Grouping and shot displacement Gew 88

[Tedly]

Shot some more Lyman #323481 ( No.2 alloy) 185gr.GC and AA5744 @ 20.5 gr. thru my Gew 88 the other day. Results are confusing. I've been very sucessful shooting jacketed full velocity loads , really shooting tight with 170gr.(2400fps) and 150gr.(2500fps) Hornady jacketed loads. Like 10 shot groups under 2" with issue sights...many clover leafs,etc. Finally got some of my cast boolit Lyman #323481 & 20.5 gr. AA5744 on the paper at 100yds. and I'm getting flyers mixed with 2 shots touching here...two shots touching there.. two more shots touching 6" away on another area of the target. Seems like 2shots touching togather all over the place, but not in a group togather like the jacketed. I think this could be tweeked into a load but I'm not sure what my next step should be ? What do you suggest?Thanks...Tedly

[Baron von Trollwhack]

I'm getting 2 1/2" patterns with full power lead loads @ 100. My plan is to shim the barrel where it exits the shroud. BvT

[Buckshot]

..............Could be a number of things. First of all what does the barrel slug, and what are you sizing the boolits to? Is there any leading?

..............Buckshot

[Tedly]

Buckshot,
Barrel slugs at .3235/.324 x.3115 . Sizing is at .3230...only sizer I've got access to right now.No leading at all,bore looks like its been polished after shooting. I would think that the boolit would be close enough at .323dia. ? Maybe not ? Definetly see improvement as charge increases...Thanls, Tedly

[BABore]

Have you measured the inside neck diameter of a fired case from a full powered load. It should be new or once fired brass. Those military chambers and throats are pretty big. In my VZ24 I can safely chamber a 0.327 diameter boolit using Remington 30'06 brass reformed to 8mm. Regular 8mm Remington brass could handle an even larger boolit as I gain 0.006" of outside case neck diameter with the reformed '06 cases.

Cast boolits rarely tolerate a loose case neck or throat as it allows the rear of the boolit to cant as it moves forward. Jacketed, due to their hardness, can overcome this and straighten out.

Fill the chamber/neck with thicker, reformed brass.

Fill the throat with boolit diameter.

Be above groove diameter and engrave upon chambering.

Incidently, my groove size is also 0.3230.

[Buckshot]

Buckshot,
Barrel slugs at .3235/.324 x.3115 . Sizing is at .3230...only sizer I've got access to right now.No leading at all,bore looks like its been polished after shooting. I would think that the boolit would be close enough at .323dia. ? Maybe not ? Definetly see improvement as charge increases...Thanls, Tedly

............Generally a cast lead slug with smokless needs to be 'AT' groove as a minimum. Best accuracy with a jacketed bullet is always best when it's as close to perfectly on axis with the barrel's bore as can be made. Then consider the cast lead slug which is no where near as tough as it's jacketed brother, and what the possibilities are if it's looking off a few degrees from the bore?

BABore brings up the military chamber, throat/leade dimensions which can for sure be contributing to the issue. I have a couple very nice 7x57 per-war (WW1) South American contract Mausers, and it appears the leade ends somewhere up around the rear sight :-) They were chambered for 172/175gr RN bullets.

"Hornady jacketed loads. Like 10 shot groups under 2" with issue sights... many clover leafs,etc."

If that's at 100 yards with the issue sights you're doing some very nice work, without a doubt! It could very well be that as bigedp51 mentioned, barrel harmonics could contribute, but if jacketed is doing that well I'd certainly think your cast loads (if paid attention to when putting them together) might do twice your jacketed group sizes with ease. I really an inclined to think that you're having a problem with the "Fit" more then anything else.

.................Buckshot

[Tedly]

Buckshot,
I was suggested to me that the #323481 Lyman @ 185 gr. dosen't have as much bearing surface as a heavier boolit would...yet any of the combos tried that won't shoot in this Gew 88 shoot like a house a fire in my Brno 98/22 Turk...its been suggested a difference in rifling pitches but mine has a late German replacement barrel and I hav'nt compared the pitches...I can believe that it should be easier to get a longer bearing surface to shoot better...But you are no doubt right about "fit". Is it too much to shoot as cast @ .3265 thru my .3235-.324 x.3115 bore ? I really don't know if I can get a sizer opened up? Also, been using AA 5744 from 16.0 up to and including 22.0 gr. with 185 GC boolit. Is this approximately the range? Maybe one of SwedeNelsons special Lee moulds?probably drop at just enough over to be good?

[HORNET]

Tedly, if an unsized boolit will fit in the mouth of a fired case, it'll work. It's fairly easy to polish a sizer out, there's an article on how to do it in Castpics (see link at bottom of page). Lee sizers don't have a very long sizing section and polish out quickly or Buckshot can make you a new Lee-style die for a very reasonable price (he also does Lyman/RCBS-style) in whatever size you want. BABore's suggestions are good ideas if you want to tighten things up more.

[Tedly]

Hornet,
An unsized boolit will start into the mouth of a fired case, but would be a press fit to keep it there, just like seating a boolit. Is it OK if the unsized boolit loads into the case and chambers? (dummy round)? After all, if it all goes togather and fits into the chamber/neck ares, should be OK?

[BABore]

Hornet,
An unsized boolit will start into the mouth of a fired case, but would be a press fit to keep it there, just like seating a boolit. Is it OK if the unsized boolit loads into the case and chambers? (dummy round)? After all, if it all goes togather and fits into the chamber/neck ares, should be OK?

You may have to flare or remove what's left of the crimp before checking this. I've got a early war, German bbl on my VZ. Using stock Remington 8mm cases, a 0.3265 boolit will fall right in. Using reformed Rem. 30'06 case, the same boolit is a slip fit.

If you decide to chamber up a dummy with an unsized boolit, ink up the case neck so you can see any interfence well. The next step is if your boolit actually touches anything in the throat and engraves in the bore.

[303Guy]

I shoot boolits so large they are a slight press fit into fired cases. The bore-ride section engauges the rifling (or what's left of it) but the neck grip stil. pulls the boolit out. This means there is little clearance between neck and chamber but because the powder charge is low the pressure remains low. BUT, the pressure is higher like that than with more chamber clearance! Harder alloy raises the pressure still further but again, still mild.

[Tedly]

Buckshot,
You were completely right about "fit".Went out today with original load format except I used UNSIZED boolits that I hand lubed(messy).Boolits mike .3255/.3260 and are going into .3245/.325 dia. grooves...shot as cast , grouped like jacketed! All 10 shots into 2 1/2" x 3" group, 3 shots into a clover leaf 1/2" in size. I shot 5 first, took a break and shot the next 5.I was shocked how well it all shot. Best part is that this shot 5" high @ 100yds. with the battle sight, so this gives me some room to play with the elevational dope .

[MtGun44]

Good that you did the unsized. My experience is that you can do fine with groove size or
+.001 most of the time with various pistols, but I have had far better results with .002-.003
over in my .30 cal rifles and at least +.002 in .45 cal rifles. Not sure why.

Bill