.318 or .323 inch?

[Gut-n-Tight]

Is my Heym drilling have a J or S bore? this is the question.

I have a Conrad Heym drilling, nothing special - a Plain Jane in 16 gauge over 8mm. Serial number is 5870. It has the standard Suhl mark inside the rectangle and a HK marking near the forearm stud. The barrel is marked 7.8mm over 57 with "St.m.G. over 13 gr. I noticed was that it had the standard 16 in the circle had an addition 70 marking stamped on both flats but the font was larger than the rest. Both shot barrels chambers are for 2 3/4". The plot thickens when I took the thing out to shoot the rifle. I grabbed a box of my reloads and factory S&B 8x57JR. My reload bullets are Hornady. 321" sized to .3182". I did not seem to get anywhere that day with the rifle portion after shooting my full & extra full choked shotgun on the skeet range.

This morning I got a bit more serious with the rifle and began all over starting at 25 yds. This time I took along a box of factory RWS 8x57IR and another box of RWS reloads that I had picked up. The jacketed spire points reloads miked at .321" This is what happened.

Bore sighted at 25 yards and things began smoothly. At 50 yards I noticed that the factory .318" shot several inches lower and the group was larger. Then I moved to 100 yards. The .321" reloads were shooting on target and twice I had two bullets touching each other while the factory RWS shot four inches lower and had a group of 6 inches. WT?

I came home and began the gun cleaning program as usual and took a nap. During that nap I thought, could the bore possibly be .323"? Could the bore be that worn? It is worn but I don't think it is that worn. I bit the bullet and slugged the muzzle. It is .323"!

My question to the Gurus is: How could this be?

[algmule]

Hello

if not worn a 7,8 marked bore could have been anything between 7,79 and 7,9 when proofed. That is, from and including 7,8 up to and including 7,89. Not much difference between 7,89 and 7,9 if you ask me. Add a bit of wear....... Also, it's difficult to exactly measure a "slug" when slugging a bore.

Tj?ta1.jpg

EDIT: have you tried putting a 0.323 bullet in one of the cartridge cases you used?

Kind regards
Peter

[mike ford]

Gut-n-Tight,
Check Peter's EDIT. What he is asking about is a common test to determine whether to use 8x57IR or 8x57IRS ammo. Take one of the cases fired in your rifle, and not resized, then check to see what diameter bullet will fit easily into the case neck. If a .323 " bullet will fit into the neck, then you can use 8x57 IRS, if a .323" will not fit, but a .321" will, hand load with .321 bullets. This test works even if the rifle had a .318" groove diameter. The chamber pressure is not significantly elevated by the bullet being a little larger than the barrel, rather it is elevated by a bullet/case neck diameter being large enough that the case doesn't have enough room to expand and release the bullet. How this can happen with the proof marks on the rifle is explained by Peter's first sentence.
Mike

[Gut-n-Tight]

To begin, I was laboring under the belief that all JRS guns would be so marked.

I went and measured the inside of the casing that I fired in the Heym with my caliper. They measure .320". Would not the brass have sprung back some? I don't have a .323" bullet. Perhaps, I have a worn J bore? Was I fortunate to have gotten those handloads with .321" bullets? I took a quick look on Graf & Sons web site and noticed that they have Privi .322" bullets besides .321" examples and JRS Privi ammo.
From what Mike & Peter have told me, I gather, the thing to do is to reload some using both the Speer 170 grain .321" Flat Point bullets and some Privi .322" HPBT 175 grain bullets and try them out. It is good that I already reload. Sadly I got box upon box of S&B JR and boxes loaded with my sized .3182" bullets but I do have about four boxes of empties on hand. When I reload 8x57R I use Norma data and load on the light side.

Would you all agree?

[algmule]

[QUOTE=Gut-n-Tight;n28606] Perhaps, I have a worn J bore?


Or maybe it was the way it is from start.

Also, I'm positive Axel has told us the German gunsmiths often wanted tighter bores because such rifle barrels were more accurate. If your Drilling shoots fine with .321 bullets and there are no pressure signs, use those bullets. Now that we've helped you, some images of the Drilling, please.

EDIT: something happened to my post and I'm too tired to fix it now (05:19). I've been up all night trying to see a comet. No luck, though. Also, I don't know when they introduced the S-marking on barrels. Maybe it became mandatory January 15, 1941. If they marked any before that date I don't know. Maybe Mauser did??

Kind regards
Peter

[sharps4590]

I believe I would use the bullet that slips easily into a fired case, be that .321 or .323, and not concern myself with the rest.

[Gut-n-Tight]

After once again sleeping on it, I thought, why not try to see if a .318" bullet goes into the muzzle. I did and it would not. WT? -again. I am now back from biting the bullet. (More of a chew with a bit of growl.) I decided that I needed to just slug the bore, all of it. The result... .321" Now I find myself asking, do I have a worn J Bore or a tight S Bore? Either way I will soon be ordering more bullets from Grafs, .321 & .322., as Mike and Sharps suggest. I may also buy a box of their Privi 8X57JRS for a test. Perhaps it would be helpful to know when this gun was made. I suspect 9/38. Now that I have been helped to clear the gun smoke... where are those photos?

[Gut-n-Tight]

Here is another photo of the drilling. When I got it the forearm had been repaired and it gave the appearance (then) that the repairman had not spared the white glue. After it came home I began to try to clean it up a bit. the glue turned out to be rubberized caulk. At this time I noticed that the wood did not match the buttstock and the checkering wasn't up to snuff. I ended up spending many hours doing what I could to make it tolerable. (What I wanted was a good drilling to take into the woods.) The bulk of the caulk was used to take up the gap between the forearm wood and metal. I took this out, squared things up a bit and ended up using some dark gray auto gasket material. It is now a lot better than it was.

I have a theory of how this repair came to be. Somebody toasted the original forearm and took his gun to the gunsmith. The smithy decides the wood is beyond repair and goes into the back room coming out with a box of used handguards. He finds one and explains, "I can do a proper job and make an all new piece of wood that matches for 200 Marks or we can do it on the cheap by using this used split one for 50 Marks. I then ended up with the substitute standard. Bitte Schon.

[Gut-n-Tight]

Does a HK marking by the forearm mounting lug mean I have a Krieghoff made barrel?

[algmule]

Does a HK marking by the forearm mounting lug mean I have a Krieghoff made barrel?

I doubt it. Let's see an image.

The following are suggestions. Nothing more. What HK performed on the barrel we may only speculate.
Heinrich Klett, Rohrmacher, Suhl (was an Emil Klett, Gewehrlauffabrik in Suhl in 1938)
Hugo Kirchner, Rohrmacher, Suhl
Hermann K?ppler, Br?unierer, Suhl (sometimes spelled Keppler)

I assume any B?chsenmacher with the initials H and K could be it, as well.

Also: was a Heinrich Klett in Zella-Mehlis as well but i don't recall if he was around in 1938.

Again: please let me remind you the above are suggestions, mere speculation on my part, as it were.

EDIT: in one of my above posts I gave the incorrect date. Should be January 15, 1940. Sorry.

Kind regards
Peter

[mike ford]

Gut-n-Tight,
You are correct as to about when your drilling was made. It was proofed(not made) in Suhl ( likely also made there or near) in September of 1938. At this time, they were not usually marked as to whether they were 8x57IR or IRS. The Proof law of 1939 was the first time they were required to be marked as the cartridge was commonly called. Before that, the marks did not indicate directly a specific cartridge, rather it indicated the bore ( not groove or bullet ) diameter and maximum case length. As Peter indicated in his first comment above, the precise diameter may vary. They made the measurements with gauge pins in .1mm steps. In your case, the barrel accepted a 7.8mm gauge, but not a 7.9mm one. This indicates the barrel could have an actual bore diameter of somewhere between 7.80mm and 7.89mm and a case up to 57mm long. I, myself, have guns with these same marks, that are actually chambered for two different cartridges( 8x57IR and 8x57R/360) . For the 8x57IR, I use commercial Norma ammo, because I bought the entire stock of a store in in 1974 and saved it. Even though the 8x57R/360 has a .318 bore, I actually hand load with some .3215 Remington bullets made for their 170 gr. 8mm Mauser ammo( I could also use .318,or .321"). To illustrate the point of the test I mentioned above; I use factory Berdan primed cases with the .3215 bullet, but if I used cases formed from 9.3x72R/ 303 British/ 30-40Krag I would likely have to use .318"( maybe .321"). Do I have you confused enough yet? As long as the forearm doesn't cause problems, I wouldn't worry much about it.
Mike

[Gut-n-Tight]

Thanks all. I'll go with having a .318" Heym made drilling that was made a bit loose and is now worn. When my .321-322" bullets arrive I'll reload some on the light side and test them. If all goes well with the .322" Privi's I'll try a Privi 8X57IRS.
I began a new question that is related. When did the S bore appear in the rimmed version and while I was thinking along this line, when did 2 3/4" 16 gauge shot shells come along?

[Gut-n-Tight]

Additional: I do understand that if a 8X57JRS offers any resistance in chambering in my drilling, the test is off!

[mike ford]

Gut-n-Tight,
If you can't perform the test we mentioned, you might try smoking the bullet and case neck with a lighter or candle ( or paint them with a magic marker). When you chamber or try to do so, the area of interference will show up. It will be harder to judge if there is enough clearance, by this method.
Mike

[Gut-n-Tight]

Okay, will do, thanks.