Do skinny barrels....

[Nukes]

Do skinny barrels show more distinct OCW results?

Most of our barrels for which we have done OCW ladders are fairly hefty and so the OCW ladders often show consistently good groups whatever the charge. Picking the "node" is not always obvious.

Yesterday we did a ladder on our only "skinny" barrel. Most of the 3-shot groups were "ho hum" barely sub-moa, but one charge was a clover leaf. I wasn't sure if this was just a statistical fluke or whether skinny barrels have a more limited "sweet spot."

I thought I'd throw the question out there for discussion.

[jurassic]

I would think barrel harmonics are greatly increased in "skinny" barrels so the effect of different loads, etc. will be more readily apparent.

[Sniper338]

I have quite a bit of experiance with m4s and i can say that yes they have certain loads they like better than others. Some of them shoot one hole with ammo, others dont shoot the same ammo near as well at are around moa at 100. Ive seen about an inch and a half difference group wise over many of the barrels with the same ammo...

[dmsims21]

That holds true for my bolt action 308. It has a sporter barrel on it. A little over half a grain difference in charge load, can make a 1 inch group into 2.5"

[LRRPF52]

There's a good discussion on this on Lilja's site.

[BjornF16]

1. A skinny barrel will exhibit more "whip" due to the pressure wave traveling through the barrel (whip really an effect of inherent strain in the barrel being affected differently by the traveling wave)

2. A skinny barrel will exhibit more bore deformation due to the pressure wave traveling through the barrel

This is the essence of the OCW theory. Christopher Long did the theory analysis proposed by Dan Newberry...see http://www.the-long-family.com/OBT_paper.htm

[Nukes]

Yes, thank you. I am familiar with that paper, but, since we did only 3-shot "groups" for the ladder, I was willing to consider it a statistical fluke. That said, since it was so pronounced a finding I suspected it was the "whip" of the skinny barrel—glad that the "bad" groups were still (barely) < 1 moa, but the winning 0.3 moa (44.2gn H4831, 95gn SMK, CCI BR2) was a joy, especially since the 'round robin string was more sustained than I expected the skinny barrel to tolerate. The plain vanilla Rem 700 in .243 was originally a 13th birthday present that was just upgraded with a Manners EH4 Stock, Seekins DBM, fore end rail, Spuhr separates, and a Vortex PST for my now-22 year old's (early) Christmas present. Glad that it is not only gorgeous and 8#4oz total, but capable still of cloverleaf groups. Now he will be shooting it in our matches (instead of our accurate, but heavy SRS). We are expecting some 90gn Scenars on Friday. We will see if these groups hold up at distance.

[BjornF16]

I recently upgraded two factory wood stocks to Manners stocks. The EH3 with DBM Mini Chassis took a >1.5 MOA R700 7mm Rem Mag rifle to 0.5 MOA with Barnes 140 TTSX and Hornady 139 GMX factory ammo. No real need to hand load for a hunting rifle like that...

Newberry uses 3 shot groups for his OCW analysis technique...your results should be valid. Nice to have a "bad" recipe that is still <1 MOA.

[Nukes]

Before this upgrade the Remmy would shoot a cloverleaf with the first 3 rounds and then open up to 2.5moa+ thereafter. We are dancing happily that, to shoot longer strings, we didn't have to re-barrel or re-chamber it at this time.