Mosin Targets... Vertical Stringing... Help?

[Joshua M. Smith]

Hi All,

I'm stumped here.

This is today's shooting. It's just surplus light ball bullets, pulled, over 45 grains of Varget and a Federal primer. This is from a clean bore, and this rifle shoots low with a clean bore.

10 shots. Square is 1"; circle is 2". 60 yards, prone, front support, fire five, stripper clip, five more, as fast as I can BRASS, about every two seconds:



Prior to that, a 174 grain Hornady o.312" Match over 51.2 grains H4350, same distance:



But 174 grain jacketed round nose o.312" bullet, under increasing amounts of Varget, this is the best I could get, and the vertical stringing is really bad though it's an improvement over the lighter loads. If I recall correctly, these are 44 and 44.5 grains, pretty much overlapping each other. 10 shots:



Do I just keep increasing until I max out or find a load that doesn't string? Where do I go from here?

Thanks,

Josh

 

[Cosmoline]

The loads are likely not causing the rifle to string. The likely culprit is too much stock interference on the barrel end. What kind of Mosin are you shooting and what kind of stock does it have? The 91/30 pencil barrels will frequently benefit from a bit of pressure upwards, but not too much. And as the barrel heats up if the stock is ill-fitting it can start to throw groups off and cause stringing.

Simple way to check--swap stocks or toss it in a Boyds or something to get a read on how it's shooting with a free barrel. If you see the stringing stop, you know the answer. Fixes are pretty simple. Stock black to find the high spots, a little chisel work, and fine tuning the tip of the stock with some cork to get it where it wants to be.

Either that or maybe your receiver screws are backing out.

 

[Joshua M. Smith]

Hi Cosmoline,

It's 91/30 that usually does about 1.2MOA. Had the barrel already had five rounds or so through it, the top target shot today would be all 10 touching. The four touching is where it's set to hit at this distance.

I'm mostly concerned about that bottom target. That's the only one in which I'm getting radical stringing.

The rifle is a 1939 (1938 on the tang) 91/30. I've shimmed it and put some cork as a pressure point near the barrel end.

It doesn't seem to string unless I shoot Varget with heavier bullets.

Thanks,

Josh

 

[midnattsolen]

Are you measuring your powder charges individually or throwing each charge from a measure ?

 

[Ditchtiger]

Check the bolts in front of and behind the mag. for being loose.

 

[Cosmoline]

Hmm. Well there must be something going on there, and I don't think the powder or bullet per se can take the blame for stringing like that. If each handload is the same you'd expect to see the same level of accuracy, not stringing. To do that with handloads you'd need to add a grain with each load, but I'm sure you didn't do that.

Best guess at this point--the increased recoil from the heavier bullet Varget load is somehow displacing the barrel or receiver a bit by bit. So something is loosening up or altering position consistently with each shot.

BTW--did you check to see what POI was AFTER that string of Varget loads? Maybe wait ten minutes till the barrel is cool, do nothing to the rifle and try again seeing if the stringing is starting from the baseline or from where it left off. If the former, then it's probably a heat related issue. If the latter then it may be something shifting out of position. Maybe your cork or shims.

 

[Joshua M. Smith]

Are you measuring your powder charges individually or throwing each charge from a measure ?

I throw it, then weigh it, then adjust it. It takes me a couple minutes to load each round.

My favorite rimfire rifle is a precision .22 that I use to knock the eyes out of squirrels at 100 yards.

I tend to be very OCD.

Josh

 

[Joshua M. Smith]

Check the bolts in front of and behind the mag. for being loose.

Both the front and back are 50in-lbs, though I found the front one a little looser after shooting. I'm ordering new screws since these are done in and I've also fitted a lock washer to the front.

This could cause it... but on one load only?

Thanks,

Josh

 

[ColtPythonElite]

My money is on a hot barrel.

 

[Joshua M. Smith]

Hmm. Well there must be something going on there, and I don't think the powder or bullet per se can take the blame for stringing like that. If each handload is the same you'd expect to see the same level of accuracy, not stringing. To do that with handloads you'd need to add a grain with each load, but I'm sure you didn't do that.

Best guess at this point--the increased recoil from the heavier bullet Varget load is somehow displacing the barrel or receiver a bit by bit. So something is loosening up or altering position consistently with each shot.

BTW--did you check to see what POI was AFTER that string of Varget loads? Maybe wait ten minutes till the barrel is cool, do nothing to the rifle and try again seeing if the stringing is starting from the baseline or from where it left off. If the former, then it's probably a heat related issue. If the latter then it may be something shifting out of position. Maybe your cork or shims.

I am not understanding why it doesn't string with 150 grain 45 grain Varget loads, or H4350 174 grain match loads, but does string with the round nose jacketed soft point with Varget.

One thing that does occur to me: I've never tried long bearing bullets in this rifle before. The jacketed round nose soft point has a bearing surface along about 3/4 of its length.

Could this be messing with things, gents?

I hard crimp the surplus 147 grain bullets as they were like that from the factory and don't always like to stay in the shell otherwise.

I only kiss the neck with the Lee Factory Crimp Die (rifle, of course, not those pistol ones which are totally different!) on the factory 150 grain bullets and the factory 174 grain bullets.

I seem to get good results either way.

Does Varget usually like hard crimp, soft crimp, or no crimp?[/i]

I think one of the first things I will do is eliminate Varget as a problem by using the last of my H4350 to load a few rounds with the same weight as the BTHP I shot the second target with. It should be safe; it's only o.2grns over minimum.

I'll try to get a target shot tomorrow. Still have to track something some folks opine is a bear in Indiana, and do some sights that got backed up a bit when the power went out with these storms that came through, but I might fire a few near toward sundown.

Thanks folks. I'll try to get to this after the work is done and report back.

Regards,

Josh

 

[midnattsolen]

I've been collecting any info I can on the Mosins as I am getting ready to start load development. A recent article I found gave this load:
174 Sierra HPBT .311 bullet.
45.0 Gr. Varget
Velocity = 2,550 fps.
Comment : "very accurate"

The rifle is listed as a Soviet model 91/30 with a 28.6 barrel. No comments were mentioned for signs of pressure or if this was a max load. Fine print on bottom of chart says "Be Alert - Publisher cannot accept responsibility for errors in published load data."

Hope this helps.

Mike

 

[Cosmoline]

I am not understanding why it doesn't string with 150 grain 45 grain Varget loads, or H4350 174 grain match loads, but does string with the round nose jacketed soft point with Varget.

Were the strung bullets the last to be shot? It could just be a matter of heat build up. To really test you'd need to cool the barrel off before testing and remove one variable at a time.

 

[Joshua M. Smith]

Cosmoline,

The strung bullets were the only ones shot that day.

I'm sorry I was not clear on that. I don't test different types of bullets in the same day. My shooting range is in the back yard and I guess I have that luxury.

It's not unusual that I send 100 150 grain spitzer-type bullets downrange and get no vertical stringing. It just seems to be this combination.

I'm working on two hypothesis:

1. The powder charge needs increased so the bullet moves at 2500fps. This rifle likes 2500fps or faster. Still very accurate when I push the envelope to 3000+fps

2. The long bearing surface of the round nosed bullet is causing heating that the barrel otherwise wouldn't experience.

I briefly thought that it was the bullet/powder combination, but there are too many good loads with Varget out there for that (like the one posted by midnattsolen – Thanks Nat!). I figure the most that would happen is the groups would open up.

Here is an early target. I stumbled across an old post where I had just tried my first rifle handloads, and it was with this rifle, Varget, and o.308" bullets:

And with some pretty fast surplus ammo:



Those were before much had been done, just the prototype front sight mod that I make my living off of now.

With the shimming and such, it just tends to shoot the middle out of anything I try, and that's why I'm confused by the stringing. It doesn't exhibit it unless it's a clean, oiled barrel, and only then until the oil is out, about three shots as shown in the first target in the first post.

Regards,

Josh

 

[midnattsolen]

It could have something to do with the bullet. If I remember one of your earlier posts mentioned a bore size of .3095". Perhaps the long bearing surface coupled with the .312 diameter is causing excess heat. Do you see any signs of excess pressure from the fired cases with this particular load ? You may want to fire a round then wait for a moment then fire another, rather than "rapid fire". As others have said let the barrel cool. You also may want to try a .311" or smaller round nose bullet and see if there is a difference.

 

[kestak]

Been there with a mosin I shot. For the life of me, with every kind of ammo I was shooting, I was getting a vertical string from sandbags or my led sled....until....I decided to shot prone with a sling deployed hasty very snug on my arm. The group got very round and uniform at about 2-3 MOA depending of the ammo with the occasional flier.

 

[Rory McCanuck]

My M-44 doesn't shoot the 174s worth a hoot, but will put 150s into an
inch or less (@50) all day long.
I've been running with what works.....

 

[Ky Larry]

I had a Rem 700 ADL .30-06 that used to string 150gr bullets like that with IMR-4350. I switched to a mag primer and cured the problem. If you try this, start at the min load and slowly work your way back up.