Max COAL for Rifle Below SAAMI Max??

[Nvhunter92]

So I just picked up a Christensen arms mesa long range in 7mm rem mag, last night I was checking the rifles max coal with a 162gr Hornady ELDX to start reloading. I'm using calipers and the hornady oal gauge and bullet comparator. I ran the gauge close to 25 times and kept coming up with a max coal of around 2.267"...SAAMI max is 2.290" and that's the length that hornady uses with that bullet in their reloading manual. I have used hornady's oal gauge for several other rifles with different bullets and they have all given me a max coal greater than saami max...any suggestions as to what's going on?

 

[Nvhunter92]

Just to clarify, my number using the comparator was less than 2.267" but I used the average number the comparator gave me with several different bullets from the box

 

[Deleted member 46119]

A couple of things.

I'm sure you meant 3.290 and 3.267 as 3.290 is book length.

It is possible for this to happen. It shouldn't but it is possible.

My recommendation. Get on the phone with Christensen.

 

[Nvhunter92]

A couple of things.

I'm sure you meant 3.290 and 3.267 as 3.290 is book length.

It is possible for this to happen. It shouldn't but it is possible.

My recommendation. Get on the phone with Christensen.

Yes I did mean 3's instead of 2's.

I just got off the phone and got about the answer I was expecting. They basically assured me that it can't be shorter than saami specs because it was already shot in the factory. He said that their tolerances are tighter than a regular factory rifle which might contribute to my measurement. He suggested I get some factory ammo and see if it touches the lands. I'm kind of scratching my head even more now. They basically told me when it comes to reloading or you measuring something we can't really believe you

 

[Deleted member 46119]

They basically told me when it comes to reloading or you measuring something we can't really believe you

It is not intended to offend you. It's just that they are not there with you. I'm not saying you made a mistake in measuring, I'm saying the gall/guy on the phone has to assume it.

Christensen seems to use a not quite match chamber. Minimum SAMMI?

Dumb thing but worth saying. Of course you cleaned it and examined the chamber. Sorry had to.

It it were me my next step would be:
Always keep the rifle pointed in a safe direction.
Remove the firing pin from the bolt. This is important for 2 reasons. 1) Safety, 2) Feel.
Remove the ejector.
Get a factory round with the same bullet.
Paint the bullet with a sharpie or dykem.
Click the round into the extractor.
With the barrel pointed down, insert the bolt and round and let it down slowly into the chamber, don't close it yet but
Gently attempt to close the bolt. If you feel any resistance at all, stop.
Remove the bolt and bullet and look for marks from the lands on the bullet.

If you see marks from the lands then it's time to take the rifle to a gunsmith and have her/him look at it and call Christensen.

 

[Nvhunter92]

It is not intended to offend you. It's just that they are not there with you. I'm not saying you made a mistake in measuring, I'm saying the gall/guy on the phone has to assume it.

Christensen seems to use a not quite match chamber. Minimum SAMMI?

Dumb thing but worth saying. Of course you cleaned it and examined the chamber. Sorry had to.

It it were me my next step would be:
Always keep the rifle pointed in a safe direction.
Remove the firing pin from the bolt. This is important for 2 reasons. 1) Safety, 2) Feel.
Remove the ejector.
Get a factory round with the same bullet.
Paint the bullet with a sharpie or dykem.
Click the round into the extractor.
With the barrel pointed down, insert the bolt and round and let it down slowly into the chamber, don't close it yet but
Gently attempt to close the bolt. If you feel any resistance at all, stop.
Remove the bolt and bullet and look for marks from the lands on the bullet.

If you see marks from the lands then it's time to take the rifle to a gunsmith and have her/him look at it and call Christensen.

Thanks for your replies. No I wasn't offended at all as I understand where they are coming from. I didn't clean it the first time I tried it so I cleaned it last night and examined the chamber for anything obvious but still produced the same results. That was going to be my next step was to get a box of factory ammo with the same bullet and mark it to see what may or may not be going on.

Would there be anything wrong with a chamber that doesn't allow for a bullet to be seated long? My thinking is that the bullet will be seated pretty far into the case and reduce case volume but I'm new enough into the reloading world that I'm not sure of the implications of this. Possibly getting a longer life out of he barrel as I have a bunch of room to chase the lands after erosion?

 

[vinson]

I suggest trying again and really press the bullet into the lands. If you do not see marks on the bullet then you're not pressing hard enough. I like to put a cleaning rod into the muzzle end and use the plastic rod and cleaning rod to slide the bullet back and forth until it I feel it truly seat into the lands, then lock it down.

 

[Deleted member 46119]

Would there be anything wrong with a chamber that doesn't allow for a bullet to be seated long?

Yes, it would be considered dangerous. If factory ammo is wedged into the lands there could be extreme pressures.

 

[Nvhunter92]

Yes, it would be considered dangerous. If factory ammo is wedged into the lands there could be extreme pressures.

Yeah I understand that I shouldn't jam any rounds, but assuming I only handload for it and work up an accurate load that is presumable some distance off the lands are there downsides to having a short throated rifle? It seems like the relatively long ELDX bullet will protrude into the case a fair ways and I might lose some velocity due to increased pressures because of a smaller combustion chamber. I'm just trying to figure out if this is an issue or not? They market the gun as a long range gun and I don't want to go with a shorter lighter bullet that isn't nearly as well suited to long range shooting. I appreciate your replies!

 

[Deleted member 46119]

Well..

The only downsides are indeed lost case capacity and danger of someone loading a factory round.

Try at least part of my suggestion.

 

[Nvhunter92]

Well..

The only downsides are indeed lost case capacity and danger of someone loading a factory round.

Try at least part of my suggestion.

Thanks, I'm planning on stripping the bolt and testing a factory cartridge tonight

 

[Nvhunter92]

So I took out the firing pin and ejector from my bolt and started to test the fit of a bullet in a hand loaded case with no powder or primer. I started really long and the bolt obviously wouldn't close but I worked down slowly and kept checking until it closed and opened with verily light pressure and then seated the bullet slightly deeper and the bolt closed and opened with no pressure at all. I came up with a max coal of 3.385" vs 3.267" using the hornady oal gauge. This makes much more sense as all the guns I've ever had have allowed for a coal over saami max. Just out of curiosity I used the oal guage with the same bullet I used with the new test and it came out at 3.268...so I'm just confused why there is over 1/10th of an inch difference but I'm going to trust the bolt closing method and go from there.

 

[bwinkle]

I had the same issue with the Mesa. Christensen told me they purposely cut their chambers to SAAMI and that's how they achieve their accuracy. I'm not too thrilled myself about hand loading 168 Bergers or 180 Bergers and having them shoved 2/3rds of the way in the case but that's what you have to do. Imade a dummy round with the bullet colored in felt pen.... no land marks were seen when chambering the round.
I also got less then SAAMI when using the Hornady gadget.
I have 100 rounds through the rifle. It shoots fine you just have no play with bullet seating.

 

[bwinkle]

A gunsmith can lengthen the throat but it's about $200 and then you lose any clout with Christensen Arms if it doesn't shoot.