700 SPS has very tight chamber

[gamestalker]

I have a 700 SPS in 7mm RM that from day one would not chamber factory rounds, too tight! My Son bought 3 boxes of factory, 1 box of Rem. and 2 of Winchester, because he wanted to shoot it ASAP, but none of them would chamber other than two rounds we litterally forced in, I mean forced. I did a complete cleaning before we took it to the range, so it had nothing to do with factory gunk or metal shavings. When reloading for it, I'm right up against the wall, so to speak. With full cam over, I'm able to obtain very desireable tight head space, but it requires full cam over or the action will barely close. But it's a nail driver, so I'm very pleased.

I'm not at all bothered by this, as it allows me to bump the shoulder's without worry of bumping to much. I couldn't get a better action to FL die match up.

Has anyone encountered one this tight, or is this one just an exception. Oh, I also tried a box of Federal that's been laying around for a number of years, no dice with that either. Other than being incapable of chambering factory, are there any concerns beyond that aspect?

 

[T Bran]

I might be inclined to do a chamber cast just to be sure that the bullet is not being pinched into the case at the neck. Though I'm sure there is a better way to measure it.
My only concern would be any possible overpressure due to a pinched bullet though probably unlikely. If the chamber is that undersized how is the neck/throat area.
If all else looks good I'd say congratulations on a fine new rifle.
T

 

[gamestalker]

I'm having no issues with the throat depth, and neck and body dimensions are completely in spec. Pressures are looking very normal for the loads I use, RL22 over 140-145 gr. bullet. However, this rifle is about 100 fps faster than other's in my collection? My brass will usually go between 12-15 reloads from my brass, this is consistent with the other actions I'm loading for. Even after a couple of thousand reloads, head space still remains much tighter than my other production rifles, and the last time I checked, still doesn't want to easily chamber a factory round without serious resistence.

 

[LoonWulf]

If it wont chamber factory ammo id would have it looked over by a competent gunsmith. Just to be safe, perhaps the throat is too short or there is some other issue. If your still happy with it in the end no big deal.

 

[gamestalker]

Well at this point I've run at least 2K of my RL22 reloads through it with zero signs of issues. And the throat allows for good seating depths too. When I seat bullets I bring them right out to the lands and I'm not experiencing any short OAL's or excessively long. An example is Sierra 140's when touching the lands will just fit the magazine and feed reliably. All is good, just wondering if anyone has bought a new one in the last 4 or 5 yrs. that had such tight head space.

I resized some brass today in fact and just love the fact that full cam over is giving me perfect head space, snug.

 

[Rob96]

I have an SPS Tactical in 223 that is the same. No pressure signs but is not as accurate as my ADL Varmint in 308 which is not as tight.

 

[helotaxi]

Is it hitting on the shoulder or the belt? Technically the belt defines the headspace.

 

[Blue68f100]

I would have it looked at by a gunsmith or talk to the factory. Get a hold of the NO Go gages and check you chamber. My experience with factory ammo is that they are below spec when it comes to should measurement. They do this so they will feed in all guns. I just got a RCBS Precision Mic to confirm what I was seeing. The factory rounds that I had left were 0.015" back from zero. My 700BDL has a 0.005" head space so bumping the should is a minor when ever needed.

 

[helotaxi]

The GO gage would be far more telling. The NO GO is longer.

 

[gamestalker]

It's obviously head spacing at the belt with factory ammo. But my hand loads are head spacing off the shoulder. It's a tack driver and doesn't eat brass any quicker than my older looser chambered 700's.

 

[helotaxi]

Well with a very tight chamber you wouldn't expect it to be hard on brass. If it's chambering hard, though, you have to wonder if it really is headspacing on the belt or if the chamber is so short that the shoulder of a factory round is hitting.

 

[918v]

Get it checked out. You don't want to gall the bolt lugs.

 

[gamestalker]

918V, what is galling? Is it a pitting appearance of the lug contact surface? If so, too late. But I guess the good news would be, that I have some room to lap back them down silghtly?

 

[918v]

Yes, pitting appearance. If the chamber is short and the shoulder is causing this, then lapping the bolt lugs will fix it.

 

[gamestalker]

You wouldn't believe how much tighter it was before I lapped it the first time! I'll lap .002" and see how she does with that. It would be nice for my Son to use factory, if he ever needs to?

 

[918v]

Gopefully it will get rid of the galling as well and at least you will have even contact on both lugs.

 

[gamestalker]

A buddy of mine who has built a few nice actions said I'm just needing to lap off .002" from the lugs. He checked the head space a while back and said it was shorter than the minimum SAAMI spec. in both head to belt, and head to shoulder. The lugs are facing up square and the brass supports these findings too.
So then, all I really need to do is another lapping job to remove as much of the galling as possible without taking off more than .002" - .003"?

 

[918v]

Yes.

.005" of headspace is perfect.

 

[Blue68f100]

That will put you as close as you need, 0.005" is very good.

 

[gamestalker]

Thanks again gentlemen!
G.S.

 

[R.W.Dale]

Check something before you go to modifying headspace

Make sure the front scope mount screws aren't too long and protruding into the bolt locking lug raceways. This can mimic tight headspace because the bolt can deflect downward and close easily on an empty chamber but cant when a case is present causing tight chambering.

 

[gamestalker]

RW Dale.

A very good point and some mightly innovative thinking too, but this is something I discovered many years ago and am very aware of. But this is a good informational point for other's who can't figure out why they are experiencing problems with their actions binding, once they've mounted the bases. I noticed this when I mounted a scope on one of my high powers back in the mid 1980's. I have to be honest though, it took me a little while to figure out what was going on.
Thanks again!
GS