Vertical stringing in 7.62x54R

[alemonkey]

I recently started trying to develop a cast load for my Finn M39 and I'm having a terrible time with vertical stringing. At 100 yards my groups are maybe 2" wide but they're 6" or more tall. I'm using the Lee 160 grain gas check mold, with 45/45/10 lube. Powder is Unique, and I've tried everything from 11 to 13.5 grains, all with bad stringing. I'm wondering if I need to try some Dacron to keep the powder back against the primer?

[JIMinPHX]

If you think that it's a powder position problem, then point the gun straight up between shots & lower it back into shooting position slowly. That should put the powder in the same position, at the back of the cartridge, for every shot.

Most of the vertical stringing that I have run into myself was caused either directly or indirectly by barrel heating. Stock fit was often also part of the issue. If you wait a full 2 minutes between shots, so that the barrel can cool down, does the amount of stringing change?

[alemonkey]

Good question on the barrel heating, but I don't believe that's the problem here. I use this rifle for a vintage miltary match with j-words and have never experienced any problems with stringing even though I'm shooting at a fairly rapid pace.

I did think after getting back from the range yesterday that I should have tried to point the gun up between shots.

[Dutchman]

Is there any kind of shim under the receiver on the recoil lug? Many m/39 will be shimmed. Could be yours was lost along the way.

Dutch

[HARRYMPOPE]

with 9-12g of Unique no filler is needed to shoot good groups.I shoot that in many military rifles.i user pistol primers with that load though i dont think it matters


George

[Larry Gibson]

Big case with low end loads of Unique.

Powder positioning and not enough psi to ignite and burn efficiently. Raise barrel and lower slowly before shooting to position powder at back of case. If that corrects the vertical stringing then an more efficient burning powder is needed. If you want that kind of low end loads with relatively light weight bullet using a fast powder at such a low loading density I suggest a switch to Bullseye starting at 6 gr and work up to 8 gr. If you want a little more oomph then try 2400, 4198, 4227 5744 or 4759 and use a dacron filler with them.

Larry Gibson

[HARRYMPOPE]

Larry no offense but not tipping light charges Unique will not result in 6" vertical.The problem is elsewhere.Unique with 12g and a 160- 200g bullet has won matches for me and i never tipped a barrel up or used a filler.

[rhbrink]

Might check the pressure at the very end of the stock you can do this by simply pulling up on the barrel while holding the the stock down. There should be 4 to 6 pounds of upward pressure of the stock against the barrel if that is not there losen up the screws and add a thin cardboard shim under the barrel at that point. Shoot it, sometimes it just takes a little bit sometimes more most of these military rifles shoot better if a few pounds is pushing up on the barrel. A couple of thick paper shims may also do it.

RB

[Larry Gibson]

No offense taken Harry but I've shot enough Unique in cartridges like that with lighter 150 - 160 gr bullets that I know tipping the barrel up or down can cause 6" of vertical stringing at 100 yards as it also can cause 100+ fps variation between the two methods. I also know that in the .308W to '06 sized cases (the 7.62x54R sits between) using 12- 14 gr Unique and a heavier 180 - 200 gr cast increases the psi where the powder is burning efficiently, the ES is normal and there isn't any vertical stringing as you say. However, even then if one tilts the barrel up for 5 shots and then down for 5 shots most often there will be a vertical dispersion, perhaps not large but still there. it also won't be as much as with the lighter load with a lighter weight cast bullet.

Also you are a very good and knowledgeable shooter/competitor who is, no doubt very consistent when shooting from the bench in picking up the cartridge and consistently loading it into the rifle, no? Perhaps the OP was not so consistent in that and the powder was positioned erratically shot to shot(?). The simple test I suggested will quickly determine whether it is the load, the shooting technique or something wrong with the rifle. I don't see it as a matter of anyone being right or wrong but simply to eliminate the obvious and easiest before we have to figure something is wrong with the rifle.

That it is something wrong with the rifle is doubtful because the OP stated he has never had vertical stringing with J bullets. My experience with vertical string is; if it occurs with all or most loads, cast and jacketed, it is the rifle. If it occurs with one load, either cast or jacketed, then the vertical stringing is more than likely caused by the load.

Again, no offense taken as I always enjoy our discussions.

Larry Gibson

[Dark Helmet]

Are you using a magnum primer? Good boolit pull?

[alemonkey]

Thanks for all the suggestions everyone. I was using a standard rifle primer but I'm thinking of trying some different brands.

I really don't think it's a problem with the rifle since it shoots jacketed bullets very well. With pulled Russian surplus 150 grain bullets and a mid range load of H4895 I've won the local vintage milsurp match a few times, so I know it shoots.

I was thinking about this some more this morning and wondered if seating depth might be an issue. I'm trying to seat the boolit just off the lands, but I just remembered that a few cartridges were a little harder to close the bolt on. Not much and I didn't think anything of it at the time, but if there was a slight variation on the boolit that caused some to seat tighter against the lands could that raise the pressure a little and cause variations in velocity? Maybe I should seat just a little deeper. Next time I will be sure to not forget my chrony.

[1Shirt]

Good thread. Keep us informed of your progress and results.
1Shirt!

[alemonkey]

I guess it's also possible that this rifle just doesn't like this boolit, too. The good thing is, Lee molds are cheap enough to try a few different ones. Even if I can't get this one to shoot in this rifle I have enough old military clunkers that I'm sure one of them like it.

[dualsport]

Try using a little different hold or position at the bench. I've found that my standard bench technique isn't always ideal for different loads. Light hold, hard, pressure against shoulder, etc. Vertical stringing can have something to do with where the muzzle is at boom. Using a rear bag? Experiment.

[alemonkey]

Hey guys, just thought I'd follow up.

I finally had a chance yesterday to head back to the range and do a little more testing. I didn't have a whole lot of time, but I shot 5 shots with the cartridges just in whatever position and 5 with the muzzle raised up between shots. The first 5 shot group had the same terrible vertical stringing, and the second (with the powder towards the back of the case) was roughly 2.5 MOA, with about the same amount of vertical dispersion as horizontal. That's about as good as my bad eyes can do with open sights. I ran them through the chronograph but didn't think about starting a different string for the second group so I can't give you exact figures, but the extreme spread for the second group was about half of what the first was.

So, it does appear to be a powder position issue. I definitely need to do some more testing to verify these results since 5 rounds could very well just be a fluke. That makes me wonder if maybe some Dacron would help matters. Tipping the barrel up between shots isn't a big deal, though, since this is just meant to be a load for plinking and shorter range competition.

[popper]

I found setting the ammo base down when shooting does make a difference and you don't need to tilt the bbl up before shooting.

[x101airborne]

Without using heavier boolits, that is why I started moving away from Unique. It works great in some cases and my neighbor loves it in 300 win mag for nite time hogs, but my 7.62x54R really started shining when I moved up to RL-7. My load for the 316-155 NOE is 30 grains of RL-7 and a .7 grain dacron buffer over the powder. Inch and a half at 100 all day long. I do get flyers, so dont think I am bragging, but I dont know what flyers are due to me using peep sights, my casting method, my loading method, etc. But in 15 rounds, I may have about three or less flyers. And by flyers, I mean about an inch or little more outside the group. Still huntable for what I do, shoot hogs and yotes at 100 yards or less. This is the best performance I have gotten out of any military rifle so far.