Precision problems on 39-2

[Jnl1000]

Hi,
I just got a 39-2 dated 1970-71 according to serial nr. I load the 9mm myself, and with 124 cast bullet its not accurat at all on 25 yards, it spreads 5 " or more. But one group could be fine, and the next completly spread out, like somethings loose. Its got the s&w adjustable rear wind/ elevation sight. Seems to sit tight. No obvious gaps in barrel/ bushing, slide. The gun looks really good, no wear. Barrel looks fine too.
It performes a little better with factory ammo. Its my first semiauto pistol, so i dont know what to expect from accuracy.
Ive been shoting in sitting with support, im a ok matchpistol shooter so i peeform better than the gun ( i hoope)
Are there any obvious things to check out before testing other loads and bullers. Is 1/ 10" twist in 4" barrel best with lighter bullets? What can i expect of accuracy on 25 yards? Any ideas,

 

[lrrifleman]

I would suggest that the culprit behind your lack of accuracy is your ammo. If you can, try to "slug" your barrel, the possibility exists that your bullets are undersized. The next step that I would suggest is working on your powder charge. While the charge that you are using may be enough to function the slide, you may have a wide velocity spread that is impairing accuracy.

Edited to add: I have a S&W 439 that I use with lead bullets. I tend to shoot a quench cast 124gr truncated cone bullet over WW231, sized to 0.356". I use a load between 4.5 and 5.0 grains. Generally, at about 50 ft, I can get groups about the size of a half dollar. That group would be the product of one handed shooting, with all shots fired single action. I am using the "old" RCBS Cast Bullet book.

 

[Jnl1000]

Thanks, im using 356 cast bullets! Ill slug it and see. Its a lot og led in the barrel after shooting, that could be a sign of undersized bullets? Its also likely that ive been a little bit to careful with the charge. It got better with 10-15% more powder. On the strongest load , i hit the target lower than the before, made no sense to me. Didnt have more than 10 rounds of each so i couldnt test that much. So, the ammo could maje that much diffrenc ? My 357 revolver is accurat on almost ecerything ill feed it with!

 

[That One Guy]

Fwiw, I have the same issue with my 639 and I haven't been able to figure it out either.

The only advice I can offer is that none of mine or my dad's 1-3 gen Smith autos like 124gr bullets AT ALL. 115gr are very accurate in all of them except my 639. 147 gr loads do well too.

 

[ralph7]

Thanks, im using 356 cast bullets! Ill slug it and see. Its a lot og led in the barrel after shooting, that could be a sign of undersized bullets? Its also likely that ive been a little bit to careful with the charge. It got better with 10-15% more powder.
On the strongest load , i hit the target lower than the before, made no sense to me. Didnt have more than 10 rounds of each so i couldnt test that much. So, the ammo could maje that much diffrenc ? My 357 revolver is accurat on almost ecerything ill feed it with!

During recoil, the less time a bullet is in the barrel, the lower it will shoot, as a slower bullet stays in the barrel longer as it is moving upward, causing a higher impact on target.
Hope that makes sense.

 

[lrrifleman]

@OP,

Lead streaks can result from undersized bullets. Out of curiosity, what recipe are you using?

 

[Coaltminer]

Accruracy of 39-2

Try plated or jacketed bullets. 9mm bullets in lead were scarcely used in time of 39-2 accuracy. Great gun BTW

 

[Jnl1000]

@OP,

Lead streaks can result from undersized bullets. Out of curiosity, what recipe are you using?

Sorry, my english is bad, do you mean loading data? Powder vithavourri n340, 4,2, 4,7, 4.9. From tumbling keyholes to 2-3" groups. I only had 10 of each round, and the first 4,9 went so low it touched the frame an splittet, so it looked like ive used a shotgun


Thanks for so many good answers. About low impact on faster/ heavier load, it makes sense when i think semi-auto pistol with 60% weight on the slide!
Ill slug, get some 115grs factory rounds, and a load of diffrent bullets to try out! I was just worried that ive got bad gun. There could several reasons why a gun from 1970 is nearly unused also bad reasons i guess!

 

[ralph7]

Sorry, my english is bad, do you mean loading data? Powder vithavourri n340, 4,2, 4,7, 4.9. From tumbling keyholes to 2-3" groups. I only had 10 of each round, and the first 4,9 went so low it touched the frame an splittet, so it looked like ive used a shotgun


Thanks for so many good answers.
About low impact on faster/ heavier load, it makes sense when i think semi-auto pistol with 60% weight on the slide!
Ill slug, get some 115grs factory rounds, and a load of diffrent bullets to try out! I was just worried that ive got bad gun. There could several reasons why a gun from 1970 is nearly unused also bad reasons i guess!

Actually, no.
The same barrel time theory works for revolvers as well as pistols.

 

[lrrifleman]

Sorry, my english is bad, do you mean loading data? Powder vithavourri n340, 4,2, 4,7, 4.9. From tumbling keyholes to 2-3" groups. I only had 10 of each round, and the first 4,9 went so low it touched the frame an splittet, so it looked like ive used a shotgun


Thanks for so many good answers. About low impact on faster/ heavier load, it makes sense when i think semi-auto pistol with 60% weight on the slide!
Ill slug, get some 115grs factory rounds, and a load of diffrent bullets to try out! I was just worried that ive got bad gun. There could several reasons why a gun from 1970 is nearly unused also bad reasons i guess!

Let me ask this, did you get your current load data from a reloading manual? What powder are you using, and how much of it are you using?

When your bullets keyhole, they could do so either because of excessive lead build up in the barrel, or the bullet is going too slow to stabilize. If you were shooting a rifle and the bullet keyholed, your bullet would have gone subsonic. Like keyholing due to low velocity, a wide (loose group) is due to an insufficient powder charge.

I would suggest that you consult a reloading manual that focuses on (cast) lead bullets. Bullseye and WW231 are two excellent powders for use with lead bullets!

 

[lrrifleman]

@OP,

Vihtavouri recommends, when using N340 with a 124gr LSWC, a starting point of 4.7 to 5.1 grains. Personally, I am not familiar with the performance of VV N340, but it sounds like (performance-wise), that your powder charge is too light.

Check your barrel to ensure that the grooves are not filled with lead, if you have a "lead-away" cloth, cut a 3/4" square to push dry through your bore ... if it comes out gray or black, you have a lead build, which affects accuracy.

 

[Jnl1000]

I use vithavourri n340 powder, i used loading data from the bulletmanufacter, but he did his test shooting in a 6" barrel. My starting load was 4,2 grs, col 28,3mm. The maxload is 5,1 with the powder. I have no experience with cast bullets. Fmj bullets in the same weight would use 15-20 % more powder from the loading data ive checked out,and that makes sense.
Maybe the barrel lenght makes that huge diffrence on this relative slow powder. Ive allways been looking out for overload signs on boltriflesload, but this is on the other end. I use to start below or on the min load, but never experienced so huge diffrence in precision and performance in boltrifles.
Im gonna get fmj/ copperplated bullets and use loading data from a 4" barrel to start with. So, its likely that this precisionproblem is a ammo-issue and not the gun itself.

 

[lrrifleman]

@OP,

May I ask where you are from? This can help all of us when we try to recommend a load. I wouldn't want to suggest a load for a powder that you can't get!

 

[Jnl1000]

Im Swedish. Vithavourti and norma powder are the most common powders here, but i can also get some american powder as well.

My lack of experience on handgunload is the problem here. Ive heard that 9 mm could be though to load, and not much to save either since ammo is cheap. Ive started with 38/357 with great sucess in a 686 6" barrel.
I should measure fps when testing loads to get an idea where i am, as the sucesswindow seems smaller. 1/10 grn in a 4,7 grn load is a huge amount compared to 1/10 in 64grn in my 338wm.
Ill try diffrent components and will let you know how i turns out! Not looking for a match gun, but i wanna get the most out this lovely pistol as a plinking gun!

 

[Tom S.]

@OP,

Vihtavouri recommends, when using N340 with a 124gr LSWC, a starting point of 4.7 to 5.1 grains. Personally, I am not familiar with the performance of VV N340, but it sounds like (performance-wise), that your powder charge is too light.

Check your barrel to ensure that the grooves are not filled with lead, if you have a "lead-away" cloth, cut a 3/4" square to push dry through your bore ... if it comes out gray or black, you have a lead build, which affects accuracy.

Light loads can explain the lead in the barrel. Leading can be caused by numerous things, but the three most common are:

1) The lead is too soft.

2) The load is too hot for the lead being used.

3) The load is too light, causing the bullet to fail to expand enough to seal the barrel and allowing hot gases by, which in turn melt the lead and leave deposits.

Given the loads being lighter than recommended, the problem is likely #3 although #1 could play a part too.

 

[Old_Cop]

I never got my 5906 to shoot lead bullets accurately. My suggestion is to use jacketed 115 or 124 gr. bullets.

 

[Rowlf]

Try searching around in Bullseye-L Forum for 9mm lead loads as I have seen some threads there on the subject. Since it is a precision pistol forum there is also discussion on 9mm loads for different twist rates of rifling.

 

[flagman1776]

My first pistol was a M39-2 & I shot a lot of lead through it. I habd cast for years before going into business with machine casting equipment.
Bullets need to be fairly hard as well as sized .356. After full length resizing your cases, you'll need to flare the case mouth as little as possible to start the bullets. After bullet seating, you'll need to turn the expanded section back in as a taper crimp. You can use your sizing die raised up in the press for that... I used a washer for consistancy until I found a spare sizer die to become my dedicated crimper.
Test a few rounds for correct seating / sizing by removing your barrel & drop the cartridge into the chamber where it should seat properly. Really a bummer to go to the range &find your test ammo won't chamber.

 

[Cyrano]

Sometime during the producion run of the 39-2 the rifling was changed from one turn in 10 inches to one turn in 18 1/4 inches, same as the 38 Special. I acn't find the exact date or SN now. Maybe this would have a bearing on your problem as the slower twist would do better with lighter bullets.

 

[Jnl1000]

Sometime during the producion run of the 39-2 the rifling was changed from one turn in 10 inches to one turn in 18 1/4 inches, same as the 38 Special. I acn't find the exact date or SN now. Maybe this would have a bearing on your problem as the slower twist would do better with lighter bullets.

Ive reed that this change in twist was 1973, i cant tell from looking trough the barrel, but is seema like more turns than 1/18.

Thanks everyone! Ill go to the range tomorrow and try some factory ammo 115 grs, heavier load cast. And ive sendt an order for 115grs jacked bullets!

 

[Jnl1000]

I promised to report how this precision issue worked out. I tryid several cast bullets, 105, 115, 122, 125 grs. I slugged the barrel, and found that it was 355.7. I did have a lot of led in the barrel after 356 cast bullets, so i went for 122grs 357 cast bullets. Now i shoot groups of 5 at 2" on 25 yards. I consider that beeing acceptable for a semi-pistol, even this is my first non-matchgun semi-pistol, and ive seen glocks beeing less accurat ( maybe bad shooters??). A have a load of 4,9 grs VIthavourti 340 powder with a col at 28,4 mm, winchester sp primers. I can still go 0,5 grs up, but that didnt improve the accuracy. I will check the velocity at the range when a chrono is availableThanks for good advices and interesting readi g