6 Creedmoor help

[Twistedtrucker1]

Question: Should I send a dummy round or stick with SAAMI for McGowen 6mm Creedmoor pre-fit?

I have a Ruger American Predator short action, and I’m planning to order a pre-fit 6mm Creedmoor barrel from McGowen. I’ll be shooting the 108gr ELD-M and using the Magpul AICS-pattern short action mags (internal COAL is 2.860”).

Would it be better to send them a dummy round seated to around 2.850” and ask them to throat it so I’m ~0.010” off the lands? Or should I just stick with SAAMI spec?


My main goal is good accuracy and consistent mag-fed performance for long-range steel shooting. Any advice or experience would be appreciated!

 

[khuber84]

Saami spec 6cm has plenty of freebore for the 108eldm, and pretty much every other heavy for cal 6mm bullet. I've shot 108 factory ammo through several Sammi spec chambers and it's performed very well in 18-22in barrels.

I'd definitely give the mcgowan prefit a heavy qc once in hand. Many reports of subpar machining of chamber and threads. Have a box of factory ammo on hand. The rounds should freely drop into the bottom of the chamber, and freely fall out, barring excessive runout of the factory ammo. If you have to push the round to bottom and use your finger or a screwdrive to unseat the round to get it to fall free, the chamber is undersized.

I have a ls wild(preferred barrels) Tikka 6cm prefit and the machining was quite good, chamber looked concentric in the freebore, it shoots well. Ammo dropped in and fell out with no resistance. I'd look into them as well, compare pricing and lead times, this may be a better option as their track record of deliver a quality product is high.

 

[Go West Old Man]

Not an apples to apples comparison, but for sharing 6CM notes & experiences, I had a 6CM built in 2023 on a Bartlein #13 ss barrel. Defiance Rukus , McMillan stock, Hawkins bm, etc. Kept it SAAMI simply for one less decision probably & was confident in the builders advice to do just that. Started break-in & initial scope zero with factory box ammo 108 ELD-M’s and immediately results & groups were darn impressive!

I’d already decided to work up a Lapua & 105 VLD hunting load, and I did. JAM on that load was COAL 2.869 I believe. Backed off that slightly, started workup, & got very lucky on first few rounds of hand loads that produced a repeatable < 0.5 MOA. Less than a month later it proved itself with that same flawless accuracy on a WY antelope. That 105 VLD is a bad little dude! OK, I’ll land the plan here on this story & just say 6CM SAAMI did fine for me.