New Ruger Precision Rifle - Chamber too short??

[Neutron Boy]

I am in the process of loading up some ammo for my brand new RPR in 6.5 Creedmoor. I want to start out with a Sierra 140gn HPBT on some Starline brass. Brass has been sized and trimmed to length. I used a Dremel to put 2 vertical cuts in the neck of a piece of brass to let me place a bullet lightly in the neck and chamber it to get the overall length for my rifle. I would then knock off 0.015" to get the bullet off the lands.

Only problem is ... I am getting numbers below the Sierra specified 2.81", even before backing the bullets off by 0.015". I am getting an average of 2.75 or so. I have been carefully closing the bolt on the loose bullet so it doesn't get jammed in too far by the force of closing. My calipers are good because they read the bullet diameter spot on.

I talked with Ruger and they dont even want to talk handloads - they only recommend ammo manufactured to SAAMI specs. I understand the legal implications, but my concern is that the chamber is too tight and that even factory ammo may yield an overpressure condition.

I dont think I should have to buy tooling to check this ...

Anybody have a similar experience?

 

[Blue68f100]

Have your removed the extractor/ejector prior to testing?

Remove the extractor/ejector and check it with a set of Go/NoGo gauges. This will tell you if the shoulder is in the correct place. If short chamber it should show up.

I have several guns with the short leads. Just need to locate where their at and go from there, shorter OAL = less powder.

 

[Demi-human]

Should make chasing the lands easier...

If the measuring case fit, the chamber is good.

Looking at it this way might work.
Sierra states to load out to two hundred and eighty one hundredths.

You are six hundredths short and will add another one and a half.
Will seven and a half, one hundredths out of two hundred and eighty drastically change anything about that chamber?
The loaded cartridge? The way it shoots?

Further, has the brand new chamber been scrubbed clean? Any burrs polished out?
A new rifle may measure very tight, but break in quickly.
The throat will change first and fastest. It won’t stay short for very long.

Use the base to ogive measurement that fits and load happy.
Perhaps they had a new finish reamer and the body is slightly bigger, sharp tools cut more, negating any short throat pressure.

If you were to use factory ammunition, would you have known?

Anyway, just trying to put your mind at ease. You’re making custom ammunition. It will be fine. Start low, work up, shoot happy!

 

[Charlie98]

Short chamber, or short rifling leade?

Do you have any factory ammos?

FWIW, I have a Browning 71, in .348WCF... they have a notorious reputation to have short leade, as mine does. I realize now my early handloads, even though they were 3grn under starting, were generating pressure issues... so it is worth checking out and making a final determination.

FWIW, I handload for a friend's RPR in 6.5CM, using the Sierra 143grn MK without issues. I was not impressed with the build quality of the RPR, and have read issues with cross-threaded parts and such, so a worn reamer wouldn't surprise me in the least.

 

[forty_caliber]

Have you tried any factory ammo and does it chamber properly? As others have suggested check with go-nogo gauges or ask your friendly local gunsmith to check it. If it fails this check send it back to Ruger.

I have an RPR in .308 and it is a well made accurate rifle. I've done the same process to determine COAL and found that the magazine (even ACS mag) was the limiting factor for length rather than the chamber/rifling.

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