The throat problem

[Catch]

Well here comes some more questions........Is the throat supposed to be the same size as the groove diameter? Is there a way I can measure the throat without making a casting? If I use a casting, should I add about .001 for shrinkage?
If the throat is larger than the bore (burnt out etc.) should I forget about accuracy in that particular gun? I guess thats enough questions to irritate the brotherhood who have probably answered them all before. :bigsmyl2:

[pdawg_shooter]

I wouldnt worry too much about the throat. I have an p17 with a badly eroded throat. the bore is .3015 ant the grooves are .309. I patch to .313 and it shoots in 2.5 @100yds. The paper will compress in the bore.

[1874Sharps]

You may experiment with slightly thicker paper or larger diameter sizing if there is an accuracy problem with throat diameter. As PDAWG has said, the paper will squeeze down a bit. If you can chamber it, it should shoot safely, as PP pressures tend to be lower for a given load compared to standard GG cast boolits or jacketed. In fact, a tighter fit would probably be advantageous.

I do not know a way to measure the throat without taking a chamber cast, but it may not be necessary. A little experimentation ought to reveal what the rifle likes the best.

[bearcove]

The paper should polish it up nice.

[303Guy]

It's not easy measuring the throat by any other means but I did do it. I measured the bore at various deptsh using the rear of the action as a reference. It required turning a land on the end of a brass rod and measuring it's diameter and depth. Hard to do accurately.

[HABCAN]

The ID of a fired case will be close enough to PP to. Presently I'm have acceptable success under 4 MOA with normal-cast unsized unlubed boolits NO GC in seven 'calibers' (four nominal bore sizes) PP'd one wrap and tightly hand fitted back into the fired case and estimating up to 2000 fps+ with no leading or apparent tipping. LEE Universal Decap die, LEE Universal Case Mouth Expander die helps. You might try that and let us all know how it works for YOU.

I'm having the same results PP-ing the smaller boolits 'up' one caliber, as in .257's to 7mm. That Lyman #287346 PP's to .303 with alarmingly fine 'results', BTW. Research continues, LOL!

[docone31]

I wouldn't worry about the throat.
The paper will compress and fill the bore.
I would just shoot it.

[45 2.1]

I wouldnt worry too much about the throat. I have an p17 with a badly eroded throat. the bore is .3015 ant the grooves are .309. I patch to .313 and it shoots in 2.5 @100yds. The paper will compress in the bore.


I wouldn't worry about the throat.
The paper will compress and fill the bore.
I would just shoot it.

Then we have the problem Dragonrider had;
http://castboolits.gunloads.com/showthread.php?t=105433
You would be safe in both your estimations provided the throat was bigger than the patched slug. The paper has to make it to the bore if its supposed to work. Think about it.......................

[pdawg_shooter]

I patch wet, with a lot of stretch. When dry, you need a sharp knife to remove the paper. I load a number of my bullets where they engrave the rifling and have no problem stripping the patch off the bullet.

[45 2.1]

I patch wet, with a lot of stretch. When dry, you need a sharp knife to remove the paper. I load a number of my bullets where they engrave the rifling and have no problem stripping the patch off the bullet.

So do I.............. never had a problem until I ran into a rifle with no throat. That one peeled the patch off before it got into the rifling. You can guess what the results were. It can happen .... even though you haven't seen it.

[pdawg_shooter]

So do I.............. never had a problem until I ran into a rifle with no throat. That one peeled the patch off before it got into the rifling. You can guess what the results were. It can happen .... even though you haven't seen it.

No throat? What kind of rifle was that. Dont guess I have ever run into one with no throat. I have had a few with a very short throat, like maybe 3/8" or so. Lengthened them with a throat reamer.

[dnepr]

No throat? What kind of rifle was that. Dont guess I have ever run into one with no throat. I have had a few with a very short throat, like maybe 3/8" or so. Lengthened them with a throat reamer.

I don;'t know about all savage 99's but my 99 in 250-3000 has a very minimal throat it is about 0.055 long and 0.260 diameter , I don't know for sure about stripping the patches but my first attempts at pp boolits were hitting the paper sideways at 10 yards. I will try it again with pp when it warms up this spring with a better pp boolit and see what happens. I have learned a lot about paper patching on this forum since then so I am hoping for better results

[bbqncigars]

My new Armi-Sport Sharps Creedmoor in 45-70 seems to have a very minimal throat (about 3/32" at most). This is historically accurate according to some sources. I won't get a chance to shoot it until the semi-glaciers retreat on the range.

[bearcove]

No throat? What kind of rifle was that. Dont guess I have ever run into one with no throat. I have had a few with a very short throat, like maybe 3/8" or so. Lengthened them with a throat reamer.

T/C Encore in 45-70 has no throat. Chamber then rifling.:idea::?:

[303Guy]

Somewhere there is a drawing of that 45-70 'throat'. The chamber ends and the rifling leade begins (45° if I recall) straight into the bore, no throat. That drawing is likely under black powder paper patching.

[leftiye]

That's the original 45-70 chamber. Supposed to utilize bore riding boolits (maybe not the very first ones). Marlin guns often have no FREEBORE, likewise H&R (NEF).

[pdawg_shooter]

Guess I have been lucky. Havent run into this problem before. I have 3 Marlins on hand and have had 6 others and they all had throat.

[45 2.1]

No throat? What kind of rifle was that. Dont guess I have ever run into one with no throat. I have had a few with a very short throat, like maybe 3/8" or so. Lengthened them with a throat reamer.

I see you've gotten some replies.................. The problem has been around for a long time. Keith used to write about sizing boolits to groove diameter......... that was because the guns of his era had no throat and the area in question was groove size. I've seen this on several rifles dated to the time he wrote that.

[Longwood]

Very interesting.

[MBTcustom]

I successfully made an accurate chamber slug from my rifle using techniques I learned here I think. I trimmed the neck off a piece of brass and filled it with lead. I chambered it. I cast a the heaviest "ie longest" boolit I had for that caliber and pushed it down the barrel with a steel rod "I protected the rifling by wrapping the rod with 2 inch masking tape to bore diameter every 2 inches" once the rod and boolit contacted the case, I hammered the rod until it bounced sharply. I ejected the case and gave the rod a few gentle taps and out came the chamber slug, exactly the right size and able to be saved for future reference. No more guessing what is going on! You can see and measure every little detail. Hope it helps!

[semtav]

I successfully made an accurate chamber slug from my rifle using techniques I learned here I think. I trimmed the neck off a piece of brass and filled it with lead. I chambered it. I cast a the heaviest "ie longest" boolit I had for that caliber and pushed it down the barrel with a steel rod "I protected the rifling by wrapping the rod with 2 inch masking tape to bore diameter every 2 inches" once the rod and boolit contacted the case, I hammered the rod until it bounced sharply. I ejected the case and gave the rod a few gentle taps and out came the chamber slug, exactly the right size and able to be saved for future reference. No more guessing what is going on! You can see and measure every little detail. Hope it helps!



http://i957.photobucket.com/albums/ae53/S2D/004-4.jpg

[Longwood]

Thanks Goodsteel.

That will help immensely.

I am obviously new here and am very slowly working my way through the archives but thankfully there are plenty of nice helpful people here that are pointing me in the right direction.

[Longwood]

Also thanks to semtav

[nanuk]

Semtav: what are those rings around the lead just above the brass?

are those the lube grooves from the boolit you used?

[semtav]

Yes, I don't have any smooth sided slugs (yet)

[Longwood]

I used the rod and soft slug to see what my chamber looked like. There was, repeat was, no throat. The rifling ended with a sharp chamfer right at the case mouth. It now ends at the same place but it now has a nice tapered leade into the rifling.
I bought a used reamer from Larry Gibson and I now have a perfect throat and PP bullets chamber beautifully. I doubt seriously that I will need to modify it more.
The reamer is now on the way to NY state and will be going to New Mexico next.