Gunsmithing 6.5 PRC feeebore questions?

[Rprecision]

I am getting ready to source a reamer for a 6.5 PRC.

I intend to run 140 class bullets (143 ELDX), handloaded, with the option of factory ammo as a last resort. I'm planning to feed from DBM out of a short action.

I would like some flexibility to change bullets if I have to, bullets changes, supply, etc.

I have read a handful of threads but am still not clear what I should choose. From what I can gather there are two freebores .130" and SAMMMI @ .188"

What do I need to consider to make a appropriate choice?

This is my first 6.5 and short mag.

Thanks

 

[samson7x]

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[just browsing]

The spec reamer was made specifically for 143/147 ELD line bullets, factory loaded or otherwise. The longer lead is much more condusive to shooting projectiles with tangent ogives (and shorter noses). If you are planning to build on a short action/load from SA magazines, you are essentially restricting yourself to shooting the ELDs or are confident enough that VLDs, SMKs, etc. loaded to mag length will shoot with 50+ thou worth of jump.

The shorter free bore pulls the lands closer to the chamber (for lack of a better way to put it), meaning that the same secant ogive bullets (VLDs, SMKs) loaded to mag length will be that much closer to the rifling.

My recommendation - build on an intermediate length action and shoot whatever bullets you want, or commit to short action and shooting Hornady bullets pretty much exclusively.

 

[6brshooter]

FWIW, I've got a short action deadline, 300wsm accurate mags, and a shilen with a .188 freebore. With 140 eldm or 142smk, I could jam them .010 into rifling on a fresh barrel and still fit in mag easily. My load is with 140eldm at 2.310 ogive length or 2.940 to tip, this is a .020 jump in a .188 freebore. It feeds great and ejects loaded rds through the tight ejection port. Original plan was 147eldm, to fit and feed from mag, I was going to be jumping .050 or .055 on a fresh chamber. As throat moved, my jump was only going to be bigger. These mag fed rds were a little too long to clear ejection port, I'd have to hit bolt release to kick out a loaded rd.

In my opinion, if you want to shoot 147,150smk,156 elite... I'd go either long action with .188 or .130 freebore. I bought the action here, with 308 and prc bolthead. I didnt know the shilen had a .188 freebore until it got here, just something I didn't think about until after the fact. It shoots pretty good with 58.7gr h1000, horn brass, cci200, and 140eldm, so I'm keeping it.

9 rds measured .320 and 10rds is right at .5", this is the 140eldm at 3090fps.

 

[Rprecision]

I ordered a reamer today from PTG. I talked to the owner Dave Kiff about this issue and my concerns with freebore. Dave probably has more exposure to these specific issues then anyone I have access to call in the industry. Moreover, Dave takes the time to talk through things on the front end. Here's what I learned:

The .130 FB is specified by GAP for their rifle's. It has a tighter neck and shorter FB then what became SAMMI. This was in part learned through the 4s and developed into the PRC. Its downsides are almost all related to factory ammo. Some SAMMI offerings (Hornady 147 ELD) jam into the rifling by about .015-.020" at the current SAMMI COAL. For the hand loader this is all but a non issue. This FB allows a short action running a DBM, the most flexibility over the life of the barrel. Initially it may require deeper seating depths but ensures a good fit in DBM. This same freebore about 500 rounds in is in the .145 - .150" ish zone, which is regarded as a sweet spot for the PRC in a short action. By this point any current factory ammo works flawlessly at peak accuracy.

.150 FB. PTG makes a custom reamer which is modified from SAMMI. little bit looser neck, .150 FB. This is a great choice if factory ammo is your sole goal. The same chamber 500 rounds in is very close to current SAMMI. Many rifle's perform great with this freebore. Its downsides are found in using some Berger bullets that need less jump and create COAL issues in DBM's after the first 500ish rounds. It was mentioned the new Sierra SMK may have similar problems, he wasn't sure.

.188" FB, SAMMI spec. This is what has been adopted as a standard industry wide. Shoots all known factory ammo period. Most of the Hornady offerings are jumping around .050" + on a fresh chamber and seem to shoot very well. For bullets thst like alot of jump this is a no brainier. Fast forward 500ish rounds and your .080"+. The downsides are you will never load touching or near the lands in all but the early stages at DBM length. The upsides are for those running a long action in picking up some case capacity by running at beyond SAMMI COAL. Although that has its issues too.

According to Dave most shooters in a competitive environment are finding a loss in accuracy around the 1k mark but still stay sub MOA until around 1500-1800. Setting the barrel back can net around another 1500, but shes getting real tired by 2500. There's obviously alot of variables in all this.

I chose the GAP inspired chamber reamer as it seems the best fit for my wants. Factory ammo is secondary but still viable. It seems to be what SAMMI should have adopted for the best function in a short action with a DBM.

Hope that helps add some insight

 

[6brshooter]

I think. 130 is the way to go. Even if you want to shoot factory, bullets can still be bumped back in them easily

 

[samson7x]

Who are y’all using to spin these barrels with different freebores? My go-to, LRI only has the .188 reamer.

 

[Kegjohn]

Do you have to neck turn using the gap reamer then? Thanks John

 

[FCS]

I am getting ready to source a reamer for a 6.5 PRC.

I intend to run 140 class bullets (143 ELDX), handloaded, with the option of factory ammo as a last resort. I'm planning to feed from DBM out of a short action.

I would like some flexibility to change bullets if I have to, bullets changes, supply, etc.

I have read a handful of threads but am still not clear what I should choose. From what I can gather there are two freebores .130" and SAMMMI @ .188"

What do I need to consider to make a appropriate choice?

This is my first 6.5 and short mag.

Thanks

Pick the bullet(s) you want to use, make a dummy round with the bullet in the ideal position, measure to get needed freebore for each bullet, make sure your magazine system will accept the OAL for each bullet you will run OTM.

Factory ammo is going to be loaded for freebore present in SAAMI chamber. If you go shorter in freebore then you'll need to adjust the factory ammo to fit chamber, not a big deal but means you get factory ammo ahead of time and reseat bullet to correct OAL.

 

[Banango]

Who are y’all using to spin these barrels with different freebores? My go-to, LRI only has the .188 reamer.

I bought the .130 freebore reamer

 

[samson7x]

I bought the .130 freebore reamer

I ended up going with Altus and requested .140 per their suggestion.