Ammo help for 9mm...poor groups

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Ammo help for 9mm...poor groups

Post by Super Dave on 3/17/2014, 3:52 am

First topic message reminder :

Hi folks,

I'm a little bummed about the accuracy of my new gun and hope you accuracy experts can help me out.  I purchased it used and the original smith was Mike LaRocca.

I don't know much about him but he has a good reputation.  It's not a bullseye gun...but I like my guns to shoot better than it is.   Today I got a 2 1/2" group from a rest at 25 yards.  That's about the best I've had.  With other ammo I usually have a couple of flyers extending the group to 5".

Anyway, I brought the gun to Ed Masaki yesterday and he said is was very well made, barrel fit good, bushing good, slide to frame good, he liked the 3 lb trigger with a slight roll.  He said it was a well made gun and he's the type of guy who will be honest if something isn't to his liking. 

Ammo used in this 2.5" group above was American Eagle 115gr FMJ.

I've also used CCI aluminum cased 115 grain ammo and those produced the worst groups.  That ammo is very accurate in my other guns.
I also tried a 124 gr. lead round nose with 4 gr of Bullseye powder that did better but not stellar...maybe 3 inches.

It has a non ramped Kart barrel.  I think the twist is 1:16 but I'm not certain.

I'm going to order the caliber conversion for 9mm so I can start testing some loads.  Is a 1 inch group at 25 yards too much to ask for this barrel?  I would appreciate any advice you guys have on where to start with accurate loads for this barrel. 

I've been playing around with my 1970 Clark Hardball over the last couple of weeks and getting decent groups.  The group on the right is 1 1/2".  I'm sure it would be tighter with a ransom rest.  Sweet old gun.

Thank you very much for your help,

Super Dave

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Re: Ammo help for 9mm...poor groups

Post by desben on 4/29/2014, 11:02 am

"1 in 7" for 77gr .223 is a faster rate than the original "1 in 12" for 55 gr. Faster, not slower.  1:1 would be extremely fast, 1:100 would be slow.

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Re: Ammo help for 9mm...poor groups

Post by JIMPGOV on 4/29/2014, 11:04 am



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Re: Ammo help for 9mm...poor groups

Post by STEVE SAMELAK on 4/29/2014, 11:06 am

once again my brain wasn't fully engaged
I stand corrected....again

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Re: Ammo help for 9mm...poor groups

Post by Dr.Don on 4/29/2014, 9:20 pm

A 1:7 is a fairly fast twist; considerably faster than the 1:9 used in many long arm barrels.  Longer the bullet the faster the twist needed in general.

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Re: Ammo help for 9mm...poor groups

Post by Fire Escape on 5/1/2014, 10:35 am

STEVE SAMELAK wrote:at the risk of censure for mentioning a long arm, but don't you use a slower twist for heavier bullets  (1 in 7 for 77gr .223)?

Right numbers but....      The 1 in the 'ratio' would be the number of rotations made by the bullet and the second number is how many inches of barrel the bullet would pass through to make that one rotation.

A 1 in 7 twist would be faster than the now common 1 in 9 or the original 1 in 12. Those being among the common numbers for AR type rifles.

With quality bullets there is little to fear from spinning one faster than required for stabilization but projectiles with any eccentricities can become more erratic with the faster spin (twist) rates.

The required rate of twist is a factor of the projectile LENGTH rather than it's weight. Generally, length and weight are more or less proportional but shape and composition can shift that relationship, i.e. a pointed bullet constructed entirely of copper would be markedly longer that an all lead wadcutter of the same weight.


Appologies for repeating what had already been mentioned (I had not yet seen page 2).

Fire Escape

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Re: Ammo help for 9mm...poor groups

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