Undersized boolit accuracy

[Griswold]

I've been loading the past year for my Uberti Win 73 in 44-40. Bore is 0.429.
Using IMR4198 at 14.7-15 grain with a .430 LRNF of 200g.
Starline brass and win Lg Pistol primers.
Went to an outdoor range yesterday and shot ten of those to check accuracy and to see if my sights needed adjusting. I'd installed a German Silver Rocky Mountain front sight........anyway.....at 25 yrds they were dead on.
Should have taken more for the 100 yrd range but didn't. I did tak a box of 100
205g. 0.428 rnlf over 15 g of Hercules 2400. RP brass, Win. Lg Primers. I had loaded these previously for a Win 92 I used to own and then stupidly sold years ago. That bore was 0.427.
These were all over the place with my 73.
I adjusted my buckhorn up and down.....finally was able to land two hits on the paper but they were a foot apart.
Thought it was my sights or my eyes (not good vision) or the fact I hadn't shot at that distance in years........(indoor range is only 25 yrds)........
I came to the conclusion that my rifle just didn't like that load or that undersized boolit...even though they were just a thousandth under.....and my eyesight needed new glasses.
So my question is: Concerning the boolit........are undersized boolits that inaccurate?
I might add that I am thinking to install a Skinner peep sight in place of the buckhorn and use it as a ghost ring or opening up the small sight gap on the buckhorn. I love this rifle but being period correct isn't necessary if I can't get a good sight picture.
Suggestions?

[Der Gebirgsjager]

Suggestions? Use what works, .429.
.429-.427=.002
Shooting boolits .002 undersized often results in inaccuracy.
Shooting boolits .002 oversized in worn bores often works well.

DG

[Griswold]

The boolits were .428.......001 undersize.......

[Fitz]

I size to the throat and don't worry about the bore , unless shooting muzzle loaders or paper patched BP .

[DougGuy]

I size to the throat and don't worry about the bore.

^^^^THIS^^^^^^ Nothing else matters!

[2TM101]

Suggestions? Use what works, .429.
.429-.427=.002
Shooting boolits .002 undersized often results in inaccuracy.DG

I ran into this with a convertible .357 / 9mm revolver. 9mm works unless you want to hit something.

[JonB_in_Glencoe]

Griswold,
Welcome to the forum.
While an undersized boolit can cause inaccuracy, you describe some severe inaccuracy from only .001" undersize and 15 gr of 2400 is a pretty good load to obturate the boolit, if it isn't too hard. I wonder if you rifle just doesn't like that boolit shape or if seating depth (or runout?) isn't conducive to a square launch causing that severe inaccuracy.

[Dusty Bannister]

Unable to get a good feel for your load data, but many times shooting undersized bullets will result in leading of the barrel. Most times cast bullets are preferred to be 1 to 3 thousandths over Groove diameter as long as they will chamber freely. It is unclear if you even tried the old reloaded bullets at 25 yards to get a comparison with the test loads.

You also mention vision issues, a different brand of cases and a new sight, but perhaps you just need to check everything for tightness, set the old ammo aside for now and work on the new load. It is also possible that you put a rest at the wrong location on the barrel and that can cause a change in bullet impact on the target. You do not mention checking for a lead build up in the barrel. Yet the conditions are favorable for that to develop.

I have had 10 year old ammo that functioned correctly, but I know it was stored in relatively stable conditions. A lot can change over the years.

[DougGuy]

I ran into this with a convertible .357 / 9mm revolver. 9mm works unless you want to hit something.

Ruger BH 9mm have the worst throats of any BH I have honed. Horribly egged, tapered, undersize, it's more of a wormhole than a throat. The Sunnen hone takes care of all that. It's no wonder people complain about them and their complaints are fully justified. They are indeed a PITB to hone, but it will save them and they will group.

[georgerkahn]

An added note is I could've gotten a deal and one-half on a "30-30" Model 94 Winchester -- early 1950s vintage -- as heartbroken owner (Steve) found he had a hard time hitting the broad side of a barn with it -- asking if I might have interest in hopefully finding the problem and rectifying it, or, give him "a few bucks" for it? The rifle was his Aunt Rose's, and he did not have as nickel in it.
Well, not thirty seconds after he put it in my hands, I asked if he had any of the ammo he was trying left. "Yup" It was the yellow box Winchester .30-30 ammo! EXCEPT -- he assumed all '94 levers to be in this calibre! Marked on the arm was ".32 Winchester Special". I gifted him a box of my .32 Win Spec handloads, and he rang me on 'phone that eve profusely thanking me -- the rifle now "shot"!
While grossly undersized, in this case -- it surely demonstrated the need for proper sized to barrel ammo!
geo

[FLINTNFIRE]

Oh yes under size will never shoot a good group , just a fact just as twist rate determines what length to weight shoots better , fit is one of the top things , then find the rest of the load and components to make the gun shoot

[.429&H110]

Thank you for this thread, about what should work and what doesn't.
Need more answers it's all anecdotal like all learning.

I have an old Legacy lever action that I bought broken. Piece of junk, he said. $50.
It keyholes .429 j words.
and loves .430+ Keith boolits. No gas check, 1200 fps, accurate until you feed it wrong.

It's a big subject...

[Griswold]

Thanks for your response. I shot ten .430's at 25 yds to test their accuracy over 25g of imr4198 and to see if my new front sight, a Rocky Mountain sight was installed correctly. Dead on. Didn't test the old ammo at 25 yrds.......that ammo is all that is left of my .428 boolits. It was for my old Win 92 which had a .427 groove barrel. I guess I will just shoot it up at 26 yds so I can reload with the newer boolits in ..430". Sight wise I ordered a Marble bullseye sight hoping that will give this old eye a better sight picture. Sure would like to know the pressure of my new loads of 25g of IMR4198 IE: whether they are safe for my SA or just the rifle.

[Good Cheer]

In the 1980's some .308's appeared that were Yugo's rebarreled with .310" groove 10" twist barrels.
A curse or an opportunity depending upon your point of view.

[popper]

.are undersized boolits that inaccurate? Yup. They get 'damaged' in the bore and don't fly right.