7mm PRC with long throat?

[nso123]

I just put a 7mm PRC Proof prefit on an Origin action and am questioning the length of the throat. I am getting a COAL of 3.418 to touch the lands with a a Berger 175 Elite Hunter. This barely has any bearing surface in the neck. I know these bullets tend to be ok with some jump, but it just seems awful long. Am I worried about nothing? Working a load up in Quick Load using these measurements shows that I would need to go quite a bit over published max loads to get any performance out of the cartridge.

 

[crashlanding]

Start load development and see what it does set to a length you're comfortable with, that's how I would approach it.

 

[nso123]

Start load development and see what it does set to a length you're comfortable with, that's how I would approach it.

That's pretty much the plan, it just seems awful long.

 

[Dmagna]

Quick load doesn't know your rifle, just start at a seating that you feel good about. Start a low charge and work up, see what it does. If you don't like it go to a 180 or 195

 

[crashlanding]

I experimented with hammer 143 gr bullets that had considerable jump to the lands, the accuracy was great, velocity was only fair so I ended up using Berger 180 hybrids that are .040 off the lands, accuracy and velocity are very good.

 

[Kmccord]

How are you verifying your touching to the lands? I used to use a Hornady tool to measure, but it was actually jamming into the lands and not touching. I have changed my way to how Alex Wheeler uses for measurements to touch, basically, take off the ejector plunger and firing pin so the bolt will have a free drop, then start seating slowly until the bolt free falls. This changed my touch quite a bit.

 

[Old Rooster]

I have to agree, the Hornady tool is not as accurate as I hoped. I recently took 3 readings and got 3 different depths.
Had not heard of the Alex Wheeler method but will try it.

 

[K.E.C. Darkside]

Berger bullets are pretty forgiving, load them boat tail to neck/shoulder and see what happens.
Just a thought.

 

[xsn10s]

Most factory rifles have long throats straight so I wouldn't worry about it. Most tangent ogive bullets are pretty forgiving of bullet jump (SMK, Hybrids, most hunting bullets). I haven't really had much problems working up a good load even with secant ogive (VLD type) bullets designs and a long jump. Just do your work up and see what happens. If it doesn't work try a different bullet. Same as with any other rifle. I hope that helps.

 

[lancetkenyon]

7PRC has a lot of FB.
I am usually around 2.740" CBTO w. 175 Elites touching. You are correct, not much bearing surface in the neck.

Seat them and don't worry about the jump.

 

[kouzman]

I am getting almost the same exact measurement on my 307 Alpine CT.

I measured three bullets, the Berger elite hunter, the 175 eldx and the Sierra gameking 165. The longest was the Berger and the shortest was the Hornady.

 

[Phil Rizzo]

And don't worry about the lack of bearing surface contact in the neck, if it shoots it shoots.
This is one of mine that taught me… it shoots ragged holes at 3900 + with fantastic ES/SD.
The gap is bearing surface length inside the neck.

 

[nso123]

How are you verifying your touching to the lands? I used to use a Hornady tool to measure, but it was actually jamming into the lands and not touching. I have changed my way to how Alex Wheeler uses for measurements to touch, basically, take off the ejector plunger and firing pin so the bolt will have a free drop, then start seating slowly until the bolt free falls. This changed my touch quite a bit.

I did use the Hornady tool. I have used it for years. I measure five times, then take the average. All of the measurements were within .003 of each other. I do get what you are saying about jammed vs touching. That makes sense.

 

[WapitiBob]

7PRC has .233 freebore, your COAL is not unusual.

7MM PRC Cartridge Guide - Long Range Only

DISCLAIMER: This is a guide. Everything listed within is for information purposes only. All loads should be worked up carefully. We have seen loads that require as much as two grains of charge weight adjustment from one powder lot to another. We have seen as much as five grains of powder...

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