the AR. May be a good idea to recheck your land measurements.

I purchased the upper and dies from someone on Armslist in 2018, The owner said it had about 700 rounds through it, but he might have not been truthful. I don't have a bore-scope or I'd look at the throat to see what it looks like. Might be it was shot a lot more than reported, and the lands are eroded. I'll look into it. I appreciate your providing measurements.
If it does have a lot of freebore, if it shoots fine I won't worry about it for now. I will call White Oak Armament and see what the freebore would be with their reamer when new, that should give me a solid reference point.

 

[TheCZKid]

Okay, just got the drawing from White Oak Armament for the 20 Practical reamer they use.


If I'm reading this correctly, the LEAD measurement is 1.8078" and Throat is 1.9281", not sure what that represents. They put a comment below the drawing, THROAT DATUM .202 X 1.8420

 

[hogpatrol]

Compare to this print, zero freebore.

20 practical reamer

I have read the two post on this, But just wanted to make things clear, I know I'm not the sharpest pencil in the drawer, Looking to put together a 20 practical bolt gun pac-nor 11 twist , My Smith doesn't have a reamer so I'm looking at supplying one, I would like to use lapua brass, so my...

forum.accurateshooter.com

 

[jelenko]

I'm assuming you mean diameter of the neck. With 32 V-max bullets loaded it varies between .2275 and .2285 OD.

The 32 V-max bullet hits the lands at 1.873" and I seat them to 1.865" as that is most accurate.

I've loaded upper mid to hot 223 rounds with 1/1000 neck tension - they don't come out of the case and NO WAY would they be propelled out of the case and into the lands with enough force to jam them in there.
I'm standing pat on the rounds are long enough to be jammed into the lands as the bolt closes. They are being jammed so much that they are acting like a bullet puller when you open the bolt.
What else would be causing the bolt to be hard to open/pull back?

 

[L.Sherm]

You have .020 freebore look at the U@V measurement thats your freebore.

 

[TheCZKid]

Compare to this print, zero freebore.

20 practical reamer

I have read the two post on this, But just wanted to make things clear, I know I'm not the sharpest pencil in the drawer, Looking to put together a 20 practical bolt gun pac-nor 11 twist , My Smith doesn't have a reamer so I'm looking at supplying one, I would like to use lapua brass, so my...

forum.accurateshooter.com

There's definitely a difference to the two Lead dimensions of the two reamers. I'll just keep load development going, and use it as it is for now.

I've loaded upper mid to hot 223 rounds with 1/1000 neck tension - they don't come out of the case and NO WAY would they be propelled out of the case and into the lands with enough force to jam them in there.
I'm standing pat on the rounds are long enough to be jammed into the lands as the bolt closes. They are being jammed so much that they are acting like a bullet puller when you open the bolt.
What else would be causing the bolt to be hard to open/pull back?

From my measurements, the distance I'm seating the bullets is about 8 thousandths off the lands. The one I had the bolt locked back on, since it's an AR we're talking about, the bolt goes forward with a pretty good force when it's in the locked back position. And when the bolt stops, the round stops, and it appears the bullet had enough inertia to be driven forward more, into the lands. That's my best guess.

The reason I think it was hard to pull the bolt back, was the bullet was still seated in the brass, but also stuck in the lands, at the same time. So breaking that tension of the bullet in the neck made it hard, and it was jammed in the lands enough it stayed, and the case came with the bolt.

 

[TheCZKid]

You have .020 freebore look at the U@V measurement thats your freebore.

Thank you! I see now.

 

[L.Sherm]

Your seating at 1.86 and your print is 1.80 to the lands

 

[TheCZKid]

Your seating at 1.86 and your print is 1.80 to the lands

I'm seating to 1.865 because when I use the Hornady OAL gauge, and push the bullet in until it stops, that measurement is 1.873. I'm not sure why it goes that much further than what the drawing shows, but I'll try to find out. So according to the AOL gauge, I would be about .008 back from the lands, but according to the drawing it would be .06 into the lands... interesting. I've typically used the Hornady OAL gauge to determine where the lands start, not a drawing.

 

[L.Sherm]

Drawing isn't gonna be exact but as you can see there .060 differnce