So I'm converting my AR10 in .308 to 6.5cm and was wondering if I needed to change my bolt or bcg. I've seen on some websites while browsing for a barrel that the bolt needs to be headspaced. I didn't do that prior to shooting my AR originally. Is that something specific for 6.5cm? How would I go about doing this? Thanks!
- Thread starter kjeff91
- Start date
If your barrel was not headspaced to the bolt your using it would be a good idea to check the headspace with a set of go, nogo gauges. This is set when the barrel extension is attached to the barrel. So if your to long, your out of luck unless you can find out whose bolt the headspace was set to and can obtain one. If your current bolt isn't a high pressure bolt, you may notice more primer flow and possibly even pierced primers... just depends on how closely your current bolt and firing pin compare with each other. As well as how warm the load is your shooting.
Your carrier doesn't need to be changed but some choose to use a low mass carrier. But changing that often requires also using a adjustable gas block and changing buffer weights and/or spring weights.
Your carrier doesn't need to be changed but some choose to use a low mass carrier. But changing that often requires also using a adjustable gas block and changing buffer weights and/or spring weights.
So I could run my current BCG safely and just check for pierced primers? And if they are I would just need a new high pressure bolt?
Yes, but keep in mind any time you change bolts your headspace could also change. Large frame AR dimensions are not as standardized as their small frame milspec brothers, this can become a problem when your mixing parts around.
Last edited:
seeing it may explain it better.
[IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/i.imgur.com\/MOn6dx1.jpg"}[/IMG2]
[IMG2=JSON]{"data-align":"none","data-size":"full","src":"https:\/\/i.imgur.com\/MOn6dx1.jpg"}[/IMG2]
Ok, I understand what it's measuring now. What is the best thing to do now? Buy a new bcg, buy a new bolt or just shoot it and see what happens.
First, what BCG do you have? At the very least you should be buying a Rubber City or JP High Pressure bolt kit which also comes with their HP firing pin. It's different than a standard 308 firing pin..
Most big name barrels are headspaced to a JP bolt like Rainier but ask. Or just buy a JP 6.5cm barrel which already comes with a HP bolt.
Most big name barrels are headspaced to a JP bolt like Rainier but ask. Or just buy a JP 6.5cm barrel which already comes with a HP bolt.
It's from a local shop called Live Fire Armory in Colorado Springs, CO. They said it was "their brand" of BCG, so not sure what that means. Waiting for them to open to call them. There's killer deals on Wilson Combat barrels right now ($250 for select barrels) and I'm looking at one of those.
If it headspaces properly it'll work....looking at the wilson combat barrels I would get 20" rifle gas, no shorter...the 16-18" barrels in that caliber with short gas systems don't seem to work as well.
Headspace too tight you'll need a smith to finish ream it, if it's too long you'll have to try another bolt
I've built several AR10s and it is a bit more of a PITA to get barrels and bolts that headspace. A barrel with a matched headspace bolt would be my personal suggestion.
Headspace too tight you'll need a smith to finish ream it, if it's too long you'll have to try another bolt
I've built several AR10s and it is a bit more of a PITA to get barrels and bolts that headspace. A barrel with a matched headspace bolt would be my personal suggestion.
I was looking at the 20" or 22" since I'll be putting on a surppressor on it when it comes home in the next month or two.
I have built many 6.5cm semis all 22". I switched some time back to +2 gas only for better brass life. Brass was getting beat up pretty good with rifle gas. +2 gas with an AGB and JP SCS runs great. I personally would never buy a 6.5cm semi barrel unless I had a bolt that was headspaced to that barrel. If you are dead set on Wilson, call them and see if you can buy a matching headspaced bolt with the barrel or ask them what bolt that barrel was headspaced to. I only use High Pressure bolts in 6.5cm semis as well from Rubber City or JP...
Thanks for all the help guys! Getting the JP bolt conversion to put into my current bcg.
When a customer orders a barrel from us at T-Box Barrels all barrels come with a properly measured MPI 9310 Salt Bath Nitride bolt. Headspacing is the basic measurement that is needed for safe operation and chambering of any firearm with ammunition.. It does not lead to accuracy or any other advantage.
John
The 6 .308 firing pin tips I have measured varied a by a few 100ths... you might order a few and use one slightly better fitting.
Also bear in mind a lot of HP firing pin tips are smaller then common .308 tips... so don't order up HP firing pins without asking what size the tip is.
Also bear in mind a lot of HP firing pin tips are smaller then common .308 tips... so don't order up HP firing pins without asking what size the tip is.
