AI mags and 6BR with CRF action

[Mike_R]

How much does the controlled feed bolt help when chambering a round that is too short for the mag?

I want to get my FN SPR barreled soon and I am debating which caliber to select. I could go .308, 6.5x47, or a variety of other longer, short action cartridges but I am drawn to the 6BR. I ran a spreadsheet and found that even if I replaced the barrel at 3000 rounds on the BR vs 8000 in .308 the BR would come out cheaper per shot after factoring barrel wear and components. I am also considering 6 XC or possibly one of the improved BR variants like the BRX or Dasher.

I have seen posts where people have modified AI mags either by adding a spacer in the front or rear of the mag. Is this necessary on with the Model 70 pre 64 style action? Either way it isn't a deal breaker, and I might still go .308 just to have a .308, but I was wondering if the CRF might let me get away without modifying mags.

Any ideas on or experience with this?

 

[dieselten]

Re: AI mags and 6BR with CRF action

The CRF does not come in to play until the rim of the case pops up AFTER leaving the magazine. So I am not sure it will help with your magazine dilemma. The CRF can help with ejection of the short case though over a Rem 700 style.

If you already have the rifle in 308 then just make some 6BR dummies and start playing around with it. Try ejecting some empties too. FYI, I had the best luck feeding 6BR rounds when loaded all the way forward in a 308 AI magazine.

edit to add - if you need some 6 BR dummies and live in the continental US, send me a pm with your address and I will mail you a few

 

[steve123]

Re: AI mags and 6BR with CRF action

Unless you tend to be one of the handy type of guys that likes projects that need tuning, retuning and re-re tuning then I'd stick with 6x47L or 6.5x47L.

I had a 6br in a benchrest rifle. It was accurate but a little harder to shoot in the wind. If my 6x47 wasn't currently throated way out for 115's I'd be working up a load for the new 105 Berger hybrid,.545BC. 3150fps or so is pretty easy to obtain with 105's. I'm getting 3020fps with 115's with a moderate load. Feeds nice out of AI mags.

 

[gregt]

Re: AI mags and 6BR with CRF action

Unless you need a 10 round mag, it's easy to get the 6BR to feed from the AI 223 magazines. I have a couple modified for mine and it's less than an hour's work to do it. They will hold 6 rounds, 7 at a pinch. Mine has fired hundreds of rounds now without any issues at all.

 

[Mike_R]

Re: AI mags and 6BR with CRF action

Thank you everyone for the replies and advice!

dieselten, that is a very generous offer. Right now the action isn't barreled so I wouldnt't be able to to test them that way yet. I might be headed towards barreling it in .308 first and then a rebarrel in 6BR.

steve123 I have thought about the 6x47 and 6.5x47 but after running component costs and barrel life I think I am going to lean towards something a little more economical. While both of those cartridges have spectacular ballistics I have a 7RM if I really need to reach way out there.

gregt- What did you do to make the mag work? I found a gentleman on the accurateshooter forums who runs a dasher out of factory 5 rd .308 mags with no problems- but the 10s don't work. I hadn't even thought of trying to mod the .223 mags. If they work well the .223 mags are cheap enough that I could afford to hack up a couple.

I am leaning towards just sticking with the system and running a .308 for now. I have the dies but currently no .308 rifle. Practicing with a .308 might help me with wind calls too. Eventually I will probably experiment with the BR or an improved version of it. If I do run the BR in this action I will try seating them forward on the .308 mags, and if not modding some of the .223 mags.

Thanks again for all the suggestions and help!

 

[CamW]

Re: AI mags and 6BR with CRF action

Here's the thread about modifying the .223 AICS mag for 6BR, post #11.

http://www.snipershide.com/forum/ubbthre...092#Post1804092

 

[Mike_R]

Re: AI mags and 6BR with CRF action

Thank you for pointing that out to me. I feel stupid for not having searched for it myself.

Again thank you everyone for the advice. Whatever I end up doing I will make sure to post it up on here. The .223 mag solution has me leaning towards the 6BR again... I might have to end up flipping a coin. I have reasons for wanting both but for some reason the lower per shot cost and better ballistics of the 6 BR are calling my name.

 

[gregt]

Re: AI mags and 6BR with CRF action

Here's some photos of my mags, it's a pretty simple job with the 223 mags. I opened the inside up with a porting roll which is just a small diameter sanding drum. I opened the feed lips to get the round sitting to the right height and then cut them a touch shorter so the round pops out at the right time without flipping the front up, that's easily seen in the first photo, the second photo doesn't have it done yet. The follower isn't modified at all and it feeds perfectly.

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[2 dogs]

Re: AI mags and 6BR with CRF action

I started that thread and since we began to make the test kit the project got derailed by other pressing (oil field tools) paying projects. We havent forgotten about it tho...