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SR 22 bolt headspace

This is a discussion on SR 22 bolt headspace within the Ruger Semi-Auto forums, part of the Rifle & Shotgun Forum category; I measured my sr22 bolt headspace with a depth mike and it is .047". I seem to remember reading somewhere that a standard 10/22 headspace ...


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Old July 14th, 2010, 06:16 AM   #1
 
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SR 22 bolt headspace

I measured my sr22 bolt headspace with a depth mike and it is .047". I seem to remember reading somewhere that a standard 10/22 headspace is above .050" up to even .055". Do any of you think I would loose some feeding reliability by reducing the headspace down to .043" or should I stick with what it is now? I mostly shoot bulk ammo with the odd box of match here and there.



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Old July 14th, 2010, 11:44 AM   #2
 
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I can't remember the numbers bandied about but on rimfirecentral I am sure you could find it......it is somewhere in the 40's, I thought around 45 thous was considered optimal. I have two of my bolts out with Que right now getting his treatment. 75 bucks gets both of them done and shipped back, jewelled, squared, pinned, headspaced, tail end radiused, the works. I have heard nothing but good about his stuff, supposed to be pretty quick turn around too, I sent mine out monday, so we shall see.

I don't think headspace has that much effect on feeding.....magazine lips and the chamber itself have the most effect on that.
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Old July 14th, 2010, 12:43 PM   #3
 
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I should have clarified about the feeding reliability. I believe from what I read somewhere that there are slight variations in LR ammunition and by reducing the headspace your jamming the contact diameter of the bullet farther up the breach. When things get a little dirty in the chamber and a slightly longer bullet is used you may not come to full close on the bolt or possibly have extraction problems (stripping the rim?). I know that if you go below .043" you run the risk of a slam fire also. Maybe someone who's had it done to the minimum could comment if they had any problems with standard ammo fodder.
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Old July 14th, 2010, 01:02 PM   #4
 
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Headspace, Accuracy and Reliability

--------------------------------------------------------------------------------

Proper headspace is paramount to consistency.

Consistency is paramount to accuracy and reliability.

Headspace is considered primarily to effect accuracy. This is because the subject of most if not all writings has been the boltgun.

Most of us have read about or experimented with headspace enough to form the opinion that keeping it to a minimum is conducive to an accurate rifle or pistol. This conclusion is true. Headspace determines the seating depth of the cartridge which in turn determines the relationship of the cartridge rim to the bolt face and firing pin.
.042"-.043" is optimal in my opinion and will insure consistent seating of the cartridge. Less is not more in this application however. If a particular lot of ammunition has an average rim thickness of .040" you will not see any positive results from headspacing your bolt to .039" or .040" (zero headspace).
Using the rim to establish headspace increases inconsistent seating of the cartridge. As we know the bolt of an autoloader needs sufficient clearance within the receiver for cycling and since the bolt cannot be placed in exactly the same position with exactly the same pressure on the cartridge rim from shot to shot a little wiggle room has proven to be far more consistent and therefore beneficial to accuracy.
Would .041"-.044" be okay? Yes. Just make sure your headspace is greater than your rim thickness and dont go over .044". Also there is no such thing as a slamfire.

Increasing headspace beyond .044" has a dramatic effect on consistent ignition.

As headspace increases the space between the breech face and the boltface increase. This allows the cartridge to seat to different depths from shot to shot and limits the firing pins travel accordingly. If your headspace is .050" and your rim thickness is .040" then you have a cartridge rim that will be anywhere from .001"-.010" away from the breechface each time the firing pin strikes it. Not only does this causes the firing pin to push the cartridge forward to seat it prior to striking the rim for ignition but it also eliminates .010" of firing pin protrusion. This pushing of the cartridge absorbs the firing pins energy, limits the firing pins impact and causes inconsistent ignition.
If your excess headspace is .002" then you will experience a 2.5% variation in seating consistency. If your excess is .010" then you will experience a 10% variation.
Calfee states that headspace is not important however I dont think he realized that his .013" oversize firing pin not only reestablished ignition but was actually seating his cartridge and therefore reestablishing headspace.

Adjusting your headspace can have a negative effect on reliability.

As we know the headspace of factory bolts varies greatly. I have measured bolts which ranged from .037"-.054" and all used the same extractor. An extractor that allows .054" of rim is fine for a rim that is .051" but is far too long for a .040" rim. This factory extractor allows the cartridge rim to shift fore and aft .014" which in turn creates inconsistent positioning of the cartridge rim. If the rim is not in the same place with the same extractor tension from shot to shot it will not contact the ejector properly. You can hit it with a hammer, file a groove in it or color it black but it is still a 3 cent stamped factory part.
Generally you need .003"-.005" clearance between the cartridge rim and the nose of the extractor. This will keep the extracted case rim close to the boltface preventing it from tipping and will insure it stays square to the ejector.

Keep these things in mind when building your next rifle and I believe you will see positive results.


TKidd

Headspace, Accuracy and Reliability - RimfireCentral.com Forums


This guy knows his stuff
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Old July 17th, 2010, 07:02 AM   #5
 
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Quote:
Originally Posted by Emmery View Post
I measured my sr22 bolt headspace with a depth mike and it is .047". I seem to remember reading somewhere that a standard 10/22 headspace is above .050" up to even .055". Do any of you think I would loose some feeding reliability by reducing the headspace down to .043" or should I stick with what it is now? I mostly shoot bulk ammo with the odd box of match here and there.
For your rifle and the type of shooting you most likely do, I would suggest that your .047" would be OK. If it was a target grade rifle I would say to adjust, but since you will likely be doing a lot more "blasting" than bullseye, I would leave it as is. Reason is ~~ with that in mind, you will need to allow for some crud build-up between cleaning cessions.
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Old December 6th, 2013, 09:32 PM   #6
 
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Is there reason for concern of "crud" build-up around the bullet face? Wouldn't there still be build-up concerns with normal gap between the bullet & rifling?
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