Headspace Tolerance?

[RickyRodney]

I read this on Blue Mountain Precision's website reporting that Impact actions have some of the tightest tolerance for headspace. Does that number matter? I was considering a Lone peak or an Impact, and was leaning toward the Lone Peak after all the reports of how nice the action feels, and its smoothness. Should I reconsider? Plan to build either a GT or a creedmoor in the .22 to 6mm category.

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[Forward543]

Unlikely this is an issue. Difference between go/no go is .010". As long as you are fine with the go/no, you are safe. Lone peak or impact will both be fine. Also, blue mountain can put the barrel on for you.

 

[spife7980]

I read this on Blue Mountain Precision's website reporting that Impact actions have some of the tightest tolerance for headspace. Does that number matter?

Yeah, but its not effectively tighter toleranced than any other action on the market that offers prefit shouldered barrels.
Anything that can offer a shouldered barrel prefit without having the action is hand has the same super tight tolerances.

 

[Wannashootit]

Anything that can offer a shouldered barrel prefit without having the action is hand has the same super tight tolerances.

I was a bit surprised to see shouldered prefits for Tikka receivers.
Not shitting on Tikka, they're a fine action- but I never expected they could hold a thou tolerance on boltface to receiver ring tolerance on a high volume production action. No experience with them, but call me skeptical.

 

[spife7980]

I was a bit surprised to see shouldered prefits for Tikka receivers.
Not shitting on Tikka, they're a fine action- but I never expected they could hold a thou tolerance on boltface to receiver ring tolerance on a high volume production action. No experience with them, but call me skeptical.

I was surprised too and supposedly what Ive read is that its only the recent ones. Someone had a tikka from a long time ago and it didnt measure the same as one of the new ones they had since the ctr became all the rage in the last half decade.

(and even more so that some have found newer howas to be able to swap factory barrels around between actions too, my howage barrel had counterbore issues so Im still super skeptical on that one)

I guess I should have clarified that all of the aftermarket actions that are claiming it as a selling point will be similarly toleranced and to not throw the LP out of consideration just because.

 

[Steel head]

My Nuke action was .0003 over listed .825 specified.





With the wide variation between go and no go I could see someone taking a bit of a risk to do prefits of production actions like the tikka if the have a go bit of experience with them.

 

[RickyRodney]

@spife7980 So basically you're saying that the tolerance of the chamber size as in how the pre-fit barrel is cut is larger than the tiny action tolerance so it doesn't lead to an issue?

Also not the original question, but how do you ensure that the curvature of the bore is facing the 12 o'clock position with a prefit? Blue mountain touches on this on their page and I have heard this is important from other smith's as well.

 

[spife7980]

@spife7980 So basically you're saying that the tolerance of the chamber size as in how the pre-fit barrel is cut is larger than the tiny action tolerance so it doesn't lead to an issue?

Also not the original question, but how do you ensure that the curvature of the bore is facing the 12 o'clock position with a prefit? Blue mountain touches on this on their page and I have heard this is important from other smith's as well.

Basically yeah. All the custom actions are like .001 tolerance, the chamber has much more wiggle room so good is good.

And you’ll hear that 12 doesn’t matter from just as many. Use a good barrel and you don’t have to worry about curve or walking, it simply alters where your zero is at within the scopes adjustment range itself and is business as usual.

 

[E. Bryant]

I was a bit surprised to see shouldered prefits for Tikka receivers.
Not shitting on Tikka, they're a fine action- but I never expected they could hold a thou tolerance on boltface to receiver ring tolerance on a high volume production action. No experience with them, but call me skeptical.

Considering the tolerances held within modern engine components and roller bearing assemblies and a whole bunch of other stuff that helps makes the world go around, it shouldn't be too surprising. It's a small tolerance chain comprised of features that are relatively straightforward to form. I'm not claiming this is "easy", but it's done everyday in mass-produced parts that sell for much less money.

What should be surprising is the apparent inability of Remington to do any better than what's capable of injected-molded plastic parts of similar size.

 

[RickyRodney]

What should be surprising is the apparent inability of Remington to do any better than what's capable of injected-molded plastic parts of similar size.

Well remington and innovation don't really belong in the same sentence. They pretty much quit after the R700.

 

[Wannashootit]

It's a small tolerance chain comprised of features that are relatively straightforward to form.

I know jack shit about CNC, but tolerance stacking exists the same whether manual or CNC.
On the receiver end- back of lugs to boltface, and lug abutments to receiver face.
Then on the barrel end, breech to shoulder and chamber depth.

For all of that to add up to +/- .001 at the end still amazes me. If one were to assume all the tolerances stacking "one way"- either + or -, that's .00025 for each of those operations. It's my understanding of basic CNC machining that these types of tolerances way exceed typical requirements.

 

[BuildingConceptsllc]

I know Eric loves him some impact actions and he has good reason to. Always had such a great experience with Blue Mountain and Eric definitely knows his stuff. His barrels hammer like none of my others, but I haven't shot Southern Precision Zeus barrel yet(will change tomorrow).

Impacts are considered by many to be the most reliable actions for prs and are definitely excellent but there's many really good ones out there now days. I have Zeus, origin, and TL3 and all are outstanding actions, I'm sure LP are as well. I'd go with what features you want, who has it, and who's doing the barrel/ where will you get other barrels ect... You definitely won't go wrong with impact and picking up used barrels is easier with impacts and Zermatt because of their popularity.

 

[nrspence]

Glad I bought an impact!