Full Length Sizing

[maverick5582]

Well, I chambered the barrel with a Manson reamer that was made by an AA print. I used the roughing reamer, the followed by the finishing reamer. Then I used the Go gauge as a guide and took just enough off the chamber till the bolt locked into the lugs. I had the instructor of the NRA course I was taking check the fit of the bolt behind me. He said it was fine. The reamers were sharp, they were not worn at all. I used a floating reamer holder as well.

I do not have any answer yet. The LBC bolt I bought works fine now after I lapped it in. It picks up the brass and locks into battery fine. I do not have a forward assist on this upper as it is a DPMS.

L.E. Wilson sent me another case trimmer this week for fired cases and the brass fits fine in it so I can trim the case length. I just wanted to make sure the brass did not get pinched in the chamber.

The hottest load I have shot is 27.8 gr of 8208 XBR that averaged out at 2473 f.p.s which should work out to about 45,376 psi.

When I used the Hornady comparator I checked the new AA brass length close to the datum line and brought the brass back to that length on the first resizing.

In the past with my bolt guns I just bumped the shoulder backed 0.003" and everything worked fine. The Grendel is a shooter and I do not want to do anything to screw it up. As long as I do my part it has not let me down it shoots tight groups with 120 and 123 grain pills.

When something like this occurs I like to use the forum for a sounding board, there is enough experience here to help me figure these issues out. Thanks for all the input, guys.

Maverick

I decided on trimming the cases to 1.520" that were over that dimension. They were only about 20 out of 100 cases. Now all the cases are 1.514"-1.520" in length. I do a slight chamfer on the inside and the outside, then I have a cap for 3/4" copper tubing with some steel wool in it that I polish the mouth of the case with in my lathe. This leaves a nice smooth finish on the case mouth and there are no burrs of any kind.

Maverick

[babaganoush]

I decided on trimming the cases to 1.520" that were over that dimension. They were only about 20 out of 100 cases. Now all the cases are 1.514"-1.520" in length. I do a slight chamfer on the inside and the outside, then I have a cap for 3/4" copper tubing with some steel wool in it that I polish the mouth of the case with in my lathe. This leaves a nice smooth finish on the case mouth and there are no burrs of any kind.

Maverick

Sweet

[Zach987]

I did think that .026 was quite a bit to be trimming off, but I went with Hornady's number when I probably should have split the difference. Will that much brass removed make a noticeable difference in neck tension or function?

[mseric]

No.

[sneaky one]

It was from Ramshot powders--trim to length of 1.1515, that I use with no issues after 12 firings thru. I should re check them this year to be okay.

[mseric]

SAAMI case length is 1.520-.020. That would put SAAMI Trim-to-Length at 1.510.

http://www.saami.org/PubResources/CC_Drawings/Rifle/6_5%20Grendel.pdf

[maverick5582]

Confused again.

SAAMI case length is 1.520-.020. That would put SAAMI Trim-to-Length at 1.510.

http://www.saami.org/PubResources/CC...%20Grendel.pdf

This is where I tend to get confused. The AA print for the reamer that I used tells me that the chamber is 1.530" long. That leads me to think that 1.520" gives me 0.010" before I run into a "pinch problem" at 1.530". So far all my AA brass has no problem loading in the 1.514"-1.520". I cannot see any reason to trim to 1.510". But then that is just me.

[mseric]

corn relish.jpg

This is where I tend to get confused. The AA print for the reamer that I used tells me that the chamber is 1.530" long. That leads me to think that 1.520" gives me 0.010" before I run into a "pinch problem" at 1.530". So far all my AA brass has no problem loading in the 1.514"-1.520". I cannot see any reason to trim to 1.510". But then that is just me.

You are correct. If you look at the SAAMI link you will also see a Reamer dimension of 1.530.

The Max case length in any cartridge is always much less than the reamer/chamber dimensions. It gives a little wiggle room so to speak. As for keeping them "long" why? Trim em to 1.510 and never again.

As an example the reamer dimension for the 223/5.56 is 1.772 with a Max case length of 1.760 and a trim-to of 1.750. Same deal, different cartridge.

[Nukes]

In the same vein (sort of), how much shoulder bump is too much? dangerous?

Tonight was my first try with a Whidden FL neck bushing sizing die and I didn't notice that the locking ring slipped so that I had about a dozen pieces of .308 Lapua brass that I had bumped between 0.010" and 0.020"—way more than the recommended 0.002" to 0.003". The rest were perfect.

What should I do with the over-bumped cases? ...fire-form them back to spec?

[mseric]

What should I do with the over-bumped cases? ...fire-form them back to spec?

I would, then I'd check em with a paper clip.

[Nukes]

Huh?

[LRRPF52]

One issue you might run into with excessive shoulder set-back is failure to fire, since the case headspaces off the shoulder. If there is enough room for the cartridge to move forward enough so that your firing pin protrusion isn't sufficient to activate the primers, then you will have FTFire.

You can make up for this with seating depth by loading long so that you now headspace off the lands with a kiss or jam, but then you need to be mindful of charge weight.

If it were me, I would prime one of the pieces of .308 brass that you feel has too much set-back, drop the primed brass into the chamber without any charge or projectile, just primed brass, and see if you have primer activation in a safe area.

[Nukes]

One issue you might run into with excessive shoulder set-back is failure to fire, since the case headspaces off the shoulder. If there is enough room for the cartridge to move forward enough so that your firing pin protrusion isn't sufficient to activate the primers, then you will have FTFire.

You can make up for this with seating depth by loading long so that you now headspace off the lands with a kiss or jam, but then you need to be mindful of charge weight.

If it were me, I would prime one of the pieces of .308 brass that you feel has too much set-back, drop the primed brass into the chamber without any charge or projectile, just primed brass, and see if you have primer activation in a safe area.

Good advice. Thank you.

"Mindful of charge weight"—as in, "low-to-mid charge weight"?

[bwaites]

I would, then I'd check em with a paper clip.

Meaning take a paper clip, make a tiny "L" on one end and run it down inside to the base of the case to check for a ridge which might indicate incipient case head separation.

LRRPF52 means be gentle with loads until you know how your rifle responds to bullets jammed into the lands.

[Nukes]

Ahhhhhhh! Thank you.