Lyman Rifle Accuracy

[ETipp]

I have a Lyman GPR in 54 and someone in an earlier post indicated that my load of 110 grs FFFG with a PRB was higher than shown in the manual that came with the gun. My GPR was purchased in 2018 and the manual does indicate a max charge of 100grs which I never checked cause I have the LYMAB BLACK POWDER HANDBOOK . However , when I bought the gun I was using the data in the Lyman Handbook which shows larger charges and that page is posted in this thread somewhere. Any way that manual has been around since the 70's and I am sure if there was a problem with a load given in that book it would be common knowledge by now. Looks to me like the authors of the Handbook tested that stuff pretty good back then and that is the data I trust besides my own personal experience.

Thought I should add this: .530 Hornaday Ball
.015" Patch
Track Mink Oil lube

Or perhaps Lyman saw something over the years that was not good and decided to correct it.

Why would they lower the maximum performance if there was not an issue?After all, testing equipment has improved over the years.

The only two things that I can see why they would deliberately shoot themselves in the foot would be fear of a lawsuit or perhaps the strength of some component(s) are not as strong as the earlier rifles.

It is not conducive to lower performance in a product in the world of sales especially during the time inlines came to be.

 

[Greenjoytj]

The 54 Deerstalker has a 1 in 48 rifling twist rate. A compromise twist rate that’s too tight for fast MV with PRB and a bit slow twist rate for conicals unless they are launch at high MV to stabilize them so the don’t key hole. Short length lighter conical are less likely to key hole.
I believe that twist rate is too fast for PRB’s to get accuracy from high muzzle velocity using large powder charge weights. Slow your PRB down, try 50 gr of 2fg or less to see if groups improve with reduced MV.

Check that the rifling is not all filled in with lead from the conical bullets.

I think you would be better off shooting conical bullets from clean rifling.

In a clean barrel start a PRB one inch into the bore then remove it using the slide hammer trick. Does your PRB show patch cloth weave marks embossed on the ball in a light and heavy pattern all the way around the equator of the ball?
If it doesn’t show this pattern the ball diameter and or patch thickness is too small, which will make your rifle shoot as if it is a smooth bore.

I shoot a Lyman GPR 54 flintlock with .535” balls my patches are .0155” (15.5 thou) measured dry with my micrometer squeezing till the clutch clicks.
A hard turn on the micrometer thimble will squeeze the cloth down to .009” (9 thou).
A 58 caliber .610” dia. .149” thick over powder wad soaked in melted TOW mink oil.
I lube by patches with Lubegard Premium Universal Lubricant (it’s JoJoba oil) in spray bottle. 80 grains 2fg Olde Eynsford powder main charge. 4fg GOEX in the pan.

Known this, even using an oiled patch and lubed OP wad there is still not enough lube present during firing to keep the fouling soft enough for easy second loading its doable but wet swabbing makes 3rd loading easier. A .54” bore has a lot of area inside to collect and quickly dry the fouling to a hard crust particularly closer to the muzzle even if firing in humid conditions.

 

[jambuster]

Or perhaps Lyman saw something over the years that was not good and decided to correct it.

Why would they lower the maximum performance if there was not an issue?After all, testing equipment has improved over the years.

The only two things that I can see why they would deliberately shoot themselves in the foot would be fear of a lawsuit or perhaps the strength of some component(s) are not as strong as the earlier rifles.

It is not conducive to lower performance in a product in the world of sales especially during the time inlines came to be.

This is fatiguing. The only reason l have a Lyman GPR is it is or was the only reasonablely priced Hawkin style rifle I could afford. If anything else was available from an American manufacturer that is what I would have. It is rather crudely assembled and probably from a relatively mild steel. .

My gun is has been sold in the US since the 80's and the data from Lyman's handbook has been available all that time. That is the data I use and have proved out myself. As I recall BP guns operate in the neighborhood of 10000 psi. Even for mild steel there is plenty of meat in my barrel and breech plug to handle that safely.

Use the information that makes you happy as the rest of us will likely do.

 

[ETipp]

This is fatiguing. The only reason l have a Lyman GPR is it is or was the only reasonablely priced Hawkin style rifle I could afford. If anything else was available from an American manufacturer that is what I would have. It is rather crudely assembled and probably from a relatively mild steel. .

My gun is has been sold in the US since the 80's and the data from Lyman's handbook has been available all that time. That is the data I use and have proved out myself. As I recall BP guns operate in the neighborhood of 10000 psi. Even for mild steel there is plenty of meat in my barrel and breech plug to handle that safely.

Use the information that makes you happy as the rest of us will likely do.

Oh I have both volumes of the older Lyman books. Honestly, it bothers me not what anyone might choose to do, in terms powder charge or anything else.
It’s their party. Not arguing one bit. Just posting the latest data and discussing why they might have reduced the maximum charge listing.

One last comment, it’s not only a barrel or breech plug that can become weak from a steady diet of too heavy of a load. The stock itself can become weak and crack over time. This is why some folks that’s modified or built up their own ML’s using a factory stock, that shoots heavy loads, had to beef up the wood.

Enjoy your GPR, I know I like mine. Very accurate.

 

[ETipp]

With my first GPR, made in the early 1990's (since stolen), I could reliably get an open hand-sized group from standing, off-hand, at 100 yards. I'd call it about 6" and considered it good enough for hunting. My marksmanship has improved significantly since then.

That’s pretty good shooting, Tx.
(No pun intended). I need to try some offhanded shooting with mine soon.

I consider the hold of my GPR one of its finest attributes. She holds steady as a rock. She’s a bit on the heavy side but she’s solid.

Mines an older model. Wanted one for years until I finally got this one.

Really like that ML.

 

[Kicking&Screaming]

Typical accuracy ‘from the bench for hunting purposes’ (are you actually hunting from a bench?) with minimal effort will likely be 6” or less groups at 100 yards with patched roundballs with either gun. It will all depend on if you are lucky and ‘choose wisely’ when selecting your common shooting components and your shooting ability. One thing you may want to spend just a bit of time on, particularly if you are starting with a gun not previously shot (Lyman has been out of the muzzleloader business for some time now, and NOS doesn’t come up that often) is cleaning up any sharp machining edges you may find at the muzzle (they tend to be rough on patches) by hand or running a couple hundred rounds through the barrel. If any burrs are present either method will typically improve accuracy once removed.

…a few hundred rounds with a lead lap and varying grades of compound will help as well