OAL - how much does it affect accuracy in 9mm (minor)?

[MilkMyDuds]

When I was shooting long range precision rifles, I understood that OAL has pretty big impact on accuracy considering the profile of the bullets and the ogive off/jam lands etc. However, based on my little experiment, I have found no noticeable differences between 1.110'' and 1.135'' OAL with the same headstamp/powder weight/crimp setting in both KKM and BarSto aftermarket barrels. I tested at 25 yards off hands. 5 shot groups for 5 groups. For both OALs, KKM was about 3.5 inches, while BarSto about 2.5 inches.

Is this normal with handguns, 9mm in particular? What's your experience?

[Hi-Power Jack]

I noticed a small improvement in group size with my BHP

as the rounds got longer, but had to settle for a little less

accuracy for the sake of feeding -

Slight tradeoff, and well worth it.

[MilkMyDuds]

I noticed a small improvement in group size with my BHP

as the rounds got longer, but had to settle for a little less

accuracy for the sake of feeding -

Slight tradeoff, and well worth it.

Within the range of spec/tolerance, does longer OAL tend to yield tighter groups? In another word, jamming the lands produces better accuracy? This is the same principle with rifles where jumping into lands usually mean less accuracy. However, I recall some precision rifles shoot best 0.01''-0.02'' off lands though. I was looking for that sweet spot for 9mm. Thanks.

[Bam Bam]

Yes, same holds for Pistols. Finding that right load for velocity, distance off lands, and no problems with chambering.

[biglou13]

ive loaded for precision long range and it borders on bench rest practices....

thing is MOA minute of angle and minute of A zone are two entirely different things

i was able to find Minute of A zone accuracy pretty quick without a whole lot of bullet jump testing. approx .018 off the lands

i imagine i may revisit but right now i have too many other skills that need work...

then you may want to ladder test powder again after finding jump......

2.5" @ 25 yards...... i'd be done testing !!!!!!!!

[Flatland Shooter]

Its been a few years since my main open gun was new, but I found that increasing length improved accuracy. I started around 1.140" OAL slowly increasing to over 1.200". My barrel was throated to allow me to seat the bullet long.

Max accuracy was at 1.195" with 124 gr Montana Gold JHP over HS-6. A few years later I switched to VV N-350 but retained excellent accuracy. The longer length also increased reliability.

Bill

[adamge]

I recently tried two loads, same except length was .010 different. I didn't see any difference in group size.

[DWFAN]

I can see a difference at 50 yards with my Bianchi gun. For USPSA accuracy needs and distances I would pick an oal that was the most reliable, the difference isnt worth it.

I tested 1.010 to 1.160 inches. Depending on bullet, 1.125 to 1.135 was the best.

[MilkMyDuds]

Thanks everyone for the inputs. Definitely saved me a ton of time from trying things on hugely diminished returns

[IDescribe]

Yeah, it's not that there's a difference between pistol and rifle; it's that there's a difference between 25 yards and 300+. Your precision rifles aren't going to show accuracy differences based off OAL variations at 25 yards either.

[9x45]

As you shorten OAL or increase powder charge, pressure goes up, it may, or may not, increase accuracy, you just have to try out your loads.

[d_striker]

I noticed a small improvement in group size with my BHP

as the rounds got longer, but had to settle for a little less

accuracy for the sake of feeding -

Slight tradeoff, and well worth it.

Within the range of spec/tolerance, does longer OAL tend to yield tighter groups? In another word, jamming the lands produces better accuracy? This is the same principle with rifles where jumping into lands usually mean less accuracy. However, I recall some precision rifles shoot best 0.01''-0.02'' off lands though. I was looking for that sweet spot for 9mm. Thanks.

In .308, I found that it's really dependent on the bullet ogive in my Remington 700 which has a really long throat. Sierra Match Kings (tangent ogive) could be loaded to mag length which meant they were making a big jump to the lands and still shot sub-moa.

Hornady BTHP Match (secant ogive) were not sub-moa unless I loaded them about .025" off the lands. They just wouldn't make the jump like the SMK's would.

[BillR1]

Think about revolvers...they have a pretty big "jumping distance" before the bullets gets to the rifling. Most revolvers are pretty accurate.

I haven't seen where OAL makes a huge difference.

[IDescribe]

Whatever the gun type, pistol or rifle, revolver or semi-auto or bolt action or break barrel, whatever the caliber, the further away the target, the more that finding the ideal OAL matters, and closer to the lands is generally better, but it's about distance to target. At 1000 yards, you better have the OAL tuned right if you want to compete. At 25 yards, it's not a factor.