20" LW Barrel-Short Throat??

[warthog]

I've got a 20" LW barrel that I have had some feeding and extraction issues with since day one. It is a couple of years old and shoots very accurate but it appears that I must seat bullets a little short to get it off the lands. I have pushed the shoulder back with the press and have the cases trimmed at the correct length. I have cleaned the barrel and throat very good and used a Hornady OAl Straight gauge to check throat lengths. this is what I have come up with:

Measurements are from back of case to OGive using the #6 .260 collet

95gr AMax - 1.578.5 1.578.5 1.575.5 1.575.5 1.575.5"

123gr AMax 1.593.0 1.590.5 1.593.0 1.593.0 1.592.0"

123gr SST 1.595.0 1.591.0 1.594.0 1.592.5 1.592.5"

As you can see, the dimensions appear to be shorter than they should be when you take in account allowing .025" jump. When I add the bullet jump factor and add the remaining part of the bullet, the dimension of the overall length is less than published lengths.
For instance: 123gr AMax dimension to Ogive 1.593"
less jump .025"
Case overall length is 2.159"

Published COAL in Hornady is 2.245"

Seems that this could add some dangerous pressures when using loading manuals.

Does anyone else have a LW barrel to verify this or member comments?

Thanks

[Tedward]

Call Woody, he will tell you everything you need to know and some. He is very knowledgeable about the Grendel and worked on the development of it before the Grendel existed as an AA Trademark. He also answers his own phone and does make a great product. I have a 223 Wylde from him and it is 1/2"MOA.

[LRRPF52]

One of the things we addressed in both Volume I and II of the 6.5 Grendel Reloading Handbooks was variant chambers, and knowing your chamber. Warthog has a very good grasp on where he is at with regard to seating depths, which is easily managed as a hand loader, but the question comes into play if he wants to shoot factory ammunition.

I have literally gone through boxes of Hornady 123gr A-MAX factory loads, and they are very consistent at 2.250"-2.252" raw COL (base to bullet tip). A few thousandths of kiss into the shallow portion of the compound throat only generates an average of 300psi increase in pressure, based on testing. Jamming into a normal throat can cause significant pressure spikes outside of the design limitations of the system.

This is why it makes sense to stick with the SAAMI spec.

[warthog]

LRRPF52,
Sir,
Would I be better off sending the upper back to builder and ask for a different reamer (chamber)?
thanks

[PA_Allen]

Warthog,
I have a 20" LW barrel that is a bit older than yours. My chamber measures about 0.060" longer for the 95 V-max and 123 SST and about 0.085" longer for the 123 A-max. Keep in mind that this barrel has had several hundred rounds through it.
Hope that helps.
Best,
PA

[cory]

Where did you get the barrel and bolt from? It certainly seems you have a short throat by about 0.1"-0.2".

Can you describe your feeding and extracting issues? Do you have any pictures of fired brass?

Sorry to hear you're having an issue, but I'm sure we can help get it straightened out.

You should add your general area in your profile. There maybe someone nearby you that can help you out.

[warthog]

Cory,
Most of my extraction issues have been resolved with camming over on my press, pushing the shoulder back. I did have earlier issues with the "belted" case and I attribute that to shoulder and going into full battery. I've also had blown primers and flattened primers on cases that were not to maximum loads. I've realize that the extraction issues have been with live rounds and having land marks on the bullets as a result of too long seating. Earlier marking of the bullets that I've reloaded to COL published and some factory has indicated short chambers. I've never had a bullet pulled with extraction but have ofter had to tap a cleaning rod in order to dislodge round.
However, i do 99.9% reload and I can take care of those issues at the bench but often wonder if I would pick up a bit of speed if I could seat the bullet closer to "Specs".

This gun is crazy accurate and is a build from Mark at Precision Firearms. I do have a close friend nearby that has the same "build" as I have and may be checking his chamber soon for reference. Maybe a response from Mark may help too.

Happy Shooting!!
Paul

[cory]

If it's from Mark than it's definitely a shooter. I would email him your measurements and see what he says.

Just to rule it out could you measure your bolt's face depth and OAL?

[seatleroadwr]

I have a LW barrel from CSS and it also had a very short throat. I extended the throat .06" and the rifle shoots better than I could have hoped. Pressure is low, and velocity is good. Check out Pacific Tool and Gauge and have them make a throat a uni throat reamer for you. It will cost a 100.00 or so but it is well worth the money.